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Doctoral Thesis
Response of terrestrial paleoenvironments to past changes inclimate and carbon-cycling: Insights from palynology and stableisotope geochemistry
Author(s): Heimhofer, Ulrich
Publication Date: 2004
Permanent Link: https://doi.org/10.3929/ethz-a-004741183
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ETH Library
DISS ETH No. 15463
Response of terrestrial palaeoenvironments to
past changes in climate and carbon-cycling:
Insights from palynology and stable isotope geochemistry
A dissertation submitted to the
SWISS FEDERAL INSTITUTE OF TECHNOLOGY ZURICH
for the degree of
DOCTOR OF SCIENCES
Presented by
Ulrich Heimhofer
Dipl. Geol. Univ. Erlangen-Nürnberg
born October 19, 1971
Sonthofen i. Allgäu / Germany
Accepted on the recommendation of
Prof. Dr. Helmut Weissert, ETH Zurich, examiner
Dr. Peter A. Hochuli, University of Zurich, co-examiner
Prof. Dr. Judith A. McKenzie, ETH Zurich, co-examiner
Dr. Stephen P. Hesselbo, University of Oxford, co-examiner
2004
Table of contents
Table of contents
Abstract ……………………………………………………………………………………..3
Zusammenfassung ……………………………………………………………………………..5
Chapter 1
Introduction …...………………………………………………………………………………...7
Chapter 2
Absence of major vegetation and palaeoatmospheric pCO2 changes associated with Oceanic
Anoxic Event 1a (Early Aptian, SE France) ……………….…...……………………………..17
Chapter 3
Palynological and calcareous nannofossil records across the late Early Aptian OAE 1a:
Implications for palaeoclimate, palaeofertility and detrital input .………………….……...43
Chapter 4
Terrestrial carbon-isotope records from coastal deposits (Algarve, Portugal):
A tool for chemostratigraphic correlation on an intrabasinal and global scale …………………73
Chapter 5
A well-dated and continuous early angiosperm pollen record from mid-Cretaceous
coastal deposits (Lusitanian and Algarve Basins, Portugal):
Implications for the timing of the early angiosperm radiation ………………………………….85
Chapter 6
Conclusions …………………………………………………………………………………..147
Appendix
A 1 to A 7 ………………………………………………………..…………………….…...149
Acknowledgements ………………..…………………………………………………………165
Curriculum vitae……………………………………………...………………………..…..…...167
Abstract 3
Abstract
The mid-Cretaceous (Aptian to Turonian, 120-90 Ma) was characterised by globally averaged
surface temperatures of up to 10ºC and is considered as one of the best examples of
greenhouse-type climate conditions in the Phanerozoic Earth history. Evidence for this
exceptional climate mode includes low latitudinal thermal gradients, increased surface and
bathyal ocean water temperatures, the occurrence of thermophilic plant assemblages in high
latitude regions and the absence of expanded polar ice-sheets. However, during this period of
global warmth, climatic conditions were far from stable. Short-term perturbations of the
global carbon-cycle and climates are reflected in the deposition of organic carbon-rich black
shales, shifts in the carbon isotope record and dramatic growth-crisis of biocalcifying
organisms. In order to investigate terrestrial environments and their response to mid-
Cretaceous global change, Late Barremian to Albian deposits are studied with a combined
approach, including palynology, carbon isotopes and organic geochemistry.
The late Early Aptian oceanic anoxic event (OAE) 1a interval in the Vocontian Basin, SE
France has been chosen to serve as a high-resolution environmental archive, covering a time
of short-term palaeo-climatic and oceanographic change. Based on the δ13C composition of
marine carbonates and individual biomarkers, palaeoatmospheric CO2 partial pressure during
and after black shale formation has been estimated. To address possible vegetation changes in
the hinterland of the Vocontian Basin, the occurring spore-pollen assemblages were
determined. Furthermore, dinoflagellate cyst and calcareous nannofossil assemblages were
analysed and Corg accumulation rates were estimated to identify changes in
palaeoceanographic conditions. Our results indicate that intensified Corg burial in black shales
during the late Early Aptian was accompanied by an only moderate drop in CO2 partial
pressure. The pollen spectrum indicates relatively stable vegetation patterns during and after
times of OAE 1a formation. Likewise, the organic-walled and calcareous plankton display no
significant changes in the prevailing palaeoceanographic conditions across the black shale
interval. In contrast to previous studies, our results exhibit no indication of enhanced humidity
and nutrient-input, which probably triggered oceanic surface water productivity and resulted
in the deposition of Corg-rich sediments. In the Vocontian Basin, the late Early Aptian OAE 1a
black shales are associated with times of low detrital input, probably due to sea-level
fluctuations and/or a shift towards more arid climate conditions.
In order to investigate the causes and consequences of long-term climatic and floral change
during the mid-Cretaceous, coastal sediments from Southern and Western Portugal (Algarve
Abstract 4
and Lusitanian Basin) serve as environmental archives. The studied sections are Late
Barremian to Middle Albian in age. A revised stratigraphic framework has been established
for both sections using dinoflagellate cyst biostratigraphy. In order to obtain a terrestrial
carbon isotope record for the Algarve section, the δ13C signature of fossil wood, cuticles,
charcoal and bulk Corg was measured. The distinct δ13C pattern of the resulting record allows
for chemostratigraphic correlation with existing carbon isotope curves, resulting in a
significant enhancement of the stratigraphic resolution. Subsequently, the accurately dated
successions are studied from a palynological perspective, with special emphasis on the
qualtitative and quantitative analysis of the occurring angiosperms (flowering plants) pollen.
A distinct increase in diversity and relative abundance of angiosperm pollen in the Barremian
to Albian interval is observed in both studied sections, reflecting the incipient radiation of
angiosperms on a resolution not obtained so far. Our results shed new light on the age
interpretation of the well-known angiosperm mesofossil floras from the Portuguese
Estremadura region, which have been assigned to a Barremian or possibly Aptian age. Several
lines of evidence, including sequence- and biostratigraphy as well as palynology indicate an
Albian or younger age for the mesofossil assemblages, hence indicating a major radiation
phase during the Early Albian.
Zusammenfassung 5
Zusammenfassung
Die mittlere Kreidezeit (Apt bis Turon, 120-90 Ma) war durch höhere globale
Durchschnittstemperaturen von bis zu 10ºC gekennzeichnet und wird als eines der besten
Beispiele für erdgeschichtliche Treibhausklima-Perioden betrachtet. Dies zeigt sich sowohl in
einem geringen latitudinalen Temperatur-Gradienten und erhöhten ozeanischen Tiefen- und
Oberflächenwasser-Temperaturen und als auch im Auftreten thermophiler Pflanzenver-
gesellschaftungen in hohen Breiten und weitgehend eisfreien Polen. Doch auch während
dieser globalen Warm-Phase waren die klimatischen Bedingungen keineswegs durchwegs
stabil und ausgeglichen. Kurzzeitige Störungen des globalen Kohlenstoff-Kreislaufs sowie
damit einhergehende klimatische Schwankungen sind in der Ablagerung organisch-reicher
Schwarzschiefer, dem Kohlenstoff-Isotopensignal sowie in dramatischen Wachstumskrisen
biokalzifizierender Organismen dokumentiert. Palynologische sowie Isotopen- und organisch-
geochemische Untersuchungen an sedimentären Abfolgen aus dem Zeitraum Spät-Barrême
bis Alb erlauben es, die Auswirkungen dieser globalen Veränderungen auf terrestrische
Ökosysteme im Detail zu studieren.
Um kurzfristige paläo-klimatische und -ozeanographische Veränderungen während einer
Schwarzschiefer-Phase im späten Unter-Apt zu untersuchen, wurde der OAE 1a Horizont
(oceanic anoxic event 1a) im Vocontischen Becken, SE Frankreich als hoch-auflösendes
Umweltarchiv ausgewählt. Gestützt auf δ13C Analysen von marinen Karbonaten sowie von
einzelnen organischen Verbindungen wurde eine Abschätzung des CO2 Partialdrucks während
und nach der Schwarzschiefer-Phase durchgeführt. Zusätzlich wurde eine Analyse der
auftretenden Pollen und Sporen Vergesellschaftung in den hemipelagischen Sedimenten
durchgeführt, um Rückschlüsse auf mögliche Änderungen der Vegetation im Hinterland des
Vocontischen Beckens zu erhalten. Darüber hinaus wurden Dinoflagellaten Zysten und
Nannoplankton Assoziationen bestimmt sowie Corg-Akkumulationsraten abgeschätzt, um
Veränderungen der paläozeanographischen Bedingungen zu identifizieren. Die Resultate
dieser Untersuchungen zeigen, dass trotz der verstärkten Ablagerung Corg-reicher
Schwarzschiefer nur ein sehr moderater Abfall des atmosphärischen CO2 Partialdrucks
stattfand. Desweiteren weisen die analysierten Pollen-Spektren auf ein relativ stabiles
Vegetationsmuster hin - sowohl in Zeiten verstärkter Schwarzschiefer Bildung als auch in den
darüber folgenden normal-marinen Sedimenten. Die Auswertung des marinen organischen
und kalkigen Planktons deutet ebenfalls auf relativ stabile paläozeanographische Bedingungen
während und nach der OAE 1a Schwarzschiefer-Phase hin. Im Gegensatz zu früheren Studien
Zusammenfassung 6
des OAE 1a fanden sich in der untersuchten Abfolge keine Hinweise auf ein direkte
Verknüpfung von erhöhter Humidität, verstärktem Nährstoff-Eintrag sowie einer daraus
resultierenden Produktivitätszunahme im ozeanischen Oberflächenwasser, welche sich
wiederum in der Ablagerung von Corg-reichen Sedimenten äusserte. Vielmehr konnte
festgestellt werden, dass die Bildung der OAE 1a Schwarzschiefer im Vocontischen Becken
mit Phasen geringen detritischen Eintrags einherging, möglicherweise ausgelöst durch
Meeresspiegel Schwankungen und/oder aride Klimabedingungen.
Um die langerfristigen Ursachen und Auswirkungen des mittel-kretazischen Klima- und
Florenwechsels zu untersuchen, wurden fossile Küsten-Sedimente in Süd- und West-Portugal
(Algarve und Lusitanisches Becken) untersucht. Die beiden Profile reichen vom Spät-
Barrême bis ins Mittlere Alb, die genaue zeitliche Einordung wurde mittels Dinoflagellaten
Zysten-Biostratigraphie wesentlich verbessert. Messungen der δ13C Signatur von fossilen
Holzresten, Blatt-Kutikulen und Gesamt-Corg ermöglichen die Erstellung einer δ13C Kurve für
das Algarve Profil, welche eine chemostratigraphische Korrelation mit existierenden
Isotopen-Kurven erlaubt und zu einer deutlich verbesserten stratigraphischen Auflösung der
sedimentären Abfolge führt. Daran anschliessend werden palynologische Analysen der neu-
datierten Sedimente durchgeführt, wobei der Schwerpunkt hierbei auf der qualitativen und
quantitativen Auswertung der auftretenden Angiospermen (Blütenpflanzen) Pollen liegt. Eine
deutlich Zunahme sowohl in der Diversität als auch in der relativen Häufigkeit der
Angiospermen Pollen vom Barrême bis ins Alb zeigt sich in beiden untersuchten Profilen und
dokumentiert in bisher nicht vorhandener zeitlicher Auflösung die Radiation der frühen
Angiospermen. Aus kontinentalen Serien (Barrême bis Apt) der west-portugiesischen
Estremadura Region wurde bereits früher ein Anzahl mesoskopischer Angiospermen
Fossilien beschrieben, welche einen wesentlichen Beitrag zur Klärung der frühen Phylogenese
dieser Gruppe leisteten. Im Vergleich mit unseren gut-datierten palynologischen Befunden
zeigt sich jedoch, dass jene Angiospermen Reste ein wesentlich jüngeres stratigraphisches
Alter besitzen als bisher angenommen.
Chapter 1 7
Chapter 1
Introduction
1. The mid-Cretaceous: a time of global change
The mid-Cretaceous period (Aptian to Turonian, 120 to 90 Ma) offers the opportunity to
study earth’s climate and its variability during times of exceptional warmth. The early Late
Cretaceous is considered to reflect the warmest conditions during the last 145 Ma and
represents one of the best examples of “greenhouse” climate conditions in the Phanerozoic
Earth history (Barron, 1983). Substantial evidence for this exceptional climate mode includes
increased surface and bathyal ocean water temperatures (Huber et al., 1999; Norris and
Wilson, 1998), low equator-to-pole temperature gradients (Huber et al., 1995) as well as
extensive forests in polar regions (Francis and Frakes, 1993; Spicer and Parrish, 1986) and the
absence of expanded polar ice sheets. According to the Cretaceous Climate Ocean Dynamics
(CCOD) workshop report (Bice et al., 2003) globally averaged surface temperatures in the
mid-Cretaceous were more than 10ºC higher than today.
Apart from a long-term rise in global mean temperatures, the study of mid-Cretaceous
sediments provides evidence for several transient events of climatic and oceanographic
perturbations. A multitude of sedimentological, geochemical and palaeotological data
provides evidence for prominent fluctuations of the thermal and chemical state of the
Cretaceous oceans and continents. Episodes of climatic cooling are reflected in the occurrence
of ice-rafted debris and glacial deposits (Frakes and Francis, 1988; Price, 1999) as well as in
shifts of the stable isotope records (Stoll and Schrag, 1996; Weissert and Lini, 1991). The
episodic and widespread deposition of organic carbon-rich black shales (Oceanic Anoxic
Events (OAEs) of Schlanger and Jenkyns, 1976), the drowning of carbonate platforms
(Weissert et al., 1998) and concomitant shifts in the carbon isotope record (e.g. Scholle and
Arthur, 1980) display sustained disturbances of the global carbon cycle.
These observations question the long-held view of an equable and stable mid-Cretaceous
climate mode and suggest the occurrence of severe short-term perturbations of the entire
ocean-atmosphere system. These changes are superimposed on a gradual warming trend,
resulting in exceptional greenhouse conditions of the early Late Cretaceous.
Chapter 1 8
2. Causes and consequences of the environmental changes
The ultimate cause for the mid-Cretaceous environmental perturbations is still a matter of
debate. Variations in the atmospheric composition are suggested to have played a key role for
the observed climatic changes. Results from geochemical modelling (Berner, 1994) are in
agreement with geochemical and stomatal-derived pCO2 estimates (Beerling and Royer,
2002) indicating strongly increased pCO2 levels (4 to 10 times preindustrial levels) during the
Aptian to Turonian greenhouse period. Accoding to several authors (e.g. Arthur et al., 1985;
Larson and Erba, 1999), the increase in greenhouse gases was triggered by extensive
submarine volcanic activity, including enhanced spreading along mid-ocean ridges and the
formation of Large Igneous Provinces (LIP) oceanic plateaus (e.g. the Ontong Java and
Manihiki Plateaus). Additional greenhouse forcing could have been triggered by the
concomitant and rapid dissociation of methane gas hydrates trapped in marine sediments (e.g.
Beerling et al., 2002).
-60ºE -30ºE-45ºE -15ºE-75ºE 0ºE
0ºN
30ºN
15ºN
-15ºN
Northern Gondwana province(arid to semi-arid)
3
2
1
transitional zone
Southern Laurasian province(subtropical to warm-temperate)
proto North Atlantic
western Tethys
EAG
Fig. 1: Palaeogeographic reconstruction of the North Atlantic and Tethyan realm during the mid-
Cretceous at ~115 Ma (modified after Geomar map generator; www.ods.de). Asterisks mark the
location of the study sites: (1), Lusitanian Basin; (2) Algarve Basin; (3) Vocontian Basin. Major floral
belts and corresponding climates after Brenner (1976) and Chumakov et al. (1995). EAG: Equatorial
Atlantic Gateway.
Chapter 1 9
On longer time-scales, plate-tectonic forcing has been invoked as an important trigger
mechanism for the observed perturbations (Fig. 1). The mid-Cretaceous rifting of South
America and Africa and the concomitant development of the Equatorial Atlantic Gateway
(EAG) is supposed to have caused a major reorganisation in oceanographic circulation and
climatic patterns (Kuypers et al., 2002; Wagner and Pletsch, 1999). Based on coupled ocean-
atmosphere model simulations, Poulsen et al. (2003) demonstrated that the onset of the
Cretaceous thermal maximum was directly related to the tectonic evolution of the proto-
Atlantic. This major tectonic rearrangement presumably resulted in significant long-term
climatic changes and had a strong impact on temperature and precipitation patterns, and
consequently on weathering and erosion processes as well as on the distribution of vegetation
(Hallam, 1985; Weissert et al., 1998). According to Chumakov et al. (1995), the
establishment of an equatorial humid belt during the Albian was probably triggered by the
opening of the South Atlantic Ocean.
The response to the above mentioned processes is reflected in different short- and long-term
perturbations of various parts of the mid-Cretaceous ocean-atmosphere system. One of the
best-studied intervals of past oceanographic and climatic change is the late Early Aptian OAE
1a, lasting for about 0.5 to 1.0 Ma. The OAE 1a represents the first globally distributed black
shale in the Cretaceous and is therefore regarded as a turning point in mid-Cretaceous
palaeoceanography. Shifts in the δ13C signature of marine sediments deposited during and
after the black shale event have been interpreted in terms of increased burial of organic carbon
in marine sediments or reflecting changes in partitioning of carbonate and organic carbon
(Arthur et al., 1988; Weissert et al., 1998). Disturbances of the Early Aptian carbon-cycle are
furthermore displayed in major growth crises of carbonate-producing organisms, reflected in
the demise of carbonate platforms (Wissler et al., 2003) and a pronounced decline in
calcareous nannoplankton (nannoconnid crisis of Erba, 1994). According to Erbacher et al.
(1996) and Leckie et al. (2002), the OAE 1a is accompanied by dramatic turnovers in
siliceous and calcareous plankton due to changes in palaeofertility during episodes of black
shale deposition.
On a longer timescale - in the order of several millions of years - the establishment of
greenhouse climate conditions during the mid-Cretaceous, with peak warmth in the Turonian
(e.g. Wilson et al., 2002), probably reflects the combined effects of tectonic rearrangement
Chapter 1 10
and concomitant CO2 forcing. Long-term changes of the prevalent weathering and erosion
processes on the continents are reflected in varying clay-mineral compositions and
sedimentation patterns (Ruffell and Batten, 1990, Wortmann et al., in press). According to
Haq et al. (1987), the increase in global mean temperatures was accompanied by a stepwise
rise in sea-level during the Aptian to Cenomanian interval.
3. Response of terrestrial environments to short- and long-term perturbations
Detailed information on the mid-Cretaceous climatic and carbon-cycle perturbations are
mainly based on marine records from DSDP/ODP cores and from on-land sections. The
available studies comprise a multitude of geochemical and micropalaeontological data
addressing the thermal state, the palaeofertility and the circulation patterns of mid-Cretaceous
oceans.
In contrast, only few studies have been carried out with focus on the response of terrestrial
ecosystems to short- and long-term changes. Land plant communities are sensitive recorders
of changes in the physical environment. Their composition and spatial distribution is strongly
influenced by variations in regional precipitation and temperature patterns. Hence, the study
of palynofloral associations (pollen and spores) represents an important proxy for the
investigation of past climate and environmental conditions on different time scales. Whereas
the palynological approach is widely applied for the reconstruction of Quaternary and
Neogene climates (Bradley, 1999 and references therein), only very few high-resolution data-
sets exist for the Mesozoic (e.g. Hochuli et al., 1999; Looy et al., 2001).
Via the consumption of atmospheric CO2, terrestrial vascular plants are directly connected to
the global carbon cycle. Prominent changes in the carbon isotopic composition of the carbon
pool are not only reflected in marine-derived carbon but also in organic carbon of land-plant
origin. Consequently, the δ13C composition of land-plant remains can be used to trace major
shifts of the global carbon isotope record allowing for correlation of marine and terrestrial
strata (Gröcke et al., 1999; Hesselbo et al., 2002). On longer time scales, the burial of
terrestrial biomass along continental margins represents a major carbon sink and is therefore
considered to play a key role in the global carbon cycle. Due to the different δ13C composition
of terrestrial and marine organic carbon, intensified burial or oxidation of continental biomass
can result in major short- and long-term shifts of the global carbon isotope record, e.g. during
the Palaeocene/Eocene (Kurtz et al., 2004) or the Carboniferous (Beerling and Royer, 2002).
Chapter 1 11
A similar mechanism has been suggested by Wissler (2001) to account for the Aptian δ13C
anomaly.
From a palaeobotancial perspective, the mid-Cretaceous period is characterised by the
evolution and rapid diversifications of the flowering plants (Fig. 2). Early evidence for the
occurrence of flowering plants (angiosperms) has been reported by Brenner (1996) who
documented angiosperm-type pollen grains from supposedly Valanginian to Hauterivian
deposits of Israel. The palaeogeographic dispersal of early angiosperm pollen suggests a
latitudinally diachronous pattern. Angiosperms probably occurred first in the palaeoequatorial
regions of Northern Gondwana (Fig. 1) and subsequently migrated towards northern and
southern high-latitudes, were they appeared some 20 to 30 Ma later (Brenner, 1976; Crane
and Lidgard, 1989). By the end of the Cenomanian, angiosperms dominated the diversity of
low-latitude floras, accounting for ~70 % of species (Crane et al., 1995; Lidgard and Crane,
1988). Palaeo-botanical and -ecological interpretations of fossil angiosperm remains indicate
that early angiosperm plants were of low stature, perhaps herbs or woody shrubs, which
flourished predominantly in unstable environments (Crane et al., 1995; Friis et al., 1999;
Wing and Boucher, 1998).
Fig. 2: Absolute species diversity of
Cretaceous macrofossil plant assemblages
(redrawn from Lidgard and Crane 1988).
Note the dramatic increase in the number of
angiosperm taxa from the Albian onwards.
Many aspects of the early angiosperm radiation during the mid-Cretaceous are still
ambiguous. In particular, the Barremian to Albian phase of the diversification is poorly
600
500
400
300
200
100
0
160 140 120 100 80 60
U Jur Neocom Ba-Ap Alb Ce T-S Cmp Ma Pal
Angiosperms
Pteridophytes
Cycadales
Conifers
Ginkgoales
nu
mb
er
of sp
ecie
s
time (Ma)
Chapter 1 12
documented with regard to timing, diversity and relative abundance. The problematic age
assignment of many records hampers detailed comparison and correlation with other
assemblages as well as with major climatic and/or tectonic changes. According to several
authors (e.g. Crane et al., 1995; Lupia et al., 2000) unstable environmental conditions during
the mid-Cretaceous might have had significant influence on the evolution of flowering plants.
4. Main objectives and general outline
The purpose of this study is to investigate the response of terrestrial ecosystems to short- and
long-term environmental changes during the mid-Cretaceous. Sedimentary deposits from SE
France and Portugal are chosen as archives for the past perturbations, which are studied with
palynological and geochemical methods. The presented thesis is closely connected to ongoing
research on the impact of mid-Cretaceous carbon-cycle perturbations on shallow water
carbonate systems, currently carried out by Stefan Burla at the ETH Zürich. The following
two main objectives are addressed in this thesis.
(i) Tracing environmental change during times of late Early Aptian black shale formation
The first two chapters focus on the climatic and oceanographic perturbations which are
accompanied by the formation of the late Early Aptian OAE 1a. The Niveau Goguel interval
of the Serre Chaitieu section (Vocontian Basin, SE France) represents a well-documented
equivalent of the OAE 1a black shale (Bréhéret, 1997; Herrle and Mutterlose, 2003) and has
been sampled on a high resolution. The hemipelagic deposits of this section provide well-
preserved organic matter and palynomorphs, allowing for detailed analysis of the organic
geochemistry and palynological assemblages.
(ii) Tracing patterns of early angiosperm radiation during the Barremian-Albian interval
The second part of the study addresses long-term changes of the mid-Cretaceous carbon-cycle
and vegetation patterns with special focus on the diversifying angiosperms. Coastal marine
deposits from the Portuguese Algarve and Estremadura regions, covering Barremian to Albian
strata have been chosen as environmental archives (Rey, 1972; Rey, 1986). Both successions
provide well-preserved land plant-derived organic matter, including cuticles, fossil wood and
excellent pollen assemblages. The chosen study sites are located close to a number of well-
known and intensely studied angiosperm mesofossil sites in the Estremadura region (Friis et
al., 1994; Friis et al., 1999).
Chapter 1 13
Chapters 2 to 5 represent discrete manuscripts, which are either published, in review or in
preparation for publication.
In Chapter 2 a combined geochemical and palynological approach is applied to study
variations in palaeoatmospheric CO2 concentrations and concomitant floral changes across the
OAE 1a interval (Vocontian Basin, SE France). The δ13C composition of carbonate and
organic carbon as well as of individual biomarkers is used to estimate past changes in pCO2.
A detailed chemostratigraphic correlation with an existing, more pelagic record (Cismon, N
Italy) allows for comparison of pollen assemblages from two different sites. Possible
consequences for the palaeoceanographic and palaeoatmospheric conditions are discussed.
Chapter 3 assesses variations of the pollen assemblage, the organic-walled plankton and the
calcareous nannofossils across the OAE 1a interval (Vocontian Basin, SE France). The
marine and terrestrial-derived microfossils serve as proxies for past climatic and
oceanographic change during times of black shale formation. In combination with tentative
estimations of sedimentation rates and organic carbon fluxes, the palynological and
nannofossil results contrast to previously proposed scenarios for the formation of late Early
Aptian black shales.
In Chapter 4 the carbon isotopic composition of land plant-derived organic material from two
coastal marine records (Algarve Basin, S Portugal) is analysed. The obtained δ13C records
display several distinct shifts, which allow for correlation on an intrabasinal as well as on a
global scale with existing Aptian carbon isotope curves. In combination with biostratigraphic
data, the applied method results in a significant enhancement of the stratigraphic resolution of
the studied records.
Chapter 5 addresses the radiation of early angiosperms within the Barremian to Albian
interval from a palynological perspective. The angiosperm pollen records of two well-dated
sections (Lusitanian and Algarve Basins, Portugal) are analysed with respect to composition,
abundance and diversity and compared with previously published records. The implications
for the timing of the early angiosperm diversification are discussed including a revised age
assignment for several angiosperm mesofossil floras from the Portuguese Estremadura region.
Chapter 1 14
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Chapter 2
17
Chapter 2
Absence of major vegetation and palaeoatmospheric pCO2 changes associated with
Oceanic Anoxic Event 1a (Early Aptian, SE France)
Abstract
The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event
(OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO2
concentrations, accompanied by significant changes in the terrestrial flora. In order to test this
hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a
combined approach including stable carbon isotopes, organic geochemistry and palynology. To
estimate changes in palaeoatmospheric CO2 levels across the OAE 1a, the δ13C composition of
presumed algal biomarkers (low-molecular-weight n-alkanes, steranes) and of bulk carbonate
carbon are used. Our results yield estimated Early Aptian pCO2 values 3 to 4 times the
preindustrial level and only a moderate drop across the black shale event. This moderate drop in
pCO2 is supported by palynological results. The frequency patterns of climate-sensitive
sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only
minor fluctuations throughout the studied section and indicate relatively stable patterns of
terrestrial vegetation during formation of the OAE 1a black shale. The occurrence of a
characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate
chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N
Italy). The contemporaneous formation of individual black shale layers at both sites indicates that
transient episodes of dysoxic-anoxic bottom waters prevailed over large areas in the W Tethys
Ocean independent of depositional setting. Comparison of the palynological data from the two
locations displays significant differences in the frequency patterns of bisaccate pollen. The
contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic
current patterns and/or selective sorting due to sea level rise rather than latitudinal shifts of the
major floral belts.
Keywords: Early Cretaceous; Aptian; black shales; OAE; carbon isotopes; palynology; organic
geochemistry; palaeoatmosphere
Chapter 2
18
1. Introduction
1.1. Palaeoclimatic and palaeoceanographic background conditions
The mid-Cretaceous is generally referred to as a greenhouse period characterized by
exceptionally warm climates (Hallam, 1985; Wilson and Norris, 2001), a weak meridional
temperature gradient (Huber et al., 1995) and considerably high levels of atmospheric carbon
dioxide (Berner, 1994; Freeman and Hayes, 1992). These extraordinary climatic conditions
are also reflected in the composition and spatial distribution of terrestrial plant assemblages.
Mid-Cretaceous fossil floras typically include ferns, conifers and cycadophytes which grew
throughout low to high latitudes, indicating tropical/subtropical to warm temperate conditions
(Hallam, 1985). The occurrence of extensive forests dominated by podocarpian and
araucarian conifers and other thermophilic taxa in polar regions in combination with the
absence of expanded polar ice sheets points to more equable and warmer climates during the
mid-Cretaceous in comparison to the present-day situation (Francis and Frakes, 1993).
During this period of greenhouse conditions, sedimentation in the world oceans was
characterized by the episodic deposition of organic carbon-rich sediments, informally called
“black shales”. The relative short-lived episodes (~ 50 to 500 ka) of organic carbon (OC)
accumulation in pelagic and hemipelagic environments were of regional to global extent and
have been termed Oceanic Anoxic Events (OAE) by Schlanger and Jenkyns (1976). The Early
Aptian OAE 1a represents the first globally distributed black shale event and therefore is
regarded as a major turning point of mid-Cretaceous palaeoceanography. The OAE 1a is
accompanied by dramatic turnovers in calcareous nannoplankton (Erba, 1994) and by high
extinction and origination rates of siliceous and calcareous plankton (Erbacher and Thurow,
1997; Leckie et al., 2002). In addition, a phase of carbonate platform demise has been
documented from the northern Tethys margin as well as from circum-Atlantic regions
(Weissert et al., 1998) which slightly predates the OAE 1a. Prominent changes in the global
carbon budget during and after times of black shale formation are reflected in the 13C/12C ratio
of organic (Corg) and carbonate carbon (Ccarb). The resulting δ13C pattern is characteristic for
Early Aptian times and has been documented worldwide from marine successions (Bralower
et al., 1999; Herrle et al., 2004; Menegatti et al., 1998) as well as from terrestrial
environments (Gröcke et al., 1999; Heimhofer et al., 2003).
According to Larson and Erba (1999) the mid-Cretaceous period of global warmth was
triggered by extensive submarine volcanic activity, including increased spreading rates along
Chapter 2
19
mid-ocean ridges and the formation of extensive oceanic plateaus termed “Large Igneous
Provinces”. The Early Aptian OAE 1a slightly postdates a period of intensive volcanic
activity on the Ontong Java Plateau and the Manihiki Plateau in the western Pacific between
125 and 120.5 Ma (Larson and Erba, 1999). The accompanying volcanic degassing may have
resulted in exceptionally high atmospheric carbon dioxide levels and related mid-Cretaceous
greenhouse warming (Arthur et al., 1985). Additional greenhouse forcing could have been
triggered by the rapid dissociation of isotopically-light methane gas-hydrates as indicated by a
negative δ13C anomaly at the onset of OAE 1a (Beerling et al., 2002). The accumulation and
burial of large quantities of OC in sediments during OAEs is assumed to result in a significant
drop in atmospheric carbon dioxide partial pressure (pCO2) and consequent climate cooling in
the aftermath of these events (Arthur et al., 1988; Kuypers et al., 1999). A prominent decline
in mean annual temperatures during or after OAE 1a formation is expected to affect terrestrial
vegetation patterns significantly. A first detailed spore-pollen record across OAE 1a (Hochuli
et al., 1999) shows a significant increase in boreal floral elements following the interval of
black shale formation and has been interpreted to reflect a major cooling episode and/or
prominent changes in oceanographic circulation patterns of the SW Tethys.
1.2. Aim of the study
To address possible changes in pCO2 across the OAE 1a and its potential impact on terrestrial
ecosystems we chose a two-fold approach. Organic and inorganic carbon isotope
geochemistry is used to obtain estimates of pCO2 based on variations in the photosynthetic
fractionation factor of marine phytoplankton. In addition, palynological analysis of climate-
sensitive floral elements offers the opportunity to study climatically induced variations in past
vegetation patterns. The distribution and abundance of pteridophyte spores, Classopollis spp.
and bisaccate pollen are strongly controlled by the prevailing palaeoclimatic conditions
(Batten, 1984; Vakhrameyev, 1982) and therefore can serve as indicator for palaeoclimatic
variations. However, in distal sedimentary facies, selective sorting of spores and pollen can
have a strong effect on the palynological composition and therefore has to be considered
carefully (Traverse, 1988; Tyson, 1995). In order to study the onset of the positive carbon
isotope excursion and the presumed palaeoclimatic changes from OAE to post-OAE
conditions, the upper part of the OAE 1a interval and the overlying sediments were analysed
from the Serre Chaitieu section (Vocontian Basin, SE France). Based on chemostratigraphic
Chapter 2
20
correlation, our geochemical and palynological results were compared in great detail with data
from the Cismon section (Belluno Trough, N Italy).
2. Palaeogeographic setting
The Serre Chaitieu section is situated in the north-eastern part of the Vocontian Basin (SE
France), which formed part of the northern continental margin of the Alpine Tethys Ocean
(Fig. 1). A palaeolatitude of 25-30°N has been inferred for the mid-Cretaceous position of the
basin (e.g. Hay et al., 1999). The section studied represents the lowest part of the “Marnes
Bleues” formation, a monotonous, up to 750 m thick succession of Aptian to Albian age,
which is composed mainly of grey to dark-grey marls intercalated with calcareous marls and
limestones. Numerous organic-rich shale horizons occur throughout the succession, some of
which can be correlated on a Tethys-wide or even global scale (Bréhéret, 1988).
Castellane
Mediterra
nean Sea
Grenoble
Die
Nice
Digne
Internal zones
of the Alps
Massif
Central
Provence Platform
Valence
0 50 km
Drowned platform faciesShallow open marine environmentsDeep open marine environmentspre-Triassic basement
Serre Chaitieusection
N
B
Spain
France
B
AIntermediate floral belt
Southern Laurasian province
(subtropical to
warm-te
mperate)
Northern Gondwana province(arid to semi-arid)
Serre Chaitieu
Roter Sattel
Cismon
40°
30°
20°
10°N
0 500 km
C
Luz
Fig. 1. A: Location of the Vocontian Basin in SE France. B: Spatial distribution of different
depositional settings within the Vocontian Basin during the mid-Cretaceous. The location of the Serre
Chaitieu section is marked with an asterisk. Map modified after Arnaud and Lemoine (1993). C: Plate
tectonic reconstruction of the W Tethys realm during the mid-Cretaceous (~115 Ma). Floral provinces
and inferred climates after Brenne (1967). Positions of the study site (black asterisk) and of the
sections used for comparison (white asterisks) are marked. Map modified after Geomar map
generator (www.odsn.de).
Chapter 2
21
During late Early Aptian times, the study area was situated in the north-western part of the
Vocontian Basin, several tens of km south of the northern palaeo-margin (Arnaud and
Lemoine, 1993). To the east the basin opened towards the Tethys Ocean facilitating exchange
with Tethyan water masses. Although deposition within the basin was largely pelagic, the
study area received a considerable amount of terrigenous detrital material from the nearby
continental areas (Bréhéret, 1994).
The studied basin was located in the southern part of the Southern Laurasian floral province
of Brenner (1976), which was restricted to the mid-latitudes of the Northern Hemisphere
during Aptian to Albian times (Fig. 1). Its microfloral assemblage is characterized by a high
diversity and abundance of pteridophyte spores - namely by spores of gleicheniaceous and
schizaeaceous affinity - and bisaccate pollen of pinaceous and podocarpaceous origin. Other
gymnosperm pollen such as Classopollis (Cheirolepidiaceae) and Araucariacites
(Araucariaceae) represent common elements of its floral assemblages (Batten, 1984; Brenner,
1976). During the mid-Cretaceous the major floral belts were broadly latitudinally arranged
and exhibited progressive compositional changes with increasing latitude, despite low
equator-to-pole thermal gradients (Batten, 1984). According to Brenner (1976) and
Vakhrameyev (1978) the Southern Laurasian floral province was characterized by a
subtropical to warm-temperate climate, whereas the climate of the Northern Gondwana
province adjacent to the south is regarded as tropical to semi-arid. In contrast, the Northern
Laurasian floral province (situated north of 60° N) is dominated by bisaccate pollen of
pinaceous origin indicating temperate and humid conditions.
3. Lithology and stratigraphy of the studied Serre Chaitieu section (SE France)
The Serre Chaitieu section, located about 1 km south of the village Lesches-en-Diois has been
studied in detail by several authors (Bréhéret, 1988; 1997; Herrle and Mutterlose, 2003). The
interval included in this study encompasses 12 m and represents the lowermost part of the
Serre Chaitieu section. The interval below the base of the sampled succession was not
accessible. The studied section is mainly composed of dark-grey marls with low to moderate
carbonate (12.0 to 36.0 %) and organic carbon (0.5 to 1.8 %) content, respectively. The lower
part of the section (0 to 6.5 m) shows elevated total organic carbon (TOC) values. The marls
are highly bioturbated with Chondrites and Planolites as the most common trace fossils
(Bréhéret, 1997). Intercalated within the homogenous marly succession, 6 distinctly laminated
paper shale horizons (PS-1 to 6) ranging in thickness from 20 cm to 35 cm can be observed.
Chapter 2
22
These finely laminated horizons yield higher contents of TOC (up to 2.3 %) and are
essentially devoid of bioturbation. According to Bréhéret (1994) the four lowermost paper
shale horizons are referred to as the Niveau Goguel interval, which corresponds to the OAE
1a. Considering the elevated TOC values, sediment thickness and chemostratigraphic results
we assign the entire lower part of the section (0 to 6.5 m) to the OAE 1a interval.
The studied interval lies within the Deshayesites deshayesi ammonite Zone (Bréhéret, 1997
and references therein) and within the middle part of the Leupoldina cabri planktic
foraminiferal zone. It comprises the first occurrence of Eprolithus floralis which marks the
onset of the NC7A (Rhagodiscus angustus) calcareous nannofossil subzone and the end of the
NC6 (Chiastozygus litterarius) nannofossil zone in the Vocontian Basin (Herrle and
Mutterlose, 2003).
Based on time series analysis and biostratigraphic data, an average sedimentation rate of 3.0
to 3.5 cm/ka was calculated for the lowermost Late Aptian part of the Serre Chaitieu section
by Kössler et al. (2001) and Herrle et al. (2003). Due to the condensed character of the
intercalated paper shale horizons, mean sedimentation rates in the lowermost part of the
section including the OAE 1a interval are probably even lower (2.5 to 2.0 cm/ka).
According to Bréhéret (1994) the OAE 1a interval can be interpreted to reflect a major
transgressive pulse or a maximum flooding (2nd order sequence). This interpretation
correspond well with the comprehensive sequence-stratigraphic framework established by
Hardenbol et al. (1998) for the major European basins.
The Serre Chaitieu record from the Vocontian Basin is compared in detail with the Cismon
section (N Italy), from which detailed bio-, magneto- and chemostratigraphic data are
available (Erba et al., 1999 and references therein). A record of palynofacies and palynology
has been published from the same section by Hochuli et al. (1999). The pelagic sediments of
the Cismon section have been deposited at a palaeolatitude of ~ 20° N in the Belluno Trough.
During the mid-Cretaceous this basin was situated on the northern continental margin of
Apulia, approximately ~ 1000 km SE of the Vocontian Basin. Based on cyclostratigraphic
studies of the Cismon section, the duration of the OAE 1a (Livello Selli equivalent) has been
estimated between 500 ka to 1 Ma (Erba et al., 1999; Herbert, 1992) resulting in a mean
sedimentation rate of 1.0 to 0.5 cm/ka.
Chapter 2
23
4. Material and Methods
4.1. Carbon isotope analysis and total organic carbon contents
To analyse the δ13C composition of bulk carbonate carbon, 36 powdered samples were treated
with phosphoric acid at 90°C. Subsequently, the liberated CO2 gas was analysed with a VG
PRISM mass spectrometer. For determination of δ13C of bulk organic carbon, samples were
treated with 3 N HCl for 24h to remove the inorganic carbonates. About 40 mg of the residue
were analysed via combustion in a CNS Elemental Analyser connected to an isotope ratio
mass spectrometer (Optima/Micromass). All carbon-isotope ratios are expressed in the
standard δ notation in per mil (‰) relative to the international VPDB isotope standard. The
δ13C values of the carbonate carbon were calibrated against a laboratory internal standard
(Carrara marble; δ13C = 2.14 ‰); analytical reproducibility was ± 0.05 ‰. For bulk organic
carbon measurements, a laboratory internal standard (Atropina; δ13C = -28.48 ‰) and an
international standard (NBS 22; δ13C = -29.74 ‰) were used; analytical reproducibility was
better than ± 0.2 ‰.
Inorganic carbon contents of 36 samples were determined using a UIC CM 5012 Coulomat;
total carbon contents were measured on a CNS Elemental Analyser (Carlo Erba Instruments).
Total organic carbon (TOC) contents were calculated from the difference between total and
inorganic carbon contents.
4.2. Biomarker analysis and compound-specific carbon isotope analysis
An aliquot (10 g) of 15 powdered samples were extracted using an UP 200s ultrasonic
disrupter probe (amplitude 50; cycle 0.5) and three successively less polar mixtures of
methanol and dichloromethane, each for 3 min. After sulphur removal and desalination, the
extracts were concentrated by rotary evaporation and evaporated under N2. Compound class
fractions were separated by column chromatography using 7 g silica gel; the apolar fraction
was eluted with 30 ml n-hexane; the polar fraction with a 1:1 mixture of dichloromethane and
methanol. Samples were then analysed by gas chromatography-mass spectrometry for
compound identification using a HP 6890 GC fitted with a HP-5MS column (30 m × 0.25
mm, df = 0.25 µm) and interfaced to a mass selective detector HP 5973.
Carbon isotopic compositions of individual n-alkanes were determined using a TRACE GC
fitted with a HP-1 column (50 m × 0.32 mm, df = 0.17 µm) and coupled to a Thermo Finnigan
DeltaPlus XL mass spectrometer. A series of 9 different n-alkanes (n-C19 to n-C40) was used as
Chapter 2
24
an internal working standard. Reported δ13C values represent the means of multiple analysis
(n = 3) expressed versus VPDB. Except for one sample, standard errors of the mean were
better than ± 0.7 ‰.
4.3. Palynological preparation
A total of 16 cleaned and weighed (10 – 12 g) samples were treated with hydrochloric and
hydrofluoric acid following standard palynological preparation techniques (Traverse, 1988).
The residue was sieved over a 11 µm mesh-sieve and a short oxidation with HNO3 was
performed on all residues. A minimum of 250 sporomorphs per sample (mean 254) were
counted from strew mounts. Only three sporomorph categories were distinguished and the
estimated standard deviation is expected to be better than ± 3% (Traverse, 1988).
5. Preservation of stable carbon isotope signals and organic matter
Strong diagenetic overprint of the carbonate carbon isotope signature can be excluded for the
following reasons: (1) The shallow burial depth of the sedimentary succession (< 700m)
according to Levert and Frey (1988). (2) The well preserved calcareous nannofossils with
only minor contribution of cements and micrite observed in nannofossil samples (Herrle and
Mutterlose, 2003). (3) The lack of covariance between δ13Ccarb and δ18Ocarb (r2 = 0.04; n = 36).
Thermally unaltered conditions of the organic matter (OM) are inferred from Tmax values of
420 to 435°C (Bréhéret, 1994), the unaltered colour of the palynomorphs (TAI < 2) and the
moderate to strong UV fluorescence of the amorphous OM fraction. Visually, the preservation
of all palynomorphs is good to excellent throughout the interval studied. In addition, several
biomarker maturity indices including the 22S/(22R + 22S)-hopane (C31) index, the Mor/(Mor
+ Hop) index and the Ts/(Ts + Tm) index confirm the immature stage of the organic matter
with respect to hydrocarbon generation (Peters and Moldowan, 1993).
6. Results and discussion
6.1. Chemostratigraphic correlation of the δ13Ccarb records from SE France and N Italy
The lower part of the Serre Chaitieu section (0 to 4.5 m) is characterized by an interval of
stable δ13Ccarb values of ~ 3.0 ‰ with the lowest value of 2.4 ‰ occurring at the base of the
studied interval. Within the first paper-shale horizon (PS-1), the δ13Ccarb signature shifts
Chapter 2
25
towards higher values of ~ 3.5 ‰. At 7.8 m the δ13Ccarb curve displays a second positive shift
and peaks at values of ~ 4.5 ‰ at 9.4 m within PS-5 (Fig. 2).
The distinct shifts in the δ13Ccarb record in combination with accurate biostratigraphic data
allow a detailed chemostratigraphic correlation between the two OAE 1a intervals from the
Serre Chaitieu section (SE France) and the Cismon section (N Italy). In the lower part of the
Serre Chaitieu record the stable δ13Ccarb values correspond well with the C5 segment of
Menegatti et al. (1998) in the Cismon record (Fig. 2). Both records show a subsequent shift
towards more positive values (C6) reaching the peak values of the Early Aptian δ13C positive
excursion (C7). In contrast to Menegatti et al. (1998), the entire shift towards more positive
values is included here in the C6 segment.
Both carbon isotope curves display not only similar patterns, but also show essentially the
same absolute δ13Ccarb values and a comparable positive shift of ~ 1.5 ‰ included in the C6
segment. The resulting correlations are in good agreement with the biostratigraphic data. In
both records the first occurrence of Eprolithus floralis is situated in the uppermost part of the
black shale interval (Fig. 2).
The chemostratigraphic correlation clearly indicates the absence of a negative δ13C spike and
the corresponding segments C2, C3 and, in part C4 in the Serre Chaitieu section. Sedimentary
evidence for an incomplete transition between the uppermost Early Aptian limestone beds and
the onset of the “Marnes Bleues” formation has been reported from other localities within the
Vocontian Basin (e.g. Les Sauziere section) by Bréhéret (1997). Except from this basal hiatus
there is no sedimentological or stratigraphical evidence for further gaps within the studied
interval.
6.2. Organic matter composition and origin
The extractable hydrocarbons are dominated primarily by short-chain n-alkanes, acyclic
isoprenoids and abundant steroidal and hopanoid hydrocarbons. In all samples studied, peak
maxima are represented by pristane and phytane, followed by short-chain n-alkanes (n-C15 to
n-C19) and steranes (C27 and C29). In contrast, long-chain n-alkanes (n-C27 to n-C33) with a
relatively low odd-over-even predominance (OEP) of 1.4 – 1.7 form only a minor constituent.
A significant algal contribution is suggested from the high abundance of short-chain n-alkanes
(Farrimond et al., 1990; Gelpi et al., 1970) and steroidal components (Volkman, 1986).
Chapter 2
26
Fig. 2. Chemo- and biostratigraphic correlation of the OAE 1a black shale interval from the Serre
Chaitieu section (Vocontian Basin, SE France) and the Cismon section (Belluno Basin, N Italy). Note
that the differences in thickness of the individual chemostratigraphic segments corresponds well with
the inferred sedimentation rates for the two different depositional settings. δ13C of bulk carbonate
carbon reported in per mil versus VPDB. Chemostratigraphy and lithology of the Cismon section after
Menegatti et al. (1998), biostratigraphy after Erba et al. (1999). Biostratigraphy of the Serre Chaitieu
section after Herrle and Mutterlose (2003). Labels C1 to C7 indicate chemostratigraphic segments
[14]. Dark grey bars refer to black shale horizons. Solid lines indicate the chemostratigraphic
correlation, stippled line reflects the boundary between NC6 and NC7. PS-1 to PS-6 represent
individual laminated black shale horizons in the Serre Chaitieu section.
Furthermore, high quantities of phytane point to a phytoplanktonic source (Didyk et al., 1978;
Kohnen et al., 1992). Bacterial contributions are recorded in the high abundance of hopanes
(Rohmer et al., 1992). There is no evidence for an important cyanobacterial contribution in
the studied interval. The low quantities of long-chain n-alkanes in the sediments indicate only
minor inputs of continent-derived vascular plant waxes (Eglinton and Hamilton, 1967).
0
2
4
6
8
10
12
mete
rs
C7
C6
C5
C3
C4
C2
C1
δ13Ccarb
Cismon section(Menegatti et al. 1998)
Serre Chaitieu section(this study)
C5
C6
C7
C4
δ13Ccarb
Lo
we
r A
pti
an
Sta
ge
Fo
ram
.-zo
ne
Na
nn
o.-
zo
ne
Le
up
old
ina
ca
bri
R.
an
gu
stu
s (
NC
7A
)C
. li
tte
rari
us
(N
C6
)Lo
we
r A
pti
an
Le
up
old
ina
ca
bri
Glo
big
eri
nello
ides b
low
i
mete
rs
-258
-263
-268
-273
-278
Sta
ge
Fo
ram
.-zo
ne
Na
nn
o.-
zo
ne
limestone
marly limestone
marl
"black shale"
lamination
1 2 3 4 5
1 2 3 4 5
Liv
ello
Se
lli I
nte
rva
l
Niv
ea
u G
og
ue
l In
terv
al
PS-1
PS-2
PS-3
PS-4
PS-5
PS-6
Ma
ioli
ca
Sc
ag
lia
Va
rie
ga
taF
orm
atio
n
Ma
rne
s B
leu
es
Fo
rma
tio
n
Lith
olo
gy
Lith
olo
gy
C.
litt
era
riu
s (
NC
6)
R.
an
gu
stu
s (
NC
7)
section notaccessible
Chapter 2
27
Within the OAE 1a interval the biomarker distribution shows no significant variation between
the laminated facies and the bioturbated marls whereas in the upper part of the section, the
decreasing TOC values are paralleled by a continuous decline in hopane and sterane
abundances.
These geochemical results are supported by optical studies of the amorphous organic matter
(AOM). AOM forms the main constituent of the bulk kerogen, up to ~ 95 % within the OAE
1a and ~ 70 % to 90 % in the interval above. Two different types of AOM can be
distinguished. Type A is composed of glossy, inclusion-rich, orange-brown floccules with
moderate to strong fluorescence and dominates within the OAE 1a interval and within the
laminated black shales. Type B has a matt, grey to grey-brown appearance with weak to
moderate fluorescence and represents the major constituent in the upper part of the section.
According to different authors (Tyson, 1995 and references therein) fluorescent AOM is
considered to be derived from phytoplankton and/or bacteria and their decompositional
products and dominates in dysoxic-anoxic environments. Although degraded terrestrial
material can have a similar appearance to marine-derived AOM (Gorin and Feist-Burkhardt,
1990), in the Serre Chaitieu section, the absence of any woody or cuticular structures and the
present fluorescence clearly suggests a marine origin for both AOM types.
In summary, the results of extractable hydrocarbon analysis and optical AOM studies
consistently indicate a marine phytoplankton and/or bacterial origin for most of the OM in the
studied section. A similar, predominantly marine OM composition with only minor terrestrial
contribution has been reported by Bréhéret (1994) for the same section based on Rock-Eval
data and by Baudin et al. (1998) for the time-equivalent Livello Selli interval in the Umbria-
Marche Basin (Italy).
6.3. Organic carbon isotope geochemistry
The carbon isotopic composition of the bulk OM displays a significant shift in δ13Corg from
mean values of ~ -25.5 ‰ in the lower part to values of ~ -23.8 ‰ prevailing in the upper part
of the section (Fig. 3). The increase in δ13Corg towards higher values has several superimposed
smaller-scale fluctuations (up to ~ 0.5 ‰). In comparison to the δ13Ccarb record, the bulk
δ13Corg record shows a similar positive excursion of ~1.7 ‰ with a stepwise shift towards
higher values in the C6 segment.
Chapter 2
28
In order to minimize secondary processes affecting the δ13C signature of bulk OM, the
isotopic composition of biomarkers derived predominantly from marine primary producers
was determined (Hayes et al., 1989; Kuypers et al., 2002; Sinninghe Damsté et al., 1998).
Short-chain n-alkanes (n-C17, n-C18) are interpreted to derive from algal precursor compounds
(Gelpi et al., 1970) and display a similar carbon isotopic shift as the bulk δ13Corg signal,
although the n-alkanes are depleted by ~ 5.0 ‰. Within the OAE 1a interval the carbon
isotopic composition of C28 steranes (24-methyl-5α-cholestane) parallels the short-chain n-
alkane record almost perfectly. This sterane derives from C28 sterol, a compound which is
biosynthesized predominantly by marine algae (Volkman, 1986). The congruence in δ13C of
C28 steranes and short-chain n-alkanes strongly supports the interpretation of an algal origin
for the latter. Due to the low abundance of C28 steranes in the upper part, δ13C values could
not be determined. The intermediate n-alkanes (n-C23, n-C24) cannot be assigned to a specific
marine source but again parallel the bulk δ13Corg pattern with a depletion in 13C of ~ 4.0 ‰.
In summary, the δ13C composition of biomarkers (short-chain n-alkanes, C28 sterane) and bulk
OM reveal a similar pattern during and after deposition of the OAE 1a interval characterized
by a stepwise shift towards higher δ13C values. Individual biomarkers show more pronounced
small-scale carbon isotope fluctuations and a stronger all-over shift in δ13C than bulk OM. In
comparison to δ13Ccarb, the biomarker record displays an increased overall shift of ~ 2.5 to 3.0
‰ (δ13Ccarb = ~ 1.5 ‰) within the C6 segment.
6.4. Estimation of pCO2 change in the course of OAE 1a formation
In general, positive carbon isotope excursions have been interpreted in terms of increased
organic carbon burial, resulting from preferential removal of 12C into the sediments and the
accompanying enrichment of 13C in the oceanic DIC reservoir (Arthur et al., 1985; Scholle
and Arthur, 1980). Intense OC burial is expected to result in a lowering of oceanic [CO2 (aq)]
and consequently in a reduction of atmospheric pCO2 (Arthur et al., 1988; Freeman and
Hayes, 1992).
The carbon isotopic composition of inorganic carbon and primary organic carbon can be used
to estimate changes in ancient pCO2 and/or in palaeoproductivity (Andersen et al., 1999;
Freeman and Hayes, 1992; Hayes et al., 1989; Joachimski et al., 2002; Pagani et al., 1999).
The δ13C composition of marine primary organic matter is determined by the isotopic
composition of the carbon source (δ13C of oceanic dissolved CO2) and by the photosynthetic
Chapter 2
29
fractionation factor (εp) of the carbon-consuming primary producers. The isotopic
fractionation is in turn a function of the concentration of dissolved CO2 ([CO2 (aq)]) (Freeman
and Hayes, 1992; Rau and Takahashi, 1989) as well as of various physiological factors
including growth rate and cell geometry (Bidigare et al., 1997; Popp et al., 1998). A decrease
in atmospheric pCO2 is expected to be paralled by a decrease in oceanic [CO2 (aq)], leading to
a reduction in εp values. This εp decrease should result in a shift towards higher δ13C values of
primary organic carbon due to reduced photosynthetic fractionation. However, a similar
signal is expected to result from an increase in palaeoproductivity, being accompanied by
increasing growth rates.
The ~1.5 ‰ positive shift in δ13Ccarb represents a well documented and characteristic feature
of the Aptian isotope curve. It has been reproduced from many sites independent of facies or
latitudinal variations (Erbacher and Thurow, 1997; Menegatti et al., 1998; Strasser et al.,
2001). Hence, the δ13Ccarb pattern measured in the Vocontian Basin is interpreted to reflect
ocean-wide variations in the carbon isotopic composition of the oceanic DIC reservoir and
can be used to determine changes in εp values.
To estimate palaeoatmospheric CO2 concentrations, the fractionation factor (εp) of marine
photosynthetic plankton needs to be determined. Therefore, the carbon isotopic compositions
of dissolved oceanic CO2 and of primary photosynthate have to be assessed. Assuming
ambient sea surface temperatures for the Early Aptian Vocontian Basin between 20°C and
30°C, the isotopic composition of oceanic dissolved CO2 can be calculated from δ13Ccarb
Based on the temperature-dependent fractionation factor of Romanek et al. (1992), the δ13C of
dissolved CO2 lies in the range of -6.6 ‰ (20°C) to -5.4 ‰ (30°C) before and -5.1 ‰ (20°C)
to -3.9 ‰ (30°C) during the positive isotope excursion. C28 steroids and short-chain n-alkanes
are assumed to show an average depletion of ~ 4 ‰ compared to primary biomass resulting in
values of -26.0 ‰ (pre-excursion, onset of segment C6) and -23.5 ‰ (excursion, end of
segment C6) for the latter. Following the method of Freeman and Hayes (1992) the calculated
εp values have been converted into surface water [CO2 (aq)] based on the empirical
relationship: log [CO2 (aq)] = 0.0551 * εp + 0.305. Finally, atmospheric CO2 concentrations
where calculated by applying Henry’s Law.
Chapter 2
30
Fig. 3. Stratigraphy, lithology, total organic carbon (TOC) content, δ13C of bulk carbonate and OM,
δ13C of individual biomarkers and calculated εp values across the OAE 1a interval, Serre Chaitieu
section (Vocontian Basin, SE France). Carbon isotope values are reported in per mil versus VPDB.
Biostratigraphy after Herrle and Mutterlose (2003). Dark grey bars refer to black shale horizons, pale
grey area corresponds to the OAE 1a interval. Labels C4 to C7 indicate chemostratigraphic segments.
02468
10
12
Meters
OAE 1a Interval
Lithology
δ13C
ste
roid
+ n
-alk
.
n-C
24
n-C
23
C28 s
tero
id
-32
.0-3
0.0
-28
.0-2
6.0
TO
C (
wt %
)
0.0
1.0
2.0
3.0
n-C
18
n-C
17
δ13C
n-a
lk (
sh
ort
-ch
ain
)
-32
.0-3
0.0
-28
.0-2
6.0
δ13C
bu
lkO
M
-27
.0-2
5.0
-23
.0
C5
C6C7
C4
12
34
5
δ13C
ca
rb
15
.01
9.0
23
.0
ε p
Chapter 2
31
The resulting estimates of palaeoatmospheric CO2 concentrations indicate that the Early
Aptian pCO2 level was about 3 to 4 times the pre-industrial level (~ 280 ppm). This result
corresponds well to estimates of Freeman and Hayes (1992) for the mid-Cretaceous (~ 900 to
1200 ppm) based on the same method. Furthermore our data are in broad agreement with
stomatal densitiy-derived pCO2 estimates (Beerling and Royer, 2002) as well as with results
of geochemical modelling (Berner, 1994). Calculation of the pCO2 drop following the OAE
1a event results in a decrease of ~ 100-130 ppm or 10-15 % respectively. Based on
sedimentary porphyrins from the Greenhorn Formation (USA) a comparable decrease in εp
values of 1.5 ‰ has been calculated by Hayes et al. (1989) during the Cenomanian-Turonian
black shale event (CTBE, OAE 2) and interpreted to reflect a ~ 20 % reduction in atmospheric
pCO2 (Freeman and Hayes, 1992).
Estimated pCO2 variations for the Vocontian Basin are based on the assumption, that no
physiological and environmental variables other than pCO2 affected εp values of marine
phototrophs. This is in contrast to several authors (Hochuli et al., 1999; Kuypers et al., 2002;
Pedersen and Calvert, 1990), who emphasize the important role of enhanced
palaeoproductivity during formation of the mid-Cretaceous OAE black shales. This indicates
that at least some portion of the estimated εp change in the Vocontian Basin might have been
caused by increased algal growth rates and average cell sizes due to higher palaeofertility.
Consequently the estimated pCO2 decrease represents a maximum value.
6.5. Palynology
In order to trace changes in terrestrial climate patterns during and after formation of the OAE
1a interval, the relative and absolute abundance of climate-sensitive spore and pollen groups
(incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) have been analysed.
Additionally, the composition of the entire palynofloral assemblage has been determined
qualitatively. The current palynological findings are compared with the results of Hochuli et
al. (1999) from the Cismon section. The cited percentages (%) refer to the total sporomorph
counts.
6.5.1. Results of Palynological Analysis
In the Serre Chaitieu section the sporomorph assemblage accounts for only ~ 10 to 15 % of
the particulate organic matter (excluding AOM). Pteridophyte spores represent an important
Chapter 2
32
constituent of the sporomorph assemblage and account for 20.6 to 41.5 % (mean 30.1).
Classopollis spp. shows an increase from 25.9 to 43.8 % in the lower part followed by a
subsequent decline in the upper part of the succession. Bisaccate pollen account for less than
12.9 % in most samples (max. 20.0 %) and display only minor variations throughout the
section.
The high abundance of pteridophyte spores – essentially represented by Deltoidospora spp.
and Gleicheniidites spp. as well as the common occurrence of Classopollis-type pollen and
the low percentage of bisaccates reflect a position in the southern part of the Southern
Laurasian floral province. Some minor influence of the Northern Gondwana floral province is
reflected by the rare, but consistent occurrences of Afropollis spp. and Ephedripites spp. Other
typical elements of this province like Tucanopollis crisopolensis are scarce or absent.
6.5.2. Comparison of the palynological records from SE France and N Italy
Based on the chemostratigraphic correlation scheme, the sporomorph findings from the Serre
Chaitieu section can be compared in detail with the palynological record of Hochuli et al.
(1999) from the Cismon section (Fig. 4). The most distinct features are: (1) relatively high
percentages of spores in the Serre Chaitieu section (mean of 30.1 % of total sporomorphs)
compared to the Cismon section (mean of 7.1 % of total sporomorphs), (2) a prominent post-
black shale increase in bisaccate pollen (from mean values of 18.6 % within to values of 72.2
% above the OAE 1a interval), accompanied by a decrease in Classopollis spp. in the Cismon
section, (3) a rather uniform stratigraphic pattern of bisaccate pollen, Classopollis spp. and
pteridophyte spores in the Serre Chaitieu section.
Besides climatically-driven variations, hydrodynamic sorting processes can cause significant
changes of the palynological assemblage in distal depositional settings. According to Tyson
(Tyson, 1995), thick-walled spores are in general deposited near-shore in the vicinity of river
mouths. The absence of large, thick-walled spores (e.g. Foveosporites spp, Impardecispora
spp.) in the Serre Chaitieu assemblage suggests that some fractionation has already occurred.
However, the percentage of pteridophyte spores is still relatively high considering the
hemipelagic depositional environment of the Serre Chaitieu section (Tyson, 1995). This is
interpreted to reflect the relatively high terrigenous flux to the basin (Bréhéret, 1994) and/or
the enclosed nature of the Vocontian Basin. In contrast, the low amount of spores in the
Chapter 2
33
0 50 100 0 50 1000 50 100
Liv
ello
Se
lli I
nte
rva
l
bisaccate
pollen
Classopollis
% total sporomorphs
pteridophyte
spores
0 50 100 0 50 1000 50 100
Lo
we
r A
pti
an
Leu
po
ldin
a c
ab
ri
-258
-263
-268
0
2
4
6
8
10
12
mete
rs
Lo
wer
Ap
tian
Sta
ge
Fora
m.-
zone
Nanno.-
zone
Le
up
old
ina
ca
bri
R.
an
gu
stu
s (
NC
7A
)C
. li
tte
rari
us
(N
C6
)
section not
accessible
Lith
olo
gy
bisaccate
pollen
Classopollis
G. b
low
i
% total sporomorphs
Cismon section(Hochuli et al. 1999)
mete
rs
Sta
ge
Fo
ram
.-zo
ne
Na
nn
o.-
zo
ne
Lith
olo
gy
Interval of selective sporomorph preservation
pteridophyte
spores
R.
an
gu
stu
s (
NC
7)
C.
litt
era
riu
s (
NC
6)
OA
E 1
a
Serre Chaitieu section(this study)
Fig. 1 Correlation of frequency patterns (in percentage of total sporomorph counts) of climate-
sensitive spores and pollen of the Serre Chaitieu and the Cismon record. Note the difference in
bisaccate pollen abundance between the two records. Biostratigraphy of the Cismon section after
Erba et al. (1999), lithology after Menegatti et al. (1998), pollen abundance after Hochuli et al.
(1999) and Hochuli (unpubl. results). Biostratigraphy of the Serre Chaitieu section after Herrle and
Mutterlose (2003). Solid lines indicate the chemostratigraphic correlation, stippled line reflects the
boundary between NC6 and NC7. For lithological explanations see Fig. 3.
pelagic sediments of the Belluno Trough (Cismon section) reflects the great distance of the
depositional setting to continental areas. According to Vakhrameyev (1978; 1982) the
abundance of Classopollis-producing cheirolepidacean plants display a climate-controlled
increase towards low latitudes. High contents of Classopollis spp. (> 50 %) have been
interpreted to indicate warm and arid climates. In contrast, bisaccates of pinaceous affinity
represent a typical floral element of the boreal realm and therefore point to comparatively
cool and humid climates (Batten, 1984; Brenner, 1976; Hochuli et al., 1999). Besides climatic
effects, bisaccate pollen are strongly affected by selective sorting processes during
transportation and deposition (Traverse, 1988; Tyson, 1995). The low amount and relatively
Chapter 2
34
stable distribution pattern of bisaccate pollen in the Serre Chaitieu section is in strong contrast
to the observations from the Cismon record where a rapid and significant increase in bisaccate
pollen (up to 86.3 % above the OAE 1a interval) is accompanied by a decrease in
Classopollis-type pollen (1999). This strong increase in boreal floral elements has been
attributed to a major cooling episode and/or a major reorganisation in the oceanographic
circulation system of the W Tethys in the aftermath of the OAE 1a.
Compared to the Cismon section, the composition of the observed spore-pollen association in
the Serre Chaitieu section remains essentially unchanged across OAE 1a and the dominant
forms persist throughout the studied record. This indicates that the continental hinterland of
the Vocontian Basin was characterized by relatively stable vegetational patterns and
associated palaeoenvironments. No signs of major climatic or oceanographic disturbances can
be observed within the corresponding time-interval in the Vocontian Basin.
7. Integration of the chemostratigraphic, geochemical and palynological results
Based on geochemical evidence (Brass et al., 1982) and ocean general circulation model
experiments (Barron and Peterson, 1990; Bice et al., 1997), deep water circulation in the mid-
Cretaceous ocean was predominantly controlled by the formation of warm and saline waters
in low latitude shelf areas. These unusual palaeoceanographic conditions favoured the
formation of thinly laminated, OC-rich black shales in hemipelagic and pelagic environments,
which reflect deposition under dysoxic-anoxic bottom water conditions. Short-lived periods
of euxinia reaching the photic zone during the OAE 1a interval have been reported by Van
Breugel et al. (2002). The occurrence of episodic oxygen deficiency in oceanic bottom waters
has been interpreted to reflect periods of pronounced water column stratification (Erbacher et
al., 2001) and/or a decrease in the rate of deep-water formation (Bralower and Thierstein,
1984). In addition, oxygen depletion and resulting anoxia due to enhanced productivity in
ocean surface waters has been invoked as a possible mechanism for the formation of mid-
Cretaceous black shales (Kuypers et al., 2002; Pedersen and Calvert, 1990).
The detailed chemostratigraphic correlation scheme presented in this study demonstrates
clearly that the occurrence of laminated horizons in the OAE 1a interval (PS-1 to PS-4) are
equivalent to individual black shale layers in the Cismon section (-263.5 to -262.5 m). The
coeval deposition of discrete black shale horizons at both locations indicates that
comparatively short episodes of oxygen deficiency in bottom waters prevailed over large
areas in the W Tethys Ocean independent of the depositional setting. In contrast to this, the
Chapter 2
35
Cismon record holds no equivalent to the upper black shale horizons (PS-5 to PS-6) occurring
in the Serre Chaitieu section. This leads to the conclusion, that dysoxic-anoxic bottom water
conditions episodically reoccurred in the Vocontian Basin in the aftermath of OAE 1a,
whereas the deposition of carbonate-rich sediments in the Cismon section above OAE 1a
points to a rapid reestablishment towards normal-marine conditions in the Belluno Trough.
The palynological analysis across the Serre Chaitieu OAE 1a interval shows that neither the
distribution of climate-sensitive pollen forms nor the qualitative composition of the
palynofloral assemblage exhibit significant changes. These findings are supported by
palynological results from time-equivalent, hemipelagic sediments from the Roter Sattel
section (Prealps, Switzerland) where no prominent variations have been identified in the
bisaccate pollen spectrum during or after formation of the OAE 1a black shale (Hochuli,
unpubl. results). Furthermore, this in accordance with palynological data from shallow-water
deposits from the Luz section (Algarve Basin, S Portugal) where bisaccate pollen account for
less than 15 % during the late Early Aptian interval (Heimhofer et al., in prep.). These results
indicate that the strong boreal pollen signal observed in the Cismon record is restricted to the
pleagic deposits in the SW Tethys whereas no prominent changes are visible in the sections
along the N Tethys and E Atlantic margins. Compared to the palaeolatitudinal position of the
Cismon site, the Vocontian Basin was located ~ 8° to 10° more to the north. Hence, a
southward shift of the Laurasian floral provinces due to climate cooling is expected to result
in a significant increase in boreal pollen types along the N Tethys margin. However, neither
in the Serre Chaitieu nor in the Roter Sattel assemblage a distinct trend towards a dominance
of boreal sporomorphs can be observed. The stable spore-pollen distribution pattern across the
Serre Chaitieu OAE 1a interval is supported by the isotopically derived pCO2 estimates which
point to a moderate decrease in atmospheric CO2 concentration of < 10 % – 15 %. This
decrease is regarded to be insufficient to cause a severe global cooling, resulting in a major
southward shift of the Laurasian floral provinces.
In order to explain the discrepancy in the pollen spectra at the different locations we propose
an alternative scenario. In offshore marine settings, continental runoff and marine currents are
the main controlling factors for the spatial distribution of sporomorphs (Tyson, 1995).
Bisaccate pollen have the capability to float for a relatively long time, which explains their
relative increase in abundance on the shelf with increasing distance from the shoreline
(Heusser and Balsam, 1977). According to Melia (1984) bisaccate conifer pollen can be
transported over long distances and represent a rare but persistent constituent of deep-sea
Chapter 2
36
sediments. Consequently, the observed differences in the spore-pollen patterns might reflect
changes in the oceanic current patterns and/or sea level rather than vast latitudinal shifts of the
major floral belts.
As mentioned above, the occurrence of dysoxic-anoxic bottom water conditions during
formation of OAE 1a is probably linked to pronounced thermohaline stratification and
decelerated renewal of relatively warm and saline deep waters. The abrupt termination of
black shale deposition in the SW Tethys basin indicates a major reorganisation of the oceanic
circulation patterns in this region.
These paleoceanographic perturbations are accompanied by a major global sea-level rise
during the Early Aptian (Hardenbol et al., 1998; Strasser et al., 2001). According to several
authors, the formation of the OAE 1a itself is directly linked to this major transgression
(Bréhéret, 1994; Erbacher and Thurow, 1997). The flooding of broad continental areas during
sea-level rise resulted in the opening of gateways and deepening of existing connections
between the Tethys and the adjacent ocean basins. The existence of N-S trending seaways
which connected the W Tethys and the boreal oceans e.g. via the Polish Trough and the
Moscow Platform during the mid-Cretaceous has been documented by palaeontological and
palaeogeographic means (e.g. Marcinowski and Wiedmann, 1988). Hence, the high
percentages of bisaccates in the distal facies of the Cismon record might reflect changes in the
paleoceanographic current system (e.g. inflow of boreal water masses) and/or the effect of
selective sorting due to a concomitant sea level rise.
8. Conclusions
The combination of organic geochemistry, carbon isotope analysis and palynology provides a
valuable tool to study past changes of terrestrial environments during times of major oceanic
perturbations. Our results indicate that during the Early Aptian OAE 1a the oceanic realm and
its ecosystems were much more affected by severe disturbances than continental
environments. Variations in palaeoatmospheric CO2 concentrations seem to be of minor
importance. The most important findings of our study include the following conclusions.
(1) Carbon isotope records measured on different substrates (Ccarb, Corg, Cn-alk) show a
similar positive excursion starting with the end of OAE 1a in the Vocontian Basin. The δ13C
curve and its individual segments can be accurately correlated on a high-resolution with the
existing Cismon record (SW Tethys). The chemostratigraphic correlation indicates the
occurrence of short-term episodes of bottom water anoxia throughout the W Tethys
Chapter 2
37
independent of depositional setting. The abrupt termination of OAE 1a in the Cismon record
contrasts with a more gradual reestablishment of normal-marine conditions in the Vocontian
Basin.
(2) Estimations of palaeoatmospheric CO2 concentrations during the Early Aptian are in
accordance with results from other palaeobarometeric proxies and yield pCO2 levels of about
3 to 4 times the preindustrial level. Calculated changes in pCO2 across the OAE 1a are only
moderate and can not account for a major cooling accompanied by a southward shift of boreal
floras in the western Tethys region.
(3) The abundance patterns of climate-sensitive spores and pollen in combination with the
observed palynofloral association reveal relatively stable patterns in vegetation and associated
palaeoenvironments during times of black shale accumulation in the adjacent basin. Evidence
for major climatic disturbances accompanied by prominent shifts of the floral belts is missing
in the Vocontian Basin.
(4) The contrasting pollen records of the Cismon and Serre Chaitieu sections are
interpreted to reflect the reorganisation of oceanic circulation patterns in the aftermath of the
OAE 1a and/or the effect of selective sorting of the palynological assemblages in the pelagic
Cismon section due to a late Early Aptian sea level rise.
Acknowledgements
We thank Luc Zwank from the EAWAG for support with the irmGC-MS measurements and
Christian Ostertag-Henning from the University of Münster for help with the sterane
identification. This manuscript was significantly improved thanks to suggestions and reviews
by R. V. Tyson and M. Pagani. Financial support from ETH-project TH-34./99-4 is greatfully
acknowledged.
Chapter 2
38
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Chapter 3
43
Chapter 3
Palynological and calcareous nannofossil records across the late Early Aptian OAE 1a:
Implications for palaeoclimate, palaeofertility and detrital input
Abstract
High resolution records of terrestrial and marine-derived palynomorphs, particulate organic
matter (OM) and calcareous nannoplankton provide new insights into the palaeoclimatic and
palaeoceanographic conditions during deposition of the late Early Aptian oceanic anoxic
event (OAE) 1a in the Vocontian Basin. The analysed spore-pollen assemblages indicate a
rich and diverse flora, dominated by various ferns (e.g. Gleicheniaceae, Schizaeaceae,
Osmundaceae), different types of cycads, bennettitales as well as by several conifer families
(incl. Araucariaceae, Cheirolepidaceae, Podocarpaceae). The observed vegetation patterns
remain essentially stable and the dominant pollen and spore types persist throughout the
studied interval. The dinoflagellate cyst assemblage and diversity patterns as well as the
calcareous nannofossil-based nutrient index provide no evidence for significant changes in the
palaeofertility conditions across the OAE 1a. Based on congruent fluctuations in absolute
abundances of terrestrial sporomorphs and marine organic-walled plankton, sedimentation
rates (SR) and organic carbon mass accumulation rates (OC MAR) have been estimated
tentatively. SR show significant fluctuations ranging from ~2.5 cm ka-1 in bioturbated marls
to ~0.5 cm ka-1 in laminated, OC-rich horizons. Estimated OC MAR fluctuate between 0.02 to
0.06 gC cm-2 ka-1 and exhibit no evidence for increased OC accumulation during deposition
of the OAE 1a black shales. Our results provide no evidence for enhanced surface water
productivity due to accelerated climate-controlled nutrient fluxes during times of black shale
deposition as previously suggested. In contrast, the concomitant occurrence of reduced
detrital input and oxygen-deficient bottom waters rather suggests that fluctuations in sea-level
and/or changes in runoff played a key role for the formation of OC-rich deposits during the
late Early Aptian.
Keywords: OAE 1a; Aptian; palynology; dinoflagellate cysts; calcareous nannofossils;
palaeoproductivity; Vocontian Basin
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44
1. Introduction
1.1. Palaeoclimatic conditions during the mid-Cretaceous
The Aptian to Turonian interval (~120-90 Ma, Gradstein et al., 1995) has been described as a
time of warm climates (Hallam, 1985; Wilson and Norris, 2001), low equator-to-pole thermal
gradients (Barron, 1983; Huber et al., 1995) and considerably high levels of atmospheric
carbon dioxide (Beerling and Royer, 2002; Berner, 1994; Freeman and Hayes, 1992).
Exceptional climatic conditions are also reflected in the composition and distribution of the
fossil floras. The occurrence of ferns, conifers and cycadophytes throughout low to high
latitudes in combination with the absence of expanded polar ice sheets points to more equable
and warmer climates during the mid-Cretaceous in comparison to the present-day situation
(Francis and Frakes, 1993; Hallam, 1985; Spicer and Parrish, 1986).
However, Cretaceous climates were far from stable. Geochemical (Stoll and Schrag, 1996;
Weissert and Lini, 1991; Wilson and Norris, 2001), micropalaeontological (Erba, 1994;
Herrle et al., 2003b) as well as sedimentological evidence (Frakes and Francis, 1988; Kemper,
1987) indicates pronounced changes in the thermal state of the Cretaceous oceans and the
climates of continental interiors. The episodic occurrence of organic carbon-rich intervals
during the Barremian to Turonian has been interpreted to reflect major perturbations of the
ocean-atmosphere system, accompanied by severe changes of the existing climatic patterns
(Arthur et al., 1988; Herrle et al., 2003b; Kuypers et al., 1999; Weissert et al., 1998). These
relatively short-lived intervals (~ 50 to 500 ka) of organic carbon (OC) accumulation were
confined to marine pelagic and hemipelagic environments and have been termed Oceanic
Anoxic Events (OAEs) by Schlanger and Jenkyns (1976).
The late Early Aptian OAE 1a represents the first globally distributed black shale event of the
Cretaceous and is accompanied by dramatic turnovers in nannoplankton (nannoconid-crisis of
Erba, 1994) as well as in calcareous (Leckie et al., 2002; Premoli Silva et al., 1999) and
siliceous plankton (Erbacher et al., 1996). In addition, a phase of carbonate platform demise
has been documented from the northern Tethyan margin and circum-Atlantic regions
(Weissert et al., 1998; Wissler et al., 2003) which shortly predates the OAE 1a. Prominent
changes in the global carbon cycle during and after times of OAE 1a formation are reflected
in the 13C/12C ratio of organic and carbonate carbon. The resulting δ13C pattern is
characteristic for the Early Aptian and has been documented worldwide from various
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depositional settings (Bralower et al., 1999; Herrle et al., 2004; Menegatti et al., 1998; Price,
2003).
The processes leading to the formation of the mid-Cretaceous OC-rich black shales are still a
matter of debate. A variety of different palaeoceanographic models have been proposed
during the last decades, most of which can be assigned to one of the two contrasting
hypotheses. (1) The productivity model is based on the observation, that enhanced fertility in
ocean surface waters results in an increased flux of OM to the sea floor. This in turn causes
increasing oxygen deficiency within the water column and hence, increased OM preservation
under dys- to anoxic bottom waters. The importance of enhanced oceanic productivity for the
formation of mid-Cretaceous black shales has been emphasised by Arthur et al. (1987),
Petersen and Calvert (1990), Premoli Silva et al. (1999) and Kuypers et al. (2002) among
others. (2) In contrast to this, the stagnant ocean model argues with a reduction of deep-water
renewal and/or the formation of thermohaline stratification. The decline in oxygen-rich deep
water production prevents the aerobic degradation of organic matter within the water column
and at the sediment-water interface, resulting in the accumulation of OC at the sea floor (e.g.
Arthur et al., 1990; Bralower and Thierstein, 1984; Tyson, 1995).
1.2. Main objectives of the study
In this study, we present a detailed palynological record, encompassing the late Early Aptian
OAE 1a interval in the Vocontian Basin (SE France). The spore-pollen record is combined
with data on calcareous nannofossils, organic-walled plankton, particulate organic matter and
with geochemical results. The main objectives of our study are: (i) to trace climate-induced
variations in the terrestrial palynofloral assemblage and concomitant changes in the marine
plankton associations during times of black shale deposition in the OAE 1a interval and (ii) to
provide new insights from independent terrestrial and marine proxies on the controlling
mechanisms for the formation of OC-rich deposits on regional and global scales.
The chosen Serre Chaitieu section from the Vocontian Basin is particularly suitable to study
changes in terrestrial vegetation patterns during times of widespread black shale formation. (i)
Deposition in the Vocontian Basin was characterized by relatively high sedimentation rates
due to prominent detrital fluxes from the adjacent continents. As a consequence, the occurring
OM is well preserved and comprises relatively abundant terrestrial spores and pollen. (ii) Due
to its favourable palaeobiogeographic position near the southern boundary of the Southern
Laurasian floral province, the Vocontian Basin was sensitive to climate-induced shifts in the
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46
major floral belts. (iii) The succession has been studied in detail from bio- and
chemostratigraphical as well as from sedimentological and palaeontological perspectives
(Bréhéret, 1988; Bréhéret, 1997; Herrle and Mutterlose, 2003; Weissert and Bréhéret, 1991).
2. Methods
2.1. Palynology
16 samples from the Serre Chaitieu section were prepared for palynological analysis. Cleaned
and weighed (10 to 12 g) samples were treated with hydrochloric and hydrofluoric acid
following standard palynological preparation techniques (Traverse, 1988). The residue was
sieved with an 11-µm mesh-sieve and a first set of strew mounts was prepared for
palynofacies analysis. A short oxidation with HNO3 was performed on all residues before the
preparation of a second set of strew mounts for palynological purposes. Lycopodium marker
spores were added prior to preparation to receive absolute counts per gram sediment. For
palynofacies analysis the following major categories of particulate OM were distinguished:
Amorphous organic matter (AOM), opaque and translucent phytoclasts, cuticles,
dinoflagellate cysts, other algae, foraminifera test linings and sporomorphs. Quantitative
analysis involved three steps: (i) for palynofacies analysis, a minimum of 350 particles were
counted per sample (excl. AOM), (ii) a minimum of 200 palynomorphs were counted for the
determination of the absolute abundances of terrestrial and marine palynomorphs, (iii) a
minimum of 200 sporomorphs were determined and counted for the pollen and spores
assemblage and at least one slide per sample was screened for additional sporomorph taxa.
2.2. Calcareous nannoplankton
Quantitative analyses of calcareous nannofossils were performed on 16 samples using the
random settling technique of Geisen et al. (1999). At least 300 individuals were counted per
sample in random traverses at x1250 magnification. In addition to total abundance of
calcareous nannoplankton, Discorhabdus rotatorius, Zeugrhabdotus erectus, Watznaueria
barnesae, Assipetra infracretacea, Rucinolithus terebrodentarius and Nannoconus spp. have
been counted separately because of their special palaeoecological and palaeoceanographic
significance. In order to assess surface water productivity the nutrient index (NI) of
calcareous nannofossils was calculated following Herrle et al. (2003b), where the high-
productivity assemblage comprises Z. erectus, D. rotatorius, and the low-fertility assemblage
Chapter 3
47
consists of W. barnesae. To assess nannofossil preservation, light microscope identification of
etching and overgrowth effects was used (Bown and Young, 1999).
2.3. Total organic carbon and carbonate carbon content
Inorganic carbon (IC) contents of 36 samples were determined using an UIC CM 5012
Coulomat; total carbon (TC) contents were measured on a CNS Elemental Analyser (Carlo
Erba Instruments). Total organic carbon (TOC) contents were calculated from the difference
between TC and IC contents.
3. Studied sections, lithology and stratigraphy
The studied OAE 1a interval has been sampled at the Serre Chaitieu section, which is located
20 km southeast of Die, about 1 km south of the village Lesches-en-Diois, Département
Drôme, SE France (Fig. 1, 2). The studied interval encompasses 12 m and is mainly
composed of dark-grey marls, which are highly bioturbated with Chondrites and Planolites as
the most common trace fossils (Bréhéret, 1997). Six finely laminated, dark-grey to black
horizons, ranging in thickness from 20 cm to 35 cm, are intercalated within the homogenous
marly succession. The individual horizons exhibit submillimetre-scale lamination. They are
essentially devoid of bioturbation and are referred to as paper-shales. According to Bréhéret
(1994) the lowermost 4 paper shale horizons represent the expression of the OAE 1a in the
Vocontian Basin, termed Niveau Goguel interval. Based on a hydrogen index (HI) of up to
500 mg HC/g TOC and a oxygen index (OI) of 0 to 50 mg CO2/g TOC, the sedimentary OM
of the Niveau Goguel interval has been classified as type II kerogen, indicating a marine
phytoplanktonic and/or bacterial origin (Bréhéret, 1994).
Based on biostratigraphic results (Bréhéret, 1994; Bréhéret, 1997; Herrle and Mutterlose,
2003; Moullade, 1966) the studied interval comprises the Deshayesites deshayesi/Tropaeum
bowerbanki ammonite Zones and the middle part of the Leupoldina cabri planktic
foraminiferal Zone (Fig. 2). The first occurrence of Eprolithus floralis can be recognized
between the paper shales PS-3 and PS-4 which marks the onset of the NC7A (Rhagodiscus
angustus) and the end of the NC6 (Chiastozygus litterarius) calcareous nannofossil Zones.
Chapter 3
48
Southern Laurasian province(subtropical to warm-temperate)
Northern Gondwana province(arid to semi-arid)
Vocontian Basin
40°
30°
20°
10°N
0 500 km
C
Castellane
Mediterra
nean Sea
Grenoble
Die
Nice
Digne
Internal zones
of the Alps
Massif
Central
Provence Platform
Valence
0 50 km
Serre Chaitieusection
N
BDrowned platform faciesShallow open marine environmentsDeep open marine environmentspre-Triassic basementGravity reworked siliciclastics
Spain
France
B
A
Intermediate floral belt
Fig. 1: (A) Location of the Vocontian Basin in SE France. (B) Spatial distribution of different
depositional settings within the Vocontian Basin during the mid-Cretaceous. The location of the Serre
Chaitieu section is marked with an asterisk. Map modified after Arnaud and Lemoine (1993). (C)
Plate tectonic reconstruction of the W’ Tethys realm during the mid-Cretaceous (~115 Ma). The
position of the Vocontian Basin is marked with an asterisk. Floral provinces and inferred climates
after Brenner (1976) and Hochuli (1981). Map modified after Geomar map generator (www.odsn.de).
The studied interval displays a prominent δ13C excursion, which allows correlation with time-
equivalent sections on a global scale (Herrle et al., 2004; Weissert and Bréhéret, 1991).
Detailed chemostratigraphic correlation with the Cismon section of northern Italy shows, that
the entire lower part (0 to 6.5 m) of the Serre Chaitieu section corresponds to the OAE 1a
interval. Furthermore, the correlation reveals, that the lowermost part of the OAE 1a (incl. the
global negative carbon isotope excursion) is not exposed at the Serre Chaitieu section
(Heimhofer et al. submitted).
Chapter 3
49
Fig. 2: Lithological column and key beds of the Serre Chaitieu section (Vocontian Basin, SE France)
plotted against biostratigraphy. The studied OAE 1a interval is located at the base of the Serre
Chaitieu section and encompasses the laminated paper-shales of the Niveau Goguel. Planktic
foraminiferal and ammonite biostratigraphy after Bréhéret (1997 and references therein), calcareous
nannofossil zonation after Herrle and Mutterlose (2003). D. des., Deshayesites deshayesi; T. bow.,
Tropaeum bowerbanki; P. n., Parahoplithes nutfieldiensis; L. cabri, Leupoldina cabri; G. ferreolensis,
Globigerinelloides ferreolensis; G. alger., Globigerinelloides algerianus; H. trocoidea, Hedbergella
trocoidea; T. b., Ticinella bejaouaensis; C. litt., Chiastozygus litterarius.
4. Palaeogeographic and palaeophytogeographic framework
During the mid-Cretaceous, the Vocontian Basin was situated at a palaeolatitude of 25° to
30°N (Hay et al., 1999), forming part of the northern continental margin of the Alpine Tethys
Ocean (Fig. 1c). The Marnes Bleues formation, a thick monotonous succession of grey to
NiveauGoguel
Lith
olo
gy
Mete
rs
Na
nn
ofo
ssil
Zo
ne
Fo
ram
inife
ral Z
on
e
Am
mo
nite
Zo
ne
Substa
ge
T. b.
P. n
.
Faisceau Nolan
Niveau Fallot
Niveau Noir
Niveau Clairs
Niveau Noir Calcaire
Niveau Blanc
black shale
marly limestone
dark-grey marlstone
studiedinterval
Chapter 3
50
dark-grey marls intercalated with calcareous marls, limestones and numerous Corg-rich black
shale horizons was deposited in the basin between Early Aptian and Early Cenomanian times
(Bréhéret, 1997). Accumulation of fine-grained sediments in the Vocontian Basin was largely
confined to pelagic and hemipelagic environments. The basin was surrounded by slope and
platform settings, resulting in the intercalation of hemipelagic facies with shallow-water
sediments in marginal settings (Arnaud and Lemoine, 1993). To the east, the basin was open
towards the Tethys Ocean facilitating exchange with Tethyan water masses. The studied
section was situated in the northern, deep marine part of the Vocontian Basin, several tens of
km south of the northern palaeo-margin (Arnaud and Lemoine, 1993).
According to Brenner (1976), four major floral provinces can be distinguished during the
Barremian to Cenomanian, which includes the Northern and the Southern Laurasian provinces
as well as the Northern and the Southern Gondwana provinces (Fig. 1c). These floral belts
were broadly latitudinally arranged and exhibited progressive compositional changes with
increasing latitude, despite low equator-to-pole thermal gradients (Batten, 1984). The studied
area was located within the southern part of the Southern Laurasian province of Brenner
(1976). The palynofloral assemblage of this province is characterised by numerous and varied
pteridophyte spores - namely by spores of gleicheniaceous and schizaeaceous affinity - and by
various bisaccate pollen of the Podocarpaceae and Pinaceae. Other gymnosperm pollen such
as Classopollis (Cheirolepidiaceae) and Araucariacites (Araucariaceae) represent common
elements of the floral assemblages of this province (Batten, 1984; Brenner, 1976;
Vakhrameyev, 1991). According to Brenner (1976), Vakhrameyev (1978) and Chumakov et
al. (1995) the Southern Laurasian province was characterized by a warm-temperate to
subtropical humid climate. The Northern Gondwana province further south is dominated by
gymnosperm pollen like Callialasporites, Araucariacites and large numbers of Classopollis.
In addition, Ephedripites and Cycadopites represent highly diverse genera, whereas
pteriodophyte spores show low diversity. Bisaccate pollen are virtually absent in these
assemblages. The climate of the Northern Gondwana province is regarded as arid to semi-arid
(Chumakov et al., 1995; Vakhrameyev, 1991). Hochuli (1981) identified an intermediate
floral belt in between the Southern Laurasian and the Northern Gondwana provinces, which
was characterised by palynofloral elements from both provinces.
Chapter 3
51
5. Results
5.1. Preservation of the particulate OM
Although the sporopollenin composition of pollen and spore walls makes them resistant to
degradation, chemical and biological processes during transport and deposition as well as
post-depositional alteration can corrode or even destroy palynomorphs (Traverse, 1988). In
general, palynomorphs are more affected by degradation processes than refractory organic
material (e.g. phytoclasts), which can result in an enrichment of the latter (Tyson, 1995).
Furthermore, thin-walled pollen grains are less resistant to biological/chemical alteration and
more easily decomposed than thick-walled spores and pollen, leading to preferential
preservation of particular thick-walled sporomorph groups. In order to exclude a strong
preservational bias of the studied fossil palynofloral assemblages, the preservation of the
particulate OM has been carefully examined.
Visually, the preservation of the palynomorphs is good to excellent. The consistent
occurrence of well-preserved, fine-sculptured and thin-walled angiosperm pollen (e.g.
Retimonocolpites spp; Clavatipollenites spp.) throughout the studied interval indicates the
absence of a strong preservational bias towards more robust, thick-walled sporomorphs. In
addition, the chemically less stable palynomorphs and the resistant phytoclasts fraction show
similar variations in absolute abundances (particles/g sediment), which is expressed in the
good correlation of the two particle groups (R2 = 0.66; Fig. 3a). This indicates that selective
preservation of palynomorphs in OC-rich horizons does not control the observed distribution
patterns of the spore-pollen assemblage.
Thermally unaltered conditions for the sedimentary OM in the section is inferred from Tmax
values of 420 to 435°C (Bréhéret, 1994), unchanged colouring of the palynomorphs (thermal
alteration index < 2) and moderate to strong UV fluorescence of the amorphous fraction and
the palynomorphs. In addition, several biomarker maturity indices including the 22S/(22R +
22S)-hopane (C31) index, the Mor/(Mor + Hop) index and the Ts/(Ts + Tm) confirm the
immature stage of the organic matter with respect to hydrocarbon generation (Peters and
Moldowan, 1993).
Chapter 3
52
Fig. 3: (A) Cross-plot of phytoclast and pollen absolute abundances of the Serre Chaitieu section
(Vocontian Basin, SE France). Squares correspond to samples from paper shales, dots represent
samples from bioturbated, marly lithology. Note the notable correlation between the chemically less
stable pollen grains and the more refractory phytoclast fraction. This indicates that degradation
processes are of minor importance and that the observed variations in the palynomorphs assemblages
are not controlled by selective preservation. (B) Cross-plot of dinoflagellate and sporomorph absolute
abundances from the Serre Chaitieu section. The two different particle groups show a strong
correlation, which emphasises the congruent pattern of the two records.
5.2. Composition and distribution of the particulate OM
The studied section is characterised by low to moderate CaCO3 (9.0 to 36.0 %) and TOC (0.4
to 2.3 %) contents, respectively (Fig. 4a). The bioturbated marls in the lower part of the
section (0 to 4.3 m) show slightly enriched TOC values (mean 1.3 %). In contrast, the upper
part (6.5 to 12.0 m) displays comparatively low TOC (mean 0.7 %), but increased CaCO3
contents. Higher TOC contents (up to 2.3 %) are restricted to the occurrence of finely
laminated paper-shales. Only horizon PS-4 exhibits an exceptional low TOC content of only
0.5 %.
The major constituent of the particulate OM is formed by amorphous organic matter (AOM),
which accounts for ~95 % within the OAE 1a interval and for 70 to 90 % in the bioturbated
marls above. Two different types of AOM can be distinguished. Type A is composed of
glossy, inclusion-rich floccules of orange-brown colouring and exhibits moderate to strong
fluorescence. In contrast, type B is characterised by matt, shard-like, grey-brown particles
with weak to moderate fluorescence. Type B represents the major constituent in the upper part
R2 = 0.66
n = 16
Phytoclasts (grains/mg sed.)
Po
llen
(g
rain
s/m
g s
ed
.)
(A)
20 40 60 80 100
10.0
8.0
6.0
4.0
2.0
0.0
0S
po
rom
orp
hs (
gra
ins/m
g s
ed
.)Dinoflagellate cysts (grains/mg sed.)
40
20
0
10
30
0 10 20 30 40 50 60 70 80
R2 = 0.86
n = 16
(B)
Chapter 3
53
of the section. The dominance of type A-AOM in the lower part (OAE 1a interval) and within
the paper-shales is interpreted to reflect dys- to anoxic bottom water conditions (e.g.
Tribovillard and Gorin, 1991; Tyson, 1995). Again, horizon PS-4 represents an exception and
comprises predominantly AOM of type B.
The phytoclast fraction is dominated by equidimensionally shaped particles, predominantly <
20 µm in size. Together, opaque and translucent phytoclasts account for 32.2 to 52.0 % (mean
37.3 %) of the particulate OM (excl. AOM). Their frequency pattern displays no distinct trend
or variations throughout the studied interval. The observed phytoclast assemblage is typical
for deep-water sediments, which are generally characterized by the dominance of small,
equidimensional, oxidized woody debris and some windblown charcoal (Habib, 1982; Tyson,
1995). The palynomorphs fraction (Fig. 4b) is clearly dominated by dinoflagellate cysts which
range from 51.2 to 81.3 % (mean 67.4 %) in relative abundance. The high amount of
dinoflagellate cysts emphasises the open marine conditions of the depositional setting.
Sporomorphs (incl. spores and pollen) account for 10.7 to 38.9 % (mean 23.6 %) and are
slightly enriched in the OAE 1a interval as well as in the laminated horizons (mean of 27.4 %)
compared to the upper part (mean of 22.5 %). Foraminifera test linings display strong
fluctuations, ranging from 18.4 % to complete absence (mean 9.0 %) in particular paper-
shales.
Absolute abundances of continent-derived sporomorphs and marine dinoflagellate cysts are
displayed in Fig. 4c. Both palynomorph groups show a strong increase in absolute abundances
within paper-shale horizons (PS-1, 2 and 5) compared to background values. Peak values of
sporomorphs are as high as 4 × 104 sporomorphs/g sediment whereas dinoflagellate cysts
account for up to 7 × 104 cysts/g sediment. In addition, continent-derived sporomorphs and
marine-derived dinoflagellate cysts display essentially similar variations throughout the
section, which is expressed in a strong correlation of the two records (R2 = 0.86, Fig. 3b). The
geochemical and palynofacies results are summarized in Table 1.
Chapter 3
54
Fig. 4: Selected geochemical and palaeontological parameters across the OAE 1a interval, Serre
Chaitieu section (Vocontian Basin, SE France) plotted against lithology. (A) TOC and CaCO3 content,
(B) relative abundances of dinoflagellate cysts, sporomorphs and foraminifera test linings expressed
as percentages of the total palynomorphs fraction, (C) absolute abundances of sporomorphs and
dinoflagellate cysts expressed as grains per g sediment, (D) calcareous nannofossil nutrient index.
Dotted lines mark the position of laminated paper shales. For lithological explanations see Fig. 2.
02468
10
12
Meters
Lithology
OAE 1aP
S-3
PS
-2
PS
-1
PS
-5
PS
-6
PS
-4
Ca
CO
3 (
wt %
)
TO
C (
wt %
)
01
23
01
02
03
04
0
(A)
ca
lca
reo
us n
an
no
fossil
nutr
ient in
dex (
NI)
40
20
60
0
hig
hlo
w
(D)
(gra
ins/g
se
d.)
pa
lyn
om
orp
hs a
bso
lute
ab
un
da
nce
2 x
10
4
ma
rin
e d
ino
cysts
po
llen
an
d s
po
res
0
(C)
40
20
60
80
01
00
(% o
f to
tal p
aly
no
mo
rph
s)
(B)
ma
rin
e d
ino
cysts
po
llen
an
d s
po
res
fora
min
ife
ra lin
ing
s
pa
lyn
om
orp
hs r
ela
tive
ab
un
da
nce
4 x
10
46
x 1
04
8 x
10
4
Chapter 3
55
5.3. Composition and distribution of the palynoflora
We distinguished 18 groups of spores and 19 groups of pollen grains in the microflora of the
Serre Chaitieu section (Fig. 5). The quantitatively most important group is represented by
Classopollis spp. which accounts for 16.7 to 42.3 % (mean 29.2 %) of the entire assemblage.
Classopollis spp. shows a gradual increase across the OAE 1a interval (from 24.6 up to 42.3
%) and a subsequent decline in the upper part of the section. Other common gymnosperm
pollen include Araucariacites spp. (5.9 to 12.9 %; mean 7.2 %), Inaperturopollenites spp. (2.5
to 11.3 %; mean 5.7 %) and Sciadopityspollenites spp. (1.0 to 5.5 %; mean 2.8 %).
Exesipollenites spp. (2.8 to 12.4 %; mean 6.0 %) displays low abundance across the OAE 1a
interval (mean 3.7 %) but is relatively common in the upper part (mean 9.7 %). Various
bisaccate pollen (incl. Podocarpidites spp., Alisporites spp.) account for less than 13.7 % in
most samples. Slightly increased abundance of bisaccates (up to 20.8 %) is essentially
restricted to the occurrence of paper shales (PS-1, 2 and 5). Common representatives of the
angiosperm pollen group include Striatopollis spp., Clavatipollenites spp. and
Retimonocolpites spp. and form a rare, but consistent element of the observed floral
assemblage (< 2.0 %; mean 0.5 %). Pteridophyte spores represent another important
constituent and exhibit a slight, but consistent increase within the laminated paper shales.
Deltoidospora spp. (11.4 to 20.6 %; mean 15.1 %) and Gleicheniidites spp. (2.5 to 10.9 %;
mean 6.1 %) dominate the spore spectrum, whereas other spores like Cicatricosisporites spp.,
Leptolepidites spp. and Retitriletes spp. are quantitatively of minor importance.
5.4. Composition of dinoflagellate cyst and calcareous nannofossil assemblages
The dinoflagellate assemblage of the Serre Chaitieu section has been studied qualitatively
(Fig. 6). A total of 61 different dinoflagellate taxa have been identified on genera or species
level. The relatively homogenous assemblage displays an Early Aptian composition and
comprises many long ranging forms. In the studied interval, the most important dinoflagellate
marker species for the Early Aptian include Pseudoceratium securigerum, Heslertonia
heslertonensis, Oligosphaeridium asterigerum, Druggidium apicopaucicum and
Rhynchodiniopsis aptian. The Achomosphaera spp. and Spiniferites spp. groups have not been
differentiated on species level. The diversity distribution displays a relatively stable pattern
throughout the succession (mean of 20 taxa per sample) with a slight increase towards the top
(Fig. 6).
Chapter 3
56
Fig. 5: Quantitative distribution pattern of selected spore and pollen types across the OAE 1a interval,
Serre Chaitieu section (Vocontian Basin, SE France). Note that the entire lower part of the section (0-
6.5 m) corresponds to the OAE 1a. Relative abundances of the spores and pollen are expressed as
percentages of the total sporomorph assemblage. Biostratigraphy of the Serre Chaitieu section after
Herrle and Mutterlose (2003).
An exceptional high diversity of 28 taxa can only be observed in the uppermost paper shale
horizon of the OAE 1a interval (PS-4).
The calcareous nannofossil assemblage is dominated by (in descending order) Watznaueria
barnesae, Zeugrhabdotus erectus, Discorhabdus rotatorius, Assipetra infracretacea,
Rucinolithus terebrodentarius and Nannoconus spp. representing 28.5 to 74.4 % (mean 46.6
%) of the total assemblage. The portion of the most dissolution-resistant species W. barnesae
ranges from 17.5 to 39.2 % of the total assemblage. Following Thierstein (1980) and Roth &
Bowdler (1981) portions of W. barnesae > 40 % often indicate dissolution to the extent that
the original assemblages no longer yield a primary signal. Both the low percentages of W.
barnesae and the etching and overgrowth ranking of E1 to E1-2 and O1 (slightly etched and
Bis
accate
Polle
n
Vitre
isporite
s p
alli
dus
Ara
uca
ria
cite
s s
pp.
Cla
ssopolli
s s
pp.
Ephedripites s
pp.
Exe
sip
olle
nite
s s
pp.
Ina
pe
rtu
rop
olle
nite
s s
pp.
Scia
do
pitysp
olle
nite
s s
pp.
Oth
er
Gym
nosperm
s
Afr
opolli
s g
rou
p
An
gio
sp
erm
s
Cic
atr
icosis
porite
s s
pp.
Deltoid
ospora
spp.
Gle
ich
en
iidite
s s
pp.
Retitr
ilete
s s
pp.
Oth
er
Spore
s
0
2
4
6
8
10
12
Me
ters
Lo
wer
Ap
tian
Sta
ge
Fora
min
ifera
l Z
one
Nannofo
ssil Z
one
Leu
po
ldin
a c
ab
ri R. an
gu
stu
s (
NC
7A
)C
. litt
era
riu
s (
NC
6)
Lith
olo
gy
0 10 20 30 40 50%
PS-3
PS-2
PS-1
PS-5
PS-6
PS-4
OA
E 1
a
Chapter 3
57
overgrown of coccoliths elements) of the studied samples indicate a good preservation of the
calcareous nannofossil assemblage. The calculated nutrient index (NI) varies between 24.5
and 48.1 % (mean 38.1 %). Low percentages (< 38 %) can be recognized in the lower part of
the succession (Fig. 4d). Just below the onset of the paper-shales the percentages of the NI
increase, characterized by minor fluctuations around 40 %. Highest percentages of A.
infracretacea/R. terebrodentarius (up to 7.6 %) occur below the paper shale interval and
between the paper shales PS-3 and PS-4. Nannoconus spp. is characterized by increasing
percentages (up to 2.8 %) in the uppermost part of the studied succession.
6. Discussion
6.1. Palaeo-environmental and -climatic significance of the micropalaeontologcial results
The palynofloral assemblage of the studied succession reflects a rich and diverse flora.
Besides various fern families (e.g. Gleicheniaceae, Schizaeaceae, Osmundaceae,
Dicksoniaceae), different types of ginkgophytes, cycads, bennettitales and several conifer
families (Araucariaceae, Cheirolepidaceae, Taxodiaceae and Podocarpaceae) can be identified
(Balme, 1995). The rare but consistent occurrences of angiosperm pollen in the Early Aptian
deposits mark the incipient radiation of this plant group. Based on the observed palynofloral
association, a tentative interpretation of the corresponding habitats can be given.
In Mesozoic assemblages, ferns are considered to be common elements of lush and moist
vegetation along riversides and/or coastal lowlands (Mohr, 1989; Van Konijnenburg - Van
Cittert and Van der Burgh, 1989). Therefore, the common occurrence of pteridophytes in the
Serre Chaitieu section indicates humid and warm habitats in the corresponding hinterland.
Evidence for predominantly lowland and/or coastal vegetation can be inferred from the
abundant occurrence of various pollen of bennettitalean and araucariacean affinity (Abbink,
1998; Vakhrameyev, 1991). In contrast, the large quantities of Classopollis spp. are produced
by the xerophythic (drought-resistant) and thermophythic Cheirolepidaceae, which are
considered to reflect well-drained slope and upland environments (Vakhrameyev, 1982;
Vakhrameyev, 1991) or mangrove-type, coastal vegetation (Watson, 1988). Abundance
patterns of Classopollis pollen are a valuable indicator of the prevailing climate. High
numbers of Classopollis spp are considered to reflect warm and arid conditions whereas low
abundances correspond to cooler and more humid climates (Vakhrameyev, 1982). Bisaccate
pollen-producing Podocarpaceae and Pinaceae are indicative of relatively dry upland
Chapter 3
58
Fig. 6: Stratigraphical distribution of dinoflagellate taxa in the Serre Chaitieu section (Vocontian
Basin, SE France) ordered to first occurrences. Selected Early Aptian dinoflagellate marker species
are printed in bold type. Dinoflagellate cyst diversity represents the number of taxa per sample.
Biostratigraphy of the Serre Chaitieu section after Herrle and Mutterlose (2003). Dotted lines mark
the position of laminated paper shales. For lithological explanations see Fig. 2.
02468
10
12
Meters
Lower AptianStage
Foraminiferal Zone
Nannofossil Zone
Leupoldina cabri
R. angustus (NC7A) C. litterarius (NC6)
Lithology
PS
-3
PS
-2
PS
-1
PS
-5
PS
-6
PS
-4
Achomosphaera spp.Callaiosphaeridium asymmetricumCassiculosphaeridia reticulataCerbia tabulataCometodinium spp.Cribroperidinium spp.Dingodinium spp.Gonyaulacysta helicoideaOdontochitina operculataOligosphaeridium complexPseudoceratium securigerumPterodinium cingulatumSpiniferites spp.Subtilisphaera spp.Systematophora spp.Tanyosphaeridium variecalamumCirculodinium spp.Florentinia spp.Heslertonia heslertonensisOligosphaeridium asterigerumPinocchiodinium erbaeTrichodinium spp.Aptea polymorphaCoronifera oceanicaCribroperidinium orthocerasDruggidium apicopaucicumDruggidium spp.Gardodinium trabeculosumHystrichosphaerina schindewolfiiKiokansium polypesOligosphaeridium spp.Pterodinium spp.Batiacasphaera spp.Florentina deaneiGardodinium spp.Gonyaulacysta cretaceaKleithriasphaeridium simplicispinumPalaeoperidinium cretaceumChlamydophorella spp.Cleistosphaeridium spp.Exochosphaeridium spp.Hystrichodinium pulchrumKleithriasphaeridium spp.Exochosphaeridium phragmitesHystrichosphaeropsis spp.Rhynchodiniopsis aptianaCallaiosphaeridium spp.Odontochitina
cf. imparilis
Wallodinium lunumDapsilidinium spp.Coronifera spp.Dingodinium cerviculumKalyptea spp.Pseudoceratium spp.Sepispinula huguoniotiiKleithriasphaeridium fasciatumProlixosphaeridium parvispinumChytroeisphaeridia spp.Kleithriasphaeridium loffrenseMicrodinium opacumProlixosphaeridium spp.
Din
ofla
ge
llate
div
ers
ity
(# ta
xa
)
10
20
30
0
Chapter 3
59
vegetation and generally dominate in boreal associations (Abbink, 1998; Vakhrameyev,
1991).
In general, the vegetation patterns remain essentially stable and the dominant sporomorph
forms persist throughout the studied record. Distinct changes can only be observed in the
abundance of the thermophilic Cheirolepidaceae (Classopollis spp.) as well as in plants of
questionable bennettitalean or taxodiacean affinity (Exesipollenites spp.). The increase in
cheirolepidaceans during the OAE 1a interval suggests a shift towards more arid conditions.
Due to the ambiguous botanical affinity and habitat preferences of the Exesipollenites-
producing plants, a climatic interpretation can not be given. Besides these fluctuations, we
observe no indication for major climatic disturbances, accompanied by prominent shifts in the
major floral belts. The observed palynoflora is typical for the late Early Cretaceous Southern
Laurasian floral province (Fig. 1c). Some minor influence of the Northern Gondwana
province is reflected in the rare, but consistent occurrence of Afropollis spp. and Ephedripites
spp. On the other hand, the pollen record provides no evidence for a southward dispersion of
boreal vegetation (e.g. bisaccate pollen of Pineacean affinity) during or in the aftermath of the
OAE 1a interval. Even though bisaccate abundance is in general considered as a
palaeoclimatic indicator (e.g. Vakhrameyev, 1991) the observed variations in bisaccate pollen
in the Serre Chaitieu section might rather reflect transportation bias than a real vegetation
signal. Due to their specific morphology, bisaccate pollen can be dispersed easily by
atmospheric or aquatic pathways (Traverse, 1988). According to Heusser and Balsam (1977)
the capability of bisaccates to float for a relatively long time period explains their relative
increase in shelf sediments with increasing distance from the shoreline. Hence, the observed
increase in bisaccates might be related to sea-level fluctuations and/or changes in runoff
patterns during times of black shale formation. The pollen record of the Vocontian Basin
contrasts with the results of Hochuli et al. (1999) who reported a significant increase in
bisaccate pollen abundance from ~20 % within to ~80 % above the OAE 1a interval at the the
Cismon site (Belluno Trough, N Italy). Based on the findings from the Vocontian Basin, the
Cismon pollen record is considered to reflect a major change in the paleoceanographic current
pattern rather than a major floral shift due to global cooling (Heimhofer et al. submitted).
The common occurrence of the dinoflagellate groups Cribroperidinium spp. and
Circulodinium spp. in all studied samples is interpreted to indicate inner neritic conditions
whereas some open marine influence is reflected in the consistent occurrences of the
Chapter 3
60
Oligosphaeridium spp. and Spiniferites spp. groups (Wilpshaar and Leereveld, 1994). Similar
assemblages have been documented from the Southern Alps (Cismon section) by Torricelli et
al. (2000) as well as from SE France (Gare de Cassis section) by Masure et al. (1998). The
observed dinoflagellate cyst assemblage and diversity patterns display no distinct variations
across the OAE 1a interval (Fig. 6). We observe neither a significant impoverishment nor a
strong diversity increase of the organic-walled plankton within or above the OAE 1a interval.
The slight increase in diversity towards the top of the studied interval is considered to reflect
the response of the dinoflagellate cyst assemblage to a rising sea level (Tyson, 1995). This is
in accordance with the results of Wilpshaar and Leereveld (1994) who report a significant
shift of the dinoflagellate cyst assemblages towards a more oceanic association due to a late
Early Cretaceous sea-level rise in the Vocontian Basin. The quantitative analysis of Toricelli
(2000) from the Cismon site (Belluno Trough, N Italy) displays a decrease in dinoflagellate
cyst diversity in the lowermost part of the OAE 1a interval (not accessible in the Serre
Chaitieu section) and, similar to the Vocontian Basin record, a gradual diversity increase
throughout the black shale interval and the overlying strata.
The calcareous nannofossil nutrient index displays no evidence for a major change in surface
water productivity during the formation of the OAE 1a interval (Fig. 4d). We observe no
consistent pattern in nutrient index corresponding to the occurrence of individual paper shale
horizons. In comparison to earlier studies on the OAE 1b from the Vocontian Basin by Herrle
et al (2003b), the observed variations of surface water productivity across the OAE 1a interval
are rather moderate. The calculated calcareous nannofossil nutrient index indicates low to
moderate surface water productivity conditions during formation of the OAE 1a and a
subsequent increase in the aftermath of the black shale episode. These findings are in
accordance to earlier studies on calcareous micro- and nannofossils. According to Luciani et
al. (2001), W’ Tethys surface waters were characterised by moderate palaeofertility
conditions during the OAE 1a interval. Premoli Silva et al. (1999) pointed out, that
eutrophication during the Early Aptian OAE 1a was less intense compared to the OAE 2
interval (Cenomanian-Turonian boundary event).
In summary, the palynological results imply, that the continental hinterland of the Vocontian
Basin was characterised by diverse but relatively stable palaeoenvironments during the
studied interval. A change towards more arid climatic patterns during the OAE 1a interval is
Chapter 3
61
documented in the rising abundance of Classopollis spp. In contrast to Hochuli et al. (1999),
we observe no prominent increase in boreal pollen forms in the aftermath of the OAE 1a.
Minor variations in the dinoflatellate cyst assemblages as well as the calcareous nannofossil
nutrient index provide no evidence for enhanced surface water productivity during the late
Early Aptian black shale episode in the Vocontian Basin.
6.2. Changes in sedimentation rates and OC accumulation across OAE 1a
In general, the flux of pollen and spores to the depositional environment is closely tied to
detrital input, both predominantly controlled by continental runoff (Traverse, 1994).
However, along arid coasts as well as in hemipelagic to pelagic environments, atmospheric
transportation of pollen can be of significant importance (Dupont and Wyputta, 2003; Melia,
1984). This results in the decoupling of fluvial siliciclastic input and airborne pollen flux.
In the Serre Chaitieu section, prominent changes are displayed in the absolute abundances of
terrestrial sporomorphs and marine dinoflagellate cysts (Fig. 4c). Even though the two
palynomorphs groups are affected by completely different processes during transportation and
deposition, they display congruent variations in absolute particle abundance. We assume that
a large part of the terrestrial sporomorph fraction has been transported via atmospheric
pathways to the depositional setting and that the input fluxes of both, marine dinoflagellate
cysts and sporomorphs were roughly constant. In consequence, the observed fluctuations in
both particle groups are essentially controlled by changes in sedimentation rates. This in turn
gives way to a tentative estimation of sedimentation rates (SR) and OC accumulation across
the OAE 1a interval. Based on time series analysis and biostratigraphic data, an average SR of
3.0 to 3.5 cm ka-1 has been calculated for the Late Aptian part of the Serre Chaitieu section by
Kössler et al. (2001) and Herrle et al. (2003a). A similar SR is assumed for the average
background sedimentation represented by dark-grey, bioturbated marls in the upper part of the
section (6.5 to 12 m). In combination with absolute palynomorph abundances (tentatively
regarded as a constant flux), this results in significant SR changes. Increased palynomorph
abundances within paper-shales correspond to very low sedimentation rates (SR as low as 0.5
cm ka-1) and therefore reduced dilution by siliciclastic detrital material. In contrast, decreased
abundances within bioturbated marls indicate periods of higher sediment flux and increased
siliciclastic input (SR between 2.0 and 3.0 cm ka-1). This is also displayed in fluctuations of
the carbonate carbon content record. Peak values in CaCO3 content within OC-rich paper-
shales reflect lowered siliciclastic dilution of the pelagic carbonate sedimentation.
Chapter 3
62
TOC content and SR exhibit a notable inverse correlation (R2 = 0.61; Fig. 7). Low SR
corresponds to increased TOC contents and vice versa. The occurrence of well-preserved OM
during periods of reduced SR seems to be somehow contradictory. To prevent the OM from
degradation during its relatively long exposure at the sea floor, strongly oxygen-depleted
conditions are required (Tyson, 1995). Evidence for anoxic bottom water conditions is
provided by the occurrence of finely laminated, non-bioturbated facies accompanied by
relatively low abundances of foraminiferal test linings, both indicating decreased benthic
activity. Based on organic facies analysis, similar low-oxygen bottom water conditions have
been inferred for several horizons of the time-equivalent Livello Selli interval in Italy (Baudin
et al., 1998; Hochuli et al., 1999; Menegatti et al., 1998) and for the Early Albian Niveau
Paquier (OAE 1b) in the Vocontian Basin (Tribovillard and Gorin, 1991).
Fig. 7: Cross-plot of inferred sedimentation rate and TOC content of the Serre Chaitieu section
(Vocontian Basin, SE France). Squares correspond to samples from paper shales, dots represent
samples from bioturbated, marly lithology. The inverse correlation between the two parameters
clearly indicates that OC accumulation in the studied section was not controlled by the effect of
increasing sedimentation rate.
Sedimentation rate (cm ka-1)
TO
C (
wt.
%)
R2 = 0.61
n = 16
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Chapter 3
63
To evaluate the sedimentary OC contents separately from the input of other components,
organic carbon mass accumulation rates (OC MAR) have been calculated. OC MAR fluctuate
between 0.02 and 0.06 gC cm-2 ka-1 throughout the section. Comparable OC MAR have been
determined for Lower Aptian sediments located in the Eastern Atlantic (Stein et al., 1986) and
Pacific oceans (Bralower and Thierstein, 1987). Our estimates for the Serre Chaitieu section
are in the range of OC MAR for the present day Panama and Canary Basins (Bralower and
Thierstein, 1987; Stein et al., 1986). Minor variations in OC MAR can be observed
throughout the studied interval. Whereas marly, bioturbated lithologies exhibit values of
~0.03 to 0.06 gC cm-2 ka-1, the paper shale horizons (except PS-3) show similar or even lower
OC MAR between ~0.02 and 0.04 gC cm-2 ka-1. These results indicate that the accumulation
of OC during the OAE 1a interval was not enhanced compared to post-OAE times in the
Vocontian Basin.
6.3. Palaeoceanographic implications
According to several authors (e.g. Bellanca et al., 2002; Jenkyns, 1999; Weissert et al., 1998)
the formation of the Early Aptian OAE 1a black shale reflects the complex interplay of
enhanced hydrological cycling and accelerated continental weathering during a period of
exceptional warmth. The intensified transport of continent-derived detrital material towards
the basins e.g. during episodes of increased runoff is interpreted to result in enhanced nutrient
levels of oceanic surface waters. High nutrient availability in turn has been interpreted to
cause enhanced phytoplankton productivity in surface waters, leading to the deposition of
OC-rich sediments.
In the Vocontian Basin, several lines of evidence contradict a causal link between accelerated
climate-controlled nutrient fluxes, high oceanic palaeoproductivity and the deposition of the
OAE 1a black shales. Neither the palynofloral record nor the dinoflagellate cyst and
calcareous nannofossil assemblages indicate strongly increased hydrological cycling
accompanied by a significant increase in surface water primary productivity in the Vocontian
Basin. Furthermore, the estimated changes in OC accumulation during and after formation of
the OAE 1a provide no evidence for increased palaeoproductivity. Even though, the above
mentioned scenario could explain an increase in continent-derived sporomorphs (enhanced
runoff) paralleled by an increase in organic-walled plankton (enhanced productivity), the
almost straight proportional dependency of the two different proxies (Fig. 3b) suggests similar
Chapter 3
64
input fluxes rather than a complex biologically feedback mechanism to account for the
observed pattern.
The reduced SR, which characterise the lower part of the OAE 1a and particularly the paper-
shale horizons, are interpreted to reflect episodes of pronounced condensation due to
decreased siliciclastic input. Furthermore, the episodic occurrence of well-developed bottom
water anoxia is accompanied by low SR. Based on the current findings two alternative
scenarios are proposed which could account for the OC accumulation during the OAE 1a
interval in the Vocontian Basin. Our interpretation suggests fluctuations in (i) sea-level and/or
(ii) runoff to account for the above mentioned observations.
(i) Sea-level fluctuations have been addressed by various authors to play a key role for the
formation of OC-rich deposits in hemipelagic to pelagic settings during OAE 1a (e.g.
Bréhéret, 1994; Erbacher et al., 1996; Strasser et al., 2001). Based on the analysis of stacking
patterns, Bréhéret (1994) considered amalgamation and condensation processes to cause the
formation of the OAE 1a paper-shales in the Vocontian Basin. According to his model, the
deposition of the paper-shales is related to small-scale sea level rises which are superimposed
on a major transgressive pulse, or maximum flooding (2nd order sequence). Small- and large-
scale sea level rises are supposed to cause a relative decrease in detrital input due to an
increase in accommodation space, resulting in condensation in the basinal environments of
the Vocontian Basin. Similarly, Strasser et al. (2001) identified several higher-frequency sea-
level changes superimposed on a major transgression, which had a marked influence on the
formation of the OAE 1a interval along the northern margin of the Alpine Tethys Ocean.
The concomitant occurrence of sea-level rise and bottom water anoxia observed in
hemipelagic settings has been related to various mechanisms. This includes vertical and
lateral shifts of the oxygen minimum zone onto the shelf during transgressive phases
(Schlanger and Jenkyns, 1976), reduced mixing of shelf waters due to increasing water depth
(Arthur et al., 1987; Tyson, 1995) or increased nutrient flux from coastal lowlands, resulting
in productivity-driven anoxia (Erbacher et al., 1996; Jenkyns, 1980).
Even though, the observed fluctuations in SR can be well explained with the occurrence of
high-frequency sea-level variations, the superimposed low-frequency sea-level rise is not well
expressed in a reduction of the estimated SR in the Serre Chaitieu section.
Chapter 3
65
(ii) An alternative explanation for reduced SR involves distinct changes in runoff patterns.
Evidence for less precipitation and drier climatic conditions is reflected in the frequency
patterns of Classopollis-type pollen (Vakhrameyev, 1982; Vakhrameyev, 1991). The increase
in Classopollis spp. from 25 % to > 40 % towards the top of the OAE 1a interval can be
interpreted to reflect a shift towards more arid conditions whereas the decline above the OC-
rich interval might indicate a return to more humid climate patterns. Such a climatic change is
supposed to result in reduced runoff and therefore in a decline of siliciclastic input to the
basin. A general increase in aridity during formation of the OAE 1a could probably account
for the observed dys- to anoxic conditions documented from various ocean basins. The
formation of black shales due to enhanced thermohaline stratification and concomitant
oxygen-deficiency in bottom waters during periods of increased aridity has been invoked in
previous studies (e.g. Barron and Peterson, 1990; Brass et al., 1982).
7. Conclusions
In the Vocontian Basin, several lines of evidence contradict the previous held view, that the
OAE 1a black shales reflect the complex interplay of accelerated hydrological cycling,
increased climate-controlled nutrient fluxes and high oceanic primary productivity. Results
from the analysis of dinoflagellate cyst and calcareous nannoplankton assemblages as well as
tentative estimates of OC accumulation indicate a rather reduced or unchanged
palaeoproductivity during times of OAE 1a formation. Similarly, the pollen-based
reconstruction of the vegetation patterns in the corresponding hinterland provide no evidence
for enhanced humidity and intensified precipitation. In contrast, the observed increase in
Classopollis-type pollen across the OAE 1a interval points rather to a shift towards a more
arid climate during deposition of the black shales in the adjacent basin. Tentatively estimated
sedimentation rates display significant fluctuations across the studied interval and are
particularly reduced within laminated, non-bioturbated, OC-rich horizons. The concomitant
occurrence of reduced detrital input and oxygen-deficient bottom waters indicates that low-
frequency sea-level fluctuations and/or changes in riverine runoff play a key role in the
formation of the OAE 1a.
Chapter 3
66
height (m) TOC (%) CaCO3 (%) phytoclasts sporomorphs sporomorphs dino-cysts dino-cysts foraminifera foraminifera sum lycopods dino-cysts sporomorphs NI % kerogen % palynos total counts % palynos total counts % palynos total counts grains/mg sed. grains/mg sed. NS-36 11.75 0.8 27.3 NS-35 11.35 0.6 25.7 NS-34 10.95 0.7 30.7 51.1 18.3 43 70.6 166 11.1 26 235 48 20.8 5.4 40.3 NS-33 10.55 0.6 35.7 NS-32 10.15 0.6 22.0 52.0 20.6 43 67.0 140 12.4 26 209 64 13.1 4.0 48.1 NS-31 9.75 0.8 20.1 NS-30 9.35 1.2 15.5 NS-29 9.15 1.8 12.6 37.6 38.9 95 55.3 135 5.7 14 244 27 32.3 22.7 43.9 NS-28 9.05 0.9 18.8 NS-27 8.6 1.1 16.7 NS-26 8.2 0.5 21.1 40.2 10.7 26 72.3 175 16.9 41 242 109 10.4 1.5 37.7 NS-25 7.8 0.4 26.4 NS-24 7.4 0.6 21.0 43.0 18.6 44 70.8 167 10.6 25 236 93 10.8 2.8 38.3 NS-23 7 0.9 23.1 37.5 15.1 34 71.1 160 13.8 31 225 67 14.3 3.0 41.4 NS-22 6.55 0.9 15.4 NS-21 6.45 0.5 16.8 35.6 13.3 32 81.3 195 5.4 13 240 53 22.1 3.6 39.7 NS-20 6.25 0.9 21.5 NS-19 6 1.1 21.7 36.5 25.0 56 61.2 137 13.8 31 224 29 28.3 11.6 41.0 NS-18 5.6 1.6 13.5 NS-17 5.5 2.2 25.8 35.2 27.0 58 73.0 157 0.0 0 215 32 31.7 11.7 44.0 NS-16 5.4 1.3 21.5 NS-15 5.3 1.4 17.4 36.0 22.5 58 67.8 175 9.7 25 258 32 32.8 10.88 33.3 NS-14 5.2 1.7 10.2 NS-13 5.1 2.1 31.5 NS-12 5 1.9 28.4 32.2 31.0 81 51.7 135 17.2 45 261 14 63.1 37.87 46.5 NS-11 4.9 1.3 15.0 NS-10 4.75 1.3 12.5 NS-9b 4.5 2.2 30.9 33.2 30.5 73 69.0 165 0.4 1 239 15 72.0 31.85 30.4 NS-9a 4.4 0.8 8.7 NS-8 3.9 1.6 18.2 38.3 30.3 74 51.2 125 18.4 45 244 33 22.7 13.5 42.8 NS-7 3.35 1.7 15.4 NS-6 2.8 1.7 14.8 36.7 23.6 54 73.4 168 3.1 7 229 39 25.8 8.3 24.5 NS-5 2.15 0.7 13.3 NS-4 1.65 1.0 12.0 42.1 23.5 52 71.5 158 5.0 11 221 46 20.6 6.8 30.3 NS-3 1.1 1.8 14.2 NS-2 0.55 1.1 13.2 37.3 27.9 64 71.2 163 0.9 2 229 38 25.7 10.1 27.6
Table 1: Geochemical and palynofacies data from the Serre Chaitieu section (Vocontian Basin, SE France)
Chapter 3
67
Acknowledgements
Financial support from ETH-project TH-34./99-4 is greatfully acknowledged.
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Chapter 3
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Chapter 4
73
Chapter 4
Terrestrial carbon-isotope records from coastal deposits (Algarve, Portugal):
A tool for chemostratigraphic correlation on an intrabasinal and global scale*
Abstract
The carbon-isotope signature of terrestrial organic matter (OM) offers a valuable tool to
develop stratigraphic correlations for near-shore deposits. A mid-Cretaceous coastal
succession of the western Algarve Basin, Portugal, displays a marked negative δ13C excursion
ranging from -21.2‰ to -27.8‰ in the Early Aptian followed by two shifts towards higher
values (up to -19.3‰) during the Early and Late Aptian, respectively. The dominance of
cuticle and leaf debris in the bulk OM fraction is confirmed by optical studies, Rock-Eval
pyrolysis and by comparison with the δ13C signature of four different types of fossilized land-
plant particles. Correlation of two terrestrial δ13Cbulk OM records from different study sites
leads to a significant enhancement of the intrabasinal stratigraphic correlation within the
Algarve Basin. Three prominent excursions in the Portuguese records can be correlated with
existing δ13C curves from pelagic and terrestrial environments. The general carbon-isotope
pattern is superimposed by small-scale fluctuations which can be explained by compositional
variations within the OM.
Keywords: carbon-13, phytoclasts, chemostratigraphy, Aptian, terrestrial environment
* published as: Heimhofer, U., Hochuli, P. A., Burla, S., Andersen, N. and Weissert, H. (2003). Terrestrial
carbon-isotope records from coastal deposits (Algarve, Portugal): A tool for chemostratigraphic correlation on an
intrabasinal and global scale. Terra Nova, 15, 8-13
Chapter 4
74
1. Introduction
Several major carbon-isotope excursions, initially reported from marine carbonates (Ccarb) and
accompanying marine organic carbon (Corg) have been recognized recently in plant material
of terrestrial origin. In these studies, different types of vascular land-plant debris served as an
isotopic substrate, including fossil wood (Gröcke et al., 1999), jet, coal and charcoal
(Hesselbo et al., 2000), cuticle and vitrinite (Jahren et al., 2001) or bulk terrestrial OM (Ando
et al., 2002; Hasegawa, 1997). Even though the δ13C composition of land-plants is affected by
different ecophysiological, taphonomic and diagenetic effects, the fossilized tissues serve to
trace changes in the carbon-isotope composition of the ocean–atmosphere system through
earth history.
One of the best-studied carbon-isotope records covers the Aptian stage (121-112 Ma), a time
of major perturbations of the global carbon cycle as documented in the widespread deposition
of organic-carbon rich shales in the world oceans (Arthur et al., 1990; Bralower et al., 1994)
occurrence of marine biocalcification crises (Erba, 1994; Weissert et al., 1998) and
accompanying biological turnover (Erbacher et al., 1996; Hochuli et al., 1999). The
corresponding carbon isotope records are marked by several pronounced negative and
positive excursions with an overall amplitude of ~4.0‰ in marine carbonates and up to
~7.5‰ in marine Corg. The diagnostic isotope pattern has been recognized and described in
detail from pelagic and hemipelagic successions (Bralower et al., 1999; Menegatti et al.,
1998; Weissert and Breheret, 1991) as well as from time-equivalent shallow water
environments (Ferreri et al., 1997; Jenkyns, 1995). More recently, similar δ13C variations
measured in terrestrial plant OM have been correlated with marine isotope records (Ando et
al., 2002; Gröcke et al., 1999) and emphasize the close linkage between the oceanic and
atmospheric carbon reservoirs.
In contrast to marine Ccarb and Corg, the carbon-isotope geochemistry of terrestrial OM has not
yet been widely applied as a tool for high-resolution stratigraphy and correlation between
different depositional environments (Hesselbo et al., 2000; Hesselbo et al., 2002). This
application is of special interest for near-shore deposits, which often lack an adequate
stratigraphic resolution due to the rare occurrence or absence of reliable biostratigraphic
markers.
In this study, we investigate the organic carbon-isotope geochemistry of an Early Cretaceous
coastal succession. We use the isotopic signature of a variety of vascular land-plant materials
Chapter 4
75
and bulk terrestrial OM to demonstrate that near-shore successions can be accurately dated
with organic carbon-isotope records of terrestrial origin.
2. Study sites
Two sections from the Algarve region (southern Portugal) have been chosen as terrestrial
archives spanning the Aptian time window. Both study sites (Luz and Burgau) are located
within the western part of the Algarve Basin (Fig. 1) and have been described in detail by Rey
(1983; 1986) from a sedimentological and biostratigraphic perspective. The sedimentary
succession consists mainly of varicolored clays and marls with some intercalated siltstone and
limestone beds (Luz Marls Formation). These sediments were deposited in a shallow lagoonal
to brackish marsh environment with only minor open-marine episodes. The Luz Marls
gradually evolve into a carbonate-dominated tidal flat setting, documented in the deposition
of thick-bedded shallow-water limestone and calcareous marls (Porto de Mos Formation).
Both sections represent pronounced near-shore depositional settings. Evidence for
sedimentary gaps is restricted to the occurrence of several hardgrounds in the upper
carbonate-dominated unit and to a depositional discontinuity at the base of a graded limestone
bed within the Luz Marls. The uniform sedimentary setting and the occurrence of
characteristic depositional patterns allow an accurate lithostratigraphic correlation of the two
sections over a distance of ~ 6.5 km.
Fig. 1: Location map of the western Algarve basin on the Iberian Peninsula. Studied sections are
marked with an arrow.
Due to the lack of common index fossils, biostratigraphy has been based on dinoflagellate
cysts (Berthou and Leereveld, 1990), benthic foraminifera and calcareous algae (Rey, 1983;
Algarvebasin
LagosBurgau
Sagres
PortimãoN
0 10 km
Al
ga r v e
Luz sectionBurgau section
Iberia
8°30'W9°W
37°N
Chapter 4
76
Rey, 1986). In combination with our new palynological data (will be published elsewhere)
these results suggest an Early Aptian age for the lower, and a Late Aptian age for the upper
part of the Luz Marls Formation.
3. Methods
Closely spaced samples (~ 1 m to 2 m) from Luz and Burgau were measured for the carbon-
isotope composition of bulk OM. To avoid possible diagenetic alteration effects of the δ13Cbulk
signature, reddish and purple colored horizons were excluded from this analysis. For bulk OM
determinations, 400 mg of each sample was treated twice with 1 N HCl for 24 h to remove the
carbonate carbon. 1-20 mg of the residue was analyzed via combustion for δ13C in a CNS
Elemental Analyzer (Carlo Erba Instruments) connected to an isotope ratio mass spectrometer
(Optima/Micromass). Carbon-isotope ratios were expressed in the standard δ notation in per
mil (‰) relative to the international VPDB isotope standard. The δ13C values were calibrated
against a laboratory internal standard (Atropina; δ13C = -28.48‰) and an international
standard (NBS 22; δ13C = -29.74‰); analytical reproducibility was ±0.2‰. Inorganic and
total organic carbon content (IC/TOC) was measured on a UIC CM 5012 Coulomat.
To assess the origin of the OM as well as the compositional variations within, bulk parameter
measurements including visual kerogen analysis and Rock-Eval pyrolysis were combined
with the carbon-isotope analysis of various types of vascular land-plant particles. Following
the method of Jahren et al. (2001) we compared the land-plant δ13C signature with that of the
bulk OM signal to determine its main components. If no macroscopic fossil wood fragments
were available, the sample was acid macerated (24 h with 3 N HCl), rinsed and sieved (>62
µm). Following this treatment, the isolated phytoclasts were picked by hand under the
microscope. Four types of different land-plant particles have been distinguished including
charcoal, lignite, translucent cuticle and opaque leaf fragments. All phytoclasts were
measured for their carbon-isotope composition via combustion using the same procedure as
for bulk OM. If possible, repeated measurements were carried out and the standard error of
the means was calculated.
4. Characterization of the sedimentary organic matter
Both studied sections represent siliciclastic-dominated coastal environments with the
sedimentary OM strongly dominated by terrestrial material. Total organic carbon (TOC)
Chapter 4
77
content (dry wt. %) of the sediment varies between 0.1% and 0.9% throughout the entire
succession with a mean value of 0.2%. Palynofacies analysis displays a high abundance of
opaque phytoclasts, cuticle fragments, spores and pollen grains. These results are supported
by low HI values (< 150 mg HC/g TOC) indicating a strong terrestrial contribution to the
sedimentary OM.
The δ13C values of the phytoclasts were compared to the bulk OM signal obtained from the
same horizons (Fig. 2). The isotopic composition of leaves (mean of -23.3‰) and translucent
cuticle (mean of –23.1‰) is very similar to the average bulk OM signature (mean of -23.4‰),
although the variability in the phytoclasts is larger (1.6‰). In contrast to this, charcoal (mean
of –20.8‰) and lignite (mean of –21.4‰) show a mean offset of 1.6‰ in the Luz Marls
Formation and of 2.8‰ in the Porto de Mos Formation. In comparison to bulk OM both
particle types display similar shifts throughout the section. Variations in the isotopic offset
between bulk OM and individual phytoclast types can occur due to changes in the proportion
of the different phytoclasts or result from additional OM to the bulk fraction from a different
source, most likely marine. The congruence of the bulk OM isotope signature and the
cuticle/leaf particles clearly indicates that the measured OM is predominantly composed of
foliage debris of continental origin. Therefore its δ13C signature can be interpreted as to
represent a terrestrial signal. Furthermore, the consistency of the isotope shifts in bulk OM
and land-plant particles demonstrates that fluctuations in the bulk terrestrial OM record are
not solely controlled by variations in the mixing ratio of terrestrial and marine OM.
Fossilized plant cuticle has been proposed as an ideal substrate for carbon-isotopic studies due
to its high resistance to decay and degradation processes (Arens et al., 2000; Upchurch et al.,
1997). Evidence for the primary nature of the measured δ13C phytoclast signature is given by
the consistent isotopic difference of ~2.0‰ between translucent cuticle and lignite. A similar
depletion in 13C of about 2.5‰ to 3.5‰ between cuticle and leaves relative to whole wood
plant carbon has been reported from extant as well as from fossil plants (Leavitt and Long,
1982; Upchurch et al., 1997) suggesting an insignificant diagenetic alteration of the isotopic
signal.
Thermally unaltered conditions for the sedimentary OM are indicated by unchanged coloring
of the palynomorphs (TAI < 2), strong UV fluorescence of the amorphous OM fraction and
low Tmax values (mean of 424.5°C). The absence of any significant correlation between δ13C
values and CaCO3- or TOC-content of the samples indicates the independence of the carbon-
isotope signature from lithological variations.
Chapter 4
78
Fig. 2: δ13Corg measurements of different types of land-plant particles (closed symbols) and the
corresponding bulk OM signature (open symbols) from the same horizon. Error bars of δ13Corg values
represent standard errors of means of repeated measurements.
5. Intrabasinal chemostratigraphic correlation
In order to test the terrestrial δ13Cbulk data for its consistency as well as for its potential as a
chemostratigraphic correlation tool, the carbon-isotope records of the Luz and Burgau
sections have been compared in detail (Fig. 3). Even though the δ13Corg record of the Luz
section is rather noisy and records an overall variation of ~8.5‰, pronounced shifts in the
magnitude of 5.0‰ to 7.0‰ can be observed. The most significant features of the δ13Cbulk
OM curve are an isotopic minimum with values down to –27.8‰ (from 17 m to 37 m) in the
Early Aptian, followed by two prominent and abrupt shifts towards higher values (–19.4‰ at
37 m; -19.3‰ at 120 m) in the Early and Late Aptian, respectively. Furthermore, intervals
with strong δ13C variability (70 m – 78 m, variation of ~4.5‰; 120 m – 157 m, variation of
~5.1‰) and intervals displaying more constant values (78 m - 120 m, variation of ~2.4‰) can
be recognized. Comparison with the Burgau carbon-isotope record (overall variation of
30
50
70
90
110
130
150
170
190
210
charcoal lignite cuticules leafs
-19-21-23-25-27 -19-21-23-25-27 -19-21-23-25-27 -19-21-23-25-27
Lo
we
r A
lbia
nU
pp
er A
ptia
nL
ow
er A
ptia
n
13Corg (%0 VPDB) δ 13Corg (%0 VPDB) δ 13Corg (%0 VPDB) δ 13Corg (%0 VPDB) δ
Lu
z M
arls
Po
rto
de
Mo
s F
m.
phytoclasts
bulk
height (m)
Chapter 4
79
~6.0‰) reveals that both curves do not only exhibit a similar shape with its distinct isotopic
shifts, but also show correspondence in the small-scale fluctuations. The obvious congruence
of the two records is furthermore supported by the similarity of the averaged δ13Corg values of
-22.8‰ (Luz) and -23.2‰ (Burgau). Based on the lithostratigraphic framework, the
correlation of large- and small-scale isotope excursions enables the establishment of 10
chemostratigraphic segments (I to X) resulting in a significant enhancement of the intra-
basinal stratigraphic correlation.
The well preserved OM and the occurrence of a similar isotopic pattern at two separate study
sites rule out a diagenetic control on the δ13C curve. Our preliminary palynological results
provide no evidence for major floral turnovers or input of a group of plants with exceptional
carbon-isotope compositions, which could explain abrupt shifts in the Aptian terrestrial δ13C
record. Even though the bulk terrestrial OM in the Luz section is predominatly composed of
cuticle and leaf debris, occasional input of isotopically less negative lignite and charcoal
particles results in δ13C shifts, which contribute to the small-scale fluctuations occurring
throughout the record. The strong δ13C variability in segment VII, IX and X of the Luz record
is interpreted to reflect compositional changes of the bulk OM due to fluctuations in the ratio
of marine to terrestrial OM. Horizons of purely terrestrial material alternate with intervals
containing a significant amount of isotopically light amorphous OM of presumably marine
origin. These alternations result in abrupt and brief carbon isotope shifts in the bulk OM
record.
Despite a variety of factors contributing to small-scale fluctuations of the terrestrial δ13C
record, the overall trend of the curve with its prominent excursions can not be explained
solely by compositional variations of the OM, changes in floral assemblage or diagenetic
alteration.
6. Global significance
Based on the palynostratigraphic framework, the Portuguese carbon-isotope profiles are
compared to an existing terrestrial δ13Cwood curve (Gröcke et al., 1999) and to a marine
δ13Ccarb reference record, including data of Erba et al. (1999) and Bralower et al.(1999). The
different curves exhibit essentially the same characteristic Aptian carbon-isotope pattern with
its distinctive anomalies (Fig. 4). A first marked negative δ13C excursion (1) in the marine
Chapter 4
80
Fig. 3: Palynostratigraphy, lithological logs and terrestrial δ13Cbulk OM data of two sections covering
the Aptian Luz Marls Formation of the western Algarve Basin, Portugal. Dotted lines correspond to
the lithostratigraphic framework. Shaded bars indicate the chemostratigraphic correlation. Only
palynomorphs with stratigraphic significance are displayed. The occurrence of Ctenidodinium
elegantulum, Rhynchodiniopsis aptiana and Pseudoceratium securigerum 30 m below the base of the
displayed section indicate an Early Bedoulian age for the lowermost part of the Luz Marls Formation.
reference record occurs in the Lowermost Aptian nannofossil Zone NC6, base of the
Leupoldina cabri planktic foraminiferal Zone. The negative excursion is followed by two
prominent shifts towards more positive values (2) at the transition from nannofossil Zone
NC6 to NC7, upper Leupoldina cabri planktic foraminiferal Zone and (3) in the uppermost
Burgau
Luz
limestonemarl
silt
claystone (<25% CaCO3)
-28 -26 -24 -22 -20 -18
13C bulk OM (‰ VPDB) δ
-28 -26 -24 -22 -20 -18
-28 -26 -24 -22 -20
-28 -26 -24 -22 -20
0 m0
20
4040
60
80
90
70
505
30
10
100
0
20
40
60
80
90
70
50
30
10
100
120
140
150
130
110
Alb
ian
Low
er A
pti
anU
pp
er A
pti
an
13C bulk OM (‰ VPDB) δ
Low
er L
uz
Mar
lsU
pp
er L
uz
Mar
ls
h
eig
ht (m
)
sta
ge
form
atio
n ~ 6.5 km
E WAlgarve basin
Hys
tric
hosp
haer
idiu
m a
rbori
spin
um
Pro
toel
lipso
din
ium
coro
llum
Din
opte
rygiu
m c
ladoid
esM
uder
ongia
pari
ata
Subti
lisp
haer
a c
hei
tC
yclo
nep
hel
ium
pauci
marg
inatu
mM
uder
ongia
sta
uro
taO
donto
chit
ina a
nca
laTeh
am
adin
ium
ten
uic
eras
Bre
nner
ipoll
is r
etic
ula
tus
Afr
opoll
is aff
. ja
rdin
us
Afr
opoll
is j
ard
inus
Bre
nner
ipoll
is p
erore
ticu
latu
sB
renner
ipoll
is cf.
div
idus
Tri
colp
its
vulg
ari
sD
ichast
opoll
enit
es sp
.
Din
ocysts
Sp
ore
s
& P
olle
n
correlation of marker beds
I
II
III
IV
V
VI
VII
VIII
IX
X
ch
em
ostr
at.
se
gm
en
t
Chapter 4
81
Fig. 4: Tentative correlation of mid-Cretaceous terrestrial δ13Corg records from the Isle of Wight,
United Kingdom (Gröcke et al., 1999) and from the Portuguese Algarve Basin (this study). In
addition, both terrestrial records are correlated with a composite marine reference curve, based on
δ13Ccarb measurements from Mexican and Tethyan sites (Bralower et al., 1999; Erba et al., 1999). A 3
point moving average was applied to the Algarve record to compensate for the noisiness of the curve
due to compositional variations in the measured bulk terrestrial OM. Shaded areas illustrate the
correlation between the records. Terrestrial curves are plotted against thickness (m) in different
scales.
nannofossil Zone NC7, Ticinella bejaouaensis planktic foraminiferal Zone. These marked
isotope excursions can be correlated with an isotopic minimum (segment II) and with two
shifts towards more positive values (segment III and IX) in our terrestrial record. The
occurrence of a distinct Aptian isotope pattern in the Portuguese record facilitates a well-
defined chemostratigraphic correlation with existing marine and terrestrial δ13C curves and
results in a significant increase in the stratigraphic resolution of these near-shore deposits.
7. Conclusions
Carbon-isotope studies on terrestrial OM obtained form near-shore depositional settings hold
a strong potential to serve as continental high-resolution records during earth history. Our
results demonstrate that despite a multitude of environmental and diagenetic factors affecting
Isle of Wight
(UK)
-18-22-26-30
150
100
50
0
200
250
300
80
60
40
0
100
120
20
140
Algarve
(Portugal)
160
he
igh
t (m
)
sta
ge
he
igh
t (m
)
13Cwood (‰ VPDB) δ 13Cbulk OM (‰ VPDB) δ
sta
ge
Lo
we
r A
ptia
nU
pp
er A
ptia
nA
lb.
2.0 3.0 4.0 5.0
Barr.
Lower
Aptian
Upper
Aptian
Albian
13Ccarb (‰ VPDB) δ
-20
Composite
marine recordN
C7
NC
8N
C6
NC
5
L. cabri
G. blo
wi
G. fe
rr.
G. alg
.
?
Lo
we
r A
ptia
nU
pp
er A
ptia
nA
lb.
Barr
.
H. pla
n. -
T
. bej.
sta
ge
Pk F
ora
m. Z
one
Na
nn
ofo
s. Z
on
e
-28 -26 -22-24
jacobi
nutfield-iensis
martinioides
forbesi
deshayesi
bowerbanki
fissicostatus
Am
monite
Zonation
Chapter 4
82
the carbon-isotope signature of bulk terrestrial OM in coastal depositional systems, the overall
trend of the δ13C record can serve as a reliable chemostratigraphic correlation tool. This is
confirmed by an intrabasinal correlation of coastal deposits using the δ13C signature of
continental-derived bulk OM. Comparison with existing mid-Cretaceous carbon-isotope
curves results in a significant increase of the stratigraphic resolution of the Portuguese near-
shore succession and points to the global significance of the terrestrial δ13C record. The higher
resolution will offer the opportunity to study the response of a near-shore sedimentary system
to major perturbations of the ocean-atmosphere-biosphere system.
Acknowledgements
We thank P. Steinmann from the University Neuchâtel for Rock-Eval pyrolysis
determinations; J. Dinis from Coimbra University and R. Gonzales from Algarve University
for field assistance. This manuscript was significantly improved thanks to suggestions and
reviews by D.R. Gröcke and an anonymous reader. Financial support from ETH-Project TH-
34./99-4 is greatfully acknowledged.
References
Ando, A., Kakegawa, T., Takashima, R. and Saito, T., 2002. New perspective on Aptian carbon
isotope stratigraphy: Data from δ13C records of terrestrial organic matter. Geology, 30, 227-230.
Arens, N.C., Jahren, A.H. and Amundson, R., 2000. Can C3 plants faithfully record the carbon isotopic composition of atmospheric carbon dioxide? Paleobiology, 26, 137-164.
Arthur, M.A., Jenkyns, H.C., Brumsack, H.-J. and Schlanger, S.O., 1990. Stratigraphy, geochemistry and paleoceanography of organic-carbon rich Cretaceous sequences. In: R.N. Ginsburg and B. Beaudoin (Editors), Cretaceous Resources, Events and Rhythms. NATO ASI Series C. Kluwer Academic Publishers, MasDordrecht, pp. 75-119.
Berthou, P.Y. and Leereveld, H., 1990. Stratigraphic implications of palynological studies on Berriasian to Albian deposits from western and southern Portugal. Review of Palaeobotany and Palynology, 66, 313-344.
Bralower, T.J. et al., 1994. Timing and paleoceanography of oceanic dysoxia/ anoxia in the late Barremian to early Aptian (Early Cretaceous). Palaios, 9, 335-369.
Bralower, T.J. et al., 1999. The record of global change in Mid-Cretaceous (Barremian-Albian) sections from the Sierra Madre, northeastern Mexico. Journal of Foraminiferal Research, 29, 418-437.
Erba, E., 1994. Nannofossils and superplumes: The early Aptian "nannoconid crisis". Paleoceanography, 9, 483-501.
Erba, E. et al., 1999. Integrated stratigraphy of the Cismon Apticore (southern Alps, Italy): A "reference section" for the Barremian-Aptian interval at low latitudes. Journal of Foraminiferal Research, 29, 371-391.
Chapter 4
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Erbacher, J., Thurow, J. and Littke, R., 1996. Evolution patterns of radiolaria and organic matter variations: A new approach to identify sea-level changes in Mid-Cretaceous pelagic environments. Geology, 24, 499-502.
Ferreri, V., Weissert, H., D'Argenio, B. and Buonocunto, F.P., 1997. Carbon isotope stratigraphy; a tool for basin to carbonate platform correlation. Terra Nova, 9, 57-61.
Gröcke, D.R., Hesselbo, S.P. and Jenkyns, H.C., 1999. Carbon-isotope composition of Lower Cretaceous fossil wood: Ocean-atmosphere chemistry and relation to sea-level change. Geology, 27, 155-158.
Hasegawa, T., 1997. Cenomanian-Turonian carbon isotope events recorded in terrestrial organic matter from northern Japan. Palaeogeography, Palaeoclimatology, Palaeoecology, 130, 251-273.
Hesselbo, S.P. et al., 2000. Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event. Nature, 406, 392-395.
Hesselbo, S.P., Robinson, S.A., Surlyk, F. and Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle perturbations: a link to initiation of massive volcanism? Geology, 30, 251-254.
Hochuli, P.A., Menegatti, A.P., Riva, A., Weissert, H. and Erba, E., 1999. High-productivity and cooling episodes in the Early Aptian Alpine Tethys
European Union of Geosciences conference abstracts; EUG 10, European Union of Geosciences conference; EUG 10. Strasbourg, France. March 28-April 1, 1999. Journal of Conference Abstracts. Cambridge Publications. Cambridge, United Kingdom. 1999., pp. 219.
Jahren, A.H., Arens, N.C., Sarmiento, G., Guerrero, J. and Amundson, R., 2001. Terrestrial record of methane hydrate dissociation in the Early Cretaceous. Geology, 29, 159-162.
Jenkyns, H.C., 1995. Carbon-isotope stratigraphy and paleoceanographic significance of the Lower Cretaceous shallow-water carbonates of Resolution Guyot, Mid-Pacific Mountains. In: E.L. Winterer, W.W. Sager, J.V. Firth and J.M. Sinton (Editors), Proceedings of the Ocean Drilling Program, Scientific Results. Proceedings of the Ocean Drilling Program, Scientific Results. Texas A & M University, Ocean Drilling Program, College Station, TX, United States, pp. 99-104.
Leavitt, S.W. and Long, A., 1982. Evidence for 13C/12C fractionation between tree leaves and wood. Nature, 298, 742-744.
Menegatti, A.P. et al., 1998. High-resolution δ13C stratigraphy through the early Aptian "Livello Selli" of the Alpine Tethys. Paleoceanography, 13, 530-545.
Rey, J., 1983. Le Crétacé de l'Algarve: Essai de Synthèse. Comunicações dos Serviços Geológicos de Portugal, 69, 87-101.
Rey, J., 1986. Micropaleontological assemblages, paleoenvironments and sedimentary evolution of Cretaceous deposits in the Algarve (southern Portugal). Palaeogeography, Palaeoclimatology, Palaeoecology, 55, 233-246.
Upchurch, G.R., Marino, B.D., Mone, W.E. and McElroy, M.B., 1997. Carbon isotope ratios in extant and fossil plant cuticule. American Journal of Botany, 84, 143-144.
Weissert, H. and Breheret, J.G., 1991. A carbonate-isotope record from Aptian-Albian sediments of the Vocontian Trough (SE France). Bulletin de la Societe Geologique de France, 162, 1133-1140.
Weissert, H., Lini, A., Foellmi, K.B. and Kuhn, O., 1998. Correlation of Early Cretaceous carbon isotope stratigraphy and platform drowning events: A possible link? Palaeogeography, Palaeoclimatology, Palaeoecology, 137, 189-203.
Chapter 4
84
Chapter 5 85
Chapter 5
A well-dated and continuous early angiosperm pollen record from mid-Cretaceous
coastal deposits (Lusitanian and Algarve Basins, Portugal):
Implications for the timing of the early angiosperm radiation
Abstract
Detailed and continuous palynological records from two well-dated successions in the
Portuguese Algarve and Lusitanian Basins are presented, which document the diversification
of early angiosperm pollen during the Barremian to Albian time interval. Based on
dinoflagellate cysts biostratigraphy, an accurate stratigraphic framework has been established
for the studied near-shore deposits resulting in distinct changes of the stratigraphic position of
individual units. The qualitative and quantitative analysis of the palynofloras of the two
sections revealed a total of 60 different types of angiosperm pollen. Most of them (51 taxa)
are monoaperturate grains of magnoliid or monocot affinity. In both records eudicots,
represented by various tricolpate taxa (9 taxa), are restricted to the post-Aptian part of the
sections. Angiosperm pollen display a distinct increase in both, diversity (up to 18 taxa per
sample) and relative abundance (up to 12 %) between the Late Barremian and Middle Albian.
Comparison with published studies shows strong similarities with regard to floral composition
and the timing of first appearances of particular angiosperm pollen forms. Our results ask for
a new age interpretation of the well-known angiosperm mesofossil floras from the Portuguese
Estremadura region which have been interpreted as Barremian or possibly Aptian in age.
Several lines of evidence, including sequence- and biostratigraphy as well as palynology,
indicate a post-Aptian age for these assemblages (incl. the Famalicão, Buarcos and Vale de
Agua mesofloras), hence demonstrating a major radiation phase during the Early Albian.
Key words: early angiosperms; radiation; mid-Cretaceous; palynology; biostratigraphy;
Portugal
Chapter 5 86
1. Introduction
The mid-Cretaceous diversification of angiosperms marks the profound change from
Mesozoic floras dominated by ferns, conifers and cycads to the modern, angiosperm-
dominated ecosystems of the Cenozoic era (e.g. Crane et al., 1995; Lidgard and Crane, 1988;
Willis and McElwain, 2002). Evidence for early angiosperms in the fossil record has been
essentially obtained from the analysis of fossil palynofloras from continental to shallow-water
deposits. Pollen grains of unambiguous angiosperm origin have been reported from
Barremian strata from various localities including equatorial and northern Africa (e.g. Doyle
et al., 1977; Gübeli et al., 1984; Penny, 1986; Schrank and Mahmoud, 2002) as well as
northwestern Europe (Hughes et al., 1979; Hughes and McDougall, 1990). These early
assemblages consist of monoaperturate pollen types with reticulate-semitectate or
columellate-tectate wall structure and display strong similarity to pollen of extant magnoliids
or monocotyledons. The occurrence of presumed eudicots is documented by the appearance of
triaperturate pollen grains from younger, post-Barremian deposits (e.g. Brenner, 1963;
Brenner, 1996; Doyle and Robbins, 1977; Penny, 1986). Quantitative analyses of genera and
species richness of numerous Cretaceous macrofossil floras display a step-wise increase of
angiosperms diversity during the mid-Cretaceous interval. Whereas flowering plants were of
only subordinate importance in Barremian to Aptian terrestrial ecosystems (on average less
than 10 %), they experienced a rapid and extensive diversification during the Albian to
Cenomanian. By the end of the Cenomanian angiosperms dominated in typical low-latitude
floras, accounting for about 70 % of the encountered species (Crane and Lidgard, 1989;
Lidgard and Crane, 1988).
Fossil floras from the Portuguese Estremadura region play a key role for investigating the late
Early Cretaceous angiosperm evolution and diversification. The continental deposits of the
Lusitanian Basin have been intensely studied with regard to macrofossil leaf floras (Teixeira,
1948) as well as with regard to the pollen and spores content (Groot and Groot, 1962). In
more recent times, several rich and well-preserved mesofossil floras including various in situ
pollen have been described in detail by Friis et al. (1997; 1994; 1999; 2000a; 2001) from
continental sediments of an inferred Barremian or possibly Aptian age. These floras display a
relatively high diversity of in situ pollen, accounting for up to 30 % of the total floral
diversity. Triaperturate pollen types represent about ~15 % of the angiosperm pollen
diversity. According to these authors, the observed fossil angiosperm reproductive structures
Chapter 5 87
(incl. flowers, stamens, anthers, fruits) represent the oldest unequivocal evidence for the
occurrence of flowering plants in the fossil record.
The proposed Barremian-Aptian age of this diverse angiosperm record contrasts with the
previously held view that the major increase in angiosperm diversity occurred during the
Albian. Furthermore, the consistent occurrence of triaperturate pollen in the in situ
assemblages is in contrast to the absence of this type of pollen in most contemporaneous
dispersed palynofloras. However, many of the early angiosperm records lack independent
stratigraphic control due to the absence of adequate markers in the fossil-bearing strata. This
hampers detailed comparison between dispersed palynofloras and the plant macro- or
mesofossil records. Furthermore, a more precise dating of the early angiosperm
diversification pattern would allow for a correlation with major climatic or tectonic events
during the mid-Cretaceous, which might have had significant influence on the evolution and
rapid diversification of the flowering plants (Crane et al., 1995; Lupia et al., 2000).
Here, we present independently dated palynological records which document the early
angiosperm diversification in Portugal on a previously not attained temporal resolution.
Changes in palynofloral composition during the Late Barremian to Early Albian interval are
traced throughout two coastal marine successions from the Algarve and Lusitanian Basins. In
a first step, the existing stratigraphic model of both successions is revised based on
dinoflagellate cyst biostratigraphy. The new results significantly change the stratigraphic
assignment of several lithological units. In a second step the palynological content of the two
sections is analysed with regard to composition, diversity and relative abundance. Both
successions provide well-preserved and diverse angiosperm palynofloras. Our angiosperm
pollen records are compared with previously published records from widespread localities
including palynofloras from the North American Potomac Group (Brenner, 1963; Doyle and
Robbins, 1977) as well as with the in situ pollen assemblages from Portugal (Friis et al. 1997;
1994; 1999; 2000a). Based on the revised stratigraphy and palynological arguments, we
provide evidence for a significantly younger, post-Aptian age of the Portuguese mesofossil
floras from the northern Lusitanian Basin.
Chapter 5 88
2. Studied sections
Two Portuguese localities have been chosen for the present biostratigraphic and palynological
study, both representing mixed carbonate-siliciclastic coastal successions and covering
Barremian to Albian strata. The first section (Cresmina) is located in the Lusitanian Basin,
western Portugal whereas the second section (Luz) is exposed in the Algarve Basin, southern
Portugal (Fig. 1).
Fig. 1: (A) Location of the Lusitanian and Algarve Basins in western and southern Portugal. (B) Map
of the Estremadura region with the locations of the studied Cresmina and São Julião sections (arrows)
and sites of angiosperm mesofossil floras (asterisks). (C) Map of the Algarve region with the location
of the Luz section.
-9°45' -9°15' -8°15'
40°30'
40°00'
39°30'
39°00'
38°30'
25 km
Figueira da FozCoimbra
Nazaré
Peniche
Cresminasection
Ericeira
São Juliãosection
Low
er
Tagus
Basi
n
Santa Cruz
Buarcos
Famalicão
Vale de Agua
Torres Vedras
Catefica
N
Palaeozoic Basement
Angiosperm mesofossil site
Naz
aré
Fault Zon
e
Faro
Silves
Lagos
25 km
-9°00' -8°30' -8°00' -7°30'
-37°00'Luz
section
Tavira
8°
IB
ER I A
Port
ugal
A
B
C
B
C
-8°45'
Cascais
Lisboa
Chapter 5 89
2.1 Cresmina section
The Cresmina section is well-exposed along the coastal cliffs north of Cabo Raso, about 5 km
northeast of the village Cascais. The studied succession spans from the cliffs below the Forte
da Cresmina along the beach towards the cliffs of Ponta da Galé (Ramalho et al., 1981; Rey,
1972). Due to unfavourable outcrop conditions at the Forte da Cresmina, the Praia da Lagoa
Member has been sampled near São Julião in the Ericeira area, about 25 km north of the Forte
da Cresmina site. Here, the Praia da Lagoa Member is exposed along the coastal cliffs below
the small village São Julião, ~0.5 km south of the Ribeira do Porto river mouth. Similarly, the
Rodízio Formation has been sampled south of Ericeira along the Praia dos Banhos, ~4.0 km
north of the Ribeira do Porto river mouth (Rey, 1972).
The Cresmina section has been studied in detail by Rey (1972; 1992) from a
sedimentological, palaeontologcial and stratigraphical perspective. The section comprises
~200 m of Barremian to Albian sediments and can be separated into five major lithological
units (Fig. 2). According to Rey (1972; 1992), the lower part of the section corresponds to the
Cresmina Formation, which itself is composed of three individual lithostratigraphic units,
including the Cobre, the Ponta Alta and the Praia da Lagoa Member. The upper part of the
Cresmina section includes the Rodízio Formation and the lower part of the Galé Formation
(Agua Doce Member). The individual lithostratigraphic units are named according to Rey
(1972).
The Cobre Member is mainly composed of strongly bioturbated and impure limestones,
alternating with oyster-rich marls, siltstones and few well-sorted conglomerate layers. These
sediments are interpreted to reflect a mixed carbonate-siliciclastic near-shore depositional
environment. The overlying Ponta Alta Member consists of massy, thick-bedded, rudist-rich
limestones. Besides various rudist taxa, the limestones comprise a diverse macrofauna
including stromatoporoids, scleractinian corals and nerinean gastropods, indicating an open-
platform depositional setting (Rey, 1979). The top of the Ponta Alta Member is marked by a
prominent hardground, which allows precise correlation with sections in the northern part of
the Lusitanian Basin (Rey, 1992). This widespread discontinuity is covered by the sediments
of the Praia da Lagoa Member, mainly calcareous, orbitolinid-rich marls and fossiliferous
sandy limestones. The marine deposits of the Praia da Lagoa Member are overlain
disconformly by the coarse-grained siliciclastics and lignite-rich mudstones of the Rodízio
Formation. According to Dinis and Trincão (1995), the boundary between the marine deposits
of the Praia da Lagoa Member and the continental conglomerates of the Rodízio Formation
Chapter 5 90
represents a major unconformity of superregional significance. The coarse-grained
siliciclastics evolve gradually into the coastal marine silts, marls and limestones of the lower
Agua Doce Member. The upper part of the Agua Doce Member is composed of fossiliferous
marly limestones with intercalated rudist-rich horizons, indicating deposition in an inner- to
mid-shelf environment.
2.2. Luz section
The Luz section is well exposed along the coastal cliffs southwest of the village Lagos in the
western Algarve region. The entire sedimentary succession is slightly tilted towards the east
and most of the studied section is accessible along a ~2.5 km long strip between the Praia da
Luz (east of the village Luz) and the Praia da Porto de Mós (2 km southwest of Lagos). Only
the lowermost part of the section (incl. the Choffatella decipiens Marls and the Palorbitolina
Beds) has been sampled along the cliffs at Ponta da Calheta, 0.5 km north of the Praia da Luz
(Rocha et al., 1983). Earlier sedimentological and biostratigraphical studies of these deposits
have been carried out by Rey and Ramalho (1974), Ramalho and Rey (1981) and Rey (1983;
1986).
Following Rey (1983) the ~260 m thick sedimentary succession can be separated into 5
lithostratigraphic units, including the Choffatella decipiens Marls, the Palorbitolina Beds, the
Lower and the Upper Luz Marls as well as the Porto de Mós Formation (Fig. 2).
The Choffatella decipiens Marls are mainly composed of alternating beds of gypsiferous
marls, bioclastic limestones and dolomicrites, which have been deposited in a shallow marine
to lagoonal setting. The overlying Palorbitolina Beds are represented by massive, oblique-
bedded coastal sandstones, containing abundant nerinean gastropod coquinas. Above a
distinct hardground, the Luz Marls consist of a monotonous succession of variegated marls
and claystones with few intercalated silt- and limestone beds. The boundary between the
Lower and Upper Luz Marls is marked by a distinct interval of thick-bedded fossiliferous
limestones with a conglomeratic horizon at the base. The abundant occurrence of charophytes,
miliolinid foraminifera and ostracods throughout the Luz Marls indicates deposition in a
restricted lagoonal to brackish marsh environment with few open-marine episodes. The Upper
Luz Marls are overlain by the Porto de Mós Formation, which is composed of thick-bedded,
bioturbated limestones alternating with calcareous marls. Typical sedimentary structures
include laminations, bored hardgrounds, desiccation cracks as well as fenestrae, indicating a
carbonate-dominated tidal flat depositional environment.
Chapter 5 91
Fig. 2: Simplified lithological log with biostratigraphic events of the Luz section (Algarve Basin) and
the Cresmina section (Lusitanian Basin). Age-dignostic rudists in the Ponta Alta Member are
displayed in grey. PDL, Praia da Lagoa Member; C. decipiens Marls, Choffatella decipiens Marls.
Lusitanian Basin
Tehamadinium tenuiceras
Muderongia staurota
Hystrichosphaerina schindewolfii
Dinopterygium cladoides
Ctenidodinium elegantulum
Pseudoceratium securigerum
Callaiosphaeridium trycherium
Rhynchodiniopsis aptiana
Pseudoceratium pelliferum
Pseudoceratium securigerum
Callaiosphaeridium trycherium
Odontochitina operculata
Palaeoperidinium cretaceum
Heslertonia heslertonensis
Ctenidodinium elegantulum
Dinopterygium cladoides(consistent occurrence)
Xiphophoridium alatum
Chichaouadinium vestitum
60
40
20
0
80
100
120
140
160
180
200
220
240
260
Lo
we
r B
ed
ou
lian
Up
pe
r B
ed
ou
lian
Up
pe
r A
ptia
n L
ow
er A
lbia
n
Po
rto
de
Mo
s F
m.
Up
pe
r L
uz M
arls
Lo
we
r L
uz M
arls
Pa
lorb
ito
lina
Be
ds
Algarve Basin
60
40
20
0
80
100
120
140
160
180
200
Lo
we
r A
lbia
nU
pp
er
Ba
rre
mia
nM
idd
le A
lbia
nL
ow
er
Be
do
ulie
n
Ro
dis
io
Fm
.
Ga
lé F
m.
Cre
sm
ina
Fm
.
Sta
ge
Me
ter
Fo
rma
tio
n
Lith
olo
gy
Sta
ge
Me
ter
Fo
rma
tio
n
Lith
olo
gy
Subtilisphaera perlucida
Cerbia tabulata
Ag
ua
Do
ce
Mb
.P
on
ta A
lta
Co
bre
Mb
.P
dL
Me
mb
er
C. decip
iens
Ma
rls
Dinopterygium cladoides(consistent occurrence)
Pachytraga paradoxa
Caprina douvilleiPraecaprina varians rudists
limestone
siltstone
sandstone/conglomerate
marl
claystone (< 25% CaCO3)
first occurrence (FO)
last occurrence (FO)
Chapter 5 92
3. Palaeophytogeographic and palaeoclimatic framework
During the mid-Cretaceous, the Algarve and Lusitanian Basins were situated at a
palaeolatitude of about 20ºN to 25ºN, forming part of the eastern margin of the evolving
North Atlantic (Fig. 3). According to Brenner (1976) and Batten (1984), both Portuguese
study sites were part of the southernmost Southern Laurasian floral province, which was
restricted to the mid-latitudes of northern hemisphere during Aptian to Albian times. The
boundary between the Northern Gondwana province in the south and the Southern Laurasian
province in the north is represented by a transitional zone, which incorporates floral elements
from both provinces (Batten, 1984; Hochuli, 1981). Palynofloral assemblages from the
Southern Laurasian province typically contain abundant bisaccates of Pinacean affinity,
conifer pollen such as Classopollis spp. and Araucariacites spp. as well as numerous and
varied pteriodophyte spores - especially representatives of the Schizaeaceae and
Gleicheniaceae. In contrast, high abundances of various gymnosperm pollen of the
Ephedripites, Cycadopites and Araucariacites group indicate a Northern Gondwana affinity.
In addition, large numbers of Classopollis spp. as well as the common occurrence of
Afropollis spp. characterise this southern floral province whereas pteridophyte spores exhibit
generally low diversity and abundance. Bisaccate pollen of Pinacean affinity are virtually
absent.
According to the palaeoclimatic reconstructions of Chumakov et al. (1995), the Northern
Gondwana floral province corresponds to a broad zone of arid to semi-arid conditions
(equatorial hot arid belt) during the Aptian interval. This is consistent with the results of
Ruffel and Batten (1990) who proposed, based on sedimentological and palynological
observations, a Barremian to mid-Aptian phase of aridity for the western European realm.
During the Albian, the development of an equatorial humid belt represents a significant
change in the palaeoclimatic patterns of low-latitudes (Chumakov et al., 1995). In general,
this pattern is supported by palaeobotanical results which indicate an arid to semi-arid climate
for the Northern Gondwana province, whereas the Southern Laurasian province was
characterised by subtropical to warm-temperate conditions during the Aptian to Albian
interval (Brenner, 1976; Chumakov et al., 1995; Vakhrameyev, 1978).
Chapter 5 93
Fig. 3: Palaeogeographic reconstruction of the North Atlantic and Tethyan realm during the mid-
Cretaceous at ~115 Ma (modified after Geomar map generator; www.odsn.de). Asterisks mark
locations of early angiosperm palynofloras which are used for comparison. 1, Lusitanian Basin,
Portugal (Friis et al. 1999 and this study); 2, Algarve Basin, Portugal (this study); 3, DSDP sites 417
and 418, North Atlantic Basin (Hochuli and Kelts 1980); 4, Potomac Group, United States (Doyle and
Robbins, 1977); 5, Wealden Group, England (Hughes et al. 1979); 6, Qattara Depression, Egypt
(Ibrahim 1996); 7, Dakhla Oasis, Egypt (Schrank and Mahmoud 2002); 8, northern Negev, Israel
(Brenner 1996); 9, Cocobeach system, Gabon (Doyle 1977). Major floral provinces and
corresponding climate after Brenner (1976) and Batten (1984).
4. Material and methods
A total of 57 rock samples from the Cresmina section and 61 rock samples from the Luz
section were prepared for palynological analysis. Despite the selection of apparently well-
suited samples, numerous samples were barren of palynomorphs (27 in the Cresmina section;
27 in the Luz section). Cleaned, crushed and weighed samples (20 to 80 g) were treated with
HCl and HF following standard palynological preparation techniques (e.g. Traverse, 1988).
The residue was sieved with a 11 µm mesh-sieve and a first set of strew mounts was prepared
for kerogen analysis. Following this, a short oxidation with HNO3 was performed on all
residues. A second set of strew mounts was prepared for palynological analysis. All
-60ºE -30ºE-45ºE -15ºE-75ºE 0ºE
0ºN
30ºN
15ºN
-15ºN
Northern Gondwana province(arid to semi-arid)
3
4
2
1
5
transitional zone
6
7
8
9
Southern Laurasian province(subtropical to warm-temperate)
Chapter 5 94
productive samples were studied for their palynological content (dinoflagellate cysts, spores
and pollen). Special attention was paid to the occurrence of angiosperm pollen. In a second
step, a minimum of 200 (average of 240) sporomorphs was determined and counted. Light
photomicrographs were taken using an Olympus BX 51 light microscope (LM) equipped with
an Olympus DP 12 digital camera.
The preservation of the studied palynomorphs is fairly good to excellent. Individual grains
exhibit no obvious signs of post-depositional degradation. Thermally unaltered conditions of
the OM are indicated by the virtually unchanged colouring of the palynomorphs (TAI < 2) as
well as by strong UV fluorescence of the amorphous OM.
5. Dinoflagellate cyst biostratigraphy
In order to establish a refined biostratigraphic framework for the mid-Cretaceous strata of the
Lusitanian and Algarve Basins, all productive palynological samples were analysed for the
distribution of dinoflagellate cysts. In the Cresmina section a total of 78 different
dinoflagellate cyst taxa have been distinguished (Fig. 4), whereas in the Luz section 74 taxa
were determined (Fig. 5). No evidence for reworking has been observed. First and last
occurrences (FO and LO) of age-diagnostic dinoflagellate cyst taxa are diplayed in Fig. 2. In
the present context aiming for an independent age framework for the pollen record,
stratigraphic evidence from pollen is not considered in this study.
As already reported by Berthou and Leereveld (1990) the observed dinoflagellate cyst
assemblages reflect a Boreal rather than Tethyan character. Therefore, comparison and
correlation refers mainly to associations from the Boreal realm and corresponding
biostratigraphic zonation schemes. To some extent comparison with Tethyan associations has
been included. The comprehensive biostratigraphic zonation scheme of Monteil and Foucher
(1998) including Boreal and Tethyan dinoflagellate taxa serves as a biostratigraphic baseline.
In addition, the zonation schemes of Costa and Davey (1992), Stover et al. (1996) and
Leereveld (1995) are applied for comparison and correlation. For regional stratigraphic
considerations, the encountered associations are compared with the results of earlier studies of
Berthou and Leereveld (1990), Hasenboehler (1981) and Berthou et al. (1980). For the
Barremian to Aptian interval, our results are compared with assemblages from N Italy
(Torricelli, 2000), SE France (Davey and Verdier, 1974; Masure et al., 1998) and south-
western Morocco (Below, 1981). For the nomenclature of the mentioned taxa, we refer to
Chapter 5 95
Williams et al. (1998). In the Ponta Alta Member, the occurrences of age diagnostic rudist
species corroborate the ages indicated by palynology.
5.1. Cresmina section
Cobre Member
The stratigraphic position of this unit is confined by the FOs of the age-diagnostic
dinoflagellate cyst taxa Cerbia tabulata, Odontochitina operculata (Pl. VII; 3) and
Palaeoperidinium cretaceum in the basal part (at 5.7 m) as well as by the LO of
Pseudoceratium pelliferum (Pl. VII; 9) in the uppermost part of the Cobre Member (at 45.0
m). These findings indicate a Late Barremian age for this part of the section.
According to Leereveld (1995), the FO of C. tabulata occurs just below the Early to Late
Barremian boundary in both, the Boreal and the Tethyan realm. This corresponds to the FO of
C. tabulata applied in the biostratigraphic schemes of Monteil and Foucher (1998), Costa and
Davey (1992) and Stover et al. (1996). The FO of P. cretaceum at the same level is in
agreement with the results of Monteil and Foucher (1998) as well as with Costa and Davey
(1992). The FO of O. operculata is known to occur above the Early-Late Barremian boundary
(Leereveld, 1995; Torricelli, 2000). The LO of P. pelliferum represents a frequently used
stratigraphic event indicating the Barremian-Aptian boundary in the Tethyan realm (Costa
and Davey, 1992; Leereveld, 1995; Stover et al., 1996). In the Boreal realm, the LO of P.
pelliferum is less consistent and has been reported from latest Barremian (Monteil and
Foucher, 1998) as well as from Bedoulian strata (Lister and Batten, 1988; Stover et al., 1996).
Ponta Alta Member
The stratigraphic position of the Ponta Alta Member is determined by the occurrence of
several age-diagnostic rudist species including Pachytraga paradoxa, Praecaprina varians
and Caprina douvillei. These rudist taxa have been reported from sediments of latest
Barremian to Bedoulian age (Masse and Chartrousse, 1998; Skelton and Masse, 1998),
suggesting a similar age for the Ponta Alta Member. Palynological samples from this interval
were barren.
Praia da Lagoa Member
The stratigraphic position of the Praia da Lagoa Member is defined by the LOs of
Pseudoceratium securigerum (at 63.0 m; Pl. VII; 2), Heslertonia heslertonensis (at 64.9 m;
Chapter 5 96
Pl. VII; 1), Callaiosphaeridium trycherium (at 66.2 m) and Ctenidodinium elegantulum (at
68.5 m). This association indicates an age not younger than Early Bedoulian for this part
Member.
The encountered taxa are considered as important marker species in most biostratigraphic
zonation schemes. Masure et al. (1998) used the LO of C. elegantulum together with
Rhynchodiniopsis aptiana as a key event in their dinoflagellate cyst zonation for the
Bedoulian stratotype, where it defines the top of the securigerum dinoflagellate zone in the
lower part of the Late Bedoulian (Deshayesi ammonite zone). Davey and Verdier (1974) and
Masure et al. (1998) reported P. securigerum as characteristic species from Bedoulian strata.
The LO of H. heslertonensis is applied by Masure et al. (1998) as a marker species for earliest
Bedoulian. According to Stover et al. (1996) the LO of C. elegantulum corresponds to the
Early Bedoulian. In the Boreal realm, the LOs of C. elegantulum and C. trycherium have been
placed into the Bedoulian by Monteil and Foucher (1998). In the zonation schemes of Costa
and Davey (1992) and Monteil and Foucher (1998) the LO of H. heslertonensis is placed
below the D. deshayesi ammonite zone within the Early Bedoulian.
Rodízio Formation
The stratigraphic position of the Rodízio Formation is determined by the FO of
Dinopterygium cladoides (at 86.0 m; Pl. VII; 5) occurring just above the second conglomerate
horizon. From this horizon onwards, D. cladoides occurs consistently throughout the upper
part of the succession. Except for an isolated record, Below (1981) reported the occurrence of
D. cladoides (reported as Oodnadattia tuberculata) from Moroccan deposits from the Albian
onwards. In addition, D. cladoides has been documented consistently from Cenomanian to
Santonian chalks in southern England (Clarke and Verdier, 1967). According to the range
chart of Monteil and Foucher (1998) the FO of D. cladoides is placed into the late Early
Albian in the Boreal realm. This event clearly indicates an Early Albian or younger age for
the upper part of the Rodízio Formation.
Agua Doce Member (Lower Galé Formation)
The stratigraphic position of the Agua Doce Member is determined by the LOs of
Subtilisphaera perlucida (at 130.6 m; Pl. VII; 4) and Hystrichosphaerina schindewolfii (at
158.8 m; Pl. VII; 7) as well as by the FOs of Chichaouadinium vestitum (at 136.4 m) and
Xiphophoridium alatum (at 140.4 m). The observed association indicates an Early to Middle
Chapter 5 97
Albian age for the Agua Doce Member. The boundary between the Early and Middle Albian
is placed at the FO of X. alatum.
According to Leereveld (1995), the LO of H. schindewolfii marks the latest Early Albian in
the Boreal realm (D. mammilatum ammonite zone). Other authors place the LO of H.
schindewolfii earlier within the Early Albian (Costa and Davey, 1992; Stover et al., 1996).
Similarly, the LO of S. perlucida has been considered typical for Early Albian (Costa and
Davey, 1992). In the Boreal realm, Monteil and Foucher (1998) report the FO of X. alatum
from the late Middle Albian (E. lautus ammonite zone). According to Stover et al. (1996) the
FOs of X. alatum and C. vestitum occur as late as earliest Late Albian.
Fig. 4: Stratigraphical distribution of dinoflagellate cysts in the Cresmina section. Horizontal bars in
the sample column represent productive palynological samples, crosses correspond to palynologically
barren samples.
Odonto
chitin
a a
ncala
Mic
rod
iniu
m s
pp.
Ch
ich
ao
ua
din
ium
spp.
Ce
pa
din
ium
ve
ntr
iosa
Ch
lam
yd
op
ho
rella
spp.
Cle
isto
sp
ha
erid
ium
spp.
Ta
nyo
sp
ha
erid
ium
va
rie
ca
lam
um
Po
lysp
ha
erid
ium
spp.
Dis
silio
din
ium
spp.
Dic
on
od
iniu
m s
pp.
Cyclo
ne
ph
eliu
m p
au
cis
pin
um
Xip
ho
ph
orid
ium
ala
tum
Vo
zzh
en
nik
ovia
spp.
Circu
lod
iniu
m s
pp.
Ch
ich
ao
ua
din
ium
ve
stitu
mA
sco
din
ium
spp.
Cyclo
ne
ph
eliu
m v
an
no
ph
oru
mO
donto
chitin
a s
pp.
Od
on
toch
itin
a im
pa
rilis
Da
psilid
iniu
m w
arr
en
iiE
xo
ch
osp
ha
erid
ium
ph
rag
mite
sF
lore
ntin
a d
ea
ne
iK
aly
pte
a s
pp.
Pin
occh
iod
iniu
m e
rba
eT
rich
od
iniu
m c
asta
ne
a
Su
btilisp
ha
era
ch
eit
+
Pro
toe
llip
so
din
ium
co
rollu
m
++
Olig
osp
ha
erid
ium
to
tum
Olig
osp
ha
erid
ium
pu
lch
err
imu
mD
ino
pte
ryg
ium
cla
do
ide
sD
ap
silid
iniu
m d
efla
nd
rei
Ge
ise
lod
iniu
m s
pp.
Cte
nid
od
iniu
m e
leg
an
tulu
m
Pse
ud
oce
ratiu
m p
ellife
rum
Ca
lla
iosp
ha
erid
ium
spp.
++
Pte
rod
iniu
m s
pp.
Kle
ith
ria
sp
ha
erid
ium
co
rru
ga
tum
Ach
om
osp
ha
era
spp.
+
+
Ba
tia
ca
sp
ha
era
spp.
+
Crib
rop
erid
iniu
m o
rth
oce
ras
+
Exo
ch
osp
ha
erid
ium
spp.
Flo
rentinia
spp.
+
Hystr
ich
od
iniu
m p
ulc
hru
m
+
Hystr
ich
osp
ha
erin
a s
ch
ind
ew
olfii
+
Te
ha
ma
din
ium
spp.
+
Ca
lla
iosp
ha
erid
ium
asym
me
tric
um
+
+
Din
go
din
ium
spp.
He
sle
rto
nia
he
sle
rto
ne
nsis
Hystr
ich
osp
ha
erin
a s
pp.
Mic
rod
iniu
m o
pa
cu
mA
pte
a p
oly
mo
rph
a
+
+
Co
me
tod
iniu
m s
pp.
Mu
de
ron
gia
pa
ria
taP
se
ud
oce
ratiu
m s
ecu
rig
eru
m "
nu
du
m"
Trich
od
iniu
m s
pp.
Su
btilisp
ha
era
spp.
++
++
Sp
inife
rite
s s
pp.
++
Olig
osp
ha
erid
ium
spp.
Olig
osp
ha
erid
ium
co
mp
lex
+
++
Mu
de
ron
gia
spp.
Hystr
ich
od
iniu
m fu
rca
tum
Go
nya
ula
cysta
cre
tace
aC
rib
rop
erid
iniu
m s
pp.
+
Circu
lod
iniu
m b
revis
pin
osu
m
++
++
Su
btilisp
ha
era
pe
rlu
cid
aP
se
ud
oce
ratiu
m s
ecu
rig
eru
mP
ala
eo
pe
rid
iniu
m c
reta
ce
um
+
Olig
osp
ha
erid
ium
aste
rig
eru
m
+
Od
on
toch
itin
a o
pe
rcu
lata
+
+
Mu
de
ron
gia
sta
uro
taK
leith
ria
sp
ha
erid
ium
spp.
Kle
ith
ria
sp
ha
erid
ium
re
ad
ei
Kio
ka
nsiu
m p
oly
pe
s
++
Ellip
so
idic
tyu
m s
pp.
Crib
rop
erid
iniu
m e
dw
ard
sii
Ce
rbia
ta
bu
lata
Ca
lla
iosp
ha
erid
ium
try
ch
eriu
mA
ch
om
osp
ha
era
ne
ptu
ni
Lo
we
r A
lbia
nU
pp
er
Ba
rre
mia
nM
idd
le A
lbia
nLo
wer
Bed
oulie
n
Ro
dis
io
Fm
.
Ga
lé F
m.
Cre
sm
ina
Fm
.
Sta
ge
Fo
rma
tio
n
Ag
ua
Do
ce
Mb
.P
onta
Alta
Co
bre
Mb
.P
dLM
em
be
r
Sa
mp
le
Me
ter
60
40
20
0
80
100
120
140
160
180
L-97
L-91L-88
L-69
L-66
L-60
L-55
L-52
L-48L-43
L-40
L-37L-31
L-19L-16L-13
L-5
L-1
K-3.1
K-2.1
E-1sE-6E-3E-1fE-1c
D-62
D-13
D-7
L-25
200
(A)
Chapter 5 98
5.2. Luz section
Choffatella decipiens Marls and Palorbitolina Beds
The stratigraphic position of the Choffatella decipiens Marls is defined by the LO of
Callaiosphaeridium trycherium (at 10.6 m) as well as by the LOs of Rhynchodiniopsis
aptiana and Ctenidodinium elegantulum at (17.5 m).
A similar age-diagnostic dinoflagellate cyst assemblage has been observed in the Praia da
Lagoa Member (see above), indicating an Early Bedoulian or older age for the Choffatella
decipiens Marls. The overlying Palorbitolina Beds contain no appropriate lithologies for
palynological analysis.
Luz Marls
The biostratigraphic interpretation of the Luz Marls is based on the FO of Tehamadinium
tenuiceras (at 129.8 m; Pl. VII; 8) and on the LOs of Pseudoceratium securigerum (at 83.4 m)
and Muderongia staurota (at 148.2 m).
The FO of T. tenuiceras represents an important event in most biostratigraphic zonations.
According to Leereveld (1995), it is slightly diachronous and appears during the Late
Bedoulian in the Boreal realm (D. deshayesi ammonite zone). This is consistent with the
reported FO of T. tenuiceras (reported as Occisucysta tenuiceras) at the top of the D.
deshayesi ammonite zone in the scheme of Lister and Batten (1988). In addition, T. tenuiceras
has been documented from the Gargasian of south-western Morocco by Below (1981).
Masure et al. (1998) propose a tenuiceras dinoflagellate biozone for SE France, which is
defined by the FO of T. tenuiceras marking the Bedoulian-Late Aptian boundary. In the
biostratigraphic zonation schemes of Monteil and Foucher (1998) and of Costa and Davey
(1992) the LO of M. staurota is placed within the Late Bedoulian at the boundary between the
D. deshayesi and T. bowerbanki ammonite zones. Following Masure et al. (1998), we use the
FO of T. tenuiceras as a marker for the Bedoulian-Late Aptian boundary. A Bedoulian age for
large parts of the Luz Marls is supported by the LOs of M. staurota and P. securigerum.
Porto de Mós Formation
The stratigraphic position of the Porto de Mós Formation is determined by the FO of
Dinopterygium cladoides (at 183.9 m) and its consistent occurrence in the upper part of the
succession (from 240 m onwards), indicating an Early Albian or younger age.
Chapter 5 99
60
40
20
0
80
100
120
140
160
180
200
220
240
260
Mete
r
+
+
Cle
isto
sphaeridiu
m s
pp.
+
+
+
+
+
+
Cyclo
nephelium
vannophoru
m
+
+
+
+
+
+
Hystr
ich
osp
ha
erid
ium
arb
orisp
inu
m
+
+
++
Pte
rod
iniu
m s
pp.
+
+
Oligosphaeridiu
m s
pp.
+
+
+
+
+
+
+
+
+
Pro
toe
llip
so
din
ium
co
rollu
m
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
++
+
Co
me
tod
iniu
m s
pp.
+
+
+
+
Ce
rbia
ta
bu
lata
+
Din
go
din
ium
alb
ert
ii
+ +
Flo
ren
tin
a d
ea
ne
i
+
+
+
+
+
Hystr
ich
osp
ha
erin
a s
ch
ind
ew
olfii
+ +
Pa
lae
op
erid
iniu
m c
reta
ce
um
+
+
+
+
+
+
+
+
+
+
Spin
iferite
s s
pp.
+
+
+
+
+
+
+
+
+
Trich
od
iniu
m s
pp.
+
+
+
Subtilisphaera
spp.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
Su
btilisp
ha
era
pe
rlu
cid
a
+
+
Rh
yn
ch
od
inio
psis
ap
tia
na
+
+
+
+
Pseudocera
tium
securigeru
m
+
+
Oligosphaeridiu
m c
om
ple
x
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Kio
ka
nsiu
m p
oly
pe
s+
+
+
+
+
+
+
+
+
+
Hystr
ich
od
iniu
m p
ulc
hru
m
+
+
+
Cte
nid
od
iniu
m e
leg
an
tulu
m
+
+
Circu
lod
iniu
m b
revis
pin
osu
m+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
Ce
pa
din
ium
ve
ntr
iosa
+
+
++
+
+
+
+
+
+
+
+
+
+
++
Ca
lla
iosp
ha
erid
ium
try
ch
eriu
m
++
Callaio
sphaeridiu
m s
pp.
+
+
+
+
+
+
+
Ca
lla
iosp
ha
erid
ium
asym
me
tric
um
+
+
+
Batiacasphaera
spp.
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
Achom
osphaera
spp.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Hystr
ichosphaeridiu
m s
pp.
+
Co
ron
ife
ra s
pp.
+
Dis
silio
din
ium
spp.
+
Apte
a p
oly
morp
ha
+A
pte
od
iniu
m s
pp.
+
Hete
rosphaeridiu
m s
pp.
+
Olig
osp
ha
erid
ium
aste
rig
eru
m
+
Ce
pa
din
ium
spp.
+
Ovo
idin
ium
spp.
+
Mudero
ngia
sta
uro
ta
+
+
+
Te
ha
ma
din
ium
te
nu
ice
ras
+
+
Odonto
chitin
a o
perc
ula
ta
+
+
Co
ron
ife
ra o
ce
an
ica
+
Exig
uis
phaera
spp.
+
Syste
mato
phora
spp.
+
Su
btilisp
ha
era
pirn
ae
nsis
+
++
Ca
nn
ing
ia s
pp.
+
+
+
Od
on
toch
itin
a s
pp.
+
+
+
+
Chla
mydophore
lla s
pp.
+
+
+
+
+
Od
on
toch
itin
a a
nca
la
Din
go
din
ium
spp.
+
+
Mic
rod
iniu
m s
pp.
+
+
+
+
Cyclo
ne
ph
eliu
m p
au
cim
arg
ina
tum
+
+
+
Su
btilisp
ha
era
se
ne
ga
len
sis
+
+
+
+
+
+
+
Va
lva
eo
din
ium
spp.
+
+
+
+
+
+
+
++
+
+
+
+
Te
ha
ma
din
ium
spp.
+
+
+
+
+
+
+
Crib
rop
erid
iniu
m s
pp.
+
+
+
+
+
+
+
+
Kaly
pte
a s
pp.
+
+
+
+
+
Kle
ithriasphaeridiu
m s
pp.
+
+
+
Crib
rop
erid
iniu
m e
dw
ard
sii
+
Cyclo
ne
ph
eliu
m p
au
cis
pin
um
+
+
++
+
+
Chytr
oeis
phaeridia
spp.
+
Mu
de
ron
gia
spp.
+
Trich
od
iniu
m c
asta
ne
a
+
Oligosphaeridiu
m totu
m
+
+
+
+
+
Exochosphaeridiu
m s
pp.
+
+
Ge
ise
lod
iniu
m s
pp.
+
++
+
+
+
+
Olig
osp
ha
erid
ium
pu
lch
err
imu
m
+
+
+
+
+
Ellip
so
idic
tyu
m s
pp.
+
Ch
ich
ao
ua
din
ium
spp.
+
+
+
+
Mudero
ngia
pariata
+
Subtilisphaera
cheit
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
Circu
lod
iniu
m s
pp.
+
+
+
+
Din
opte
rygiu
m c
ladoid
es
Low
er
Bedoulia
nU
pp
er
Be
do
ulia
n U
pp
er A
ptia
n L
ow
er A
lbia
n
Port
o d
e M
os F
m.
Up
pe
r L
uz M
arls
Lo
we
r L
uz M
arls
Pal
orbi
tolin
aB
eds
Sta
ge
Form
ation
C. d
ecip
iens
Mar
ls
A-201
A-196
A-194A-193
A-188
A-179
A-176
A-172
A-169
A-162
A-154
A-148
A-137A-134
A-121
A-115
A-112
A-108A-106
A-101
A-94
A-79
A-59
A-46A-41
A-33
B-13
B-8
A-125
A-114
A-110
A-97
A-81
A-37
Sa
mp
le(B)
Fig. 5: Stratigraphical distribution of dinoflagellate cysts in the Luz section. For explanations see Fig.
4.
Chapter 5 100
6. Discussion of the biostratigraphic results
6.1. Cresmina section
The mid-Cretaceous deposits of the Lusitanian Basin have been studied in detail from a bio-
and sequence-stratigraphic perspective by Rey (1972; 1992), Rey et al. (1977), Berthou and
Schroeder (1979) and Dinis et al. (2002). Palynostratigraphic studies have been carried out by
Hasenboehler (1981), Berthou et al. (1980) and Berthou and Leereveld (1990).
Our results, presented in this study provide not only a refinement of the biostratigraphic
framework (Fig. 6). Distinct changes in the age of individual lithological members will lead to
a better understanding of the temporal evolution of the depositional history.
(1) The well-constrained Late Barremian age of the Cobre Member corroborates the
biostratigraphic results of Rey (1992), who attributed an latest Barremian to Bedoulian age to
this interval. Berthou and Leereveld (1990) interpreted the occurring dinoflagellate cyst
assemblage (including Pseudoceratium pelliferum) to represent a Bedoulian age and
commented on the lack of evidence for Upper Barremian strata in the Western Portuguese
Basin. However, in most recent biostratigraphic zonation schemes, the consistent occurrence
of P. pelliferum is regarded as a marker for Barremian or older strata, thus supporting a Late
Barremian age for the Cobre Member.
(2) Based on the occurrence of Pachytraga paradoxa, Praecaprina varians and Caprina
douvillei, the Bedoulian age reported by Rey (1992) for the rudist-bearing limestones of the
Ponta Alta Member can be confined to Early Bedoulian.
(3) Based on the occurrence of several age-diagnostic dinoflagellate cysts, an Early Bedoulian
age for the Praia da Lagoa Member is well-constrained, refining a previously reported
Bedoulian to early Late Aptian age (Berthou and Leereveld, 1990; Rey, 1992).
(4) Up till now, the stratigraphic position of the Rodízio Formation was loosely defined and
an age range between early Late Aptian and Middle Albian has been inferred from
palynological evidence (Dinis and Trincão, 1995; Hasenboehler, 1981). Based on the
occurrence of Dinopterygium cladoides, an Early Albian or younger age can now be assigned
to the top of the Rodízio Formation. The assemblages from the lower part of this formation do
not contain age-diagnostic dinoflagellate cysts. However, the spore-pollen assemblages from
the uppermost and the lower part of this formation show very similar compositions, indicating
an Early Albian age for the entire Rodízio Formation. Consequently , the presence of a major
Chapter 5 101
hiatus can be located between the marine marls of the Praia da Lagoa Member and the coarse
siliciclastics deposits of the Rodízio Formation. This sedimentary gap encompasses at least
the Late Bedoulian and entire Late Aptian and corresponds to the so-called “Lower Aptian
unconformity” of Dinis and Trincao (1995). The existence of a major hiatus between the two
formations has already been suggested by Berthou and Leereveld (1990).
(5) Some stratigraphic discrepancies exist with regard to the Agua Doce Member.
Palynological evidence, including the consistent occurrence of Dinopterygium cladoides
indicates an Early Albian or younger age for the lower part of this member. Furthermore,
Berthou and Leereveld (1990) reported the occurrence of Ovoidinium diversum, O. rhakodes
and O. tuberculata from the upper part, which corresponds to a Middle Albian age. These
results contradict the orbitolinid-derived biostratigraphy of Rey et al. (1977) and Berthou and
Schroeder (1979), who attributed a Late Albian age to the upper part of the Agua Doce
Member. Generally, Late Albian dinoflagellate assemblages include several distinct marker
species. The absence of these markers in both palynological studies strongly suggests a
Middle Albian age.
Fig. 6: Comparison of the different biostratigraphic assignments for the lithostratigraphic units of the
Cresmina section (Lusitanian Basin). Grey bars represent stratigraphic rangees of individual units,
cross hatch indicates hiatuses, sinuous line indicates major unconformities. Uncertain stratigraphic
ranges at are marked with a question mark.
Stage Rey (1992) Berthou and
Leereveld (1990)
This study
Lower
Bedoulian
Upper
BedoulianLower
Aptian
Upper Barremian
Upper Aptian
Lower Albian
Middle Albian
Upper Albian
?
Co
bre
Mb
.
Po
nta
Alta
Mb
.
Pra
ia d
a L
ag
oa
Mb
.
Ro
diz
io F
m.
Ag
ua
Do
ce
Mb
.
Co
bre
Mb
.
Po
nta
Alta
Mb
.
Pra
ia d
a L
ag
oa
Mb
.
Ag
ua
Do
ce
Mb
.
Co
bre
Mb
.
Po
nta
Alta
Mb
.
Pra
ia d
a L
ag
oa
Mb
.
Ro
diz
io F
m.
Ag
ua
Do
ce
?
?
Chapter 5 102
6.2. Luz section
In comparison to the Lusitanian Basin, the biostratigraphic assignment of the mid-Cretaceous
deposits of the Algarve Basin is less precise. This is mainly a consequence of the proximal
position and the resulting restricted conditions of the depositional environment. For this
reason, the stratigraphy of the Luz Marls and the Porto de Mós Formations has been mainly
based on orbitolinids, calcareous algae and ostracods (Damotte et al., 1988; Ramalho and
Rey, 1981; Rey, 1983; Rey, 1986). Additional stratigraphic information is provided by the
palynological study of Berthou and Leereveld (1990) and the chemostratigraphic results of
Heimhofer et al. (2003). Fig. 7 provides an overview of the refined stratigraphic framework in
comparison to earlier studies.
(1) The LOs of several age-diagnostic dinoflagellate cysts within the Choffatella decipiens
Marls indicate an Early Bedoulian age. In contrast, a Barremian age has been reported by Rey
(1983; 1986) for this unit based on the occurrence of calcareous algae and orbitolinid
assemblages. The overlying Palorbitolina beds have been dated as Bedoulian by the same
author.
(2) The Luz Marls Formation is Late Bedoulian to Late Aptian in age. The FO of
Tehamadinium tenuiceras, indicating the Late Bedoulian to Early Aptian boundary
corresponds well with the carbon-isotope data (Heimhofer et al., 2003). These results are in
general agreement with the Bedoulian to Gargasian biostratigraphic assignment of Rey (1983;
1986) and Damotte et al. (1988) as well as with the undifferentiated Aptian age reported by
Berthou and Leereveld (1990).
(3) Although the Porto de Mós Formation comprises a relatively diverse dinoflagellate
assemblage, only one age-diagnostic marker has been identified. An Early Albian age is based
on the common occurrence of Dinopterygium cladoides throughout the Porto de Mós
Formation. Negative evidence for Middle Albian is provided by the lack of Middle Albian
dinoflagellate cyst markers. The position of the Aptian-Albian transition is marked by a
characteristic negative shift in the δ13C record (Herrle et al., 2004).
These results are in contrast with earlier age interpretations of the Porto de Mós Formation.
Based on microfossil assemblages including calcareous algae, benthic foraminifera and
ostracods, Rey (1983; 1986) and Damotte et al. (1988) proposed a Gargasian to Clansayesian
age. However, the combined evidence from the dinoflagellate cyst biostratigraphy presented
Chapter 5 103
here and the independent carbon-isotope record (Heimhofer et al., 2003) support an Early
Albian age.
Fig. 7: Comparison of the different biostratigraphic assignments for the lithostratigraphic units within
the Luz section (Algarve Basin). For explanations see Fig. 6.
7. Palynological results of the studied sections
54 samples of both successions are analysed quantitatively with regard to the occurring spores
and pollen. Gymnosperm pollen and pteridophyte spores were determined on the genera level
and several forms were treated as groups (e.g. Classopollis group, bisaccate group). Special
attention was paid to the occurring angiosperm pollen assemblages, which were analysed with
regard to composition, relative abundance and diversity. The recorded angiosperm taxa and
their distinctive morphologic features are listed in Table. 1. The two studied successions
comprise a total of 60 different angiosperm pollen types within the Upper Barremian to
Middle Albian interval. The most important group (incl. 51 taxa) is represented by
monoaperturate grains of probably magnoliid and monocotyledonous affinity. Presumed
eudicotyledons are represented by 9 tri- and one stephanocolpate taxa. The angiosperm
palynoflora is dominated by columellate-tectate and reticulate-semitectate forms with
ornamented or smooth muri. The occurrence of a striate, verrucate or crotonoid pattern is
restricted to few taxa. Due to their ambiguous systematic position, pollen of the Afropollis
group are not included in the angiosperm assemblage.
Stage Rey (1986) Berthou and
Leereveld (1990)
This study
Lower
Bedoulian
Upper
BedoulianLower
Aptian
Upper Barremian
Upper Aptian
Lower Albian
Middle Albian
C. depie
ns M
arls
Pa
lorb
iolin
a B
ed
s
Luz M
arls F
m.
Po
rto
de
Mo
s F
m.
C. depie
ns M
arls
Pa
lorb
iolin
a B
ed
s
Luz M
alrs F
m.
Port
o d
e M
os F
m.
? ?
Luz M
alrs F
m. &
Po
rto
de
Mo
s F
m.
?
Chapter 5 104
7.1. Cresmina section
In the sediments of the Cresmina section, 16 different types of gymnosperm pollen, 25 types
of spores and a total of 48 angiosperm pollen taxa have been differentiated. Based on
quantitative distribution of the major pollen groups four different local pollen zones (LPZ) are
distinguished (Fig. 8).
The lowermost Upper Baremian to Lower Bedoulian LPZ I (0 m to 68.5 m) is characterised
by high abundances of Classopollis spp. (up to 65 %) and bisaccate pollen grains (up to 45
%). The uppermost part this zone (63 m to 68.5 m, Praia da Lagoa Member,) displays a
significant increase in Inaperturopollenites spp and Perinopollenites spp. (up to 20 %). Other
gymnosperm pollen and trilete spores account for less than 10 %, respectively. Above the
major unconformity (MU), LPZ II (78.5 m to 104.5 m) comprises Lower Albian strata. The
palynoflora of LPZ II is characterised by an increase in Classopollis spp. (from < 5 % up to
~50 %), high abundance of Inaperturopollenites spp. (~30 %) and a decline in
Perinopollenites spp. (from ~25 % to less than 10 %). Other gymnosperm pollen (incl.
bisaccate pollen, Araucariacites spp., Exesipollenites spp.) occur in low number whereas
trilete spores account for 10 % to 20 %. LPZ III includes the Lower to Middle Albian interval
between 104.5 m and 145.5 m. A prominent peak in trilete spores up to ~55 % (incl.
Cicatricosisporites spp., Leptolepidites spp., Concavisporites spp. and Echinatisporites spp.)
represents the most remarkable feature within this interval. This increase is accompanied by a
strong decline in Classopollis spp., Inaperturopollenites spp. and Perinopollenites spp.
whereas bisaccate pollen remain essentially stable. In contrast, Araucariacites spp. and
Exesipollenites spp. display a slight increase and account for 5 % to 15 %, respectively. The
palynoflora of the Middle Albian LPZ IV (145.5 m to 191 m) is characterised by a rapid
increase of Exesipollenites spp. up to 45 % and the subsequent decline to less than 10 %
towards the top of the succession. This decline is accompanied by a significant increase in
Inaperturopollenites spp. as well as by an increase in trilete spores, which account for 10 % to
15 % in this part of the section. Perinopollenites spp. is virtually absent in this zone.
The distribution, relative abundance and diversity of angiosperm pollen taxa in the Cresmina
section are shown in Fig. 9. The Upper Barremian sediments (3 samples) comprise only two
types of angiosperm pollen grains, which are both attributed to the Clavatipollenites group. In
the Lower Bedoulian (3 samples) the assemblage is characterised by the appearance of several
additional forms of the Retimonocolpites, Asteropollis and Pennipollis groups. Almost all of
the taxa recorded in the Barremian to Lower Aptian interval are common throughout the
Chapter 5 105
upper part of the section. In the Lower Albian (11 samples), above the major unconformity
(MU), the observed angiosperm palynoflora is significantly enriched and additional
monoaperturate pollen genera can be distinguished, including Dichastopollenites,
Stellatopollis and Racemonocolpites. In addition, various forms of the Retimonocolpites,
Clavatipollenites and Asteropollis group are identified. The first tricolpate angiosperm pollen
appear in the Lower Albian, including forms of the Tricolpites, Senectotetradites and
Striatopollis groups. The Middle Albian (9 samples) interval exhibits further diversification of
the angiosperm palynoflora. Numerous FOs of monocolpate pollen are observed within the
Retimonocolpites and Dichastopollenites groups whereas the association of tricolpates
remains essentially the same as in the Lower Albian.
Fig. 8: Biostratigraphic interpretation, lithology and quantitative distribution of spores and pollen
(Cresmina section). Grey bars mark palynologically barren intervals. Relative abundance of the
spores and pollen are expressed in percentages of the total sporomorph assemblage. Local Pollen
Zones (LPZ) are marked with dotted lines. MU, major unconformity.
Po
do
ca
rpid
ite
s s
pp
.
Eu
co
mm
iid
ite
s s
pp
.
Ve
rru
co
sis
po
rite
s s
pp
.C
on
ve
rru
co
sis
po
rite
s s
pp
.
Ha
mu
latisp
orite
s s
pp
.Is
ch
yo
sp
orite
s s
pp
.
Fo
ve
osp
orite
s s
pp
.C
ing
utr
ile
tes s
pp
.E
ch
ina
tisp
oris s
pp
.
Klu
kis
po
rite
s s
pp
.
Re
ticu
latisp
orite
s s
pp
.
Co
nca
vis
po
rite
s s
pp
.C
osta
top
erf
oro
sp
orite
s s
pp
.Im
pa
rde
cis
po
ra s
pp
.
Cic
atr
ico
sis
po
rite
s s
pp
.
Plica
tella
sp
p.
Ru
bin
ella
sp
p.
Trile
te s
po
res in
de
t.
Sta
ge
60
40
20
0
80
100
120
140
160
180
200
Mete
r
Lith
olo
gy
Gymnosperm pollen Trilete sporesAngiosperm
pollen
Ca
llia
lasp
orite
s s
pp
.
Vitre
isp
orite
s p
allid
us
Scia
do
pitysp
olle
nite
s s
pp
.E
ph
ed
rip
ite
s s
pp
.
De
lto
ido
sp
ora
sp
p.
Gle
ich
en
iid
ite
s s
pp
.L
ep
tole
pid
ite
s s
pp
.
Bire
tisp
orite
s s
pp
.C
on
ca
vis
sim
isp
orite
s s
pp
.
Bis
accate
Polle
n
Cla
sso
po
llis s
pp.
Ara
ucariacites s
pp.
% T
rile
te s
po
res
% A
ng
iosp
erm
s
Exe
sip
olle
nte
s s
pp.
Ina
pe
rtu
rop
oll.
spp.
Pe
rin
op
olle
nite
s s
pp.
% A
fro
po
llis s
pp.
0 100 %
barren interval
Sa
mp
le
LP
Z
I
II
III
IV
MU
L-97
L-91L-88
L-69
L-66
L-60
L-55
L-52
L-48
L-43
L-40
L-37
L-31
L-19L-16L-13
L-5
L-1
K-3.1
K-2.1
E-1sE-6E-3E-1fE-1c
D-62
D-13
D-7
L-25
Lo
we
r A
lbia
nU
pp
er
Ba
rre
mia
nM
iddle
Alb
ian
Lo
we
rB
ed
ou
lien
Ro
dis
io
Galé
Fm
.C
resm
ina F
m.
Chapter 5 106
The Barremian to Middle Albian deposits show distinct changes in angiosperm pollen relative
abundance and diversity. The prominent shift in both parameters corresponds to the major
hiatus. The Barremian interval is characterised by the sporadic occurrence of very few
angiosperm pollen grains (relative abundance < 2 %). In the Lower Bedoulian angiosperm
pollen content is still low (< 2 %) whereas diversity is slightly increased (up to 4 taxa per
sample).
Fig. 9: Distribution, diversity and within-palynofloral abundance of angiosperm pollen types plotted
against biostratigraphic interpretation and lithology (Cresmina section). Angiosperm diversity
represents the number of taxa per sample; relative abundance reflects the percentage of angiosperm
pollen within the total palynoflora. Note the abrupt increase in angiosperm pollen diversity and
within-pollen abundance above the major unconformity (MU). For explanations see Fig. 8.
MU
barren interval
monocots and magnoliidsLusitanianBasin
60
40
20
0
80
100
120
140
160
180
200
Lo
we
r A
lbia
nU
pp
er
Ba
rre
mia
nM
idd
le A
lbia
nL
ow
er
Bedoulie
n
Ro
dis
io
Galé
Fm
.C
resm
ina F
m.
Sta
ge
Mete
r
Form
ation
Lith
olo
gy
+
+
+
+
+
+
+
+
Cla
va
tip
olle
nite
s s
pp
.
+
+
+
+
Cla
va
tip
olle
nite
s c
f. h
ug
he
sii
+
+
+
+
Cla
va
tip
olle
nite
s c
f. m
inu
tus
+
+
Re
tim
on
oco
lpite
s s
p. 6
+
+
+
+
+
Aste
rop
ollis
cf. a
ste
roid
es
+
Pe
nn
ipo
llis
sp. 2
+
+
Re
tim
on
oco
lpite
s s
p. 4
+
+
Aste
rop
ollis
sp
. 2
+
+
+
Dic
ha
sto
po
lle
nite
s c
f. g
ha
za
late
nsis
+
+
Ste
lla
top
ollis
sp
p.
+
+
+
Aste
rop
ollis
sp
. 4
+
+
Dic
ha
sto
po
lle
nite
s s
p. 2
+
Re
tim
on
oco
lpite
s c
f. e
xce
lsu
s
+
Re
tim
on
oco
lpite
s c
f. s
p. 11
+
+
+
+
+
+
+
Re
tim
on
oco
lpite
s s
pp
.
Aste
rop
ollis
aste
roid
es
+
Aste
rop
ollis
sp
p.
+
+
Cla
va
tip
olle
nite
s c
f. s
p. A
+
+
+
+
+
Dic
ha
sto
po
lle
nite
s s
p. 1
Ra
ce
mo
no
co
lpite
s c
f. e
xo
ticu
s
+
+
+
Re
tim
on
oco
lpite
s s
p. 3
Re
tim
on
oco
lpite
s s
p. 8
Ste
lla
top
ollis
sp.1
Cla
va
tip
olle
nite
s c
f. t
en
ellis
+
Re
tim
on
oco
lpite
s s
p. 5
+
Dic
ha
sto
po
lle
nite
s d
un
ve
ga
ne
nsis
+
Ste
lla
top
ollis
ba
rgh
oo
rnii
+
Pe
nn
ipo
llis
sp
. 3
+
+
Re
tim
on
oco
lpite
s s
p. 2
+
+
+
Dic
ha
sto
po
lle
nite
s s
p. 4
Re
tim
on
oco
lpite
s s
p. 1
0
+
Re
tim
on
oco
lpite
s s
p. 1
2
+
Re
tim
on
oco
lpite
s s
p. 1
1
+
Cla
va
tip
olle
nite
s s
p. 3
Dic
ha
sto
po
lle
nite
s c
f. s
p. 5
Re
tim
on
oco
lpite
s s
p. 1
+
Re
tim
on
oco
lpite
s s
p. 1
3
+
+
Re
tim
on
oco
lpite
s s
p. 1
6
Dic
ha
sto
po
lle
nite
s s
p. 5
Re
tim
on
oco
lpite
s s
p. 7
+
+
+
+
+
Trico
lpite
s s
pp
.
+
Se
ne
cto
tetr
ad
ite
s s
pp
.
+
+
Str
iato
po
llis t
roch
ue
nsis
+
Ste
ph
an
oco
lpite
s a
ff. fr
ed
ericksb
urg
en
sis
+
Str
iato
po
llis s
pp
.
+
Re
titr
ico
lpite
s a
ff.
ve
rmim
uru
s
Sa
mp
le
eudicots
0 25%0 30
angiosperm
diversity
relative
abundance
Dic
ha
sto
po
lle
nite
s s
p. 6
+
+
+
+
+
+
Dic
ha
sto
po
lle
nite
s s
pp
.
L-97
L-91L-88
L-69
L-66
L-60
L-55
L-52
L-48
L-43
L-40
L-37
L-31
L-19L-16L-13
L-5
L-1
K-3.1
K-2.1
E-1sE-6E-3E-1fE-1c
D-62
D-13
D-7
L-25
LP
Z
I
II
III
IV
Chapter 5 107
In the Lower Albian strata above the hiatus, angiosperm pollen represent a common element
of the palynoflora and account for 5 % to 8 % of the entire pollen assemblage. At the same
time, pollen diversity reaches up to 16 taxa per sample. This increasing trend continues into
the Middle Albian part of the section, where peak diversity (up to 18 taxa per sample) and
highest relative abundance (up to 12 %) are observed.
7.2. Luz section
20 different types of gymnosperm pollen, 39 different types of spores and a total of 55
different angiosperm pollen taxa have been distinguished in the Luz section (Fig. 10).
The Classopollis group accounts for 40 % to 85 % (mean of ~70 %) of the palynoflora
throughout the section. Despite some fluctuations, a general increase in the relative abundance
of the Classopollis group from ~60 % in the Bedoulian to ~75 % in the Upper Aptian to
Lower Albian part can be recognized. This general pattern is interrupted by the virtual
absence of Classopollis spp in a single sample at 96.5 m. In contrast, bisaccate pollen (incl.
Podocarpidites spp.) display a declining trend from up to ~20 % in the lower part to < 10 %
in the upper part of the Luz section. The relative abundance of Araucariacites spp. (up to ~25
%) fluctuates in the opposite direction to the frequency pattern of the Classopollis group.
Other gymnosperm pollen (e.g. Exesipollenites spp., Ephedripites spp., Inaperturopollenites
spp.) occur rarely and account together for < 5 %. Similarly, pollen of the Afropollis spp.
group are sporadically observed. Trilete spores represent a subordinate element of the
palynoflora and account for < 10 % on average. Two peaks in relative spore abundance (at
96.5 m and 184 m) reflect increased abundances of Cicatricosisporites spp. and
Concavisporites spp., respectively.
Relative abundance and diversity of the angiosperm pollen are shown in Fig. 11. In the Lower
Bedoulian (2 samples) the assemblage is characterised by several monocolpate types of the
Clavatipollenites, Retimonocolpites and Asteropollis groups. In addition, taxa of Pennipollis
and Stellatopollis appear in the lowermost samples. These pollen types are relatively common
and occur throughout the entire record. The Upper Bedoulian (5 samples) comprises several
additional forms of the above mentioned groups. In the Upper Aptian (9 samples), the
angiosperm palynoflora shows further diversification which is displayed in the FOs of several
forms of the Clavatipollenites, Retimonocolpites, Pennipollis, Stellatopollis and
Racemonocolpites groups.
Chapter 5 108
Fig. 10: Biostratigraphic interpretation, lithology and quantitative distribution of spores and pollen
(Luz section). For explanations see Fig. 8.
The Lower Albian (12 samples) is characterised by several new forms of the
Dichastopollenites group and other monocolpates. The appearance of tricolpate pollen in the
Lower Albian strata marks an important event in the composition of the angiosperm
palynoflora. Tricolpate forms are predominantly represented by the Tricolpites and the
Senectotetradites groups, whereas Rousea spp. and Phimopollenites spp. occur only
sporadically.
Both, the relative abundance and the diversity of angiosperm pollen display a distinct increase
throughout the Luz section. During the Aptian, angiosperm pollen represent a minor
constituent of the palynoflora and account for less than 2 % in most Bedoulian samples and
Bis
acca
te P
olle
nV
itre
isporite
s p
allid
us
Podocarp
idites s
pp.
Cla
sso
po
llis s
pp
.
Ara
uca
ria
cite
s s
pp
.
Exe
sip
olle
nite
s s
pp.
Ina
pe
rtu
rop
olle
nite
s s
pp.
Pe
rin
op
olle
nite
s s
pp.
% T
rile
te s
po
res
Cla
vatisporite
s s
pp.
Cry
be
losp
orite
s p
an
nu
ce
us
Ham
ula
tisporite
s s
pp.
Ne
ora
istr
ickia
spp.
Costa
toperf
oro
sporite
s s
pp.
Nodosis
porite
s s
pp.
Densois
porite
s s
pp.
Impard
ecis
pora
spp.
Sta
plin
isp
orite
s c
am
inu
s
Gle
ich
en
iid
ite
s s
pp.
Retitr
ilete
s s
pp.
Verr
ucosis
porite
s s
pp.
Cic
atr
icosis
porite
s s
pp.
Cin
gu
trile
tes s
pp.
Co
nca
vis
po
rite
s s
pp.
Converr
ucosis
porite
s s
pp.
Deltoid
ospora
spp.
Echin
atisporis s
pp.
Foveosporite
s s
pp.
Lepto
lepid
ites s
pp.
Plicate
lla s
pp.
Trile
te s
pore
s indet.
Klu
kis
porite
s s
pp.
% A
ng
iosp
erm
s
Gymnosperm pollen Trilete sporesAngiospermpollen
Low
er B
ed.
Up
pe
r B
ed
ou
lian
Up
pe
r A
ptia
n L
ow
er A
lbia
nS
tage
60
40
20
0
80
100
120
140
160
180
200
220
240
260
Mete
r
Sam
ple
barren interval
0 100 %
Lith
olo
gy
A-201
A-196
A-194A-193A-188
A-179
A-176
A-172A-169
A-162
A-154
A-148
A-137A-134
A-121
A-115
A-112
A-108A-106
A-101
A-94
A-79
A-59
A-46A-41
A-33
B-13
B-8
A-125
A-114
A-110
A-97
A-81
A-37
Chapter 5 109
for < 4 % in the Upper Aptian samples. Similarly, their diversity is low in the Bedoulian (< 5
taxa in most samples) and increases throughout the Upper Aptian (5 to 10 taxa per sample).
From the Upper Aptian to Lower Albian transition onwards, angiosperm pollen represent a
consistent and important element (between 5 to 10 %). Their diversity displays a similar
trend, reaching 10 to 15 (max. 18) taxa per sample in the Lower Albian part of the succession.
Fig. 11: Distribution, diversity and within-palynofloral abundance of angiosperm pollen types plotted
against biostratigraphy and lithology (Luz section). For explanations see Fig. 8 and 9.
Aste
rop
ollis
cf.
aste
roid
es
Cla
va
tip
olle
nite
s c
f. h
ug
he
sii
Cla
va
tip
olle
nite
s a
ff. h
ug
he
sii
Cla
va
tip
olle
nite
s s
pp
.
Pe
nn
ipo
llis
sp
. 2
Re
tim
on
oco
lpite
s s
p.
4
Re
tim
on
oco
lpite
s s
pp
.
Ste
lla
top
ollis
sp
p.
Re
tim
on
oco
lpite
s a
ff. sp
. 3
Re
tim
on
oco
lpite
s s
p. 9
Cla
va
tip
olle
nite
s c
f. m
inu
tus
Pe
nn
ipo
llis
aff
. sp
. 3
Re
tim
on
oco
lpite
s s
p. 2
Re
tim
on
oco
lpite
s s
p.
8
Re
tim
on
oco
lpite
s s
p. 1
0
Tu
ca
no
po
llis
cf.
criso
po
len
sis
Aste
rop
ollis
aste
roid
es
Cla
va
tip
olle
nite
s s
p. 1
Ste
lla
top
ollis
ba
rgh
oo
rnii
Aste
rop
ollis
sp
. 1
Cla
va
tip
olle
nite
s c
f. s
p. A
Pe
nn
ipo
llis
sp
. 1
Pe
nn
ipo
llis
sp
. 4
Cla
va
tip
olle
nite
s c
f. te
ne
llis
Dic
ha
sto
po
lle
nite
s s
p. 1
An
gio
sp
erm
e in
c. se
d. 3
Ra
ce
mo
no
co
lpite
s c
f. e
xo
ticu
s
Ste
lla
top
ollis
cf. s
p. 1
Aste
rop
ollis
sp
. 4
Re
tim
on
oco
lpite
s s
p. 6
Aste
rop
ollis
sp
p.
Re
tim
on
oco
lpite
s s
p. 3
Dic
ha
sto
po
lle
nite
s s
pp
.
Re
tim
on
oco
lpite
s s
p. 7
Ste
lla
top
ollis
sp
. 1
An
gio
sp
erm
e in
c. se
d. 1
An
gio
sp
erm
e in
c. se
d. 2
Cla
va
tip
olle
nite
s s
p. 2
Dic
ha
sto
po
lle
nite
s c
f. g
ha
za
late
nsis
+
+ + + +
Dic
ha
sto
po
lle
nite
s c
f. s
p. 1
+ ++ + +
Cla
va
tip
olle
nite
s s
p. 3
+ +
Re
tim
on
oco
lpite
s s
p. 1
6
+ + + + + + + +
+ + +
+ + + + +
+ + + +
+ + +
+ + + + + + +
+ + + + +
+ + + +
+ + + + + +
+ +
+ + + + + +
+ + + + +
+ + + + + +
+ + + ++ + + + + + +
+ +
+ + + + + + + + +
+
+ +
Aff
. S
en
ecto
tetr
ad
ite
s s
pp
.
Re
tim
on
oco
lpite
s a
ff. sp
. 6
+
Aste
rop
ollis
sp
. 3
Re
tim
on
oco
lpite
s s
p. 1
Dic
ha
sto
po
lle
nite
s a
ff. sp
. 4
Re
tim
on
oco
lpite
s s
p. 1
5
Pe
nn
ipo
llis
sp
. 3
Re
tim
on
oco
lpite
s s
p. 1
3
Ph
imo
po
lle
nite
s s
p.
S
en
ecto
tetr
ad
ite
s s
pp
.
+
+
+
Ro
use
a s
pp
.
Trico
lpite
s s
pp
.
+
+
+
Trico
lpite
s v
ulg
aris
+
+
60
40
20
0
80
100
120
140
160
180
200
220
240
260
Lo
we
r B
ed
ou
lian
Up
pe
r B
ed
ou
lian
Up
pe
r A
ptia
n L
ow
er A
lbia
n
Po
rto
de
Mo
s F
m.
Up
pe
r L
uz M
arls
Lo
we
r L
uz M
arls
Pa
lorb
ito
lina
Be
ds
Algarve
Basin
Sta
ge
Me
ter
Fo
rma
tio
n
Lith
olo
gy
monocots and magnoliids eudicots
0 25%0 30
angiosperm
diversity
relative
abundance
Sa
mp
le
barren interval
A-201
A-196
A-194A-193
A-188
A-179
A-176
A-172
A-169
A-162
A-154
A-148
A-137A-134
A-121
A-115
A-112
A-108A-106
A-101
A-94
A-79
A-59
A-46A-41
A-33
B-13
B-8
A-125
A-114
A-110
A-97
A-81
A-37
Chapter 5 110
8. Discussion of the palynological results
8.1. A continuous pollen record of early angiosperm diversification from Portugal
Despite strong differences with respect to depositional setting, tectonic history and overall
vegetation patterns, the Cresmina and Luz sections display two closely comparable records of
dispersed angiosperm pollen. It is not only the composition of the assemblage, but also the
relative abundance and diversity of angiosperm pollen which reflects similar patterns. The
occurrence of similar palynofloras at two different localities provides strong evidence, that the
observed increase in relative abundance and diversity primarily reflects the incipient
dispersion of angiosperm plants in the hinterland of the studied coastal settings. The observed
changes in the angiosperm community appear to be less affected by physical environmental
factors, including changes in sea level and depositional environment.
Combination of the palynological findings from the two studied successions results in a
composite record, which covers the Late Barremian to Middle Albian time interval. The here
proposed bio- and chemostratigraphic framework allows to trace the successive changes of
the angiosperm pollen association through time. Our results are comparable with existing
palynological studies of dispersed angiosperm pollen from geographically widespread
locations ranging from Barremian to Cenomanian in age (Fig. 3). These sites from
palaeolatitudes between ~10°S and ~60°N are mostly situated along the margins of the Tethys
Ocean and the evolving North Atlantic and include palynofloras from N-America (Singh,
1971; Singh, 1983; Srivastava, 1977), the North Atlantic basin (Hochuli and Kelts, 1980),
northern and western Africa (Doyle et al., 1977; Ibrahim, 1996; Penny, 1986; Schrank and
Mahmoud, 2002), Middle East (Brenner, 1996) as well as south and north-western Europe
(Friis et al., 1994; Friis et al., 1999; Friis et al., 2000a; Groot and Groot, 1962; Hughes et al.,
1979; Hughes and McDougall, 1990; Laing, 1975). Our results from Portugal are compared in
detail with published material from the Potomac Group, which represents the oldest exposed
Cretaceous unit of the Atlantic coastal plain of the United States. Both palynofloras originate
from the southern part of the Southern Laurasian floral province and have been deposited in
coastal to continental settings along the margins of the North Atlantic Basin. A first
comprehensive description of the Potomac palynology including a pollen-based zonation has
been established by Brenner (1963). Subsequent studies of the palynological and macrofossil
content of the Potomac Group resulted in additional angiosperm pollen records and further
Chapter 5 111
refinement of the pollen-based biostratigraphy (Doyle, 1992; Doyle and Hickey, 1976; Doyle
and Robbins, 1977).
When possible, the observed pollen grains were assigned to published and described forms.
However, many of the presented taxa from the Portuguese successions can not be assigned to
any previously reported pollen grains, resulting in a large number of informal species. This
seems to be caused by the improved resolution of present-day LM as well as by the
fragmentary documentation and partly imprecise description of earlier records. Furthermore,
detailed correlation with previously published pollen floras is hampered by the lack of
independent stratigraphic control for many records. Due to the absence of adequate marker
fossils the age of the pollen-bearing, predominantly continental deposits was based on the
occurring palynofloral assemblage (incl. angiosperm pollen) and therefore has to be
considered carefully.
- Barremian
The Late Barremian angiosperm pollen assemblage of the Portuguese record is restricted to
the occurrence of two monocolpate forms including Clavatipollenites spp. and
Clavatipollenites cf. hughesii (Pl. I; 1-2). Small, columellate-tectate pollen grains of the
Clavatipollenites group represent a common constituent in early angiosperm assemblages and
have been reported by various authors from pre-Aptian sediments around the world (e.g.
Doyle et al., 1977; Hughes et al., 1979; Schrank and Mahmoud, 2002). According to Brenner
(1996) Clavatipollenites-type pollen occur in sediments from Israel, dated as old as Late
Hauterivian. In accordance to our results, Clavatipollenites hughesii and C. cf. hughesii
constitute early elements in angiosperm pollen records from the Western North Atlantic
(Hochuli and Kelts, 1980) as well as in deposits from the North American Potomac Group
(Brenner, 1963; Doyle and Robbins, 1977). Based on comparison with extant forms and in
situ palynological records, a strong affinity of the early Clavatipollenites pollen types to
pollen of the extant Chloranthaceae family has been inferred (Pedersen et al., 1991).
- Aptian
The Early Bedoulian of the Portuguese successions is characterised by a significant increase
in angiosperm pollen diversity, including the FOs of the monocolpate taxa Pennipollis sp. 2
(Pl. IV; 12-13), Clavatipollenites cf. minutus (Pl. I; 3-4) Asteropollis cf. asteroides (Pl. III;
Chapter 5 112
13-14), Stellatopollis spp. as well as several forms of the Retimonocolpites group including
Retimonocolpites sp. 4 (Pl. II; 3-4), R. aff. sp. 3 and R. sp. 6 (Pl. IV; 1). The genera
Pennipollis of Friis Pedersen & Crane (2000a) corresponds to the former Peromonolites
(Brenner, 1963) and comprises reticulate-acolumellate pollen with pronounced supratectal
sculpture elements. This characteristic pollen type has been frequently reported from Early
Aptian palynofloral assemblages (e.g. Brenner, 1996; Doyle and Robbins, 1977; Hochuli and
Kelts, 1980; Hughes et al., 1979; Ibrahim, 1996). Doyle (1992) highlights the potential
importance of the acolumellate Pennipollis group as a stratigraphic marker for post-
Barremian strata. The observed taxa Pennipollis sp. 2 can be compared to Peromonolites
reticulatus (Brenner, 1963, Pl. 41, 3-4).
Based on in situ studies of Friis et al. (2000a) pollen of the Pennipollis-type display an
alismatalean affinity and probably represent early monocots. In accordance to the Portuguese
results, small, monocolpate pollen types resembling Clavatipollenites minutus have been
reported by Doyle and Robbins (1977) from the Lower to Middle Aptian (lower part of Zone
I) of the Potomac Group as well as by Doyle et al. (1977) from deposits from north-western
Gabon of probably Aptian age. The columellate-tectate forms Asteropollis asteroides and A.
cf. asteroides with a distinct tri- or tetrachotomocolpate aperture have previously been
reported from post-Aptian deposits (Doyle and Robbins, 1977; Laing, 1975; Singh, 1983;
Srivastava, 1977). In our record, Asteropollis cf. asteroides represents a relatively common
form in samples from the Lower Bedoulian to Middle Albian interval. This form shows strong
similarities to the microreticulate-tectate pollen form with branched sulcus, described by
Doyle and Robbins (1977, Pl. 1, Fig. 24, 25) from the Middle Aptian (upper part of Zone I) of
the Potomac Group. Based on analysis of in situ Asteropollis-type pollen and the associated
floral organs Friis et al. (1999) mention an affinity to the extant genus Hedyosmum of the
Chloranthaceae family. Another typical element of most early angiosperm assemblages are
the reticulate-semitectate forms of the Retimonocolpites group. Most of the observed forms
show distinct differences to previously published taxa.
Besides several long-ranging forms, the Late Bedoulian assemblages comprise several so far
not described reticulate-semitectate monocolpate pollen grains including the forms
Retimonocolpites sp. 2 (Pl. II; 5-6), R. sp. 8 (Pl. II; 9), R. sp. 9 (Pl. II; 12) and R. sp. 10 (Pl. II;
16-17). The observed Retimonocolpites-type forms are not directly comparable to existing
pollen records. Only Retimonocolpites sp. 8 is similar to the form Liliacidites textus of Singh
(1971, Pl. 29, Fig. 1-4), which has been reported from Lower Albian sediments of the Peace
Chapter 5 113
River area. A form comparable to Tucanopollis crisopolensis (T. aff. crisopolensis, Pl. VI; 3)
occurs only in this interval. Reported occurrences of Tucanopollis crisopolensis and T. cf.
crisopolensis are restricted to the Northern Gondwana floral province ranging in age from
Barremian to Early Aptian (Doyle et al., 1977; Regali, 1989; Schrank and Mahmoud, 2002).
A further increase in the diversification of angiosperms characterises the Late Aptian
angiosperm assemblage. Besides several additional monocolpate forms of the Asteropollis,
Pennipollis and Retimonocolpites groups, the FOs of crotonoid forms including Stellatopollis
barghoornii and Stellatopollis sp. 1 (Pl. VI; 12) as well as of Clavatipollis cf. tenellis (Pl. 1;
8-9) and Clavatipollis cf. sp. A sensu Doyle and Robbins (1977) (Pl. I; 5-6) are of particular
interest for comparison with published records. Representatives of the Stellatopollis group are
part of the earliest angiosperm pollen assemblages and have been documented from pre-
Aptian deposits in southern England (Hughes et al., 1979; Hughes and McDougall, 1990) and
Egypt (Penny, 1986; Schrank and Mahmoud, 2002). Stellatopollis barghoornii and cf. S.
barghoornii cover a relatively long stratigraphic interval from possible Barremian (Doyle et
al., 1977) to the Aptian (Ibrahim, 1996) to Early Albian (Doyle and Robbins, 1977). Reported
occurrences of Clavatipollenites tenellis and cf. Clavatipollenites tenellis from Upper Aptian
to Lower Albian sediments (Subzone II-A) of the North Atlantic (Hochuli and Kelts, 1980)
and the Potomac Group (Doyle and Robbins, 1977) correspond well with our findings. Singh
(1983) reported the occurrence of C. tenellis from the significantly younger deposits of the
Cenomanian Dunvegan Formation of western Canada. The coarsely columellate-tectate
Clavatipollenites sp. A sensu Doyle and Robbins (1977) represents one of the earliest pollen
types in the basal part of the Potomac Group, which is thought to be Early to Middle Aptian
age (Doyle, 1992; Doyle and Robbins, 1977).
- Albian
The Early Albian interval is characterized by further diversification of the monocolpates and
the first appearance of tricolpate pollen of presumed eudicotyledonous origin. A remarkable
event is the consistent occurrence of relatively large, coarsely reticulate-semitectate pollen
assigned to the Dichastopollenites group. Our record includes Dichastopollenites cf.
ghazalatensis (Pl. IV; 9), D. dunveganensis (Pl. IV; 8), D. sp. 1 (Pl. I; 1-2), D. sp. 2 (Pl. IV; 4-
5) and D. aff. sp. 4. Except for a single occurrence of Dichastopollenites sp. 1 in the Upper
Aptian of the Algarve Basin, pollen of this group are restricted to post-Aptian deposits. In
previous studies, pollen of the Dichastopollenites group have been reported from Cenomanian
Chapter 5 114
deposits of North Africa (Ibrahim, 1996; Schrank and Mahmoud, 2000) and North America
(May, 1975; Singh, 1983). The consistent occurrence of Dichastopollenites cf. ghazalatensis
in Albian deposits of both studied sections may reflect the influence of the nearby Northern
Gondwana floral province. According to May (1975), Dichastopollenites-type forms resemble
operculate pollen of the extant Nymphaeaceae. The discovery of various Dichastopollenites
types in the Portuguese Lower Albian deposits results in a significant extension of the
stratigraphic range of this group. Further diversification includes the Retimonocolpites,
Asteropollis and Clavatipollenites groups. Only few of these forms can be compared to
published records. The taxa Retimonocolpites sp. 7 (Pl. II; 10) shows similarities to
Retimonocolpites dividuus, which represents a common taxa in Late Aptian to Late Albian
assemblages (Brenner, 1963; Doyle and Robbins, 1977; Hochuli and Kelts, 1980; Singh,
1971).
In contrast to several published probably Barremian to Aptian assemblages (e.g. Doyle et al.,
1977; Doyle and Robbins, 1977; Hughes and McDougall, 1990; Ibrahim, 1996; Penny, 1986),
the occurrence of unequivocal tricolpate pollen morphologies is restricted to post-Aptian
sediments in the studied Portuguese successions. In our material various tricolpate forms
including Tricolpites vulgaris, Senectotetradites spp. (Pl. VI; 10-11) and Striatopollis
trochuensis (Pl. VI; 2) appear at or near the base of the Albian. Aff. Stephanocolpites
fredericksburgensis (Pl. VI; 9) is the earliest polyaperturate form (stephanocolpate) in the
studied succession. In accordance to our results, Doyle and Robbins (1977) reported
Stephanocolpites fredericksburgensis from the Lower Albian Zone II B of the Potomac
Group. The same species has been observed in deposits as young as Cenomanian by Singh
(1983). The occurrence of tetrads of tricolpate pollen grains such as aff. Ajatipollis sp. A is
documented from the Early Albian by Doyle and Robbins (1977). This form displays strong
similarities with Senectotetradites spp. of the Portuguese records as well as with
Senectotetradites amiantopollis described from the Albian by Srivastava (1977). Small,
striato-reticulate tricolpates of the Striatopollis group represent another regular constituent of
many post-Aptian angiosperm pollen assemblages and have been reported from widespread
locations (e.g. Doyle and Robbins, 1977; Groot and Groot, 1962; Hochuli and Kelts, 1980;
Laing, 1975; Singh, 1971; Srivastava, 1977). Occurrences of Striatopollis spp. of supposed
pre-Albian age are restricted to a few sites located in the Northern Gondwana floral province
(Doyle, 1992; Doyle et al., 1977). The species Striatopollis trochuensis has been documented
by Ibrahim (1996) from the Cenomanian of Egypt. In accordance to our findings from the
Chapter 5 115
Early Albian, Tricolpites vulgaris has been reported e.g. from Middle to Upper Albian
deposits of the southern United States (Srivastava, 1977) and western Canada (Singh, 1971).
The Middle Albian interval of the Portuguese record is characterised by increasing diversity
in the monocolpate Dichastopollenites group, reflected in the FOs of 4 additional taxa (incl.
Dichastopollenites sp. 4 (Pl. V; 5-6), D. sp. 5 (Pl. IV; 6-7), D. cf. sp. 5 and D. sp. 6 (Pl. V; 3-
4). These relatively large, coarsely reticulate-semitectate pollen types exhibit no clear
similarities to published forms and are reported here as informal species. Further
diversification is also observed in the Retimonocolpites group (FOs of Retimonocolpites sp.
11 (Pl. II; 13-14) and R. sp. 12 (Pl. III, 7-8). The only additional tricolpate form is represented
by a single grain of aff. Retitricolpites vermimurus. Small tricolpates with a vermiculate
reticulum have been originally described as Retitricolpites vermimurus by Brenner (1963)
from Aptian to Albian deposits of the Potomac Group. According to Doyle and Robbins
(1977) the same formation comprises aff. Retitricolpites vermimurus in the Late Aptian to
Early Albian Subzone II A.
In general, the composite angiosperm pollen record from the Portuguese sections corresponds
well with the published results from the Potomac Group (Brenner, 1963; Doyle and Robbins,
1977) and the North Atlantic Basin (Hochuli and Kelts, 1980). These palynofloras show
strong similarities in the composition of the angiosperm assemblage as well as in the temporal
appearance of specific taxa. Differences seem to exist considering the first occurrence of
triaperturate pollen types, restricted to post-Aptian deposits in the Portuguese successions and
reported form Subzone II B from the Potomac Group (Brenner, 1963; Doyle and Robbins,
1977). Originally dated as Middle Albian by Doyle and Robbins (1977) the age of this
Subzone has been considered as Early Albian by Doyle (1992). The similarity of the
assemblages, in particular the appearance of tricolpate forms in the Middle Albian of Portugal
and in Subzone II B of the Potomac Group suggests a similar age for the two records.
8.2. Palaeoecological and palaeophytogeographic implications
The total palynological assemblage of the Luz section reflects a low diversity of the
corresponding flora. The large quantities of Classopollis spp. are produced by xerophytic
(drought resistant) and thermophytic Cheirolepidaceae, which are considered to reflect well-
drained upland environments (Vakhrameyev, 1982) or mangrove-type, coastal vegetation
(Watson, 1988). Other conifers (e.g. Araucariaceae, Pinaceae) as well as different types of
Chapter 5 116
ferns are of only subordinate importance. The strong dominance of Cheirolepidaceae pollen in
tidally-influenced shallow water deposits (Luz Marls and Porto de Mós Formation) points to a
presumable habitate of these plants in the vicinity of the palaeo-shoreline. The high number of
Classopollis pollen probably overprinted the vegetation signal from the more distal parts of
the catchment area. In the Cresmina section, the observed floral pattern is less stable and
exhibits several marked shifts. In general, the vegetation was dominated by various conifer
types (incl. Cheirolepidaceae, Araucariaceae, Podocarpaceae, Pinaceae, Taxodiaceae) which
occurred in varying abundances. Different types of ferns (e.g. Schizaeaceae, Gleicheniaceae,
Dicksoniaceae) were only of subordinate importance in the floral assemblage. A significant
increase in fern spores during the Lower Albian (LPZ III) might reflect a shift towards
increased humidity in the corresponding hinterland (Herrle et al., 2003; Mohr, 1989).
The palynofloral composition of the studied sections clearly supports a
palaeophytogeographic position near the southern boundary of the Southern Laurasian floral
province (Batten, 1984; Brenner, 1976; Vakhrameyev, 1991). A strong Laurasian influence is
reflected in the high abundance of various conifer pollen (incl. Pinacea-derived bisaccates) as
well as in the common occurrence and high diversity of fern spores. The proximity of the
Northern Gondwana floral province adjacent to the south is documented by typical floral
elements such as the rare, but consistent occurrences of the taxa Ephedripites spp. and
Afropollis spp. as well as sporadic findings of aff. Tucanopollis crisopolensis.
Even though strong differences are observed with respect to the overall palynofloral patterns,
the Cresmina and Luz sections display strong similarities in the angiosperm records. In both
successions angiosperm pollen represent only a subordinate element of the total palynofloral
assemblage. Despite their relatively low overall abundance, the incipient radiation of
angiosperms is clearly displayed in the consistently increasing diversity of monoaperturate
pollen taxa with time. This trend is paralleled by the rise in relative abundance of these pollen
types. Whereas monoaperturates occur only sporadically in Barremian assemblages, they
account for up to 12% in the Middle Albian. This distribution pattern indicates that
angiosperms successively became an important element of the vegetation at least in low- to
mid-latitudes from the Late Aptian onwards. In our successions, presumed eudicots,
represented by tricolpate pollen types, appear not before the Early Albian. Compared to the
record of monoaperturate forms, their diversity (max. 3 taxa per sample) and relative
abundance (less than 7% of the angiosperm pollen count) remain low throughout the Lower to
Middle Albian interval. This clearly indicates that eudicot plants formed only a minor
Chapter 5 117
constituent of the Portuguese angiosperm flora during the Early to Middle Albian. These
findings are in broad agreement with the results of Crane and Lidgard (1989), which indicate
that a significant rise in non-magnoliid dicots (eudicots) clearly postdates the Aptian to
Albian boundary at palaeolatitudes north of 30°N.
Due to major differences in pollen production and dispersal between different plant groups
(e.g. insect vs. wind pollination), relative pollen abundances can not be directly translated into
vegetation patterns. Detailed examination of early angiosperm reproductive structures and
pollen morphologies provide strong evidence for insect pollination and consequently for
rather low pollen production (Crane et al., 1995; Friis et al., 1994; Wing and Boucher, 1998).
An exception is represented by the Asteropollis-type pollen, which have been interpreted to
originate from wind pollinated plants (Friis et al., 1999). Considering insect pollination for the
majority of early angiosperms, these plants probably represented a significant part of the late
Early Cretaceous vegetation flourishing in the hinterland of the study area.
8.3. Implications for the timing of early angiosperm diversification
8.3.1. Angiosperm mesofossil floras from the Lusitanian Basin
According to our palynological and stratigraphic results, the Portuguese angiosperm
palynofloras show a stepwise increase in relative abundance and diversity during the Late
Barremian to Middle Albian interval. Assemblages from pre-Albian deposits are characterised
by low diversity (max. 11 taxa), low relative abundance (> 4 %) and the lack of tricolpate
pollen types.
These results are in strong contrast to earlier studies, which suggested a Barremian or possibly
Aptian age for highly diverse mesofossil floras from the northern part of the Lusitanian Basin
(Friis et al., 1997; Friis et al., 1994; Friis et al., 1999; Friis et al., 2000b; Friis et al., 2001).
According to these authors the findings from the Lusitanian Basin comprise the earliest
angiosperm reproductive structures and thus, the oldest unequivocal evidence for the
occurrence of angiosperms in the fossil record. A high number of well-preserved fossil
angiosperm remains such as stamens, flowers, fruits, anthers and seeds have been described.
In addition, a variety of in situ pollen from reproductive structures of angiosperms have been
documented. The assemblages comprise rich and diverse floras and according to Friis et al.
(2001) a conservative estimates accounts for a total of ca. 140 to 150 different angiosperm
taxa. These mesofloras are obtained form several localities in the Estremadura region
Chapter 5 118
including the Torres Vedras, Catefica, Famalicão, Buarcos and Vale de Agua localities (Fig.
1). A detailed description is provided by Friis et al. (1997; 1999). The fossiliferous deposits
are mainly composed of varicoloured clays and silts, intercalated within coarse, cross-bedded
sandstones, which reflect deposition in fluvial and/or lacustrine settings. Due to the lack of
marine deposits and adequate age-diagnostic fossils, the stratigraphic assignment of these
deposits remains problematic. So far, a Barremian or possibly Aptian age has been inferred
from the studies of Rey (1972) for the Torres Vedras and the Catefica sites. Due to the strong
similarities to the fossil floras from Torres Vedras and Catefica, a similar age has been
tentatively assigned to the angiosperm mesofloras from the Famalicão, Buarcos and Vale de
Agua sites (Friis et al., 1997; Friis et al., 1999).
8.3.2. Evidence for a post-Aptian stratigraphic position of the mesofossil floras
Several lines of evidence, including palynology, sedimentology and biostratigraphy indicate a
post-Aptian age for the angiosperm mesofloras of the Famalicão, Buarcos and Vale de Agua
localities.
- Palynological evidence
Friis et al. (1999; 2001) reported a relatively high diversity of up to 30 individual pollen taxa,
which have been observed in situ within reproductive organs or adhering to fruiting
structures. In the in situ assemblages pollen with a tricolpate aperture configuration account
for up to 15 %, the rest consists of monocolpate forms. Considering the suggested Barremian
or Aptian age of the mesofossil floras, these results contradict the palynological findings of
the dispersed pollen assemblages from the Cresmina and Luz sections. Although not directly
comparable, the Barremian to Aptian time interval comprises a significantly lower number of
dispersed pollen (2 taxa in the Barremian and up to 11 taxa in the Aptian). In contrast,
increased diversity of angiosperm pollen (up to 18 taxa) can be recognized in the post-Aptian
part of the successions. Another distinct difference to the in situ results is reflected in the
post-Aptian appearance of tricolpate forms and their low relative abundance in the dispersed
pollen assemblages (less than 7 %) of the Cresmina and Luz sections.
As pointed out by Friis et al. (1999; 2001), standard palynological preparation of the
mesofossil-bearing sediments yielded very low pollen diversities at the Famalicão, Buarcos
and Vale de Agua sites. Similarly, Pais & Reyre (1981) reported only two angiosperm pollen
Chapter 5 119
types (Clavatipollenites cf. hughesii and Asteropollis vulgaris) in dispersed pollen
assemblages from the Buarcos location. The observed discrepancy between pollen abundance
from dispersed and in situ assemblages has been interpreted as preservational bias or low
pollen production and reduced dispersial into the environment of deposition.
Even though these processes might result in significant differences between the two types of
records, they fail to explain the lack of tricolpates in pre-Albian deposits and their low relative
abundance in post-Albian sediments. In addition the palynological results from the Buarcos
site contrast to the findings of Groot and Groot (1962) who described various tricolpate and
tricolporate pollen types from the same locality in the lower part of the Arenitos de Carrascal
unit, clearly indicating a younger, post-Aptian age.
A correlation between the in situ pollen assemblage of the Vale de Agua location and the
dispersed Albian assemblages is further supported by the occurrence of Dichastopollenites-
type pollen. The comparison of SEM micrographs showing Dichastopollenites reticulatus
(May, 1975, Pl. 2, Fig. 1-6) with the reticulate-semitectate Pollen Type G of Friis et al. (1999,
Fig. 86) displays strong similarities considering size, type and size of muri and luminae as
well as the configuration of the colpus. Resemblance between Pollen Type G and LM
micrographs of Dichastopollenites cf. ghazalatensis in our material (Pl. IV; 9) is evident. The
presence of Dichastopollenites–type pollen grains in the Vale Agua material suggest an age
not younger than Albian for this assemblage.
- Sedimentological and biostratigraphic evidence
Additional evidence for an Albian age of the mesofossil-bearing sediments is provided by the
refined stratigraphic assignment of the siliciclastic Rodízio Formation and the major
unconformity (MU) at its base (Fig. 12). The occurrence of the dinoflagellate marker species
D. cladoides in sediments directly above the basal conglomerates indicates an Early Albian or
younger age for the Rodízio Formation. The MU represents an important angular discordance
in the Lusitanian Basin and corresponds to a break-up unconformity (type 1 sequence
boundary), which marks the beginning of oceanic opening of the Atlantic sector adjacent to
the Lusitanian Basin (Cunha and Pena dos Reis, 1995; Dinis and Trincão, 1995; Hiscott et al.,
1990). The duration of the hiatus between the basal conglomerates above the MU and the
underlying strata increases from SSW to NNE. In the Lisbon region (e.g. Cresmina section),
the hiatus encompasses Early Bedoulian to Late Aptian, whereas north of Nazaré, mid-
Chapter 5 120
Cretaceous siliciclastics rest unconformable on Upper Jurassic to Triassic deposits (Cunha
and Pena dos Reis, 1995; Dinis and Trincão, 1995).
In the northern part of the Lusitanian Basin, the MU corresponds to the lower limit of the
Figueira da Foz Formation (informally termed Belasian Sandstone). The Figueira da Foz
Formation comprises an up to 500 m thick continental siliciclastic succession, which covers
large areas in the northern Estremadura region. The sedimentary sequence is basically
composed of conglomerates, sand- and mudstones, which are arranged in two prominent
fining-upward cycles. The basal unit of the lower cycle is represented by the coarse
conglomerates of the Calvaria Member. Depositional environments of the Figueira da Foz
Formation range from prograding alluvial systems to deltaic and prodelta settings (Dinis et
al., 2002). A comparison with earlier studies of Rocha et al.(1981), Teixeira and Zbyszewski
(1968) as well as with the recent work of Manuppella et al. (2000) indicates that the
mesofossil-bearing, fine-grained deposits of the Famalicão, Buarcos and Vale de Agua sites
are intercalated within the siliciclastic sediments of the Figueira da Foz Formation.
Towards the south, the basal conglomerates of the Calvaria Member correspond to the coarse
siliciclastic deposits of the Rodízio Formation (Cresmina section). The identification of
several 2nd-order transgressive-regressive cycles in the Lusitanian Basin allows for an
accurate sequence stratigraphic correlation between the lower part of the Rodízio Formation
in the south and the Calvaria conglomerates in the north. According to (Dinis et al., 2002) this
correlation implies that the base of this lowermost sedimentary cycle (corresponding to the
MU) must have approximately the same age throughout the entire Lusitanian Basin or might
become slightly younger towards the north.
The sedimentological observations clearly indicate that the MU marks the base of the Lower
Cretaceous deposits in the northern part of the basin. North of Nazaré there is no evidence for
the presence of Cretaceous strata below the MU. Based on the correlation of the basal Figuera
da Foz siliciclastics with the conglomerates of the Rodízio Formation, a post-Aptian age is
inferred for the onset of sedimentation in the entire Lusitanian Basin. Consequently, the
angiosperm mesofossil-bearing deposits of the Famalicão, Buarcos and Vale de Agua sites,
which are intercalated within in the Figuera da Foz Formation, are not older than Early Albian
in age (Fig. 12).
The stratigraphic assignment of the angiosperm mesofloras from the Torres Vedras and
Catefica locations remains still problematic. According to Friis et al. (1997; 1999), these
mesofloras have been collected from strata ranging from supposedly Valanginian to Lower
Chapter 5 121
Barremian. Due to the lack of age-diagnostic fossils, the stratigraphic assignment of the
corresponding continental deposits is based on lithostratigraphic correlation with marine strata
from the SW part of the basin (Rey, 1972). At the Torres Vedras and Catefica sites, the
position of the MU can not be determined clearly and therefore, an unequivocal stratigraphic
assignment of the fossil-bearing deposits is not possible on the basis of sedimentological
arguments. However, the similarities of the mesofloras from the northern sites (Famalicão,
Buarcos and Vale de Agua) with those from further south (Torres Vedras and Catefica) has
been taken as evidence for a similar age for all five mesofossil assemblages by Friis et al.
(1997; 1999; 2001).
Fig. 12: Schematic stratigraphic cross-section throughout the northern part of the Lusitanian Basin
from the Cresmina towards the Buarcos study site. The distribution of siliciclastic sediments is marked
in grey. Presumed stratigraphic positions of different angiosperm mesofossil sites are marked with an
asterisk (1, Buarcos flora; 2, Famalicão flora; 3, Torres Vedras flora). Note the increasing age of the
strata below the major unconformity (MU) from SSW towards NNE. Modified after Dinis and Trincão
(1995).
The various discrepancies in comparison to our palynological results as well as the refined
age of the MU indicate that the Portuguese mesofossil floras are significantly younger than
previously suggested. The Early Albian age would not contradict with any of the
palaeobotanical findings. In contrast, a revised post-Aptian age for the mesofossil flora clears
many discrepancies, which occur in comparison with angiosperm remains (incl. pollen,
leaves, wood) from other regions of the world.
SSW
Lower - Middle
Albian
Low
er
Be
do
ulia
n
Lo
we
r
Ba
rre
mia
n?
Cresmina
section
Torres Vedras
section
NNE
Up
pe
r
Ju
rassic
Caranguejeira
section
Up
pe
r
Ju
rassic
Upper Albian
Cenomanian
Buarcos
section
123Rodizio
Formation
MU
Calvaria
Member
Figueira da Foz
Formation
Chapter 5 122
9. Conclusions
(1) The biostratigraphic study of dinoflagellate cyst associations of mid-Cretaceous deposits
from the Lusitanian and Algarve Basins results in significant changes of the existing
stratigraphic positions of the individual lithological members. (i) In the Lusitanian Basin
(Cresmina section), the Cobre, Ponta Alta and Praia da Lagoa Member are assigned to
distinctly older ages than previously suggested. The revised Early Albian age for the major
unconformity (MU) and the overlying Rodízio Formation is of significant importance with
regard to the sedimentary history and tectonic evolution of the Estremadura region. (ii) In the
Luz section (Algarve Basin) a detailed survey of the dinoflagellate cyst assemblages resulted
in a shift towards younger ages of almost all lithostratigraphic units. An Early Bedoulian
(instead of Late Barremian) age is assigned to the Choffatella decipiens Marls, whereas the
Porto de Mos Formation holds an Early Albian instead of a Late Aptian age. The refined
stratigraphic framework is consistent with chemostratigraphic results.
(2) The changing pattern in the distribution of the pollen and spores assemblages in the
studied sections indicates different vegetation types in the corresponding hinterland. The
palynological content of the Luz record is strongly dominated by pollen of the Classopollis
group, reflecting probably mangrove-type vegetation adjacent to a tidally-influenced, shallow
water depositional setting. In the Cresmina section, the more varied palynological
composition is essentially composed of various conifer pollen and fern spores. Several
significant shifts in the palynological composition suggest changes in the regional
palaeoclimatic conditions. The composition of the palynofloral assemblage is consistent with
the previously inferred position of the study sites at the southern rim of the Southern
Laurasian floral province.
(3) Both sections provide well-preserved angiosperm pollen assemblages which are studied in
detail considering composition, diversity and relative abundance. The occurrence of similar
angiosperm pollen patterns at the two different study sites indicates that physical
environmental factors are of only subordinate importance for the observed changes in the
angiosperm pollen assemblages. Monocolpate pollen with reticulate- and columellate-
semitectate sculpture dominate the assemblages, whereas tricolpate pollen types are of only
subordinate quantitative importance. Comparison of the Portuguese angiosperm pollen
records with previously published results from the North American Potomac Group shows
Chapter 5 123
strong similarities in the composition of the assemblage as well as in the temporal appearance
of particular pollen types. In addition to well-documented pollen species, the Portuguese
sediments comprise a variety of previously unreported Aptian to Albian taxa which have been
assigned to represent informal species.
(4) The composite Portuguese angiosperm pollen record displays a clear and continuous
increase in relative abundance and diversity which primarily reflects the incipient dispersion
of angiosperm plants during the Late Barremian to Middle Albian interval. Based on the
refined stratigraphic framework, our results imply that early angiosperm pollen were of only
subordinate importance in Late Barremian to Bedoulian palynological assemblages of the
western and southern Portuguese Basins. With the first occurrence of tricolpate forms and a
variety of additional monocolpate pollen in the Early to Middle Albian, a significant
expansion and diversification of the angiosperm flora is observed. This trend is paralleled by
an increase in relative abundance which displays the rising importance of angiosperm plant
communities in mid-Cretaceous floras. However, presumed eudicotyledons represented by
tricolpate pollen types, show relatively low diversity and also low relative abundance
throughout the Early to Middle Albian interval. This indicates that plants with eudicot affinity
were only a subordinate component of the Portuguese angiosperm flora within this interval.
(5) Our biostratigraphic and palynological results contradict previous stratigraphic
assignments of the well-known angiosperm mesofossil floras from the Portuguese
Estremadura region. The plant-fossil bearing sediments have been assigned to a Barremian or
Aptian age and consequently interpreted to bear the oldest unequivocal remains of
angiosperms. However, compared to our palynological results, the occurrence of various
tricolpate pollen forms as well as of Dichastopollenites-type pollen within the mesofossil
floras indicates an Early Albian or younger age. Stratigraphic evidence for a significantly
younger position is provided by the revised Early Albian age for the major unconformity in
the Lusitanian Basin. In the northern Estremadura region, this unconformity predates the
mesofossil-bearing deposits, clearly indicating a post-Aptian age for the angiosperm plant
fossils.
Chapter 5 124
Genus Clavatipollenites (COUPER) Species Author Size and shape Exine Columellae Aperture Plate
C. cf. hughesii Couper (1958) 22 circular-elliptical
columellate-tectate sexine: 0.5 nexine: 1.0
widely spaced length: 0.5
monocolpate well-defined
Pl. 1; Fig. 1-3
C. cf. minutus Brenner (1963) ~20 circular-elliptical
columellate-tectate sexine: 0.6 nexine: 0.4
densely spaced length: 0.5
not visible Pl. 1; Fig. 3-4
C. cf. tenellis Phillips & Felix (1972)
~30 irregular spherical
perforate-tectate sexine: 1.0 nexine: 1.2
very densely spaced length: 1.0
not visible Pl. 1; Fig. 8-9
C. sp. 1 informal species ~15 spherical
columellate-tectate sexine: 1.0 nexine: 1.0
distinct, widely spaced length: 1.0 head Ø: 0.5
monocolpate well-defined
Pl. 1; Fig. 7
C. sp. 2 informal species ~30 circular-elliptical
columellate-tectate sexine: 1.0 nexine: 1.0
very fine barely visible
monocolpate elongate
Pl. 1; Fig. 12-13
C. sp. 3 informal species ~40 circular-elliptical
columellate-tectate sexine: 1.0 nexine: 0.5
densely spaced length: 1.0
monocolpate Pl. 1; Fig. 10-11
C. cf. sp. A Doyle & Robbins (1975)
~22 spherical
microreticulate-tectate sexine: 1.0-1.5 nexine: 1.0
densely spaced length: 1.5-2.0
monocolpate Pl. 1 Fig. 5-6
Genus Asteropollis (HEDLUND & NORRIS) Species Author Size and shape Exine Columellae Aperture Plate
A. cf. asteroides Hedlund & Norris (1968)
20-25 circular-elliptical
columellate-tectate sexine: 1.5 nexine: < 0.5
densely spaced length: 0.5 club shaped
trichotomocolpate Pl. 3; Fig. 12-13
A. sp. 1 informal species 25-30 irregular spherical
columellate-tectate sexine: 1.0 nexine: 0.5
densely spaced club shaped length: 1.0 head Ø: ~0.5
not visible Pl. 3; Fig. 7-8
A. sp. 2 informal species ~50 irregular spherical
microreticulate-tectate verrucate tectum
very densely spaced barely visible
not visible Pl. 3; Fig. 11
A. sp. 3 informal species ~20 circular-elliptical
perforate-tectate exine: < 1.0
densely spaced barely visible
trichotomocolpate Pl. 3; Fig. 9-10
A. sp. 4 informal species ~25 circular-elliptical
microreticulate-tectate sexine: 1.0 nexine: < 0.3
densely spaced club shaped length: 0.5 - 0.8 head Ø: 0.6
trichotomocolpate Pl. 4; Fig. 2-3
Genus Pennipollis (FRIIS, PEDERSEN & CRANE) Species Author Size and shape Exine Reticulum Muri width Aperture Plate P. sp. 1 informal
species ~20 spherical
reticulate-semitectate sexine: 1.5-2.0 nexine: 0.5
lumina: 1.5-2.5 1.2-1.3 transverse ridges
monocolpate Pl. 4; Fig. 10-11
P. sp. 2 informal species
15 - 20 circular-slightly elliptical
reticulate-semitectate sexine: 0.75 nexine: 0.75
homobrochate lumina: 1.3-2.8
0.5-0.7 verrucate
monocolpate Pl. 4; Fig. 12-13
P. sp. 3 informal species
~20 spherical
reticulate-semitectate sexine: 0.7 nexine: 0.8
homobrochate lumina: 1.0-2.5
0.5-0.8 double-row verrucae
monocolpate Pl. 4; Fig. 14-15
P. sp. 4 informal species
~15 circular-slightly elliptical
reticulate-semitectate sexine: 0.5 nexine: 1.0
heterobrochate lumina: 1.5-4.0
0.5 fine ornamentation
monocolpate Pl. 4; Fig. 16
Genus Dichastopollenites (MAY) Species Author Size and
shape Exine Reticulum Muri width Columellae Aperture Plate
D. cf. ghazalatensis Ibrahim (1996)
28–31 reticulate-semitectate polygonal lumina width: 1.5-4.0
0.8-1.2 widely spaced Ø: 1.1-1.3
zono- aperturate
Pl. 4; Fig. 9
D. dunveganensis Singh (1983)
~45 reticulate-semitectate heterobrochate; polygonal lumina width: 3.5-6.5
1.0-1.3 very widely spaced Ø: 1.2-1.6
zono- aperturate
Pl. 4; Fig. 8
D. sp. 1 informal species
26–35 circular-elliptical
reticulate-semitectate sexine: ~1.5 µm nexine: 0.5 – 0.7 µm
heterobrochate; polygonal lumina width: 2.0-6.0
0.6-0.8 very widely spaced Ø: 0.8-0.9
zono- aperturate
Pl. 5; Fig. 1-2
D. sp. 2 informal species
23–27 circular-elliptical
reticulate-semitectate sexine: 1.5 – 2.0 µm nexine: 0.5 µm
heterobrochate; polygonal lumina width: 1.0-3.0
0.6-0.8 widely spaced Ø: 0.7-0.8 club shaped
zono- aperturate
Pl. 4; Fig. 4-5
D. sp. 4 informal species
45–48 circular-elliptical
reticulate-semitectate sexine: 2.5 – 3.0 µm nexine: 0.5 µm
irregular-heterobrochate incomplete meshes
0.8-1.0 widely spaced Ø: 1.1-1.3 club shaped
zono- aperturate
Pl. 5; Fig. 5-6
D. sp. 5 informal species
~31 elliptical
reticulate-semitectate sexine: 1.3 – 1.5 µm nexine: 0.5 µm
irregular-heterobrochate incomplete meshes
0.5-0.7 triangular profile
widely spaced Ø: 0.8-1.0 spindle shaped
zono- aperturate
Pl. 4; Fig. 6-7
Chapter 5 125
Genus Retimonocolpites (PIERCE) Species Author Size Exine Reticulum Muri width Columellae Aperture Plate R. cf. excelsus
Ward (1986)
~35 reticulate-semitectate nexine: 0.6-0.7
coarse reticulate irregular, loosely attached
0.6-0.8 widely spaced length: ~1.0
monocolpate Pl. 2; Fig. 11
R. sp. 1 informal species
~15 reticulate-semitectate sexine: 0.6 nexine: 0.7
heterobrochate loosely attached lumina width: 1.0-2.5
0.5 length: ~1.0 monocolpate Pl. 2; Fig. 1-2
R. sp. 2 informal species
~25 reticulate-semitectate sexine: 2.0 nexine: < 0.4
homobrochate; polygonal lumina width: 2.0-5.0
0.8 dispersed verrucae
widely spaced club shaped length: ~2.0 head Ø: 1.0
monocolpate Pl. 2; Fig. 5-6
R. sp. 3 informal species
~25 reticulate-semitectate sexine: 2.0 nexine: 0.5
heterobrochate; irregular lumina width: 2.0-3.5
0.5 few verrucae
widely spaced length: ~2.0 head Ø: ~0.8
monocolpate Pl. 2; Fig. 7-8
R. sp. 4 informal species
~22 reticulate-semitectate sexine: 1.3-1.5 nexine: 0.5
heterobrochate; polygonal lumina width: 1.2-3.0
0.2-0.3 dispersed verrucae
widely spaced length: 1.2-1.5 head Ø: ~0.5
monocolpate Pl. 3; Fig. 3-4
R. sp. 5 informal species
~30 microreticulate-tectate sexine: 1.0 nexine: 0.5
irregular microreticulate lumina width: < 0.5
very dense densely spaced length: 0.5-1.0 head Ø: ~0.5
monocolpate Pl. 2; Fig. 15
R. sp. 6 informal species
30-36 reticulate-semitectate sexine: 0.5 nexine: 0.5
heterobrochate; polygonal microreticulate lumina width: < 1.0
0.2-0.3 densely spaced barley visible
monocolpate elongate colpus
Pl. 4; Fig. 1
R. sp. 7 informal species
30-33 reticulate-semitectate sexine: 1.0-1.5 nexine: 1.0
homobrochate smaller towards colpus lumina width: 1.0-3.0
0.5-1.2 irregular; beaded
densely spaced club shaped length: 1.0 head Ø: 1.0-1.2
monocolpate long colpus
Pl. 2; Fig. 10
R. sp. 8 informal species
~15 reticulate-semitectate very thin sexine nexine: 0.5
heterobrochate loosely attached lumina width: < 1.0
< 0.3 regular
widely spaced length: 0.3
monocolpate Pl. 2; Fig. 9
R. sp. 9 informal species
~24 reticulate-semitectate sexine: 1.5 nexine: 0.8
homobrochate lumina width: 2.0-3.0
0.5 regular
widely spaced club shaped length: 1.5-2.0 head Ø: ~0.5
monocolpate Pl. 2; Fig. 12
R. sp. 10 informal species
~16 reticulate-semitectate sexine: 1.0 nexine: 0.5
extremely heterobrochate irregular lumina width: < 1.5
0.2-0.3 thin length: < 0.5
monocolpate Pl. 2; Fig. 16-17
R. sp. 11 informal species
~21 reticulate-semitectate sexine: 2.0 nexine: 0.5
heterobrochate irregular lumina width: 2.0-5.5
0.5-0.8 triangular profile
widely spaced spindle-shaped, length: < 2.0
monocolpate Pl. 2; Fig. 13-14
R. sp. 12 informal species
~22 reticulate-semitectate sexine: 1.8 nexine: 0.7
homobrochate smaller towards colpus lumina width: 1.0-2.0
0.7 widely spaced club-shaped length: 0.7-1.0
monocolpate elongate colpus
R. sp.13 informal species
~37 reticulate-semitectate sexine: 1.7 nexine: 0.3
homobrochate lumina width: < 2.0
0.3 densely spaced club shaped length: 1.7 head Ø: 0.5-0.7
monocolpate elongate colpus
Pl. 3; Fig. 3-4
R. sp. 15 informal species
~28 reticulate-semitectate sexine: 1.3 nexine: 1.2
heterobrochate loosely attached lumina width: 0.5-1.7
0.3 densely spaced, club shaped length: 1.2
monocolpate Pl. 3; Fig. 5-6
R. sp. 16 informal species
25-30 reticulate-semitectate sexine: 1.2 nexine: 0.6
homobrochate lumina width: < 1.3
< 0.3 dispersed verrucae
densely spaced club shaped length: 1.2
monocolpate elongate colpus
Pl. 3; Fig. 1-2
Table 1: Descriptive data for the observed pollen mentioned in the text. Due to the lack of documentation of comparable forms in earlier studies, most pollen are reported as informal species. All morpholocial specifications are given in µm.
Acknowledgements
We thank R. Gonzales from Algarve University and P. Skelton from the Open University,
Milton Keynes for field assistance and determination of rudist bivalves. Financial support
from ETH-Project TH-34./99-4 is greatfully acknowledged.
Chapter 5 126
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Chapter 5 130
Scale bar is 10 µm in all photomicrographs Plate I
1-2 Clavatipollenites cf. hughesii (Couper 1958),
L-13, 106.9 m, (late Barremian-middle Albian)
3-4 Clavatipollenites cf. minutus (Brenner 1963),
L-60, 154.6 m, (early Aptian-middle Albian)
5-6 Clavatipollenites cf. sp. A (Doyle and Robbins 1977),
L-52, 145.5 m, (early to middle Albian)
7-8 Clavatipollenites sp. 1, A-106, 146.6 m, (late Aptian)
9-10 Clavatipollenites cf. tenellis (Phillips and Felix 1971),
A-112, 157.8 m, (late Aptian-early Albian)
11-12 Clavatipollenites sp. 3, L-66, 158.8 m, (early to middle Albian)
13-14 Clavatipollenites sp. 2, A-106, 146.6 m, (early Albian)
Plate II
1-2 Retimonocolpites sp. 1, A-176, 225.8 m, (early to middle Albian)
3-4 Retimonocolpites sp. 4, L-52, 145.5 m, (early Aptian-middle Albian)
5-6 Retimonocolpites sp. 2, L-52, 145.5 m, (early Aptian-middle Albian)
7-8 Retimonocolpites sp. 3, L-52, 145.5 m, (late Aptian-middle Albian)
9 Retimonocolpites sp. 8, A-108, 148.3 m, (early Aptian-middle Albian)
10 Retimonocolpites sp. 7, A-154, 200.7 m, (early to middle Albian)
11 Retimonocolpites cf. excelsus (Ward 1986), L-1, 92.6 m, (early Albian)
12 Retimonocolpites sp. 9, A-106, 146.6 m, (early Aptian-late Aptian)
13-14 Retimonocolpites sp. 11, L-60, 154.6 m, (middle Albian)
15 Retimonocolpites sp. 5, L-31, 121.1 m, (early Albian)
16-17 Retimonocolpites sp. 10, A-79, 116.3 m, (early Aptian-middle Albian)
Plate III
1-2 Retimonocolpites sp. 16, L-66, 158.8 m, (early to middle Albian)
3-4 Retimonocolpites sp. 13, L-66, 158.8 m, (early to middle Albian)
5-6 Retimonocolpites sp. 15, A-193, 245.7 m, (late Aptian-early Albian)
7-8 Retimonocolpites sp. 12, L-55, 149.7 m, (middle Albian)
9 Asteropollis sp. 1, A-193, 245.7 m, (late Aptian-early Albian)
10-11 Asteropollis sp. 3, A-176, 225.8 m, (early Albian)
12 Asteropollis sp. 2, L-40, 130.6 m, (early Albian)
13-14 Asteropollis cf. asteroides (Hedlund and Norris 1968),
L-16, 108.9 m, (early Aptian-middle Albian)
Chapter 5 131
Scale bar is 10 µm in all photomicrographs
Plate IV
1 Retimonocolpites sp. 6, L-1, 92.6 m, (early Aptian-middle Albian)
2-3 Asteropollis sp. 4, L-37, 125.0 m, (late Aptian-middle Albian)
4-5 Dichastopollenites sp. 2, L-66, 158.8 m, (early Albian-middle Albian)
6-7 Dichastopollenites sp. 5, L-66, 158.8 m, (middle Albian)
8 Dichastopollenites dunveganensis (Singh 1983),
L-37, 125.0 m, (early to middle Albian)
9 Dichastopollenites cf. ghazalatensis (Ibrahim 1996),
L-1, 92.6 m, (early to middle Albian)
10-11 Pennipollis sp. 1, A-106, 146.6 m, (late Aptian)
12-13 Pennipollis sp. 2, A-79, 116.3 m, (early Aptian-early Albian)
14-15 Pennipollis sp. 3, L-52, 145.5 m, (early to middle Albian)
16 Pennipollis sp. 4, A-108, 148.3 m, (late Aptian)
Plate V
1-2 Dichastopollenites sp. 1, L-16, 108.9 m, (late Aptian-middle Albian)
3-4 Dichastopollenites sp. 6, L-66, 158.8 m, (middle Albian)
5-6 Dichastopollenites sp. 4, L-88, 184.1 m, (middle Albian)
Plate VI
1 Racemonocolpites cf. exoticus,
A-188, 240.1 m, (late Aptian-middle Albian)
2 Striatopollis trochuensis (Ward 1986),
L-66, 158.8 m, (early to middle Albian)
3 Tucanopollis cf. crisopolensis (Regali 1989),
A-79, 116.3 m, (early to late Aptian)
4 Angiosperme inc. sed. 3, A-179, 231.4 m, (late Aptian-early Albian)
5-6 Angiosperme inc. sed. 1, A-162, 206.5 m, (early Albian)
7-8 Angiosperme inc. sed. 2, A-162, 206.5 m, (early Albian)
9 Aff. Stephanocolpites fredericksburgensis (Hedlund and Norris 1968),
L-31, 121.1 m, (early Albian)
10-11 Senectotetradites spp., A-188, 240.1 m, (early to middle Albian)
12 Stellatopollis sp. 1, A-188, 240.1 m, (early to middle Albian)
Chapter 5 132
Scale bar is 10 µm in all photomicrographs
Plate VII
1 Heslertonia heslertonensis, E-3, 64.9 m, (LO: Early Bedoulian)
2 Pseudoceratium securigerum, D-13, 12.3 m, (LO: Late Bedoulian)
3 Odontochitina operculata, L-19, 110.7 m, (FO: Late Barremian)
4 Subtilisphaera perlucida, E-1, 63.4 m, (LO: Early Albian)
5 Dinopterygium cladoides, K-3, 86.0 m, (FO: Early Albian)
6 Hystrichosphaeridium arborispinum, A-112, 152.9 m, (LO: Late Aptian)
7 Hystrichosphaerina schindewolfii, E-1, 63.4 m, (LO: Middle Albian)
8 Tehamadinium tenuiceras, A-94, 129.9 m, (FO: Late Aptian)
9 Pseudoceratium pelliferum, D-62, 45.0 m, (LO: Late Barremian)
Plate I
1
2
3
4
5
6
7
11
12
9
10
13
14
8
133
Plate II
1
2
3
4
9
5
7
6
8
10
11
12
16
1713 14 15
135
Plate III
1
3
9
7
2
5
6
10 11
4
13
1412
8
137
Plate IV
8 9 16
10
12
14
11
13
15
4 5
6 7
1
2 3
139
Plate V
1 2
3
5 6
4
141
Plate VI
1
2
3
10
11
12
7
8
9
5
6
4
143
1
4
2
3
65
7 8 9
145
Plate VII
Chapter 6 147
Chapter 6
Conclusions
In order to understand the causes and consequences of past environmental change during the
mid-Cretaceous, this thesis addressed the role of terrestrial palaeoenvironments during times
of major perturbations. Accurate stratigraphy is crucial for the proposed study and therefore,
much effort has been put on the establishment of a detailed time framework for the chosen
sedimentary archives. The combined approach of palynology, carbon isotope studies and
organic geochemistry is demonstrated to be a successful strategy to investigate the response of
continental vegetation patterns to major changes of the ocean-atmosphere system. The most
important findings of this study include the following conclusions:
• Prominent shifts in the Early Aptian δ13C record can be reproduced in marine
carbonates, individual organic compounds of probable marine origin as well as in land
plant-derived organic matter allowing for chemostratigraphic correlation on a high
resolution. Furthermore, this indicates that fluctuations in the Aptian δ13C record were
not restricted to the marine realm but affected the entire ocean-atmosphere system.
• Palynological and geochemical studies of the late Early Aptian OAE 1a black shales in
the Vocontian Basin provide no evidence for prominent climate cooling, accompanied
by a significant drop in palaeoatmospheric pCO2 as previously proposed.
• The micropalaeontological results from the Vocontian Basin question the commonly
held few of a high-productivity scenario for the formation of OAE 1a black shales.
Instead, sea-level fluctuations, probably associated with decreased runoff are
suggested to have played a key role for the deposition of black shale.
• Based on chemo- and biostratigraphical results, a revised, more accurate stratigraphic
framework for the Upper Barremian to Middle Albian deposits of the Portuguese
Algarve and Lusitanian Basins is presented.
Chapter 6 148
• A continuous and well-dated angiosperm pollen record from the Portuguese basins
displays the incipient diversification of flowering plants during the Late Barremian to
Middle Albian interval on a so far not obtained resolution. Due to the general lack of
well-dated angiosperm records, these results are of significant importance for the
temporal calibration of existing angiosperm pollen and macrofossil data.
• Based on palynological, bio- and sequence-stratigraphic arguments, a previously
supposed Barremian to Aptian age for several well-known angiosperm floras from the
Estremadura region is shown to be Early Albian or younger in age. The revised age of
the Estremadura angiosperm floras directly influences the current view of the early
angiosperm evolution.
These findings contribute significantly to the understanding of past environmental and floral
change during the mid-Cretaceous. The presented study emphasizes the value and importance
of continent-derived data for a better understanding of the Mesozoic climate and carbon-cycle
perturbations and their possible link to major floral changes.
Appendix
149
A1: Total organic carbon (TOC), total inorganic carbon (TIC) and carbon isotope results, Luz section
Sample
Hight (m)
TOC (dry wt %)
TIC (dry wt %)
δ13Cbulk OM (‰ VPDB)
δ13Ccharcoal (‰ VPDB)
δ13Clignite (‰ VPDB)
δ13Cleaves (‰ VPDB)
δ13Ccuticle (‰ VPDB)
A-1 46.3 0.1 86.0 -22.9 A-3 46.8 0.0 34.3 -22.6 A-5 49.7 0.1 59.4 -22.7 A-8 52.1 0.1 64.7 -25.1 A-10 52.6 0.1 30.6 -24.7 A-12 54.7 0.1 22.5 -21.1 A-13 54.7 0.3 25.8 -22.1 A-15 55.5 0.2 13.2 -23.3 A-18 56.5 0.0 31.5 -22.0 A-20 56.9 0.1 67.7 -22.6 A-22 58.9 0.2 28.8 -21.2 A-23 62.7 -24.3 A-25 64.9 0.1 22.6 -23.8 A-27 69.4 0.1 35.7 -24.9 A-30 74.5 0.1 0.0 -27.8 A-31 77.1 0.0 1.3 -26.0 A-32 81.0 0.1 0.0 -25.8 A-33 81.5 0.0 0.0 -21.6 -19.4 -20.9 A-35 83.1 0.2 27.3 -25.2 A-36 83.2 0.2 19.5 -23.7 A-37 83.5 0.1 3.9 -21.7 -19.2 A-38 85.6 0.0 6.5 -22.5 A-39 86.9 0.1 7.2 -21.7 A-40 88.2 0.2 56.3 -19.4 A-41 89.1 0.3 43.8 -21.1 -19.6 -20.0 A-43 89.4 0.1 90.9 -24.6 -22.7 A-44 89.5 0.1 46.9 -21.3 A-46 90.2 0.3 8.1 -21.6 A-47 90.5 0.4 84.0 -21.4 A-48 91.8 0.1 92.3 -19.6 A-49 91.9 0.1 51.1 -19.9 -19.2 A-50 92.0 0.1 83.4 -20.9 A-51 92.2 0.0 86.9 -23.1 A-53 93.0 0.1 74.0 -22.1 A-55 94.1 0.0 46.3 -21.4 A-57 95.0 0.1 75.7 -22.1 A-59a 96.7 -20.1 A-62 101.4 0.1 76.9 -22.1 A-63 103.2 0.1 47.1 -21.6 A-65 104.4 0.1 1.1 -22.9 A-66 104.8 0.1 84.4 -23.8 A-68 105.8 0.0 37.3 -23.4 A-70 107.7 0.1 37.2 -22.8 A-71 110.4 -22.4 A-72 112.8 0.1 44.4 -23.5 A-74 114.5 0.1 31.5 -23.4 A-75 115.8 0.3 83.7 -22.3 A-76 115.9 0.1 58.8 -25.3 -23.2 A-77 116.1 0.1 70.1 -25.4 A-78 116.2 0.1 78.1 -24.8 A-79 116.3 0.5 56.7 -25.3 -24.0 -24.1 A-80 116.5 0.1 81.2 -24.3 A-81 116.7 0.3 58.8 -24.6 -23.8 -26.5 A-82 117.3 0.1 72.8 -25.1 A-84 118.8 -21.6 A-85 119.9 0.1 39.5 -23.8 A-87 122.8 0.1 35.5 -20.5 A-88 123.6 0.0 28.2 -24.0 A-90 125.3 0.1 56.4 -22.2 A-91 127.4 0.1 35.0 -21.9 A-93 128.2 0.1 67.7 -22.9 A-94 129.9 0.3 15.5 -22.5 -21.7 -21.8 -19.1 A-95 130.2 0.0 76.7 -22.2 A-97 132.7 0.1 28.6 -22.2 A-98 135.4 0.2 55.8 -22.3 A-99 137.2 0.1 44.8 -21.4 A-100 139.9 0.0 70.1 -21.2 A-101 140.7 0.3 71.5 -22.8 -21.9
Appendix
150
A-102 141.2 0.1 82.8 -23.6 A-105a 141.4 -23.8 -21.3 A-104 142.1 0.4 71.9 -23.1 A-105 145.8 0.1 50.7 -21.7 A-107 147.5 1.0 0.0 -23.1 -20.0 -22.3 -21.7 A-108 148.3 0.3 32.7 -23.4 -22.8 A-109 150.1 0.0 78.7 -23.8 A-110 152.9 0.1 87.5 -22.5 A-112 157.8 0.6 35.4 -23.5 -21.3 -23.0 -22.1 A-112a 158.4 -23.2 -19.8 A-113 158.7 0.4 84.1 -23.1 A-114 159.9 0.2 30.6 -22.4 A-115 162.9 0.3 73.7 -22.7 A-116 166.8 0.1 75.1 -23.3 A-117 167.8 0.4 62.0 -20.8 A-119 170.3 0.1 77.8 -21.6 A-120 170.9 0.5 54.6 -20.8 -19.8 A-121 171.8 0.1 77.6 -22.2 -22.1 A-122 172.6 0.1 87.2 -24.5 A-123 173.1 0.5 89.6 -24.2 A-125 174.1 0.2 90.2 -19.4 A-126 175.3 -21.3 A-128 176.1 0.1 57.9 -19.3 A-129 178.5 0.2 70.4 -21.9 A-130 181.4 0.1 58.9 -22.7 -20.8 A-131b 181.9 -21.0 -21.5 A-131a 182.4 0.1 79.8 -23.2 A-132 183.1 0.1 51.1 -21.7 A-134 184.0 0.3 88.4 -25.8 A-135 185.2 0.2 20.9 -21.5 -24.2 A-137 186.7 0.1 82.7 -24.7 A-138 187.2 0.3 83.4 -23.7 A-140 188.9 0.1 63.8 -22.4 A-141 190.5 0.2 88.2 -21.1 A-142 191.3 0.1 64.4 -21.3 -22.3 A-143 192.7 0.0 88.6 -22.6 A-145 193.8 0.4 91.6 -22.9 A-146 194.3 0.3 63.9 -21.0 A-148 195.3 0.3 22.6 -23.1 -21.6 -23.1 -25.6 A-149 196.7 0.1 91.5 -25.0 A-151 197.2 0.3 80.5 -25.6 -23.0 A-152 198.5 0.1 93.3 -23.9 A-153 200.1 0.3 48.0 -22.2 -20.9 -21.6 A-155 201.4 0.3 91.9 -22.7 A-156 201.9 0.0 93.4 -23.9 A-158 203.2 0.5 73.4 -23.4 -22.5 A-159a 204.5 -18.3 -21.8 A-160 205.7 0.0 94.9 -24.9 A-160a 206.1 -24.3 A-162 206.5 0.8 75.9 -24.2 A-165 208.9 0.1 92.4 -23.0 A-166 210.4 0.3 38.2 -22.8 A-168 212.3 0.1 94.0 -25.1 A-169 213.1 1.2 64.1 -24.9 -26.9 -25.9 A-170 214.4 0.4 89.2 -22.7 A-171 215.3 0.8 71.5 -26.0 -24.2 -26.3 A-172 217.4 0.2 82.5 -20.7 A-173 219.3 0.3 93.0 -21.9 A-174a 221.9 -23.1 A-175 222.9 0.1 93.4 -24.2 A-176 225.9 0.3 48.4 -23.1 -24.8 A-178 229.9 0.2 89.7 -24.0 A-179 231.4 0.1 91.0 -22.7 A-180 232.6 0.1 90.9 -23.0 -20.3 A-182 233.7 0.2 93.3 -23.3 A-183 234.4 0.1 82.6 -22.9 A-185 235.1 0.2 88.7 -23.7 A-186 235.4 0.1 51.7 -22.2 A-187 237.2 0.1 92.2 -24.3 A-188 240.1 0.2 89.4 -24.3 -20.1 A-188a 240.4 -23.5 A-190 242.1 0.2 79.2 -24.0 A-191 242.9 0.2 67.6 -23.2 A-192 244.1 0.2 91.6 -24.4
Appendix
151
A-193 245.7 0.6 66.7 -24.2 -19.6 -21.3 -23.3 -23.5 A-194a 248.2 -19.8 A-195 250.4 0.1 84.5 -23.8 A-196 254.9 0.7 51.0 -22.5 -22.1 -21.6 -21.9 A-198 256.5 0.1 88.4 -24.4 A-199 257.4 0.1 59.1 -24.3 -20.1 A-200 258.9 0.0 85.9 -24.2 -21.1 A-202 264.1 0.0 86.7 -22.1 A-203 265.6 0.3 88.7 -21.5 A-205 268.5 0.0 41.7 -24.4 A-207 271.5 0.1 72.1 -22.2 A-208 273.4 0.3 85.6 -21.8 A-210 275.7 0.0 68.3 -23.7 A-211 277.0 0.1 93.4 -24.8 A-212 280.2 0.1 87.1 -23.3 A-213 282.9 0.2 94.4 -22.0 A-214 284.7 0.1 78.0 -22.1 A-216 285.4 0.3 67.0 -25.6 A-218 289.4 0.0 90.6 -23.5 A-219 291.9 0.4 80.2 -23.2 A-220 294.4 0.3 88.7 -25.4 A-222 296.9 0.2 97.1 -23.0 A-223 298.0 0.0 47.4 -23.0
A2: Total organic carbon (TOC), total inorganic carbon (TIC) and carbon isotope results, Burgau section
Sample
Hight (m)
TOC (dry wt %)
TIC (dry wt %)
δ13Cbulk OM (‰ VPDB)
G-41 0.2 0.1 11.5 -22.3 G-42 2.2 0.1 31.5 -23.1 G-43 4.4 0.1 20.9 -21.5 G-44 5.4 0.2 71.5 -22.6 G-45 7.0 0.0 0.8 -24.5 G-46 9.0 0.0 0.0 -24.4 G-47 12.6 0.1 0.0 -25.1 G-48 18.7 0.0 1.4 -25.0 G-49 20.0 0.1 2.6 -25.9 G-50 21.0 0.0 2.5 -25.1 G-4 21.4 0.0 25.7 -24.9 G-5 22.2 0.1 34.9 -22.7 G-6 23.6 0.1 55.9 -21.3 G-9 24.4 0.3 38.3 -21.4 G-10 24.8 0.1 54.4 -22.6 G-11 25.8 0.2 72.1 -21.3 G-12 26.7 0.1 65.8 -23.1 G-13 27.7 0.2 79.1 -21.6 G-14 28.4 0.1 71.0 -23.4 G-15 31.6 0.1 76.4 -23.9 G-16 38.8 0.1 21.7 -21.3 G-17 40.8 0.1 65.6 -23.1 G-18 41.2 0.3 79.7 -23.5 G-19 41.8 0.1 72.8 -22.5 G-20 51.5 0.6 80.4 -25.0 G-21 52.0 0.0 93.8 -23.4 G-22 57.0 0.1 50.7 -23.0 G-24 61.3 0.1 73.4 -23.1 G-26 67.3 0.0 10.0 -22.7 G-27 71.9 0.0 6.4 -22.9 G-30 77.0 0.1 25.0 -21.1 G-32 81.0 0.2 79.7 -23.3 G-33 85.2 0.1 31.8 -22.7 G-34 87.5 -25.3 G-35 91.0 0.1 30.1 -20.9 G-36 93.3 -24.6 G-37 94.6 0.3 44.3 -20.4 G-39 96.2 0.0 93.1 -26.8 G-40 97.8 -23.2
Appendix
152
A3: Total organic carbon (TOC), total inorganic carbon (TIC) and carbon isotope results, Cresmina section
Sample
Hight (m)
TOC (dry wt %)
TIC (dry wt %)
δ13Cbulk OM (‰ VPDB)
D-1 1.0 0.0 0.0 -23.8 D-3 2.4 0.0 0.0 -23.1 D-4 3.1 0.4 0.0 -22.9 D-5 3.9 0.3 81.9 -22.9 D-7 5.7 0.7 80.7 -24.1 D-8 7.7 0.0 78.8 -22.8 D-9 8.7 0.2 46.5 -23.8 D-12 11.8 0.0 92.3 -24.0 D-16 14.3 0.0 92.7 -23.3 D-19 17.2 0.0 94.2 -24.2 D-26 20.7 0.1 0.0 -24.6 D-27 21.1 0.1 91.6 -24.4 D-33 22.9 0.0 94.3 -21.9 D-34 23.2 0.0 3.4 -22.4 D-35 24.3 0.1 80.2 -23.2 D-38 25.4 0.1 93.9 -21.9 D-39 25.9 0.0 32.2 -22.9 D-42 29.2 0.1 0.8 -21.7 D-44 30.7 0.1 93.2 -23.3 D-45 31.8 0.1 93.0 -24.2 D-47 34.7 0.3 92.6 -23.4 D-48 36.1 0.1 66.1 -23.1 D-49 37.4 0.1 7.5 -23.0 D-52 38.9 0.0 95.6 -21.6 D-57 42.6 0.0 64.7 -23.1 D-60 44.1 0.0 77.3 -22.5 D-62 45.0 0.1 79.2 -24.3 D-65 47.5 0.1 37.6 -23.2 D-68 51.3 0.0 96.7 -23.8 D-72 54.6 0.0 95.4 -23.0 D-74 57.4 0.0 97.3 -21.9 D-77 61.1 0.1 97.5 -21.9 D-79 63.7 0.1 59.0 -22.7 D-83 69.0 0.0 98.2 -21.6 D-87 72.0 0.4 0.0 -21.7
Appendix
153
A4: Total organic carbon (TOC), total inorganic carbon (TIC) and carbon isotope results, Serre Chaitieu section
Sample
Hight (m)
TOC (dry wt %)
TIC (dry wt %)
δ13Ccarb (‰ VPDB)
δ13Cbulk OM (‰ VPDB)
NS-36 11.75 0.8 27.3 -24.1 NS-35 11.35 0.6 25.7 3.9 -23.7 NS-34 10.95 0.7 30.7 3.9 -23.6 NS-33 10.55 0.6 35.7 3.5 -24.1 NS-32 10.15 0.6 22.0 4.1 -23.8 NS-31 9.75 0.8 20.1 4.3 -24.0 NS-30 9.35 1.2 15.5 4.5 -24.2 NS-29 9.15 1.8 12.6 4.4 -24.2 NS-28 9.05 0.9 18.8 4.1 -24.2 NS-27 8.60 1.1 16.7 4.0 -23.8 NS-26 8.20 0.5 21.1 3.8 -23.8 NS-25 7.80 0.4 26.4 3.5 -23.9 NS-24 7.40 0.6 21.0 3.6 -23.7 NS-23 7.00 0.9 23.1 3.6 -24.5 NS-22 6.55 0.9 15.4 3.8 -24.7 NS-21 6.45 0.5 16.8 3.5 -24.7 NS-20 6.25 0.9 21.5 4.0 -24.5 NS-19 6.00 1.1 21.7 3.5 -24.9 NS-18 5.60 1.6 13.5 3.6 -24.1 NS-17 5.50 2.2 25.8 3.4 -25.4 NS-16 5.40 1.3 21.5 3.3 -25.3 NS-15 5.30 1.4 17.4 3.3 -25.2 NS-14 5.20 1.7 10.2 3.5 -25.2 NS-13 5.10 2.1 31.5 3.4 -25.1 NS-12 5.00 1.9 28.4 3.4 -24.9 NS-11 4.90 1.3 15.0 3.4 -24.8 NS-10 4.75 1.3 12.5 3.4 -24.8 NS-9b 4.50 2.2 30.9 3.2 -25.7 NS-9a 4.40 0.8 8.7 3.0 -25.4 NS-8 3.90 1.6 18.2 3.0 -26.2 NS-7 3.35 1.7 15.4 3.0 -25.8 NS-6 2.80 1.7 14.8 3.1 -25.3 NS-5 2.15 0.7 13.3 3.1 -25.2 NS-4 1.65 1.0 12.0 3.1 -25.2 NS-3 1.10 1.8 14.2 3.0 -25.7 NS-2 0.55 1.1 13.2 3.0 -25.3 NS-1 0.00 0.9 14.8 2.4 -25.7
A5: Total organic carbon (TOC), total inorganic carbon (TIC) and carbon isotope results, Tarendol section
Sample
Hight (m)
TOC (dry wt %)
TIC (dry wt %)
δ13Ccarb (‰ VPDB)
δ13Cbulk OM (‰ VPDB)
NJ-13 1.94 0.7 34.9 3.3 -23.2 NJ-12 1.84 1.5 21.2 3.2 -23.2 NJ-11 1.66 1.9 25.8 3.3 -23.1 NJ-10 1.56 1.8 31.9 3.2 -24.2 NJ-9 1.46 0.8 35.4 3.2 -23.6 NJ-8 1.28 1.2 29.6 3.2 -23.8 NJ-7 1.18 1.5 25.8 3.4 -23.8 NJ-6 1.08 2.2 27.5 3.4 -23.4 NJ-5 1.00 1.6 32.0 3.9 -23.7 NJ-4 0.80 0.8 33.0 3.3 -23.4 NJ-3 0.60 1.1 28.4 3.4 -23.3 NJ-2 0.45 0.3 36.1 3.4 -23.3 NJ-1 0.25 0.6 29.6 3.4 -23.5
Appendix
154
A6: Carbon isotope results of individual n-alkane measurements (GC-irm-MS), Serre Chaitieu section
Sample
Height (m)
δ13C n- C17 stdev
δ13C n- C18 stdev
δ13C n- C23 stdev
δ13C n- C24 stdev
δ13C n-C28aaa stdev
NS-36 11.75 NS-35 11.35 NS-34 10.95 -27.8 0.3 -26.96 0.37 -26.71 0.07 -26.94 0.03 NS-33 10.55 NS-32 10.15 NS-31 9.75 NS-30 9.35 NS-29 9.15 -28.6 0.0 -28.24 0.34 -26.93 0.19 -27.09 0.18 NS-28 9.05 NS-27 8.60 NS-26 8.20 -28.6 0.1 -28.78 0.05 -27.08 0.04 -27.61 0.03 NS-25 7.80 NS-24 7.40 -27.8 0.7 -27.30 0.09 -26.60 0.01 -27.06 0.10 NS-23 7.00 -28.9 0.1 -28.81 0.07 -26.97 0.08 -27.45 0.08 -29.53 0.07 NS-22 6.55 -29.5 0.2 -30.06 0.05 -28.25 0.04 -28.82 0.12 NS-21 6.45 -29.8 0.1 -30.24 0.20 -28.65 0.08 -28.77 0.04 -30.40 0.33 NS-20 6.25 NS-19 6.00 -29.6 0.0 -30.29 0.23 -28.62 0.09 -28.88 0.05 NS-18 5.60 NS-17 5.50 NS-16 5.40 NS-15 5.30 -29.5 0.0 -29.35 0.07 -28.11 0.03 -28.12 0.06 -29.38 0.11 NS-14 5.20 NS-13 5.10 NS-12 5.00 -30.00 0.04 -28.30 0.03 -28.56 0.12 -29.78 0.02 NS-11 4.90 NS-10 4.75 NS-9b 4.50 -30.46 0.04 -29.59 0.04 -29.72 0.08 -30.48 0.01 NS-9a 4.40 NS-8 3.90 -31.15 0.01 -29.82 0.03 -30.14 0.08 -31.22 0.04 NS-7 3.35 NS-6 2.80 -31.3 0.0 -31.51 0.13 -29.80 0.08 -30.09 0.04 -31.46 0.13 NS-5 2.15 NS-4 1.65 -30.4 0.3 -29.90 0.04 -28.76 0.05 -29.14 0.07 -30.01 0.21 NS-3 1.10 NS-2 0.55 -30.8 0.3 -30.32 0.22 -28.59 0.08 -29.11 0.08 -30.21 0.10
Appendix
155
A7: Palynofacies results, Luz section
Sample
Hight (cm)
Phytoclasts trans. < 25
Phytoclasts trans. >25
Phytoclasts opaque <25
Phytoclasts opaque >25
Membranes
Cuticle
Sporomorphs
Dinocysts
other cysts
Forams
AOM
Sum
A-201 262.1 5 6 2 6 104 4 16 21 15 28 100 307 A-196 254.9 9 7 12 20 50 2 31 18 51 2 140 342 A-193 245.7 8 18 10 26 45 0 105 39 63 13 23 350 A-188 240.1 8 15 8 21 69 4 57 21 33 2 150 388 A-186a 236.4 5 2 2 3 75 0 14 22 5 20 273 421 A-179 231.4 7 5 9 5 47 1 11 11 13 1 195 305 A-176 225.9 19 9 26 18 38 0 73 6 20 1 155 365 A-172 217.4 3 14 6 20 102 0 57 56 41 9 30 338 A-169 213.1 12 2 10 1 35 0 25 70 0 13 140 308 A-162 206.5 2 26 9 38 145 0 29 5 11 42 22 329 A-154a 200.7 7 21 2 13 92 2 34 45 23 21 70 330 A-148 195.3 18 30 17 22 83 4 40 61 27 0 22 324 A-142 191.3 50 5 90 5 98 0 3 0 36 0 7 294 A-137 186.7 12 20 30 36 46 2 76 15 40 2 46 325 A-134 184.0 3 4 3 7 101 6 6 9 45 55 239 A-125 174.1 15 24 2 37 65 4 21 12 103 1 69 353 A-120 170.9 34 3 263 23 6 1 6 336 A-117 167.8 3 0 4 25 48 35 0 2 65 182 A-115 162.9 11 29 7 56 90 5 68 25 27 1 23 342 A-114 159.9 77 28 97 115 19 12 20 11 1 6 386 A-112 157.8 30 57 15 54 51 3 62 63 22 3 25 385 A-110 152.9 0 0 7 13 4 1 33 1 190 249 A-108 148.3 20 36 25 35 72 6 51 96 36 6 383 A-106 146.7 9 31 6 52 21 2 188 7 15 13 344 A-101 140.7 21 20 15 24 97 11 29 12 20 9 58 316 A-97 132.7 0 2 3 6 9 0 86 31 215 352 A-94 129.9 6 19 12 67 52 7 68 92 39 8 16 386 A-81 116.7 12 12 18 20 80 1 69 54 38 3 54 361 A-79 116.3 32 17 13 15 66 3 101 20 19 46 332 A-59a 96.7 6 18 41 146 50 92 8 7 17 30 415 A-46 90.2 76 81 76 40 17 10 21 3 8 1 333 A-41 89.1 58 27 41 35 39 1 60 32 28 321 A-37 83.5 87 43 81 15 8 3 1 20 3 6 267 A-33a 81.5 11 15 23 30 53 151 21 7 23 334 B-15 20.1 12 0 0 2 190 8 212 B-13 17.9 21 25 12 35 178 68 23 10 7 11 390 B-8 12.0 33 15 19 14 135 99 35 20 2 372
Appendix
156
A8: Ericeira section, lower part
H-1
H-2H-3H-4H-5H-6H-7H-8
H-9H-10
H-11
H-12
H-13
H-14
H-15H-16
H-25
H-24
H-23H-22H-21
H-20
H-19
H-18
H-17
H-26
H-27
H-28
H-29
H-30
H-31H-32
H-33
H-34
H-44
H-43H-42H-41
H-40
H-39
H-38
H-37H-36H-35
H-53
H-52
H-51
H-50
H-49
H-48H-47H-46
H-45
H-54
H-55
H-56
H-63
H-62H-61H-60
H-59H-58
H-57
H-64
H-65
H-70
H-69
H-66
H-67
H-68
H-71
H-72
H-73
H-74
H-75
H-76H-77
H-80
H-79
H-78
H-83
H-82
H-81
H-85
H-84
H-86
H-87
H-88
H-89
H-90
H-91
H-103
H-102
H-101H-100H-99
H-98
H-97
H-96
H-95
H-94
H-93
H-92
K-1
K-2
K-3
K-2.1
10
20
15
5
25
30
35
40
45
50
Ro
dis
io F
orm
atio
nC
resm
ina
Fo
rma
tio
n
Fo
rma
tio
n d
e R
ibe
ira
de
Ilh
as
Qz
Qz
Qz
Qz
Qz
Qz
Qz Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
QzQz
Qz
Qz
Qz
Qz
Qz
K
K
K
Re
ga
tão
Fo
rma
tio
n
65
75
70
60
80
85
90
95
100
55
500
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Appendix
157
A8: Ericeira section, upper part
K-4
K-5
K-6
K-7
K-14
K-13
K-12
K-11
K-10
K-9
K-8
K-18K-17
K-16
K-15
K-25
K-24
K-23
K-22
K-21
K-20
K-19
K-31
K-30
K-29
K-28K-27
K-26
K-38
K-37
K-32
K-33
K-34K-35K-36
K-3.1
120
130
125
115
135
140
105
110
Galé
Form
ation
Qz
Qz
Qz
Qz
Qz
100
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Appendix
158
A9: Cresmina section , lower part
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
QzQz
Qz
Qz
Qz
QzQz
Qz
Qz
Qz
D D
K
K K
D 1D 2
D 3
D 4
D 5
D 6
D 7
D 8
D 9
D 10
D 11
D 12
D 13
D 14
D 15
D 16
D 17D 18
D 19
D 20/21D 22
D 23
D 24D 25D 26D 27
D 28D 29D 30D 31D 32D 33D 34
D 35D 36D 37
D 38
D 39
D 40
D 41
D 42D 43
D 44
D 45
D 46
D 47
D 49
D 50D 51
D 52
D 53
D 54
D 55
D 56
D 57D 58
D 59
D 60D 61
D 63
D 64
D 65
D 66
D 67
D 62
D 48
Cre
sm
ina F
orm
ation
Co
bre
Me
mb
er
D 87
D 88
D 89
D 90
D 91
D 92
D 93
L1
L2
Qz
Rodis
io F
orm
ation
Galé
Form
ation
Ag
ua
Do
ce
Me
mb
er
Qz
K
K
K
80
90
100
50
60
70
D 67
D 68
D 69
D 70
D 71
D 72
D 73
D 74
D 75
D 76
D 77
D 78
D 79
D 80
D 81
D 82
D 83
D 84
D 85
D 86
Cre
sm
ina F
orm
ation
Ponta
Alta M
em
ber
Pra
ia d
a L
agoa
10
20
30
40
50
0
Mete
rs
Form
ation
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Mete
rs
Form
ation
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Appendix
159
A9: Cremina section , upper part
L47L48
L49
L50
L51
Qz K
L52
L53
L54
L55
L56
L57
L58
L59
L60
L61L62L63
L64
L65
L66
L67
L68
L69
L70
L71
L77
L78
L79
L80
L81
L82
L83
L84
L85
L86
L87
L88
L89
L90
L91
L92
L93
L94
L95
L97
L98
L99
L100L101
L102
L103
L96
L74
L73
L75L76
L72
K
K
Qz
K
K
K
K
Qz
L22L23
L24
L25
L26
L27
L28
L30L31
L34
L35
L36
L37L38
L39
L40L41
L42
L43
L44
L46
L45
L32L33
L29
L3
L4
L5L6L7
L8
L9
L10
L11
L12
L13
L14
L15
L16
L17L18L19L20L21
Qz
Qz
Qz
K
K
K
K
K
K
K K
Ga
lé F
orm
atio
nA
gu
a D
oce
Me
mb
er
Galé
Form
ation
Ag
ua
Do
ce
Me
mb
er
100
110
120
130
140
150
150
160
170
180
190
200
Mete
rs
Form
ation
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Mete
rs
Form
ation
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Qz
Qz
Qz
Qz Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Appendix
160
A10: Luz section, lower part
B 1
B 2
B 3
B 4
B 5
B 6
B 7
B 8
B 9
B 10
B 11
B 12
B 13B 14
B 15
B 16
B 17
B 18
B 19
B 20
B 21
B 22
B 23
Qz
Qz10
20
30
40
50
70
80
90
100
Pa
lorb
ito
lina
Be
ds
G.
tro
ch
ilisco
ide
s F
m
50
60
0
Lo
we
r L
uz M
arls
A10
A11
A13
A15
A16A17A19
A20
A21
A22
A23
A24
A25
A26
A27
A28
A29
A30
A31
A32
A33
A35
A37
A38
A39
A40
A41A43A45A46A47
A49A51
A52A53
A54
A55A56
A57
A58
A59A60
A61
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
Qz
K K K K
Fe
Fe
Fe
K
K
K
K
K
K
K
K
K K
A7A8A9
Up
pe
r L
uz M
arls
Mete
rs
Form
ation
Lith
olo
gy
Sa
mp
les
Mete
rs
Form
ation
Lith
olo
gy
Sa
mp
les
Se
dim
en
tolo
gy
Se
dim
en
tolo
gy
Fossils
Fossils
Appendix
161
A10: Luz section, middle part
110
120
130
140
150
100
A133
A62
A63
A64
A65
A66
A67A68
A69
A70
A71
A72A73
A74aA74A75
A78A76
A79A80A81A82
A83
A84
A85
A86
A87
A88A89
A90
A91
A92
A93
A94A95
A96
A97
A98
A99
A100
A101A102A103
A104
A105
A106
A107
A108
A109
A110
A111
A112
A113
A114
A115
A116
A117
A118
A119
A120
A121
A122
A123
A124A125
A126
A127
A128
A129
A130
A131a
A131A132
A134
A135
A136
A137
A138
A139
A140
A141
A142
A143
A144
A145A146
A147
A148
A149A150A151
A152
A153
A154
A155
A156
A157A158
A159
A135a
Qz
Qz
KK
K
K
K
K
KK
K K
K K
160
170
180
190
200
150
Up
pe
r L
uz M
arls
Up
pe
r L
uz M
arls
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Se
dim
en
tolo
gy
Fo
ssils
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Se
dim
en
tolo
gy
Fo
ssils
Po
rto
de
Mo
s F
m.
Appendix
162
A10: Luz section, upper part
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Se
dim
en
tolo
gy
Fo
ssils
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Se
dim
en
tolo
gy
Fo
ssils
A 200
A 201
A 202
A 203
A 204
A 205
A 206
A 207
A 208
A 209
A 210A 211
A 212
A 213
A 214A 215
A 216
A 217
A 218
A 219
A 220
A 221
A 222
A 223
A196
A197
A198
A199
250
260
270
280
290
A160
A161
A162A163
A164
A165
A166
A167
A168
A169
A170
A171
A172
A173
A174
A175
A176
A177
A178
A179
A180
A181
A182
A183A184A185A186
A187
A188
A189
A190
A191
A192
A193
A194
A195
K
?
200
210
220
230
240
250
Po
rto
de
Mo
s F
m.
Po
rto
de
Mo
s F
m.
Appendix
163
A11: Burgau section, lower part
Qz
Qz
Qz
K
Qz
Qz
Qz
QzQz
G1/48
G2/49
G3/50
G4
G5
G6
G10
G11
G12
G13
G14
G15
G16
G17
G18
G19
G7/8/9
G41
G42
G43
G44
G45
G46
G47
10
20
30
40
50
Pa
lorb
itolin
a B
ed
sG
. tr
och
ilisc
oid
es
Fm
.
Qz
K K
K
K K
C 1
C 2
C 3
C 4
60
70
80
90
100
500
Lo
we
r L
uz
Ma
rls
Lo
we
r L
uz
Ma
rls
Up
pe
r L
uz
Ma
rls
Mete
rs
Form
ation
Lith
olo
gy
Sam
ple
s
Fossils
Se
dim
en
tolo
gy
Mete
rs
Form
ation
Lith
olo
gy
Sam
ple
s
Fossils
Se
dim
en
tolo
gy
Appendix
164
A11: Burgau section, upper part
Echinoderms
Sponges
Cyclamminidae
Agglutinating benthic foram.
Miliolinids
Undifferentiated benthic foram.
Corals
Serpulids
Bryozoans
Bivalves
Brachiopods
Gastropods
Ostracods
Green algae
Charpophytes
Fish debris
Nodular bedding
Cross bedding
Birdseyes
Burrow
Quarz grainsQz
Teepe structure
Small wavy stratification
Current ripples
Bioturbation
Wave ripples
Bioclasts (undifferentiated)
Fossil wood
Orbitolinids
Lithoclasts
Fining upward
Oysters
Graded bedding
Calcareous nodulesK
Dolomitic nodulesD
Trough cross bedding
Tabular cross bedding
Heringbone cross bedding
Flaser bedding
Load cast
Channel
Rudists
Stromatoporids
G26
G27
G28
G29
G30
G31
G32
G33
G34
G35
G36
G39
G38
G37
G40
G25
G20
G21
G23
G22
G24
Up
pe
r L
uz
Ma
rls
130
140
150
110
120
100
Me
ters
Fo
rma
tio
n
Lith
olo
gy
Sa
mp
les
Fo
ssils
Se
dim
en
tolo
gy
Hardground
Sedimentary structures
Fossil content
Lithology
Limestone
Calcareous marl
Claystone
Siltstone
Sandstone
Conglomerate
Acknowledgements 165
Acknowledgements
First of all I thank Helmi Weissert, Peter Hochuli and Nils Andersen, who initiated the
Portugal project, for their enthusiastic support and ongoing motivation during my PhD.
Dear Helmi, thank you for giving me the great opportunity to join your group here at the ETH
Zurich as your PhD student. I really enjoyed the collaborative fieldwork along the wonderful
Portuguese coasts and the fruitful and inspiring discussions in front of the outcrop. At the
ETH, your office door was always kept open for all of your students, entering to discuss
scientific results, philosophical hypotheses or personal hardships. This is something I will
truly miss and always remember. Thank you for encouraging and motivating me so much
during the last four years of my PhD time.
Dear Peter, I am very grateful for the never-ending patience, you exercised in teaching me
palynolgy. You never got tired of all my frequent questions and visits, over there in the
Palaeontological Museum. Thank you for spending so much time, patience and effort on our
project with its demanding stratigraphic issues and challenging paleobotanical problems.
Working with you on the microscope was very motivating and instructive and I profited
incredibly from your extensive palaeobotanical expertise.
Dear Nils, thank you for your help and technical assistance with the stable isotope
measurements and for introducing me to the organic-geochemical methods and the GC-MS
analytics. I very much appreciate your corrections and comments on earlier versions of the
manuscripts as well as the stimulating and inspiring discussions.
Furthermore I want to thank Judy McKenzie for her interest in this work and for the great
opportunity to join her on an exciting field trip to Brazil. I am thankful to Stefano Bernasconi
for the ongoing support in the stable isotope lab and the critical discussions of the final
results. Thanks to Jens Herrle for the introduction to the sediments of the Vocontian Basin. I
really appreciate the ongoing discussions on mid-Cretaceous palaeocanography as well as the
helpful and constructive comments on earlier drafts of the manuscripts. Special thanks to my
co-worker Stefan Burla for the absolutely amazing times during field work in Portugal - this
was for sure the most hilarious part of the project.
Acknowledgements 166
My thanks go to Jorge Dinis, Ramon Gonzales and Martina Bachmann for their support
during field work in Portugal and to Peter Skelton for the biostratigraphic support and the
helpful suggestions and discussions during our last field campaign. Furthermore, I am very
grateful to Stephen Hesselbo, who did not hesitate to join the scientific committee as a co-
examiner. Thanks to Luc Zwanc from the EAWAG and Christian Ostertag-Henning from the
University of Münster for support with the compound-specific measurements and the
identification of particular organic compounds in my samples. Furthermore I want to thank
Rui Pena dos Reis, University of Coimbra, for providing the beautiful cover picture.
Moreover, I want to thank all my friends and colleagues in the Geological Institute, who
provided a wonderful working atmosphere during my stay here in Zürich. Thanks to all of you
for giving me such a great and exciting time, filled with unique humor, sincere friendship and
respect. Doing a PhD in the Earth System Sciences group at the ETH was really great fun.
Lastly, I’d like thank my family for their persistent encouragement and support during my
studies and my girlfriend Uta for being at my side and sharing the ups and downs of a PhD
student’s life.
Curriculum Vitae
Ulrich Heimhofer
Date of birth: 19. October 1971
Place of birth: Sonthofen i. Allgäu, Germany
Nationality: German
Education
1978-1982: Grundschule Burgberg, Germany
1982-1991 Gymnasium Sonthofen, Germany
1991-1993: Civilian national service at the Red Cross, Immenstadt, Germany
1993-1999: Undergraduate student at the Faculty of Natural Sciences at the
Friedrich-Alexander University Erlangen-Nürnberg, Germany
1995-1996: Visiting student at the Department of Earth Sciences, ETH Zurich,
Switzerland
1996-1999: Diploma student (Geology/Palaeontology) at the Department of
Geology, Friedrich-Alexander University Erlangen-Nürnberg, Germany
2000-2004: Doctoral student and research assistant at the Geological Institute, ETH
Zurich, Switzerland
Dissertation: Response of terrestrial palaeoenvironments to past
changes in climate and carbon-cycling: Insights from
palynology and stable isotope geochemistry
Supervisors: Prof. Dr. Helmut Weissert
PD Dr. Peter A. Hochuli
Dr. Nils Anderson