Integrated biomagnetostratigraphy of the Alano section (NE...

ABSTRACT

The Alano section has been presented at the International Subcommission on Paleogene Stratigraphy (ISPS) as a potential candidate for defi ning the global boundary stratotype section and point (GSSP) of the late Eocene Priabonian Stage. The section is located in the Venetian Southern Alps of the Veneto re-gion (NE Italy), which is the type area of the Priabonian, being exposed along the banks of the Calcino torrent, near the village of Alano di Piave. It consists of ~120–130 m of bathyal gray marls interrupted in the lower part by an 8-m-thick package of laminated dark to black marlstones. Intercalated in the sec-tion, there are eight prominent marker beds, six of which are crystal tuff layers, whereas the other two are bioclastic rudites. These distinctive layers are useful for regional cor-relation and for an easy recognition of the various intervals of the section. The section is easily accessible, crops out continuously, is unaffected by any structural deformation, is rich in calcareous plankton, and contains an expanded record of the critical interval for defi ning the GSSP of the Priabonian. In order to further check the stratigraphic complete-ness of the section and constrain in time the critical interval for defi ning the Priabonian Stage, we performed a high-resolution study of integrated calcareous plankton biostratig-raphy and a detailed magnetostratigraphic analysis. Here, we present the results of these studies to open a discussion on the criteria for driving the “golden spike” that should defi ne the middle Eocene–late Eocene boundary.

INTRODUCTION

Chronostratigraphy, the subdivision and classi fi ca tion of Earth’s geologic record on the base of time (Hedberg, 1976), represents the most widely used “common language” of com-munication in the earth sciences. The develop-ment of a standard global chronostratigraphic scale (GCS), based on rigorous agreement upon stratigraphic principles, terminology, and clas-sifi catory procedure, is one of the long-standing objectives of the Inter national Commission on Stratigraphy (ICS).

A fundamental step toward this goal is the elaboration of a standard series and stage divi-sion of each system, together with precise defi ni-tion of boundaries between them (Bassett, 1985). With regard to the latter effort, the principle has become fi rmly accepted that the base of each division be defi ned at a unique point in a rock sequence, representing a unique point in time, to serve as standard against which other sequences can be correlated by the different available time correlation tools. The standard section and point of the defi nition are referred to as the global boundary stratotype section and point (GSSP) of the designated stratigraphic boundary.

During the last decades, signifi cant progress has been made in establishing the standard GCS, which, integrated with other tools for “geologic time telling,” was synthesized in 2004 in an up-dated geologic time scale (GTS04; Gradstein et al., 2004). In the GTS04, the Paleogene Sys-tem, that is the Paleocene, Eocene, and Oligo-cene Series, remains in a state of major fl ux (Berggren and Pearson, 2005; Hilgen, 2008) for multiple reasons: (1) existing age models of the geologic time scale (in pre-Oligocene times) are not yet well established, (2) in some inter-

vals, the biomagnetostratigraphic framework is confused because it is based on a limited database, and (3) only the GSSPs of the basal stages of the series (i.e., Danian, Ypresian, and Rupelian) have been defi ned to date (Premoli Silva and Jenkins, 1993; Molina et al., 2006c; Aubry et al., 2007). As a result, the practice of recognizing intraseries stages and subdivisions is highly contradictory. For example, as reported in Figure 1, the recognition of the base of the Priabonian, i.e., the middle Eocene–late Eocene boundary, varies by more than 1.5 m.y. among various authors. In order to rapidly overcome the current situation, the International Subcom-mission on Paleogene Stratigraphy (ISPS) has promoted working groups for defi ning all the Paleogene stages, and proposals are expected soon for all of them (Hilgen, 2008). Within this activity of the ISPS, we were asked to explore the possibility of defi ning the Priabonian Stage in the Veneto region, NE Italy, where a classi-cal record of early Paleogene stratigraphy is preserved that has served as reference for intro-ducing the Priabonian Stage for over a century (Munier Chalmas and de Lapparent, 1893). All the sections indicated by Munier Chalmas and de Lapparent, located in the Lessini Mountains and Berici Hills (western Veneto; Fig. 2), and in particular, the stratotype section near the vil-lage of Priabona, in the eastern Lessini Moun-tains (Roveda, 1961; Hardenbol, 1968; Fig. 2), were deposited in shallow-water sediments that are diffi cult to precisely frame in time and, hence, are unsuitable for usefully defi ning a chronostratigraphic unit. Therefore, at the Eo-cene Colloquium held in Paris in 1968 (Cita, 1969), several parastratotypes sections were proposed, among which the deep-water section of Possagno (Treviso Province; Fig. 2), where

For permission to copy, contact [email protected]© 2011 Geological Society of America

841

GSA Bulletin; May/June 2011; v. 123; no. 5/6; p. 841–872; doi: 10.1130/B30158.1; 18 fi gures; 2 plates; 4 tables.

†E-mail: [email protected]

Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal for defi ning the middle-late Eocene boundary

Claudia Agnini1,2, Eliana Fornaciari1, Luca Giusberti1, Paolo Grandesso1, Luca Lanci3,4, Valeria Luciani5, Giovanni Muttoni4,6, Heiko Pälike7, Domenico Rio1, David J.A. Spofforth7, and Cristina Stefani1

1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy2Istituto di Geoscienze e Georisorse, CNR-Padova c/o Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy3Facoltà di Scienze Ambientali, Università di Urbino, Loc. Crocicchia, 61029 Urbino, Italy4Alpine Laboratory of Paleomagnetism (ALP), Via Madonna dei Boschi 76, I-12016 Peveragno (CN), Italy5Dipartimento di Scienze della Terra—Polo Scientifi co Tecnologico, Università di Ferrara, Via G. Saragat, 1, I-44100, Ferrara, Italy6Dipartimento di Scienze della Terra, Università di Milano, Via Mangiagalli 34, I-20133 Milano, Italy7National Oceanography Centre, University of Southampton Waterfront Campus, European Way, SO14 3ZH Southampton, UK

Agnini et al.

842 G

eological Society of Am

erica Bulletin, M

ay/June 2011

2n

G. seminvoluta

G. index

Berg

gren

and

Pe

arso

n, 2

005

M. crassatus

O. beckmanni

G. nuttalli

M. aragonensis

G. kugleri

ADDITIONAL BIOHORIZONS

G. seminvoluta

T. cunialensis

Cr. erbae AB

C. inflata FO

1n

1r

1n

3n2r2n1r

2n

1n1r

34

35

36

37

38

39

40

41

42

43

44

45

AGE (Ma)

S. furcatolithoides

S. obtusus

Cr. erbae AE

C. reticulatum

E. obruta LCO

CP

13b

NP

15N

P16

NP

17N

P 18

CP

13c

CP

14a

CP

14b

CP

15a

CP

15b

CP

16a

NP

19-N

P20

NP

21M

artin

i, 197

1

Okad

a an

d B

ukry,

198

0

BKSA This work and Fornaciari et al. (2010)

E11-

E10(P12)

E9(P11)

E12(P13)

E13(P15 pars)

E14(P15 pars)

E15(P16 pars)

E16(P16 pars)

POLA

RITY

CHRO

N

I. recurvus

C. oamaruensis

R. umbilicus

C. solitus

C. grandis

D. saipanensis

C. gigas

B. gladius

S. pseudoradians

standard biohorizon

E8

BA

RTO

NIA

NP

RIA

BO

NIA

NBK

SA95

PLANKTICFORAMINIFERA

CALCAREOUS NANNOFOSSILS

CHRONOSTRATIGRAPHYCK95

LUTE

TIA

N

BA

RTO

NIA

N

LUTE

TIA

N

GTS0

4P

RIA

BO

NIA

NU

MB

RIA

-M

AR

CH

EB

AR

TON

IAN

PR

IAB

ON

IAN

D. bisectus LCO

MECO(Bohaty & Zachos, 2003)

C 19r event(Edgar et al., 2007)

PALEOCLIMATE

Tem

pora

ry re

vers

al

(Sex

ton

et a

., 20

06)

stable and cool conditions

LUTE

TIA

NR

UP

ELI

AN

Late Eocene warming event

(Bohaty and Zachos, 2003)

Cooling event (Tripati et al., 2005)

Cooling event (Villa et al., 2008)

Cooling event (Villa et al., 2008)

Cooling event (Vonhof et al., 2000)

Coo

ling

trend

(S

exto

n et

al.,

200

6)C

oolin

g tre

nd

(Sex

ton

et a

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006)

C

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nd

(Zac

hos

et a

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001)

long-term trend

warm ing event

cooling event

Oi-1 event(Miller et al., 1991)

Coo

ling

trend

(S

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t al.,

200

6)

20 40 60 80

CaC

O3 p

rese

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inte

rval

s(T

ripat

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l., 20

05)

SBZ 20(N. retiatus, H. gracilis)

SBZ 19(N. fabianii, D. prattii minor)

SBZ 18(N. biedai, N. cyrenaicus)

SBZ 17(Al. elongata, Al. fusiformis, N. brognarti, N. perforatus)

“strati di Roncà”early Bartonian

SBZ 16(N.aturicus, Al. gigantea,D. pulchra balatonica)

late Lutetian

SBZ 14(Al. munieri, As. spira spira)

SBZ 15(N. millecaput, N. crassus)

SBZ 13(N. laevigatus, Al. stipes As. parva)

middle Lutetian“strati di S. Giovanni Ilarione”

early Lutetian

SHALLOW BENTHIC FORAMINIFERA SEA LEVEL

Miller et al., 2005

RU

PE

LIA

N

RU

PE

LIA

N

m

SBZ 21

C20r

C20n

C19r

C19n

C18r

C18r

C18

nC

17n

C16r

C16

n

C15rC15n

C13r

C13n(N. vascus, N. fichteli )

SBZ(Serra-Kiel, 1998)

STANDARDBIOHORIZONS

CW

I. recurvus LCO

Figure 1. Time frame of the middle to late Eocene. The chronology is based on the geomagnetic polarity time scale (GPTS) of Cande and Kent (1995). Planktic foraminiferal zones are from Berggren and Pearson (2005). Calcareous nannofossil standard zones are those of Martini (1971) and Okada and Bukry (1980); several additional calcareous nannofossil biohorizons are also reported. Age estimations of calcareous plankton bioevents are after Berggren et al. (1995; BKSA95), Fornaciari et al. (2010), and this work. The chonostratigraphies used are those previously proposed by Berggren et al. (1995; BKSA95) and more recently by Gradstein et al. (2004; GTS04). On the right, the main paleoclimatic events and/or long-term trends are presented together with enhanced preservation interval of CaCO3 (Lyle et al., 2005; Tripati et al., 2005) and the sea-level curve of Miller et al. (2005).


Geological Society of America Bulletin, May/June 2011 843

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Agnini et al.

844 Geological Society of America Bulletin, May/June 2011

calcareous plankton are abundant and facies are suitable for long-distance correlations, was particularly promising. The section was inten-sively studied in the seventies (Bolli, 1975). Unfortunately, the transition from the Middle to the Upper Eocene is poorly outcropping, and no meaningful proposal of the GSSP of the Pria-bonian could be made. However, detailed geo-logical mapping executed close to the village of Alano di Piave, some 8 km NE of Possagno (Treviso Province; Fig. 2), indicated that the transition from the Middle to Upper Eocene was present there in a deep-water, expanded succes-sion that spectacularly outcrops with absolute continuity (Fig. 3). This section, in the follow-ing termed the Alano section, which has been orally presented at the ISPS since 2004 (the an-nual reports are available at the Web site http://wzar.unizar.es/isps/priabonian2004.htm), is fi rst described in this paper, wherein:

(1) we provide a detailed lithologic descrip-tion and report a high-resolution integrated calcareous plankton biostratigraphy and mag-neto stratigraphy carried out in the section;

(2) we present an improved biomagnetostrati-graphic framework of the middle to late Eocene transition based on the results obtained from the Alano section and data collected specifi cally for this work on the calcareous nannofossils at Ocean Drilling Program (ODP) Site 1052, in the western North Atlantic, a reference section for the time interval of interest here;

(3) we show that the Alano section is com-plete, straddling the critical interval for defi ning the middle Eocene–late Eocene boundary, and it is well and widely correlatable worldwide;

(4) we propose a specifi c lithologic level in the Alano section as the GSSP of the Priabonian, discussing the rationale for the proposal in terms of historical appropriateness and global correla-tion; and

(5) we discuss the work that still is lacking for making the geologic time scale at the transition from the middle to late Eocene more reliable.

ALANO DI PIAVE SECTION

In the following, we provide general geo-graphic and geologic information on the Alano section, with a special emphasis in its lithostratigraphy.

Location and Outcropping Conditions

The Alano section is located in the southern part of the Belluno Province, Veneto region, in NE Italy, ~8 km NNE from the well-known deep-water Possagno section and ~50 km NE from the Priabona section, the historical strato type of the late Eocene Priabonian Stage

(Fig. 2). Its latitude is 45°54′51.10″N, and its longitude is 11°55′4.87″E (WGS84).

The study section is exposed for ~500 m along the banks of Calcino Creek, between the small villages of Colmirano and Campo, ~1 km NE of the Alano di Piave village (Fig. 2). In correspon-dence to the section outcrop, Calcino Creek has deeply eroded the Quaternary deposits (Figs. 3 and 4), exposing the marly substratum in banks 2 m up to 6 m high, along which the succession outcrops with total continuity (Fig. 5).

The lithology is mainly represented by gray-ish hemipelagic marls with intercalated numer-ous millimeter-thick sandy-silty layers and 8- to >6-cm-thick sandy-silty layers that represent useful marker beds. Six of these thicker lay-ers are crystal tuff layers and have been named from the bottom to the top after famous Vene-tian painters: Mantegna, Giorgione, Tiziano, Tiepolo, Tintoretto, and Canaletto beds (Fig. 6); the other two marker beds are biocalcarenite-rudite beds and have been named Palladio and Canova after famous Venetian artists (Fig. 6).

The general bedding strike is 130–140°N and the dip is ~20°–25°. The section is unaffected by any structural deformation. The numerous thin sandy layers can be traced laterally and in-dicate that no, not even small, fault is present in the section. Actually, tectonic deformation in the Southern Alps was less severe than elsewhere in the Alps and Apennines (Channell and Medizza, 1981), thus making this region ideally suited for studying the early Paleogene deep-water record in on-land sections (Giusberti et al., 2007). In addition, the marls outcropping in the Alano section seem to have not been deeply buried, as testifi ed by the good preservation of micro-fossils and the scarce maturity of the organic matter (Spofforth et al., 2010).

The section measured for the present work is ~105 m thick (Fig. 6). Above the study interval, there are at least 15 m of continuously outcrop-ping marls, followed downstream only by spot-ted outcrops.

Access to the Section

The Alano di Piave village is easily reached by regional road SR 348 and provincial road SP10 (Fig. 2D). The best way to access the section is to pass the small Colmirano village and reach the soccer fi eld reported in Figure 2D. From the parking lot of the soccer fi eld to the base of the section, there is an easy walk of some 300–400 m in a plain grass fi eld (Fig. 2D).

Regional Geologic Context

The Veneto region is part of the eastern Southern Alps (NE Italy; Fig. 2), a major struc-tural element of the Alpine chain interpreted as

a south-verging fold-and-thrust belt (Doglioni and Bosellini, 1987) resulting from the poly-phasic deformation of the southern passive continental margin of the Mesozoic Tethyan Ocean (Bernoulli, 1972). This continental mar-gin is interpreted either as a part of a promon-tory of the Africa continent (Channell et al., 1979; D’Argenio et al., 1980) or an independent micro continent (Adria; e.g., Dercourt et al., 1986). During the Middle–Late Triassic, this area was characterized by extensive shallow-water carbonate platforms (e.g., Dolomia prin-cipale; Costa et al., 1996) that were broken up during the Early Jurassic because of regional rifting that resulted in the separation between Europe and Africa. In particular, this process led to the drowning of the entire Southern Alps, where several NNE-SSW–trending “lows” and “highs” began to develop. From east to west, these are the Friuli Platform, the Belluno Basin , the Trento Platform (or Trento Plateau), and the Lombardian Basin (Bernoulli and Jenkyns, 1974; Bernoulli et al., 1979; Winterer and Bose-llini, 1981; Fig. 2A). As the rifting process came to an end, widespread, rather uniform pelagic sedimentation (Rosso Ammonitico Veronese, Biancone, Scaglia Rossa; Costa et al., 1996) began throughout the Southern Alps, spanning from the Middle Jurassic to the early Eocene (Bosellini, 1989; Channell et al., 1992). This widespread pelagic sedimentation was termi-nated in the early Eocene, when a major paleo-geographic reorganization of the Southern Alps, tied to the complex collision between Europe and the African promontory (or Adria micro-plate; Doglioni and Bosellini, 1987), occurred. The former Trento Plateau was uplifted and block-faulted, and signifi cant basic to ultrabasic volcanic activity characterized the area in be-tween the Garda Lake and the Brenta River since the Paleocene (e.g., Beccaluva et al., 2007). An articulated and complex paleogeography devel-oped that resulted in rapid changes of facies, from continental to deep marine deposits. In the western part of the Veneto region, carbonate shallow-water sedimentation resumed with the formation of an articulated carbonate platform referred to as Lessini Shelf (Bosellini, 1989; Fig. 2A). This platform represents, albeit reduced in size, the renewed Trento Platform (Bosellini, 1989; Fig. 2). In the eastern part of the region, where the Jurassic Belluno Basin was set, deep-water sediments persisted up to early Eocene time. These pelagic and hemipelagic sediments attributable to the Scaglia Rossa (Dallanave et al., 2009) were capped by a turbiditic succes-sion, locally up to 1000 m thick, referred to as the Flysch di Belluno (Stefani and Grandesso, 1991; Costa et al., 1996; Stefani et al., 2007), which represents the foredeep deposits linked to



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Agnini et al.


the erosion of the Dinaric chain; these sediments become younger southwestward (Grandesso, 1976) due to the migration of the Dinaric thrusts system (e.g., Doglioni and Bosellini, 1987). Be-tween the Belluno Basin and the Lessini Shelf, a transition area developed, where a hemipelagic sedimentation, referable to Scaglia Rossa sensu latu persisted up to the early–middle Eocene. These deep-water deposits were later capped by slope to outer-shelf marlstones and claystones, referred to in the literature as Scaglia Cinerea (see following) and Marna di Possagno from the middle to late Eocene (Cita, 1975; Trevisani, 1997), that show a clear regressive trend eventu-ally leading, in the advanced Priabonian, to the deposition of inner-shelf mud and sand (upper part of the Marna di Possagno) and shelf car-bonates (Calcare di Santa Giustina). Both the Alano and Possagno sections are located in this transitional area.

Local Geologic Context

In order to frame the Alano section in its geo-logic context, we provide a geological map of the area (Fig. 3). The section is located in the core of a wide fold that is W-E oriented and composed of Upper Jurassic–Eocene deep-water units (e.g., Biancone, Scaglia Rossa; Figs. 3 and 4). This fold is referred to as the Alano-Segusino syncline and is located between the Tomba Mountain anticline to the south and the Grappa Mountain–Tomatico Mountain anti-cline to the north, and it is bounded to the west by the Schievenin line (Fig. 2C).

Lithostratigraphic Assignment

Despite the fact that the Paleogene of the Veneto region has been investigated for a long time, the lithostratigraphic assignment

of the succession outcropping at Alano is not straightforward. The marly sediments at Alano are virtually identical to those observed in the upper part of the Carcoselle segment of the classical Possagno section (middle Eo-cene), where they have been referred to as Scaglia Cinerea (Agnini et al., 2006). How-ever, Scaglia Cinerea is one of the traditional Italian lithostratigraphic units fi rst described in the Umbria-Marche area by Bonarelli at the end of nineteenth century (Bonarelli, 1891) and later ascribed to late Eocene–Miocene age (Canavari, 1894; Selli, 1954; Coccioni et al., 1988). In addition, this term was improperly used for describing a Paleocene lithostrati-graphic unit outcropping in eastern part of the Belluno Basin (Di Napoli Alliata et al., 1970). The ambiguous signifi cance of this term cre-ates confusion and uncertainty and should be abandoned in the Veneto region. The litho-logic assignment of the Alano section still remains problematic, because at Alano , the succession shows a carbonate content higher than 20%, thus preventing a possible asso-ciation with Marna di Possagno, which is de-fi ned by CaCO

3 values never exceeding 20%

(Cita, 1975).Because none of the existing formational

units available can be properly applied to the succession outcropping at Alano, we have de-cided to provisionally and informally intro-duce the term “Marna Scagliosa di Alano” for referring to the entire succession of the Alano section. However, it is noteworthy that at the Possagno section, similar sediments, interposed between Scaglia Rossa and Marna di Possagno , have been previously referred to as Scaglia Cinerea . On this basis, we thus stress the strong need for a systematic revision of the regional Paleogene lithostratigraphy to overcome the current situation.

Detailed Lithologic Description

We logged the lithology of the Alano sec-tion at very high resolution with observation at the centimeter scale. A simplifi ed columnar log of the section is reported in Figure 5, together with the CaCO

3 contents (%) determined by the

EUROPA Scientifi c GEO 20–20 isotope mass spectrometer (Spofforth et al., 2010). The rather monotonous mudstone facies is interrupted by a distinctive ~8-m-thick package of often lami-nated dark to black, organic-rich clayey marls in the lower part of the section. A repetitive charac-teristic feature throughout the section is also the presence of sandy-silty layers, six of which are more prominent, being thicker than 6 cm.

Crystal Tuff LayersIn order to avoid repetitions in describing

the sandy-silty layers, in the following text, we provide a general overview of the simi-lar petro graphic characters while referring to Table 1 for a detailed description of each layer. These beds are dark gray–black in color, and a millimeter- to centimeter-thick greenish plas-tic clay is sometimes present at the top. There is no evidence of current activity, while the bed thickness is slightly laterally variable. Quite abundant, small (4–10 mm in diameter), horizontal to subvertical, cyclindrical burrows sometimes fi lled with greenish clays, suggest a quick depositional mechanism. The optical analyses reveal that these layers are almost ex-clusively made of angular crystal-shape twinned or zoned feldspars, quartz grains, biotite fl akes, vitric or microlithic volcanic rock fragments, scarce heavy minerals, and sporadic bioclasts. All data, which include mineralogical composi-tion, grain size, lack of cementation, common vertical burrowing, and the lack of current activ-ity, point to a common volcanic source for these type of layers, which are suspected to be tephra layers, i.e., linked to fallout deposits. Due to prevailing types of grains, they are classifi ed as crystal tuffs (Schmid, 1981). The scattered bio-clastic content is linked to common bioturbation traces or to normal water-column deposition. X-ray analyses on the clay intervals show great abundance of Illite-Smectite clay (IS) material (Tateo, 2009, personal commun.).

Lithozone DescriptionField observations integrated with carbonate

values allow the subdivision of the section into four lithozones:

Lithozone A (0–17 m level). The marly fa-cies of the basal lithozone up to 13.4 m level is the more calcareous interval in the section. Carbonate content ranges from 57% to 21%, with average values of 45%. In the interval,

M. Bastia T. Calcino T. Formisel T. Ornic

NW SE

500

300

100 masl

reverse fault

A BColmirano

Quaternary continental deposits Scaglia rossaLower Eocene – Upper Cretaceous p.p.

Marna di Possagno – “Marna scagliosa diAlano”Upper Middle Eocene

Biancone p.p.Cretaceous p.p.

Figure 4. Geologic cross section showing the stratigraphic and structural relationships of rock units present in the study area.



crystal tuff layer > 6 cm thickbioclastic layer > 6 cm thick σ σ

V V V

V V V

V V V

V V V

V V V

σ σ σ

σ σ σ

Lit

ho

log

y

Po

lari

ty/C

hro

n

C17r

C18r

C17n.1r

C17n.2r

C16r

?

C18n.1r

C18n.2n

C18n.1n

C17n.1n

C17n.1n

NP

18N

P17

CP

14b

CP

Nan

no

zon

e

NP

Nan

no

zon

eB

ergg

ren

et a

l. (1

995)

P13

P14

P15

P12

Oka

da a

nd B

ukry

(19

80)

Mar

tini (

1971

)

P F

ora

msz

on

e

20

10

30

40

50

70

60

80

90

100

Th

ickn

ess

(m

)

0

C17n.2n

NP

19-2

0

E10

-11

E12

E13

Ber

ggre

n an

d P

ears

on (

2005

)E

Fo

ram

szo

ne

C17n.3n

E14

CP

14a

NP

16C

P15

aC

P15

b

Tintoretto

Tiepolo

Canaletto

Canova

Palladio

Giorgione

Mantegna

V V V Tiziano

4020 8060

4020 8060

CaCO3 (%)

v v

prominent layer of variable compositiondark marlstone locally clay rich and laminated

light gray marlstone CaCO3 (%)

Lit

ho

zon

e

A

B

C

D

Figure 5. Lithologic column of the Alano section. The main volcaniclastic/bioclastic beds are positioned in the log and named after famous Venetian artists. CaCO3 content throughout the section is presented in the central part of the section (after Spofforth et al., 2010). The total carbonate content allows the subdivision of the section into four lithozones reported on right side.

Agnini et al.


we recognized several millimeter-thick lay-ers and two major crystal tuff layers that have been named Mantegna and Giorgione (Figs. 5 and 6; Table 1).

Lithozone B (17–25.5 m level). A promi-nent package of dark to black, more clayey lithologies interrupts the monotonous lithol-

ogy of the section. This interval is easily rec-ognized in the fi eld and is reminiscent of the classical Cretaceous black shales widely out-cropping in the Southern Alps. The base of the interval is sharp with a marked contrast in color that is caused by an increase in organic carbon content, from the background values of

~0.1% to 3% (Spofforth et al., 2010). The stra-tigraphy within the package is structured: it is interrupted at 18.90 m level by a 2-m-thick interval of marls similar to those present in the underlying and overlying intervals. The car-bonate content reaches the lowest values in the section (around 22%) and mimics the triparti-tion observed in the lithology, even if the de-crease of the carbonate contents starts below the base of the interval at 13.4 m level (Figs. 5 and 6). This peculiar lithozone corresponds largely to a global major climatic perturba-tion, the so-called middle Eocene climatic op-timum (MECO) as detailed in Spofforth et al. (2010) see also Bohaty and Zachos, [2003] and Bohaty et al. [2009] for an overview). Up-ward, two prominent bioclastic arenitic/ruditic layers, the fi rst one located in lithozone B and the second one lying in lithozone C (Fig. 5), are observed in the lower-middle part of the section. The faunal associations and sedimen-tological characters of both strata point to resedimentation processes of shallow-water clasts from the nearby Lessini Shelf.

Lithozone C (25.5–59.95 m level). The middle-upper part of the section, starting from 25.5 m level up to the top, cannot be differ-entiated in the fi eld, but the carbonate content undergoes a major change at 59.95 m level, where a decrease, used for separating the two lithozones C and D, is observed (Fig. 5). Spe-cifi cally, from 25 to 59.95 m level, the total car-bonate content curve shows wide oscillations ranging from 31% to 56%, with an average value of 46%. Lithozone C is characterized by the absence of thick volcaniclastic layers that are present both in lithozone A and the overly-ing lithozone D. The only marker bed observed in this interval is represented by the bioclastic Canova bed (Fig. 5), which can be classifi ed as a bioclastic rudstone (Table 1).

Lithozone D (59.95 m level to section top). From ~60 m level up to the section top, total carbonate contents range from 29% to 51%, with an average value of 41%. In lithozone D, four prominent crystal tuff layers are present, in ascending order, they are the Tiziano Bed, the Tiepolo Bed, the Tintoretto Bed, and the Cana-letto Bed (Fig. 6). The Tiziano Bed is the most prominent, being 16 cm thick (Table 1).

Paleontological ContentThe hemipelagic marls of Alano section

contain abundant calcareous nannofossils, planktic foraminifera, and common benthic forami nif era, and rare ostracods. Palinomorphs are abundant as well (Brinkhuis, 2009, per-sonal commun.). Scattered bryozoans have been found in the upper part of lithozone D (e.g., Batopora spp.; Braga, 2009, personal

1 m 1 m

1 m 1 m

1 m 1 m

BA

1 m 1 m

1 m 1 m

1 m 1 m

DC

FE

Figure 6. Alano section. (A) View of the lower part of the Alano section (lithozone A). (B) Detail of lithozone A with indication of the crystal tuff layer Giorgione. (C) Basal por-tion of the sapropelic interval, the lithological expression in the study area of the middle Eocene climatic optimum (lithozone B). (D) The upper part of the sapropelic interval with indication of the prominent bioclastic layer Palladio (lithozones B and C). (E) Close-up view of the critical interval showing the prominent crystal tuff layer Tiziano (basal lithozone D). (F) Upper part of the sampled section with indication of the crystal tuff layer Canaletto (lithozone D).



commun.). The macrofossils are conspicuously absent, as expected in deep-water sediments like those cropping out in the Alano section. In our detailed fi eld work, we found just two badly preserved bivalves in lithozone C and scattered plant debris throughout the section. Ichno fossils are commonly present through-out the section and are mainly represented by Zoophycos in the gray marls and Chondrites in the black interval during the middle Eocene cli-matic optimum.

DATA AND RESULTS

We fi rst present benthic foraminiferal assem-blages data and planktic/benthic (P/B) ratios that were used to infer the paleodepth of the Alano succession and thus better constrain the depositional setting throughout the section. Suc-cessively, we illustrate the magnetostratigraphy and calcareous plankton biostratigraphy of the Alano section in an attempt to establish an ac-curate chronology.

Benthic Foraminifera and Paleodepth at Alano

Samples used for studying benthic and plank-tic foraminiferal assemblages were prepared following standard methods. Briefl y, the indu-rate marlstones were disaggregated with hydro-gen peroxide at concentrations varying from 10% to 30%. When necessary, samples were ad-ditionally treated using Neo-desogen, a surface-tension–active chemical product of the Ciba Geigy Company. Finally, to break up clumps of residue, some samples were placed in a gentle ultrasonic bath.

Paleobathymetric estimates of the section were based both on P/B ratio and presence of index taxa. The P/B ratio is expressed as 100 × P/(P + B), i.e., the percentage of planktic fora-minifera in the total foraminiferal assemblages, using >63 μm size fraction. The presence of benthic foraminiferal paleobathymetric index taxa (e.g., Van Morkhoven et al., 1986) was evaluated within 23 samples throughout the

entire section, scanning residues splits of both >63 and >125 μm size fractions. Bathymetric divisions follow van Morkhoven et al. (1986) and Berggren and Miller (1989): upper bathyal 200–600 m, middle bathyal 600–1000 m, and lower bathyal 1000–2000 m.

The small benthic foraminiferal assemblages at Alano are highly diverse and dominated by calcareous taxa, indicating deposition well above the calcite compensation depth. The most common calcareous taxa are bolivinoids (Bolivinoides crenulata latu sensu and Bolivina antegressa group), uniserial taxa, lenticulinids, Osangularia pteromphalia, Globocassidulina subglobosa, Oridorsalis umbonatus, Cibici-doides spp., Anomalinoides spissiformis, and gyroidi nids (namely Gyroidinoides girardanus). Representatives of the triserial morphogroups such as Bulimina and Uvigerina consistently occur in some samples, especially from the sapropelic interval. Miliolids, which include mainly Spiroloculina sp., are generally rare. The agglutinated foraminiferal assemblages are mostly represented by clavulinids, Ammodiscus, Karrerulina, Karrierella, vulvulinids, and Plec-tina dalmatina. Resedimented small benthic shallow-water taxa, e.g., asterigerinids, Schlos-serina asterites, Sphaerogypsina globula, and Thalmannita sp., were solely observed in the marls just above bioclastic macroforaminifera-bearing layers (e.g., Canova bed).

The P/B ratio shows values >95% at the base of the section, decreasing up to ~90% at 76 m level, whereas in the remaining 30 m, it fl uctu-ates around 85% (Fig. 7). Percentages >90% are consistent with deposition at bathyal and greater depths (e.g., Gibson, 1989; van der Zwaan et al., 1990). However, it must be noted that P/B values <90%, recorded from 81 to 105 m, are probably affected by a general up-section decrease in the planktic foraminiferal preservation state. In order to better constrain the paleo depth of the Alano section, the distributions of frequently occur-ring, cosmopolitan benthic taxa useful to infer paleobathymetric position are reported in Fig-ure 7. The paleodepth ranges used here are those of Tjalsma and Lohmann (1983), van Mork-hoven et al. (1986), Berggren and Miller (1989), Müller-Merz and Oberhänsli (1991), Bignot (1998), and Barbieri et al. (2003). Throughout the investigated section, many taxa occur with an upper bathyal upper depth limit or are com-mon at bathyal depths, e.g., Bolivina antegressa group, Osangularia pteromphalia, Rectuvigerina mexicana, Cibicidoides eocaenus, C. hettneri, C. micrus, Bulimina tuxpamensis, Hanzawaia ammophila, Anomalinoides capitatus, A. spissi-formis, and A. alazanensis (e.g., Van Morkhoven et al., 1986; Holbourn and Henderson, 2002; Barbieri et al., 2003). Bolivinoides crenulata

TABLE 1. PETROGRAPHIC CHARACTERIZATION OF CRYSTAL TUFF AND BIOCLASTIC BEDS

Bed namethickness (cm) Field observations Optical analyses

Rock classifi cation

Mantegna(11 cm)

Uncemented sand, with biotite fl akes at the base

Sand consisting of more than 80% of feldspars, quartz, biotite, volcanic lithics, and heavy minerals, with scattered planktonic foraminifera and small calcite spars

Crystal tuff

Giorgione(4–5 cm)

Slightly cemented sand with horizontal burrowing

Sand consisting of almost 70% feldspars, quartz, biotite, and heavy minerals, with scattered planktonic foraminifera and small calcite spars

Crystal tuff

Palladio(12–16 cm)

Normal graded bioclastic horizontal lamination arenite with sparse green grains. Quite frequent large (up to 8 cm) pelitic intraclasts at the base; common bioturbation

Carbonate rock with clastic texture; at the base, fl oatstone with pelitic intraclasts and scattered debris of corallinacean algae, echinodermata, bryozoa, and nummuliths, rapidly grading to a bioclastic packstone

Bioclastic-intraclastic rudstone-packstone

Canova(3–6 cm)

Bioclastic rudite with large forams with closed-sutured contacts

Carbonate rock with clastic texture; the grains are biosomes and clasts of nummuliths, discocyclinids, debris of bryozoans, corallinacean algae, molluscs, and echinodermata. Green particles are present both as individual grains and as infi ll of foraminifera tests. Sutured and concave-convex contacts between grains and mechanical fractured bioclasts

Bioclastic rudstone

Tiziano(14–16 cm)

Sandy-silty bed: at the base, horizontal burrowing, sometimes crossing the entire bed. At the top a centimeter-thick green pelitic plastic interval

Uncemented sand to silt made of transparent zoned and twinned feldspar crystals, vitric fragments, quartz, and biotite and green particles. Scattered heavy minerals, calcite gouges, and foraminifera texts

Crystal tuff

Tintoretto(10–12 cm)

Very fi ne-grained sands, with horizontal burrowing at the base

Slightly cemented sand consisting of almost 80% feldspars, quartz, biotite, and volcanic lithics

Crystal tuff

Tiepolo(11 cm)

Coarse-grained silt, with concentrations of large biotite fl akes in parallel laminae; horizontal burrowing at the base

Sand consisting of almost 70% feldspars, quartz, biotite fl akes, and heavy minerals, with scattered bioclastic debris

Crystal tuff

Canaletto(6 cm)

Medium- to fi ne-grained sands with cross lamination and abundant biotite; on the top, 2-mm-thick interval of large (up to 3 mm in diameter) biotite fl akes

Sand made of about 80% crystal-shape feldspars, quartz, biotite, volcanic lithics, and scattered heavy minerals

Crystal tuff

Agnini et al.


latu sensu, the most common and continuously present taxon at Alano, has a wide bathymetric distribution (e.g., Sztrákos, 2005; Nomura and Takata, 2005; Ortiz and Thomas, 2006; Molina et al., 2006a; Alegret et al., 2008). Nuttallides truempyi is present, up to 83.6 m level, and the Bulimina impendens-trinitatensis group is pres-ent up to the top of the section. These two taxa are described commonly as having an upper depth limit around 5–700 m (e.g., van Mork-hoven et al., 1986; Barbieri et al., 2003; Molina et al., 2006b), which further constrains the deposi-

tion of the Alano section to at least upper-middle bathyal depths. In their bathymetric zonation of the Possagno section (7 km south of Alano), Grünig and Herb (1980) used the disappearance of N. truempyi to separate their deeper assem-blage 1 (nearly 1000 m for the uppermost part) from the shallower assemblage 2 (between 1000 and 600 m). The presence of specimens of Cibici-doides grimsdalei, a cosmopolitan and easily rec-ognizable taxon for which an upper depth limit within the lower bathyal zone has been reported (van Morkhoven et al., 1986; Bignot, 1998; Bar-

bieri et al., 2003; Katz et al., 2003), suggests for the lower two-thirds of the measured section, deposition occurred close to the lower-middle bathyal boundary. It must be noted, however, that C. grimsdalei has been recently reported by some authors (Mancin and Pirini, 2002; Ortiz and Thomas, 2006; Živkovic and Glumac, 2007) in supposed upper-middle bathyal sediments. Sum-marizing the aforementioned considerations, we can hypothesize a bathymetric evolution for the Alano section from a full middle bathyal depo-sitional depth (lower two-thirds of the section,

Selected benthic foraminiferaP/(P+B)*100

Mid

dle

bath

yal

Upp

er-m

iddl

e ba

thya

l bou

ndar

y

BB

4B

B5

ZO

NE

1 Z

ON

E 2

Ber

ggre

n an

d M

iller

(19

89)

Grü

nig

and

Her

b (1

980)

Infe

rred

pal

eode

pth

Bul

imin

a im

pend

ens-

trin

itate

nsis

gro

up

Cib

icid

oide

s gr

imsd

alei

Ano

mal

inoi

des

capi

tatu

s

Glo

boca

ssid

ulin

a su

bglo

bosa

Han

zaw

aia

amm

ophi

la

Orid

orsa

lis u

mbo

natu

s

Osa

ngul

aria

pte

rom

phal

ia

Rec

tuvi

gerin

a m

exic

ana

Cib

icid

oide

s tr

unca

nus

Nut

talli

des

true

mpy

i

Bol

ivin

a an

tegr

essa

gro

up

Bol

ivin

oide

s cr

enul

ata

Cib

icid

oide

s m

icru

s

Cib

icid

oide

s eo

caen

us

V V V

V V V

V V V

V V V

V V V

σ σ σ

σ σ σ

Lith

olog

y

NP

18N

P17

P13

P14

P15

P12

20

10

30

40

50

70

60

80

90

100

0

NP

19-2

0

E10

-11

E12

E13

E14

NP

16

Tintoretto

Tiepolo

Canaletto

Canova

Palladio

Giorgione

Mantegna

V V V Tiziano

σ σ σ

Mar

tini (

1971

)B

KS

A95

Ber

ggre

n an

d P

ears

on (

2005

)T

hick

ness

(m

)

ALANO SECTION

80 90 100

Figure 7. The P/(P + B) (%) (= planktic to planktic and benthic ratio) and stratigraphic distri-bution of selected small benthic foraminifera plotted against lithology and calcareous plank-ton biostratigraphy (NP—Mar-tini, 1971; P—Berggren et al. 1995; E—Berggren and Pear-son, 2005). Benthic foraminif-era biozonation (Berggren and Miller, 1989) and inferred paleo-depth of the Alano section are reported on the right side.



600–1000 m paleodepth) up to an upper-middle bathyal boundary depth (~600 m paleodepth) for the remaining one-third of the section.

In terms of benthic foraminiferal biozonation, the exit of Cibicidoides truncanus (C. parki auctorum), recorded between 81 and 83.6 m, marks the BB4/BB5 boundary of the Berggren and Miller (1989) bathyal biozonation (Fig. 7). In addition, the highest occurrence (HO) of N. truempyi, an important benthic foraminiferal event that has been proposed by Berggren and Miller (1989) for defi ning the AB7/AB8 bound-ary of their abyssal biozonation in the same in-terval, is also recorded. The exit of this species is a strongly diachronous event: in the abyssal settings, it roughly approximates the Eocene-Oligocene boundary, whereas in bathyal set-tings, it disappears earlier in the late Eocene or within the middle to late Eocene transition (e.g., Barbieri et al., 2003; Coccioni and Galeotti , 2003). At Alano, the HOs of both C. truncanus and N. truempyi occur much earlier than in the deeper Umbria-Marche Basin, where the two events are spaced further apart (Coccioni and Galeotti, 2003), as in the southern Tethyan Nahal Nizzana section (Barbieri et al., 2003).

Paleomagnetism

Paleomagnetic samples were drilled and oriented in the fi eld at an average sampling in-terval of ~0.6 m, giving a total of 159 standard ~11 cm3 specimens for analysis (Figs. 8A–8B), conducted at the Alpine Laboratory of Paleo-magnetism (ALP). The intensity of the natural remanent magnetization (NRM), measured on a 2G DC-SQUID cryogenic magnetometer located in a magnetically shielded room, ranged between 0.03 and 24 mA/m (mean of 2.7 ± 8 mA/m), with a single sample reaching 89 mA/m; higher values were prevalently associated with volcani-clastic-rich intervals (Fig. 8C). All samples were thermally demagnetized from room temperature to 400–600 °C. The component structure of the NRM was monitored after each demagnetization step by means of vector end-point demagnetiza-tion diagrams (Zijderveld, 1967). Magnetic com-ponents were calculated by standard least-square analysis (Kirschvink, 1980) on linear portions of the demagnetization paths and plotted on equal-area projections. Fisher (1953) statistics were ap-plied to calculate overall mean directions.

After removal of spurious initial magnetiza-tions, the presence of a bipolar characteristic (Ch) component trending to the origin of the demagne-tization axes was observed in 65% of the samples on average between ~200 and ~400 °C. Above ~400 °C, the Ch component usually became unstable, and the origin of the demagnetization axes was rarely approached at ~550–575 °C, sug-

gesting the presence of (titano)magnetite as main carrier of the magnetic remanence (Fig. 9A). The Ch component, characterized by maximum angular deviation values usually below 10° (Fig. 8D), was oriented either northwest and shallow down or southeast and shallow up in geographic (in situ) coordinates, and it becomes steeper after correction for homoclinal bedding tilt (azimuth of dip/dip = 130–140°E/20–25°) (Figs. 9A–9B). These populations depart from antipodality by ~11°, which we attribute to residual contamina-tion from spurious lower-temperature compo-nents. The effect of the contaminating bias on the mean direction can be minimized by inverting all directions to common polarity, which resulted in a tilt-corrected mean direction of declination (Dec.) = 351°, inclination (Inc.) = 39.5° (N = 104, k = 12, α

95 = 4°; Table 2).

We compare the mean paleomagnetic pole (paleo pole) from Alano (65.4°N, 211.7°E; Table 2), calculated from the characteristic component mean direction in tilt-corrected co-ordinates, to the Late Cretaceous–Cenozoic (80–0 Ma) synthetic apparent polar wander (APW) path in African coordinates of Besse and Courtillot (2002). The Alano paleopole (A. obs in Fig. 9C) falls at lower latitudes with re-spect to the 40 Ma African paleopole (77.3°N, 191.6°E, A95 = 7.2°). This is because the charac-teristic component mean inclination from Alano (39.5° ± 4°) is ~13° shallower compared to the inclination expected at the site from the 40 Ma African paleopole (53° ± 5°). Syn- and/or post-depositional compaction can produce an incli-nation fl attening of the magnetic remanence in sediments (e.g., Tauxe, 2005); hence ,we used the elongation/inclination (E/I) method of Tauxe and Kent (2004) to detect and correct for the shallow bias of paleomagnetic directions (see also Krijgs-man and Tauxe, 2004; Kent and Tauxe, 2005).

We unfl attened the Alano characteristic direc-tions by applying fl attening (f) values ranging from 1 to 0.3, and for each unfl attening step, we evaluated the E/I value of the directional data set (Fig. 9D, heavy line with ticks). The E/I pair consistent with those expected from a statistical geomagnetic fi eld model (TK03.GAD, Tauxe and Kent, 2004; Fig. 9D, dashed line) was at-tained at f = 0.57. The analysis was repeated 5000 times by means of bootstrap technique (examples of bootstrapped curves are plotted as light curves in Fig. 9D). In Figure 9E, we show a cumulative distribution of all inclinations de-rived from the bootsrapped crossing points. We obtained a corrected mean inclination (and asso-ciated 95% confi dence interval) of Incc = 53° (42°–69°), which is virtually identical to the in-clination expected from the coeval 40 Ma Afri-can paleopole (Ince = 53° ± 5°), and indicates a mean paleolatitude for Alano of ~34°N.

The unfl attened mean characteristic direc-tion of the Alano section (Dec. = 351.2°, Inc. = 53°) yielded a corrected paleopole (A. corr in Fig. 9C; 75.9°N, 223.5°E) that falls on the early Cenozoic portion of the African APW path and is only moderately rotated counterclockwise by 9° ± 8° with respect to the 40 Ma African paleopole. We can therefore consider this part of the Southern Alps as tectonically coherent with Africa since at least the Eocene, in sub-stantial agreement with previous fi ndings from the nearby Paleocene–Eocene Possagno sec-tion (Agnini et al., 2006) as well as from sites of Permian–Mesozoic age from elsewhere in the Southern Alps, e.g., the Dolomites (e.g., Muttoni et al., 2003, and references therein).

A virtual geomagnetic pole (VGP) was calculated for each characteristic component direction in tilt-corrected coordinates. The latitude of the sample characteristic magnetiza-tion VGP relative to the mean paleomagnetic (north) pole axis was used for interpreting po-larity stratigraphy (Lowrie and Alvarez, 1977; Kent et al., 1995). VGP relative latitudes ap-proaching +90°N or –90°N are interpreted as recording normal or reverse polarity, respec-tively (Fig. 8E). For polarity magnetozone identifi cation, we adopted the nomenclature used by Kent et al. (1995). We assigned integers in ascending numerical order from the base of the section to polarity intervals as defi ned by successive pairs of predominantly normal and predominantly reversed magnetozones. Each ordinal number is prefi xed by the acronym for the source of the magnetostratigraphy (i.e., “A” for Alano), and has a suffi x for the dominant polarity (“n” is normal, “r” is reversed) of each constituent magnetozone. An overall sequence of 13 polarity magnetozones, labeled from A1r to A4r(?), has been established starting from the section base (Fig. 8F); of these magnetozones, one is poorly defi ned by only intermediate VGP latitudes (A1n.1r), and two are defi ned by only one sample (A2n.2r, A4r).

Planktic Foraminifera

For the planktic foraminifera study, 264 samples were prepared using standard meth-ods (see benthic foraminifera and paleodepth at Alano). All samples were washed through a 38-µm-mesh sieve in order to avoid the loss of the very small specimens; the fi nest fraction was separated from the 63 µm residue. Foraminifera are continuously present, abundant, and diverse throughout the section, except for some levels from the sapropelitic interval. The preservation varies from moderate to good, and micro fossil assemblages are generally well recogniz-able even if recrystallization of tests commonly

Agnini et al.


V V V

V V V

V V V

V V V

V V V

V V V

s s s

s s s

20

10

30

40

50

70

60

80

90

100

0

0 10 20 300 10 20

89

24

NRM (mA/m) MAD (°)

–90 –45 0 45 90

VGP Lat. (°)

Pal

eom

ag.

sam

ples

Lith

olog

y

Thi

ckne

ss (

m)

A1r

A1n.2n

A1n.1r(?)

A1n.1n

A2r

A2n.3n

A2n.2r(?)

A2n.2n

A2n.1r

A2n.1n

A3r

A3n

A4r(?)

Polarity

A B C D E F

Figure 8. Stratigraphic syn-thesis of the Alano section with (A) lithology, (B) stratigraphic position of samples for paleo-magnetic analysis, (C) natural remanent magnetization (NRM) intensity, (D) mean angular de-viation (MAD) of the character-istic magnetic component, and (E) virtual geomagnetic pole (VGP) latitude used for polarity interpretation (F); black is normal polarity; white reverse polarity.



A

B

ED

C

sample 150W,Up

575 °C

550 °C300 °C

100 °CNRM NRM

400 °C

500 °C

550–600 °C

N N

IN SITU

sample 640 W,Up W,Up sample 1150

N

550 °C

300 °C

100 °C

NRM

NRM100 °C

300 °C

500 °C

sample 2870 W,Up

N

IN SITU

GAD

TILT CORRECTED

Figure 9. (A) Vector end-point demagnetization diagrams of Alano samples. Closed symbols are projections onto the horizontal plane, and open symbols are projections onto the vertical plane in geographic (in situ) coordinates. Demagnetization temperatures are expressed in °C. NRM—natural remanent magnetization. (B) Equal-area projections before (in situ) and after bedding tilt correction of the characteristic component directions from Alano (Table 2). Closed symbols are projections onto the lower hemisphere, and open symbols are projections onto the upper hemisphere. The geocentric axial dipole (GAD) is indicated by the solid star. (C) The paleopole from Alano calculated from the mean characteristic component in tilt-corrected coordinates (A.obs; Table 2) falls at lower latitudes compared to the reference Late Cretaceous–Cenozoic (80–0 Ma) synthetic apparent polar wander (APW) path in African coordinates of Besse and Courtillot (2002) (solid line with A95 error circles), probably because of anomalously shallow paleomagnetic inclinations recorded in the Alano sediments. After inclination shallowing correction, obtained by using the elongation/inclination (E/I) method of Tauxe and Kent (2004), the corrected paleo-pole (A.corr; Table 2) is in latitudinal agreement and only moderately rotated counterclockwise by 9° ± 8° with respect to the broadly coeval 40 Ma African paleopole. The Alano sampling site is also indicated together with the poles–site colatitude great circle (dashed line). (D) Plot of elongation versus inclination for the TK03.GAD (Tauxe and Kent 2003. Geomagnetic Axial Dipole) model (dashed line) and for the Alano data (line with ticks) for different fl attening (f) values from 1 to 0.3. The ticks indicate the direction of elongation, horizontal being E-W and vertical being N-S. Also shown are the results from 20 (out of a total of 5000) bootstrapped data sets. The crossing points represent the inclination/elongation pair most consistent with the TK03.GAD model. (E) Histogram of crossing points from 5000 bootstrapped data sets. The most frequent inclination (Incc = 53°; 95% confi dence interval = 42°–69°) is in good agreement with the inclination expected at Alano from the 40 Ma synthetic pole of Besse and Courtillot (2002) (Ince = 53° ± 5°). The mean inclination of the raw data in tilt-corrected coordinates (Inco = 39.539.5° ± 4°) is also indicated. See text for discussion.

Agnini et al.


occurs . Taxonomic criteria adopted in this study are after Pearson et al. (2006). Illustrations of selected signifi cant species, including zonal markers, are provided in Plate 11.

The biostratigraphic classifi cation of the late Middle Eocene and late Eocene is in a state of fl ux. An extensive review is available in the revised tropical to subtropical Paleogene planktonic foraminiferal zonation by Berg-gren and Pearson (2005), to which we refer (Fig. 1), though the biozonal scheme proposed in Berggren et al. (1995) is reported as well. We have also taken into account the scheme of Toumarkine and Bolli (1970), later updated in Toumarkine and Luterbacher (1985), based on the evolution of the Turborotalia cerroazu-lensis plexus, and specifi cally developed for midlatitude areas, with specifi c reference to sections located in the Veneto region. In the scheme of Berggren and Pearson (2005), we have combined zones E10 and E11, altogether equivalent to the long zone P12 in the scheme of Berggren et al. (1995), because at Alano, the highest consistent occurrence Gumbelitriodes nuttalli is recorded at 57.52 m level, after the HO of Orbulinoides beckmanni (Fig. 10). In-deed, rare and small specimens of G. nuttallii (Plate 1; Fig. 10) are present up to 75.61 m level, within zone E14.

In this study, we carried out planktic forami-niferal analysis for the >63 µm size fraction. Samples were fi rst studied qualitatively to check for presence-absence of index species. Quanti-tative analysis was performed for establishing the distribution patterns of the zonal markers, including key species of middle Eocene–late Eocene transition (e.g., morozovellids, acarini-nids). The sample spacing is on average 40 cm, except in critical intervals, for instance, near the middle to late Eocene transition, where the sam-pling spacing is ~20 cm (roughly 8000 k.y.).

At Alano, the assemblage composition is distinctive of subtropical-temperate latitudes and shows variations in the relative abundance of different taxa throughout the section. Sub-botinids and globigerinathekids are among the

more frequent and common groups. The large acarininids are abundant in the lower part of the section, but they neatly decrease concomitantly with the sapropel-like interval corresponding to the middle Eocene climatic optimum (Fig. 10). Consistent with previous records from other NE Italian sections (Toumarkine and Luterbacher, 1985; Luciani and Lucchi Garavello, 1986), the middle–late Eocene genus Hantkenina displays an uneven distribution and, where present, con-stitutes a minor component of the assemblages.

Biostratigraphic classifi cation of the Alano section, based on standard and additional bio-horizons, is commented as follows:

(1) The basal part of the section, up to 14.40 m level, can be confi dently assigned to the upper part of the combined zone E10/E11 (P12 in the zonal scheme of Berggren et al., 1995), because of the absence of Morozovella aragonensis and O. beckmanni. A noteworthy feature of this in-terval is the occurrence, from 13.20 m level, of rare and discontinuous specimens of T. cerro-azulensis (Fig. 10). This is the lowest occur-rence so far documented for this species, which is normally reported within E13 or higher up (e.g., Nocchi et al., 1986; Coccioni et al., 1988; Gonzalvo and Molina, 1992; Berggren et al., 1995; Berggren and Pearson, 2005). However, it should be observed that the species is rare and unevenly distributed up to 26.10 m level, becoming relatively common and continuously distributed from 46.52 m level (Fig. 10).

(2) The 5.1-m-thick interval from 14.40 to 19.50 m levels is assigned to zone E12 (or P13) based on the total range distribution of Orbu-linoides beckmanni. According to Edgar et al. (2007), the origination, subsequent evolutionary development, and extinction of this short-lived species was intimately linked to environmental changes associated with the middle Eocene cli-matic optimum warming event. The recognition of the O. beckmanni lowest occurrence (LO) can however be affected by some degree of subjec-tivity, because the species derives from Globi-gerinatheka euganea, and transitional forms of problematic assignment with sec ondary aper-tures along the inner spire occur from 12.80 m level. Pearson et al. (2006) proposed that O. beckmanni has a greater number of apertures

than G. euganea, without specifying their exact number. On the other side, Berggren and Pear-son (2005) recommended a relatively broad tax-onomical concept for O. beckmanni in order to permit a consistent identifi cation of the base of E12 zone, but they did not provide details on the nature of the broad taxonomical concept to be applied. In this work, we have decide to assign to O. beckmanni forms having, beside numerous secondary apertures, a more compact, almost spherical test with less depressed sutures, almost indistinguishable, in the earlier chambers of the last whorl (Plate 1). It is interesting to note that in the Alano section, the total range distribution of O. beckmanni appears to be virtually con-fi ned to the middle Eocene climatic optimum interval, in agreement with Edgar et al. (2007). However, the identifi cation of the O. beck manni HO is diffi cult to precisely recognize because of its scarce abundance and the moderate preserva-tion state of planktic foraminiferal assemblages within the sapropel-like interval.

Within zone E12, we observed the fi rst speci-mens ascribable to Turborotalia cocoaensis that in the past was considered restricted to the late Eocene (e.g., Toumarkine and Bolli, 1970). At Alano, typical T. cocoaensis, distinguishable from its ancestor T. cerroazulensis by an acute profi le of the fi nal chamber (Plate 1), fi rst occurs as low as 15.60 m level, even if the specimens recorded at this level are very few. Nevertheless, the occurrence and abundance of the species are highly variable throughout the section, alternat-ing intervals of extreme scarcity in abundance with others of relatively common and continu-ous presence. This feature is likely controlled by as-yet unidentifi ed environmental factors.

(3) The 38.02-m-thick interval from 19.5 m level and 57.52 m level, where the HO of the genus Morozovelloides is observed, is attributed to zone E13. The top of this zone represents one of the major faunal changes in the evolutionary history of planktic foraminifera in the Cenozoic and has implications for defi ning the middle Eocene–late Eocene boundary (see following). Specifi cally, these prominent changes in plank-tic foraminiferal assemblages include the fi nal extinction of large muricate planktic forami nif-era (large Acarinina and Morozovelloides) that

1Plates 1 and 2 are on a separate sheet accompany-ing this issue.

TABLE 2. CHARACTERISTIC COMPONENT DIRECTIONS AND PALEOMAGNETIC POLE FROM THE ALANO SECTION

In situ detcerrocDAG.30KTdetcerroctliTN k α95 Dec. Inc. k α95 Dec. Inc. Plat Plong dp/dm Inc.c Err.Inc Plat.c Plong.c104 12 4.2 344.1 20.5 12 4.2 351.2 39.5 65.4 211.7 3/5 53.0 42-69 75.9 223.5

Note: Site latitude, longitude—45.92°N, 11.87°E. N—number of samples; k—Fisher precision parameter of the mean paleomagnetic direction; α95—Fisher angle (°) of half cone of 95% confi dence about the mean paleomagnetic direction; Dec. and Inc.—declination (°) and inclination (°) in geographic (in situ) coordinates or bedding (tilt-corrected) coordinates of the mean paleomagnetic direction; Plat and Plong—latitude (°N) and longitude (°E) of the mean paleomagnetic pole in bedding (tilt-corrected) coordinates (pole A.obs); dp/dm—error (°) about the mean paleomagnetic pole; Inc.c—TK03.GAD corrected mean inclination (°); Err.Inc—error band of the TK03.GAD corrected mean inclination (°); Plat.c and Plong.c—latitude (°N) and longitude (°E) of the TK03.GAD corrected mean paleomagnetic pole (A.corr). The declination and inclination predicted at Alano from the Besse and Courtillot (2002) 40 Ma synthetic pole (in S. Africa coordinates) is 0.3°E, 52.6° (±5.2°).TK03—Tauxe and Kent 2003; GAD—Geomagnetic Axial Dipole.



dominate low- and mid latitude assemblages in the early and middle Eocene. Therefore, we detailed the faunal patterns observed in this in-terval as sketched in Figure 10. In the Alano sec-tion, the extinction of distinctive muricate group occurred in three steps involving, respectively, the “large” (~>250 µm) Acarinina (i.e., A. rohri,

A. pretopilensis, A. topilensis, A. bullbrooki, A. primitiva, A. collactea), the genus Morozo-velloides (i.e., M. crassatus, M. coronatus), and fi nally the “small” (~<200 µm) Acarinina (i.e., A. medizzai, A. echinata).

The extinction level of large Acarinina bear-ing well-developed muricae occurs at 57.32 m

level and is immediately followed (20 cm above, some 8000 k.y.) by the disappearance of M. crassatus and M. coronatus. It is worth pointing out, however, that muricate forms, par-ticularly large Acarinina, display a signifi cant decline in abundance well below the horizon of their highest occurrence, precisely within zone

V V V

V V V

V V V

V V V

V V V

σ σ σ

σ σ σ

Lith

olog

y

Pol

arity

/Chr

on

C17r

C18r

C17n.1r

C17n.2r

C16r

?

C18n.1r

C18n.2n

C18n.1n

C17n.1n

C17n.1n

20

10

30

40

50

70

60

80

90

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Thi

ckne

ss (

m)

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C17n.2n

E10

-11

E12

E13

C17n.3n

E14

V V V

large acarininids

small acarininids

O. beckmanni

P. capdevilensis

G. semiinvoluta

0 40

0 10

0 1

0 10

0 5

0 5

G. nuttallii0 5

T. cocoaensis% %

%

%

%

%

%

Morozovelloides0 5%

T. cerroazulensis0 10%

P13

P14

P12

P15

Ber

ggre

n et

al.

(199

5)

P F

oram

szon

e (m

)B

ergg

ren

and

Pea

rson

(20

05)

E F

oram

szon

e (m

)

ALANO SECTION

Figure 10. Planktic foraminifera data and resulting biostratigraphic classifi cation of the Alano section according to the zonal schemes of Berggren et al. (1995) and Berggren and Pearson (2005). The relative abundance of each taxon is reported in terms of percentage with respect to the entire assemblage. Positions of the biohorizons are reported in Table 3.

Agnini et al.


E12, in correspondence to the middle Eocene climatic optimum event. Even if these forms are not frequent close to their extinction level, their disappearance constitutes a signifi cant, easily recognizable event.

(4) The upper 47 m of the investigated section, above the 57.52 m level, are assigned to zone E14 because Globigerinatheka semiinvoluta is present, although discontinuously, up to the top of the section (Fig. 10). This species fi rst appears at 68.37 m level, i.e., 10.85 m above the HO of Morozovelloides. The presence of a signifi cant gap between the LO of G. semiinvoluta and the HO of Morozovelloides, i.e., the disappearance of large muricate forms, has also been found by several other workers (e.g., Benjamini, 1980; Nocchi et al., 1986; Pearson and Chaisson, 1997; Norris et al., 1998). In particular, this datum is in agreement with data from the Cordillera Betica sections (Spain; Gonzalvo and Molina, 1996). However, in some areas (western North Atlan-tic Ocean Drilling Program [ODP] Site 1052; Wade, 2004, Umbria-Marche sections; Nocchi et al., 1986), the LO of G. semiinvoluta oc-curs just above the HO of large acarininids and M. crassatus.

Within zone E14, we observed the HOs of the small acarininids (<200 µm), A. medizzai and A. echinata, that overlap with the range of Glo-bigerinatheka semiinvoluta, up to 80.41 m level (Fig. 10). These species represent a minor but characteristic component of the planktic forami-nif eral fauna, evenly distributed up to their highest occurrence. The persistence of small acarininids into the Upper Eocene, contrary to the large forms, was noted as well in high lati-tudes at ODP Sites 702 and 703 (South Atlan-tic) by Nocchi et al. (1991), at Sites 738 and 744 (Kerguelen Plateau) by Huber (1991), and at Site 1052 (western North Atlantic) by Wade (2004). The acarininid lineage thus extends after the major biotic turnover in the latest middle Eo-cene. Data so far available suggest however that the extinction of this group was not a synchro-nous event. Further investigation is needed to verify possible regional use of this event.

Calcareous Nannofossils

We studied calcareous nannofossils assem-blages in 303 samples that were prepared from unprocessed material as smear slides and exam-ined under a light microscope at 1250× magni-fi cation. Samples immediately across the main useful biostratigraphic biohorizons were ana-lyzed every 20 cm. Outside these critical inter-vals, samples were studied every ~60–120 cm. First, all samples were examined with qualitative methods to evaluate the abundance and state of preservation of calcareous nannofossil assem-

blages. We applied the following counting meth-ods to check the presence or absence and esti mate the abundance of index species: (1) counting spe-cies versus total assemblage, taking into account at least 500 nannofossils (Thierstein et al., 1977), (2) counting a prefi xed number of taxonomically related forms, i.e., 50–100 sphenoliths (Rio et al., 1990); and (3) counting the number of rare but biostratigraphically useful species, that is species of genus Chiasmolithus and Istmo lithus, in an area of ~9 mm2 (three vertical traverses; Backman and Shackleton, 1983). The last, time-consuming counting method was used for checking the presence-absence of key index species that are particularly rare in the Alano section (Chiasmo-lithus grandis, Chiasmolithus oamaru ensis, and Istmolithus recurvus). Taxonomic concepts used follow Perch-Nielsen (1985) and Fornaciari et al.

(2010). Index species are illustrated in Plate 2 (see footnote 1).

For the purposes of this work, we have made an effort to establish in the section the standard zonations of Martini (1971; Nannoplankton Paleogene [NP] zones) and Okada and Bukry (1980; Coccolith Paleogene [CP] zones; Fig. 1). However, these zones are of problematic recog-nition, and therefore we will strongly rely in our correlation on a set of additional biohorizons that have been proposed in the literature over the years (e.g., Perch-Nielsen, 1985; Fornaciari et al., 2010).

Generally, the calcareous nannofossil assem-blages are rich, well preserved, and diversi-fi ed throughout the section. To illustrate the makeup of the calcareous nannofossil assem-blages at Alano, we present Figure 11, where

0 100

ALANO SECTION

Cribrocentrum spp.

Dictyococcites spp.

Coccolithus spp.

Cyclicargolithus spp.Reticulofenestra spp. Others

Lanternithus spp.

Z. bijugatus

Sphenolithus spp.Discoaster spp.

Ericsonia spp.

10

20

30

40

50

60

70

80

0

Chi

asm

olith

us s

pp.

rew

orki

ng

0 3 0 3% %%Position

(m)

Figure 11. Cumulative percentage curve of selected calcareous nannofossil taxonomic groups in the Alano section. The relative abundance (%) of Chiasmolithus spp. and reworked forms are also reported on right side.



the quantitative distribution of selected taxo-nomic groups is reported. The assemblages are strongly dominated by placoliths, among which Cribrocentrum and Dictyococcites are promi-nent (together up to ~70% of the total assem-blage). Discoasterids and chiasmoliths (Fig. 1), which provide important datums in the standard zonations of Martini (1971) and Okada and Bukry (1980), are exceedingly rare at Alano, as they are normally in low to middle latitude areas (Perch-Nielsen, 1985; Wei and Wise, 1989).

In Figure 12, we report the quantitative distri-bution patterns of index species from the Alano section that allow us to defi ne the following types of biohorizons: lowest rare occurrence (LRO), lowest occurrence (LO), lowest com-mon occurrence (LCO), highest common occur-rence (HCO), highest rare occurrence (HRO), highest occurrence (HO), acme beginning (AB) and acme end (AE).

A biostratigraphic classifi cation of the Alano section, based on standard and additional calcar-

eous nannofossil biohorizons, is provided next. The positions and calibrations of used bioevents are reported in Table 3:

(1) The basal part of the section up to 44.73 m level is assigned to zones NP16/CP14a (Fig. 12) because of the rare occurrence of Chiasmo lithus solitus and the scarce/common presence of Cribrocentrum reticulatum and Reticulofenes-tra umbilicus (see Fig. 1).

(2) The interval from 44.73 m level, where the HO of C. solitus was observed, to 62.85 m level,

V V V

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σ σ σ

σ σ σ

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olog

y

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arity

/Chr

on

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C18r

C17n.1r

C17n.2r

C16r

?

C18n.1r

C18n.2n

C18n.1n

C17n.1n

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NP

18N

P17

CP

14b

CP

15a

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ss (

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14a

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16

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15b

2 %0 %

0 60 0 6

0 7 0 30 4

0 3

0 %

0

% within Sphenolithus

N/9mm2

S. furcatolithoides

S. obtusus

R. umbilicus

D. bisectusD. scrippsae gr.

7

9

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7

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HO

HO

LCOLCO

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C. erbae0 50

C. oamaruensisN/9mm2

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N/9mm2

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0 % 1

C.grandis

C. solitus

% within Sphenolithus % %

20

no d

ata

no d

ata

ALANO SECTION

NP

Nan

nozo

neM

artin

i (19

71)

CP

Nan

nozo

neO

kada

and

Buk

ry (

1980

)

Figure 12. Quantitative distribution patterns of selected calcareous nannofossils and resulting biostratigraphic classifi cation of the Alano section according to the zonal scheme of Martini (1971) and Okada and Bukry (1980). Additional biohorizons shown by Fornaciari et al. (2010) as useful for correlations are evidenced. The position of the biohorizons is reported in Table 3. LRO—Lowest Rare Occurrence; LO—Lowest Occurrence; LCO—Lowest Common Occurrence; HCO—Highest Common Occurrence; HO—Highest Occurrence; AB—Acme Beginning; AE—Acme End.

Agnini et al.


in correspondence with the LRO of Chiasmo-lithus oamaruensis, is assigned to zone NP17. It should be observed that the recognition of the top of this zone has been diffi cult at Alano because C. oamaruensis is exceedingly rare and exhibits a discontinuous abundance pattern, es-pecially in the lower part of its range. However, a single specimen ascribable to C. oamaruensis was observed and used for recognizing the top of zone NP17. Okada and Bukry (1980) de-fi ned the top of their zone CP14b on the basis of the HO of Chiasmolithus grandis, which in the Alano section occurs at 66.47 m level. This event is also not easily detectable because of the scarcity of this species at Alano as in other Italian sections (Monechi and Thierstein, 1985; Fornaciari et al., 2010).

(3) In a short interval, between 78.11 and 79.91 m levels, we observed the occurrence of rare specimens of Istmolithus recurvus, which is termed I. recurvus spike. The LO of this taxon defi nes the bottoms of zones NP19–20/CP15b (Fig. 1). Therefore, the upper 26.38 m of the section are to be assigned (Fig. 12) to zone NP19–20/CP15b. It should be pointed out that the fi rst occurrence of I. recurvus at Alano, just above the HO of C. grandis and LO of C. oamaruensis, is much earlier than generally assumed in the literature (Berggren et al., 1995), but it is consistent with data from the South and North Atlantic and central west-ern Tethys (Backman, 1987; Villa et al., 2008; Fornaciari et al., 2010).

The recognition at Alano, as well as in other Tethyan sections, of all the aforementioned late middle Eocene and late Eocene standard zones

is sometimes tricky because they are based on index species that are exceedingly rare and dis-continuous. Nevertheless, we will show later herein that the observed positions of the “stan-dard” biohorizons in the Alano section are fairly consistent with magnetochronologic evaluations from Blake Nose (Fig. 13; ODP Site 1052; For-naciari et al., 2010), but they are poorly reliable if compared to the biochronology proposed in Berggren et al. (1995). The low abundances and scattered occurrence of index species make these biohorizons have little practical utility for reliable biostratigraphic correlations. For these reasons, previous authors have proposed the use of alternative biohorizons (e.g., Perch-Nielsen,1985; Lyle et al., 2002), and we have undertaken a project with the specifi c purpose of improving resolution and reliability of cal-careous nannofossil biostratigraphy in the late middle Eocene (Bartonian) and late Eocene (Priabonian) interval (Fornaciari et al., 2010). In particular, at Alano, there are at least fi ve bioho-rizons that are based on the quantitative distri-bution patterns of species common in Tethyan sections, which thus provide confi dent long-distance correlation tools. They are in ascending stratigraphic order:

(1) The HO of Sphenolithus furcatolithoides, at 6.30 m level; this well-defi ned and easily recognizable biohorizon was fi rst proposed by Perch-Nielsen (1985) as an alternative event to the HO of Chiasmolithus solitus (Fig. 12). Al-though the HO of S. furcatolithoides has been observed well below the HO of C. solitus, it is found to maintain the same relative position with respect to other additional events (Fig. 14).

(2) The LCO of Dictyococcites bisectus, at 9.5 m level; this biohorizon, observed just 3.20 m above the HO of S. furcatolithoides, was reported by Perch-Nielsen (1985) up to the upper part of zone NP16, consistent with our fi ndings; the species is deeply affected by taxonomic ambi guities (e.g., Wei and Wise, 1989) that in our opinion could be overcome if a biometric defi nition were adopted assigning only forms larger than 10 µm to D. bisectus (Bralower and Mutter lose, 1995). These large forms appear in Alano and in other Tethyan sections abruptly and provide a neat event (Fornaciari et al., 2010), although specimens of D. bisectus have been re-ported from ODP Site 1052 and Agost section also at lower stratigraphic levels (e.g., Mita, 2001; Larrasoaña et al., 2008), and this species is widely considered to be biogeographically controlled (e.g., Perch-Nielsen, 1985; Wei and Wise, 1989). On this basis, it is thus possible to assume that the appearance at Alano is the fi rst common and continuous occurrence of the spe-cies, possibly environmentally controlled. This interpretation is reinforced by the fact that in co-incidence with the abrupt entrance of D. bisec-tus, a sharp increase in Dictyococcites scrippsae is also observed (Fig. 12).

(3) The HO of Sphenolithus obtusus, at 49.58 m level; this easily recognizable species has been reported by Perch-Nielsen (1985) as having a restricted distribution range in zones NP16–18, but it has never been formally utilized before. At Alano, the form is well distributed, showing a neat appearance and a neat extinc-tion; by comparison with other sections, we consider that its HO is a reliable biohorizon.

TABLE 3. CALCAREOUS PLANKTON BIOHORIZONS AT THE ALANO SECTION AND ODP SITE 1052

59KCegApotnorhcotevitalernoitatoNnoitisoPnozirohoiBAlano Site 1052 Alano Site 1052 Alano Site 1052 Multisite

)aM(ega)aM(ega)aM(ega)dcmr(htpeD)m(noitisoP 1 I. recurvus 63*787.63–891.0n1.n71C–98.55–)N(OL 2 A. medizzai–A. echinata HO (F) 80.41 – C17n.1n 0.765 – 37.272 – – 3 I. recurvus spike end (N) 79.91 72.415 C17n.1n 0.784 C17n.1n 0.795 37.288 37.298 * – 4 I. recurvus spike beginning (N) 78.11 81.285 C17n.1n 0.853 C17n.1r 0.885 37.347 37.589 * – 5 C. erbae –*714.73944.73439.0n1.n71C279.0n1.n71C72.6710.57)N(EA 6 G. semiinvoluta LO (F) 68.37 91.67 C17n.2n 0.250 C17n.3n 0.160 37.665 38.000 † 38.4 7 P. capdevilensis HO(F) 68.37 38.32 C17n.2n 0.250 C16n.2n 0.793 37.665 36.240 † – 8 C. grandis 1.73*527.73427.73694.0n2.n71C294.0n2.n71C17.4874.66)N(OH 9 C. erbae –*128.73338.73198.0n2.n71C939.0n2.n71C526.7869.26)N(BA10 C. oamaruensis LRO (N) 62.85 86.5 C17n.2n 0.953 C17n.2n 0.722 37.837 37.780 * 3711 M. crassatus–M. coronatus HO (F) 57.52 92.37 C17.3n 0.394 C17n.3n 0.264 37.996 38.020 † 38.112 Large acarininids HO (F) 57.32 92.77 C17.3n 0.418 C17n.3n 0.324 38.001 38.030 † 38.5–37.513 S. obtusus –*904.83352.83449.0r71C844.0r71C21.70195.94)N(OH14 C. solitus 4.04*893.83094.83019.0r71C750.0n1.n81C67.60137.44)N(OH15 O. beckmanni HO (F) 19.5 135.69 C18n.2n 0.582 C18n.2n 0.615 39.922 39.980 † 40.116 T. cocoaensis ––722.04–r81C–6.51)F(OL17 O. beckmanni 5.04–352.04–r81C–4.41)F(OL18 T. cerroazulensis LO (F) 13.2 – C18r – 40.366 – –19 D. bisectus 83*453.04095.04r81Cr81C49.3415.9)N(OCL20 S. furcatolithoides HO (N) 6.3 144.54 C18r C18r 40.780 40.384 * –

Note: (F)—foraminifera; (N)—calcareous nannofossils. CK95—Cande and Kent, 1995; LO—Lowest Occurrence; LCO—Lowest Common Occurrence; HO—Highest Occurrence; AB—Acme Beginning; AE—Acme End.

*From this work and after Fornaciari et al, 2010.†After Wade (2004).



(4) The AB of Cribrocentrum erbae, at 62.96 m level; although this new species (For-naciari et al., 2010; Plate 2) occurs virtually throughout the entire section with rare/scarce and sometimes discontinuous abundances, it shows a neat increase in abundance, up to 40%, within zone NP18. At Alano, the peculiar abun-dance pattern of C. erbae is used to identify an

acme event defi ned as the interval characterized by percentages of C. erbae greater than 4%–5%. This biohorizon has also been tested at ODP Site 1052, where it maintains the same ranking and spacing, virtually coinciding with the LO of C. oamaruensis (Fig. 14).

(5) The AE of Cribrocentrum erbae, at 75.01 m level; this biohorizon marks the return of C. erbae

to background abundances. The AE of C. erbae is more diffi cult to defi ne because it shows a more gradual pattern, but the abundances of C. erbae during the acme are substantially more copious from that characterizing the rest of the section. Surprisingly, a comparison between the Alano section and ODP Site 1052 points out that the AB and AE of C. erbae have to be

Dep

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Hia

tus

Figure 13. Quantitative distribution patterns of selected calcareous nannofossils and resulting biostratigraphic classifi cation of the Alano Ocean Drilling Program (ODP) Site 1052 according to the zonal scheme of Martini (1971) and Okada and Bukry (1980). Additional bio-horizons shown by Fornaciari et al. (2010) as useful for correlations are evidenced. The position of the biohorizons is reported in Table 3. LRO—Lowest Rare Occurrence; LO—Lowest Occurrence; LCO—Lowest Common Occurrence; HCO—Highest Common Occurrence; HO—Highest Occurrence; AB—Acme Beginning; AE—Acme End; rmcd—revised metres composite depth.

Agnini et al.


considered as promising biostratigraphic tools for correlations over wide areas (Fig. 14; Forna-ciari et al., 2010).

Interpreting Magnetostratigraphy by Correlation with ODP Site 1052

The calibration of calcareous plankton bio-horizons to the geomagnetic polarity time scale (GPTS; Cande and Kent, 1995) at the transition from the middle to late Eocene is controversial (see Berggren et al., 1995; Table 3). For exam-

ple, the HO of morozovellids and large acarini-nids, probably the most critical biohorizon in the interval, has been associated with the top of chron C18n in the Apennines (Nocchi et al., 1986; Premoli Silva et al., 1988), while in the oceans, it has been often associated with chron C17n (Berggren et al., 1995), with a discrepancy of some 1.0 m.y. There has been a dearth of good low- and midlatitude sections for establish-ing a reliable calcareous plankton magnetobio-chronol ogy until the recovery in ODP Leg 171 of expanded and well-preserved successions in

the subtropical western North Atlantic. In par-ticular, a succession that can be considered a reference deep-sea section for the middle Eo-cene to late Eocene transition is that recovered at ODP Site 1052 in the Blake Nose, in which magnetostratigraphy (Ogg and Bardot, 2001), cyclostratigraphy (Pälike et al., 2001), and high-resolution planktic foraminifera biostratigraphy (Wade, 2004) have been carried out.

In order to obtain an improved and sound correlation between the Alano section and ODP Site 1052 reference section, we decided to conduct a high-resolution study of the calcare-ous nannofossils at this site, using a consistent counting methodology and taxonomy. The results of this study are presented in detail in Fornaciari et al. (2010). Here, we report (Fig. 13) the distribution patterns of the same index species that have been monitored at Alano, and in particular, the distributions of the index species not used in the standard zonations, the stratigraphic range of which is poorly known. In Figure 14, we report the correlations of calcar-eous plankton biohorizons between Alano and ODP Site 1052 based on data of Wade (2004) and our own data. The correlation shows that 10 biohorizons maintain the same ranking and spacing and occur in the same position with respect to the magnetic polarities. This correla-tion suggests a straight forward interpretation of magnetostratigraphic data from the Alano sec-tion in terms of the standard GPTS, as indicated by Figure 14 and summarized in Table 3. Spe-cifi cally, Alano magnetozone A1r corresponds to magnetochron C18r, A1n.2n to C18n.2n, A1n.1n to C18n.1n, A2n.3n to C17n.3n, A2n.2n to C17n.2n, and A2n.1n to C17n.1n (Figs. 8 and 14). Based on the correlation inferred between the Alano section and ODP Site 1052 (Fig. 14), A4r is considered to be equivalent of C16r, and, as a consequence, the short magnetozone A3r at Alano is apparently missing in the geomagnetic polarity time scale of Cande and Kent (1995) time scale. In particular, the basal part of the section correlates with the upper part of chron C18r, while the single sample with a reversed polarity at the top of the section should correlate to the base of chron C16r.

Chronology and Sediment Accumulation Rates

The chronology of the middle–late Eocene GPTS is in a state of fl ux (see Berggren and Pearson, 2005, p. 284), and using the various available calibrations (Cande and Kent, 1995; Pälike et al., 2001; Ogg and Smith, 2004), the chronology of the Alano section varies, as do the calcareous plankton biochronology and sedi-ment accumulation rates.

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40

S. obtusus HO

C. erbae AE

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I. recurvus spike C. oamaruensis LOG. semiinvoluta LO

C. erbae AB

C. solitus LO

Figure 14. Calcareous plankton correlation between the Alano section and Ocean Drilling Program (ODP) Site 1052 (western North Atlantic) and resulting interpretation of the mag-netostratigraphy of the Alano section. The geomagnetic polarity time scale of Cande and Kent (1995) is plotted on the left side.



In Figure 15, we constructed an age-depth plot and derived sediment accumulation rates by means of magnetostratigraphic correlation to the geomagnetic polarity time scale of Cande and Kent (1995), taking into account the avail-able biostratigraphic constraints. The Alano magnetostratigraphy straddles magnetochrons C18r–C16r with an average sediment accumula-tion rate of ~2.4 cm/k.y. (not corrected for com-paction) throughout the entire section (Fig. 15).

The extrapolated age of the base of the section is 41.15 Ma, assuming for chron C18r the mean accumulation rate estimated during chron C18n, and the age of the top of the section is 36.48 Ma according to the geomagnetic polarity time scale of Cande and Kent (1995), thus extending over a 4.40 m.y. time interval. Adopting the chronol-ogy of Ogg and Smith (2004), the section would extend from 40.09 Ma to 36.40 Ma, spanning a time interval of 3.70 m.y., and if we use the time scale of Pälike et al. (2001), with the same as-sumptions, the bottom and the top of the section are at 40.82 and 36.26 Ma, respectively, cover-ing a time interval of 4.56 m.y.

Calcareous Plankton Biochronology

Though the early Paleogene time scale is far away from being established defi nitively, the integrated calcareous plankton and magneto-stratigraphic data reported in Figure 14 suggest that at least 10 biohorizons should be consid-ered synchronous between the Alano section and ODP Site 1052. These datums thus provide a precise framework and a precious correlation tool that can be used to approximate the base of the Priabonian Stage.

In Table 3, we synthesize the calcareous plankton biochronology obtained in these two successions, but a more comprehensive and de-tailed discussion on the calcareous nannofossil biochronology can be found in Fornaciari et al. (2010). Here, we will only concentrate on bio-chronologic data concerning the chronostratig-raphy of the middle and late Eocene.

In particular, high-resolution studies on planktic foraminifera and calcareous nanno-fossil biohorizons reported in this study improve our capability of correlation over wide areas by enhancing and strengthening the biomagneto-stratigraphic scheme available to date.

Planktic Foraminifera BiochronologyOver the last decades, several planktic

forami nifera biohorizons have been used to subdivide the middle Eocene–late Eocene tran-sition; a brief discussion summarizes the three main bioevents next.

The Extinction of Muricate Morozovellids and Large Acarininids. The most important

single point in the considered interval is the calibration of the extinction of morozovellids and large acarininids. The calibration of the fi nal exit of morozavellids in Umbria-Marche sections has been associated with the top of chron C18n (Nocchi et al., 1986), while Wade (2004) associated this event with the middle part of chron C17n.3n in the NW Atlantic ocean. Our data are in perfect agreement with age estimation from Blake Nose, suggesting that the event as recorded in the Apennines might have been affected by tectonic distur-bances (Jovane et al., 2007a).

The First Appearance of Globigerinatheca semiinvoluta. The FAD of Globigerinatheca semiinvoluta has been used as a primary crite-rion for defi ning the base of zone P15 of Berg-gren et al. (1995). The LO of G. semiinvoluta has been observed within chron C17n.2n (37.66 Ma) at Alano and is younger than previ-ously indicated by Berggren et al. (1995), who placed the LO of the species close to the base of chron C17r (38.4 Ma), thus being older than the HO of Morozovelloides (38.1 Ma). Our data strongly suggest that the LO of G. semiinvoluta

is likely a diachronous event, as already noted by Berggren et al. (1995) and Berggren and Pearson (2005), and thus is not suitable to be used for correlations over wide areas.

The Final Exit of Small Acarininids. At Alano , the extinction of small acarininids occurs within chron C17n.1n (37.27 Ma) and is older with respect to data from Wade (2004), who re-ported the presence of small acarininids at least up to 34.59 Ma in chron C16n. This discrepancy indicates a possible diachroneity of this event and suggests caution in considering even a pos-sible regional use for this biohorizon.

This overview clearly shows that the ex-tinction of muricate morozovellids and large acarini nids could be considered a valuable cor-relation tool over wide areas, except for the Umbria-Marche region, where the presence of a major fault has likely produced an incorrect age estimation for this event.

Calcareous Nannofossil BiochronologyPrevious literature has proposed that the

Bartonian-Priabonian boundary is defi ned at the base of calcareous nannofossil zone NP18,

37 38 39 40

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Figure 15. Age-depth plot and derived sediment accumula-tion rate function for the Alano section obtained by magneto-stratigraphic correlation to the geomagnetic polarity time scale of Cande and Kent (1995) (CK95).

Agnini et al.


where the LO of C. oamaruensis occurred (see Berggren et al. (1985, 1995). According to these authors, the LO of C. oamaruensis oc-curs at 37.00 Ma in chron C17n.1n, and as a consequence, the base of the Priabonian Stage correlates with chron C17n.1n, with an age of 36.9 Ma (Berggren et al., 1995).

The placement of the Bartonian-Priabonian Stage in chron C17n.1n has been commonly used without any criticisms at least in the last two decades. However, the recognition of fi rst specimens of C. oamaruensis, at least in the lower part of chron C17n.2n, both in the Alano section (37.84 Ma) and at ODP Site 1052 (37.78 Ma), in turn implies, adopting the defi ni-tion of Berggren et al. (1995), that the base of the Priabonian Stage now correlates with chron C17n.2n, not with chron 17n.1n. Unfortunately, the LO of C. oamaruensis as well as the HO of C. grandis have a low degree of reproducibil-ity in many areas because of their scarce abun-dances. Nonetheless, the integration of these poor reference datums with the AB and AE of C. erbae, at 37.833 Ma and 37.449 Ma, re-spectively, provides alternative biostratigraphic correlation tools that also better constrain this interval.

The Middle Eocene Climatic Optimum Interval

Though the focus of this paragraph is on the middle to late Eocene transition, we would just note that from the biostratigraphic point of view, another interesting interval in the Alano section is that between 6.3 m level (40.60 Ma) and 22.70 m level (39.66 Ma) (Fig. 16). Several biohorizons, which include the LOs of Spheno-lithus predistentus, Dictyococcites scrippsae, D. bisectus, and S. obtusus and HOs of S. fur-catolithoides and S. spiniger, have been found to occur close to the middle Eocene climatic opti-mum event. Calibrations of these additional cal-careous nannofossil biohorizons (Table 3) and of planktic foraminifera recorded in the same interval, for instance the LO and HO of O. beck-manni, provide a fi ne integrated biochronologic framework.

CHRONOSTRATIGRAPHIC POTENTIAL OF THE ALANO SECTION: PROPOSING THE DEFINITION OF THE PRIABONIAN

The chronology discussed herein indicates that the Alano section straddles the middle Eocene–late Eocene boundary, whatever prac-tice is followed for its recognition (Fig. 1). The section meets all the requirements for serving as the global stratotype section and point (GSSP) of the chronostratigraphic unit (Remane et al.,

1996). Hence, the Alano section is here pro-posed as a candidate GSSP for defi ning the Pria-bonian, the accepted stage/age corresponding to the entire Upper/late Eocene (Luterbacher et al., 2004). According to the practice recommended by ICS (Hedberg, 1976; Cowie et al., 1986; Salvador, 1994; Remane et al., 1996), the Pria-bonian Stage is formally defi ned by the GSSP of its base, which serves also as the defi nition of the top of the underlying Bartonian Stage and middle Eocene–late Eocene boundary. Within this practice, the chronostratigraphic units are defi ned solely by the GSSPs of their bases. However, recently, Hilgen et al. (2004) recom-mended that the practice of unit stratotype for standard chronostratigraphic units should be re-covered. In the following, we detail our proposal of defi nition of the Priabonian Stage that is to be submitted to the ICS.

Rationales in Choosing the GSSP

The chronostratigraphic principles and prac-tice recommended by the ICS have been largely infl uenced by Hollis Hedberg and are summa-rized in Hedberg (1976), Cowie et al. (1986), Salvador (1994), and Remane et al. (1996). They have received a wide consensus, but they are not, however, universally accepted (e.g., see discussions in Walsh, 2005a, 2005b, 2005c) and, when accepted, not uniformly applied. We, therefore, feel the need to make clear the ratio-nales underlying our proposal of defi nition of the Priabonian Stage.

First, contrary to some recent views (see Walsh, 2004), we consider, in agreement with Hedberg (1976, p. 71), the stages (and the equiv-alent ages) to be “one of the smallest units in the standard chronostratigraphic hierarchy that in prospect may be recognized worldwide.” Hence, the most important single criterion that needs to be met by our proposal is its amenabil-ity to worldwide correlation. There is an almost unanimous consensus that a modern defi ni-tion of global chronostratigraphic units should be defi ned in points of geologic time where a wealth of correlation tools is available so that the boundaries of the stage can be recognized in the different stratigraphic records. In addition, we consider that, for an elemental need of stabil-ity of the stratigraphic nomenclature, the mod-ern defi nition of the global chronostratigraphic units should be historically appropriate. The historical appropriateness of redefi ned chrono-stratigraphic units has been widely discussed in the last years, and we refer to Walsh (2005a, 2005b, 2005c) for an extensive review.

In other words, in making our proposal, the rationales driving our choice of a specifi c point in the section will be such that: (1) the

Priabonian should be recognized worldwide, (2) the historical stratotype sections of the Pria-bonian and Bartonian should remain largely Priabonian and Bartonian in age, and (3) the most followed practice in the recognition of the Priabonian, i.e., of the middle–late Eocene boundary, should be respected as much as pos-sible; the latter is the most diffi cult task, and we are aware that it is impossible to completely fulfi ll this latter requirement, as well as to ob-tain a general consensus.

In the following, we fi rst address the histori-cal appropriateness issue by briefl y reviewing (1) the status of the Priabonian and Bartonian Stages (and the middle–late Eocene boundary) with reference to the classical sections upon which they are based, including the historical stratotypes, and (2) the practice followed in recognizing the middle–late Eocene boundary in the different biogeographic areas and strati-graphic settings. The potential of global correla-tion, a major point of dispute, will be discussed after having proposed the position in the section of the GSSP that is the “golden spike.”

The Middle–Late Eocene Boundary: An Historical Overview

The history of the chronostratigraphic sub-division of the middle and late Eocene is ex-tremely complex and is not reviewed here. Complete information is available in the litera-ture to which we refer the reader (e.g., Berggren et al., 1995; Luterbacher et al., 2004). In the International Chronostratigraphic Scale by ICS, the upper part of the Middle Eocene is repre-sented by the Bartonian Stage, while the Upper Eocene is represented by the Priabonian Stage (Luterbacher et al., 2004; Fig. 1).

As argued by Berggren et al. (1985, 1995), the problem with the placement of the Middle–Upper Eocene boundary, i.e., the base of the Priabonian, has been intimately linked with the diffi culties in correlating the classical NW Europe Eocene sections, mainly located in the Paris and London Basins, with those cropping out in the Veneto region of the Mediterranean area (Munier-Chalmas and de Lapparent, 1893). Actually, for a long time, they have been consid-ered time equivalent, and have been used for in-dicating the late Eocene (e.g., Berggren, 1971).

The Bartonian StageThough the stage was fi rst introduced with

reference to rocks in the Paris Basin, its name was derived from the Barton Clay in the Hamp-shire Basin of England (Mayer-Eymar, 1857), and it is best known today from spectacular exposures, serving as a “unit stratotype” for the Bartonian, on the Isle of Wight (Fluegeman ,



PLANKTICFORAMINIFERA

CALCAREOUS NANNOFOSSILS

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standard calcareous plankton biohorizon

Figure 16. Summary of the biomagnetostratigraphic results obtained in the Alano section. The position of the middle Eocene climatic opti mum (MECO) as evidenced by Spofforth et al. (2008, 2010) is indicated in the lower part of the section. The shaded light-gray band between 57.32 and 68.37 m highlights the critical interval for defi ning the base of the Priabonian Stage. LRO—Lowest Rare Occurrence; LO—Lowest Occurrence; LCO—Lowest Common Occurrence; HCO—Highest Common Occurrence; HO—Highest Occurrence.

Agnini et al.


2004). On the base of data reported in Aubry (1986), Berggren et al. (1995) assigned the Bartonian Stage to nannofossil zones NP16 and NP17, and questionably to a part of zone NP18. Specifi cally, Aubry reported the presence of Sphenolithus furcatolithoides as restricted to the Lower Barton Beds (Fig. 15 in Aubry, 1986), whereas Sphenolithus obtusus was observed just in lower part of the Middle Barton Beds. The calcareous nannofossil magnetobiochronology established in this paper (Table 3) suggests that the Lower Barton Beds should be older than the mid-late chron C18r, where S. furcatoli thoides becomes extinct (Fig. 1) and lie within the early NP16 zone, and that the Middle Barton Beds, containing S. obtusus, should correlate with chron C18n and upper NP16 to lowermost NP17 zones. To our knowledge, no data are available for time constraining the Upper Barton Beds and, hence, the top of the Bartonian as defi ned in its type area.

The Priabonian StageThe Priabonian Stage, named after the village

of Priabona in the eastern Lessini Mountains (NE Italy), was proposed by Munier-Chalmas and de Lapparent (1893, p. 479) on the basis of several localities in the Lessini Shelf, in order to overcome problems in correlating the NW Europe and Mediterranean middle–late Eocene marine stratigraphic records. Hardenbol (1968) formally proposed, among the different sections indicated by Munier-Chalmas and de Lapparent (1893), to choose as the stratotype section of the Priabonian that at Priabona (Fig. 2). This proposal was accepted at the Eocene Collo-quium held in Paris in 1968, where, however, fi ve parastratotype sections were also proposed; these were the Granella and Ghenderle (or Val Bressana) sections in the Lessini Mountains, the Brendola and Mossano sections in the Berici Hills, and the Possagno section in the Veneto pre-Alps (Cita, 1969; Fig. 17).

The sections in the Lessini Mountains (Pri-abona, Granella, and Ghenderle) were located in the inner part of Lessini Shelf, close to emerging lands. Their content in calcareous plankton is very poor, and their precise time framing is very diffi cult (e.g., Verhallen and Romein, 1983). The sections in the Berici Hills (Brendola and Mossano) were as well located in the Lessini Shelf, in more distal conditions, and have scarce content in calcareous plankton (Luciani et al., 2002). Finally, the deep-water Possagno section, located at the transition from the Lessini Shelf to the Belluno Basin, is the only one, among those proposed as parastratotype of the Pria-bonian, that can be framed in time accurately (Bolli, 1975; Agnini et al., 2006). To follow, we will concentrate on three of these parastratotype

sections, the Priabona, Mossano, and Possagno sections, adding some remarks also on the pe-lagic Contessa Highway section (central Italy), which has been proposed by Luterbacher et al. (2004) as a candidate section for defi ning the Priabonian.

Traditional Criteria Used in Locating the Base of the Priabonian (Upper Eocene)

In the shallow-water sections, the master paleontologic guiding criterion used for recog-nizing the Priabonian has been the fi rst appear-ance of Nummulites fabianii. This biohorizon defi nes the base of the shallow benthic forami-nifera zone SBZ19 (Serra-Kiel et al., 1998) and has been utilized in the Priabona and Mos-sano section (Hottinger, 1977; Parisi et al., 1988; Bassi and Loriga Broglio, 1999; Bassi et al., 2000) as well as in all other Tethyan shallow-water successions (e.g., Strougo, 1992; Serra-Kiel et al., 1998).

In the deep-water sections, the base of the Priabonian (Upper Eocene) has been tradition-ally associated with the extinction of the large muricate globorotalids, which virtually coin-cide with the base of zone E14 (Berggren and Pearson, 2005; Fig. 1), and with the lowest ap-pearance of C. oamaruensis, which defi nes the base zone NP18 (Martini, 1971). These two bio horizons have been observed both in the Tethyan domain (Alano, Possagno, and Con-tessa Highway sections; Jovane et al., 2007a; this study) and in and NW Atlantic ODP Site 1052 (Wade, 2004; this study).

It is noteworthy that the LO of N. fabianii, that is the base of zone SBZ 19, was considered as correlative with the base NP18 (Serra-Kiel et al., 1998), although this correlation is not warranted by sound data to our knowledge.

Time Frame of the Base of the Priabonian at Priabona

The time frame of the Priabona section is par-ticularly diffi cult because of the shallow-water transgressive nature of the succession (Setiawan, 1983). Probably the most reliable time frame of the section was established by Brinkhuis (1994) by means of a dinofl agellate cyst biostratigraphy from previously magnetostratigraphically well-calibrated pelagic sequences from central Italy. Brinkhuis concluded that the Priabona section belongs to Melitasphaeridium pseudorecur-vatum cone, correlative with chron C15–C16 and zones NP19–20 and P16 (Brinkhuis and Biffi , 1993; Brinkhuis, 1994). This interpreta-tion is supported by the evidence at Priabona where I. recurvus has been detected virtually from the base of the section with good continu-ity (Ver hallen and Romein, 1983), and this form becomes well established in the Mediterranean

sections only in advanced chron C16n time (Coccioni et al., 1988; Fornaciari et al., 2010). Hence, we concur with Brinkhuis (1994) that the historical Priabonian stratotype starts indeed in advanced Priabonian time, if all the current prac-tices for its recognition are considered (Fig. 1).

Time Frame of the Base of the Priabonian at Mossano

The Mossano section has been intensively studied because of its rich paleontologic con-tents (for a comprehensive review, see Bassi et al., 2000). The Bartonian-Priabonian bound-ary, i.e., the LO of N. fabianii, has been placed in coincidence with a major facies change from shallow-water carbonate facies (Calcare num-mulitico Auctorum) to deeper-water terrigenous facies (Marna di Priabona). The Priabonian at Mossano is more than 100 m thick (Ungaro, 1969), although useful fairly detailed data have been collected only in the basal most part by Lu-ciani et al. (2002), who studied the calcareous plankton across the transition between the two formations. Specifi cally, they observed the total lack of calcareous plankton in the upper part of Calcare nummulitico and documented poor planktic foraminifera and calcareous nanno-fossils assemblages in 10 samples from the basal ~11 m of the Marne di Priabona, where signifi cant datums are the occurrences of Glo-bigerinatheca semiinvoluta (in the lower 6 m of the Marne di Priabona), I. recurvus (in a single sample at 8 m above the base of the Marna di Priabona), and Turborotalia cunialensis (in two samples at 9 and 10 m above the base of the Marna di Priabona). The presence of the latter form, appearing in chron C15r time (Berggren et al., 1995), strongly suggests, as for the type Priabonian at Priabona, an advanced Priabonian age with reference to the conventional criteria used for its recognition (Figs. 1 and 17). The oc-currence of I. recurvus at ~8 m from the base would reinforce this interpretation. However, detailed interpretation of the Mossano data is diffi cult. Specifi cally, it is diffi cult to interpret the short spacing (just 3 m) between the HO of G. semiinvoluta and the LO of T. cunialen-sis, because these two biohorizons would be separated by some 0.6 m.y. on the basis of the available biochronology (Fig. 1). Three options are possible: (1) the current distribution models of the two species are not completely known, (2) the sediment accumulation rate is exceed-ingly (and unreasonably) low for shelf sedi-ments, or (3) there is a hiatus within the short interval considered. Whatever the interpretation is, it can be conservatively stated that the basal sediments at Mossano are younger than the late chron C17n.2n to which we have calibrated the LO of G. semiinvoluta at Alano (Fig. 10;



0

100

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(m)

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(198

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140

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Agnini et al.


Table 3). However, probably, the most impor-tant output of this discussion is that the LO of N. fabianii, i.e., the base of zone SBZ19, is to be correlated with a time younger, probably much younger, than the late chron C17n.2n.

Correlation among Alano, Possagno, and Contessa Highway Sections

In Figure 17, we show the correlation of the Alano section with the classical deep-water sec-tions of Possagno and Contessa Highway. The correlation with Possagno is straightforward, even if the available data for Possagno have been collected in low resolution. The correla-tion to the Contessa Highway section is more problematic, because the position of the ex-tinction of large acarininids, one of the most distinctive biohorizons in late Eocene planktic foraminifera, is located in chron C17n.3n in the Alano section, whereas it was interpreted to lie in chron C18n.1n in the Contessa High-way section (Jovane et al., 2007a; Fig. 17). The apparent inconsistency between these data is likely explained by the presence of a major previously undescribed fault. We agree with Jovane et al. (2007a) that this signifi cant fault zone has removed a portion of the record, but in our interpretation, the missing interval is much more important than indicated by these authors, covering at least the entire C18n.1n, and thus suggesting that the HO of large acarininids falls in chron C17n.3n, now in accordance with data from the Alano section and ODP Site 1052.

Current Practice in Recognizing the Base of the Priabonian (Middle–Upper Eocene Boundary)

We can confi dently state that, in the past 30 yr, the most infl uential authors in determining the practices in Cenozoic chronostratigraphic as-signments have been William Berggren and coworkers, in particular, with their compila-tions of 1985 and 1995. Marine and continental stratigraphers have, sometimes uncritically, fol-lowed the proposals of Berggren and coworkers, which have become an unoffi cial standard in the absence of a formally defi ned International Chronostratigraphic Scale. Concerning the Pria-bonian, Berggren et al. (1985), after carefully reviewing the status of the Bartonian-Priabonian boundary in the literature, and considering both the time frame of historical sections and the correlation tools available at that time, placed the Bartonian-Priabonian boundary, i.e., the middle–late Eocene boundary, at NP17/NP18 zonal boundary, correlated with the younger part of chron C17n (Fig. 5 in Berggren et al., 1985). Berggren et al. (1995) confi rmed this placement of the boundary, assigning a revised estimated

age of 37.0 Ma to the LO of C. oamaruensis, that is, the base of zone NP18 (Fig. 2 in Berg-gren et al., 1995). Actually, data on the calcare-ous plankton biostratigraphy and biochronology available in Berggren et al. (1985, 1995) were contradictory and poorly constrained (see Tables 9 and 15 in Berggren et al., 1995), as shown by Wade (2004) and in the present work (Table 3).

Surprisingly, Berggren et al. (1985, 1995) did not attach a major importance to the extinc-tion of large muricate globorotalids, which they calibrated to late chron C18n, and associated the base of the Priabonian with chron C17n.1n, to which they calibrated the LO of C. oamaru-ensis (Fig. 2 in Berggren et al., 1995). Hence, they privileged the latter two poor biostrati-graphic datums and underplayed an event that we consider to be reliable. However, the pro-posal of Berggren and coworkers has become widely accepted, and it can be safely stated that the most widespread practice for locating the base of the Priabonian has been to equate the Middle–Upper Eocene boundary with the base of zone NP18 lying in late chron C17n.1n (e.g., Serra-Kiel et al., 1998). As a matter of fact, even planktic foraminifera specialists (e.g., Wade, 2004; Berggren and Pearson, 2005) have placed the Middle–Upper Eocene boundary above the extinction of large muricate planktic foraminif-era. Actually, in the present work (Table 3), we have shown that our LO of C. oamaruensis, al-though scarcely reproducible, is much closer to extinction of large planktic spinose foraminifera than reported by Berggren et al. (1995), and this fi nding is of considerable importance for pro-posing the GSSP of the Priabonian put forward in the following section.

Proposal of the GSSP of the Priabonian

In synthesis, the previous discussion shows that these are the paleontologic criteria that have been widely used for recognizing the base of the Priabonian in the marine stratigraphic records:

(1) the LO of Nummulites fabianii, i.e., the base of zone SBZ19, applied in shallow-water facies (e.g., Serra-Kiel et al., 1998);

(2) the HO of large muricate planktic forami-nifera, correlating with the base of zone E14 (e.g., Mancin and Pirini, 2002); and

(3) the base of zone NP18, i.e., the LO of C. oamaruensis (i.e., Berggren et al., 1985, 1995).

In the deep-water Alano section, the LO of N. fabianii is not recorded, while events defi n-ing the other two criteria are clearly detected and occur in the lower chron C17n, in a ~6–7 m interval, corresponding to ~0.16 m.y. (Fig. 18). This is the critical interval to consider for driving the “golden spike,” if we wish to guarantee both correlatability and historical appropriateness.

The most widespread practice in proposing GSSPs has been and still is to locate the “golden spike” exactly in the lithologic level where a specifi c, arguably widely correlatable, biostrati-graphic or magnetostratigraphic event occurs. Within this practice, there would be three viable options at Alano for defi ning the base of the Pria bonian (see Figs. 16 and 18):

(1) the HO of large muricate globorotalids foraminifera at 57.32 m level, which is here considered a reliable and widely traceable event (see previous discussion); this choice would be probably the best preferred by planktic forami-nifera specialists;

(2) the base of zone NP18, at 62.85 m level, which we have shown to be defi ned by a poor biohorizon (LO of C. oamaruensis), but which appears to be a commonly followed practice in the last years and would be probably the best preferred by calcareous nannoplankton spe-cialists; or

(3) the polarity reversal at the base of chron C17n, which would allow a correlation with continental records, and would be probably the best preferred choice by magnetostratigraphic specialists.

However, we disagree this practice and con-cur with Berggren et al. (1985, p. 1409) that: “...proper stratigraphic procedure requires that paleontologic criteria, although defi nitive for regional correlation (i.e., recognition) beyond the stratotype region, should not be part of the defi nition itself... (Hedberg, 1976).”

Therefore, in order to preserve harmony within the stratigraphic community, we pre-fer to propose as the GSSP a lithologic level easily recognized in the fi eld around which signifi cant changes occur that allow its ap-proximated correlation in the different strati-graphic rec ords worldwide. Such an approach, beyond having the advantage of making the GSSP easily recognizable in the fi eld, serves also to make it clear that chronostratigraphy is not biostratigraphy and/or magnetostratig-raphy, and that long distance and different facies (marine and continental) correlations are essentially geochronologic in nature (Van Couvering and Berggren, 1977). It is to say, time, and not a particular biostratigraphic or magnetostratigraphic feature, is used for rec-ognizing with approximation a chronostrati-graphic boundary. Therefore, what is crucially important is to know the exact age of the litho-logic point that defi nes a boundary. Ideally, as it has been done for the late Neogene, a GSSP should be defi ned in orbitally tuned sections, i.e., framed in an astrochronology with an ac-curacy that is not attainable with other tools. Such a chronology is not yet available in the Alano section, even if the cyclicity apparently



present in geochemical and lithologic proper-ties is presently under study.

Within this strictly Hedbergian conceptual frame, we propose to the ICS that the base of the Priabonian should be defi ned at the base of the Tiziano bed at 63.57 m level in the Alano section. In Figure 18, we report the chronology of the Tiziano bed with refer-ence to the geomagnetic polarity times scale available models, none of which is probably defi nitive. The proposed defi nition allows the recognition of the Priabonian worldwide with a good approximation. The defi nition we propose is historically appropriate and rea-sonably respectful of the most recent strati-graphic practices; in fact:

(1) the Priabonian, as defi ned in its strato-type at Priabona and recognized in the classical Veneto region, is comprehended in the proposed defi nition;

(2) classical middle Eocene taxa like the large muricate planktic foraminifera remain in the middle Eocene;

(3) Istomolithus recurvus, an unquestionable late Eocene calcareous nannofossil taxon, re-mains in the late Eocene; and

(4) Nummulites fabianii, an unquestionable Late Eocene large foraminiferal taxon, remains in the late Eocene.

A major drawback of the proposed defi nition is represented by the fact that we do not know with accuracy the chronology of the large foraminifera evolution at the transition from the middle to the late Eocene, and there is a chance that large ben-thic foraminifera traditionally considered middle Eocene could result in the late Eocene moving within the proposed defi nition. However, looking at the stratigraphic information available in the critical interval for defi ning the Priabonian, we do not see alternative to the proposed defi nition.

Global Correlation

The GSSP is the only place where we actually know (by defi nition) that time and rocks coincide within our classifi cation (Holland, 1984, p.149). Elsewhere from the type section, a chrono-stratigraphic boundary can only be approxi-mated by using and cross-checking the different available correlation tools. In the following, we discuss the correlatability potentials of the pro-posed GSSP of the Priabonian at Alano.

MagnetostratigraphyThe chron C17r–chron C17n boundary is lo-

cated 10.95 m below the proposed GSSP and serves as good approximation of the base of the Priabonian in continental and marine settings. Within the current age models of the geomag-netic polarity time scale, the approximation range from 309 to 250 ka depends on the model considered (Fig. 18).

Marine BiostratigraphyIt is beyond our scope to review all the marine

fossil groups that may provide tools for recog-nizing the base of the Priabonian in the differ-ent depositional settings and biogeographic regions. In Figure 18 (and Table 4), we compare the age of the Tiziano bed, that is the base of the Priabonian, with the biochronology of cal-careous plankton, the most powerful correlation tool available in marine sediments. The extinc-tion of the large muricate planktic foraminifera would approximate the base of the Priabonian within 200 k.y. The well-consolidated practice of recognizing the Priabonian by the means of its original defi nition, i.e., the LO of C. oamaru-ensis, should be used with caution. Instead,

C17r50

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60

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TIZIANO BED�

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large acarininids HO (57.32 m)

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�(37.833)

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Chron Lithology

Posit

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(m)

� Chron C17n.3n base (52.62 m)

�(38.113)

38.2

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Figure 18. Close-up of the critical interval for defi ning the base of the Priabonian. Biomagnetostratigraphic events considered as useful for approximating the middle–late Eocene boundary, that is the base of the Tiziano bed, are plotted against magnetostratigraphy and lithology. Age estimations for the Tiziano bed as well as for biomagnetostratigraphic events are calculated using different time scales (geomagnetic polarity time scale of Cande and Kent [1995]; GTS04; Pälike et al., 2001) and are reported on the right side. LO—Lowest Occurrence; LCO—Lowest Common Occurrence; HO—Highest Occurrence.

Agnini et al.


we are confi dent that the acme beginning of C. erbae , at 61 cm below the base of the Tiziano bed, recorded in many sections in Italy and in the Atlantic Ocean (see Fornaciari et al., 2010), represents an easy to recognize event and accu-rate approximation (within less than 20 k.y.; Fig. 18; Table 4) of the base of the Priabonian.

Required Future Work

The proposed defi nition of the GSSP of the Priabonian will serve to overcome the present unacceptable state of uncertainty and contradic-tions in recognizing the middle Eocene–late Eo-cene boundary. However, further work is needed to better constrain in time the absolute age of the proposed GSSP. In particular, we are working on the radioisotopic dating of the Tiziano bed and the orbital tuning of the Alano section in order to assess a better age of the GSSP.

Other work that is needed is a better tie be-tween the large benthic foraminifera biostratig-raphy and the geomagnetic polarity time scale in order to provide a better correlation potential between shallow- and deep-water successions.

Toward a Unit Stratotype of the Priabonian

Within the current rules of the ICS, the top of the Priabonian, equivalent to the base of the Rupelian and to the Eocene-Oligocene boundary, is defi ned by the GSSP approved at Massignano, in the Marche region (North-ern Apennines, Italy). If our proposal at Alano will be accepted, the Priabonian Stage may be formally and unequivocally defi ned according to the approved rules of the ICS. However, we concur with Hilgen et al. (2004) that a stage is a kind of stratigraphic unit that is best represented by succession of strata rather than by two single points in the stratigraphic record. It is proposed here that if the orbital tuning at Alano is suc-cessful, the unit stratotype of the Priabonian could be represented by the composite section constituted by the Alano and Massignano sec-tions. As shown in Figure 17, these two sections

together seem to represent the entire interval of time that we have proposed as representing the Priabonian.

CONCLUSIONS

The major output of this paper is the proposal to the ICS of designating the base of a promi-nent crystal tuff layer (Tiziano bed) in the Alano section, NE Italy, as the GSSP of the Priabonian Stage, the standard chronostratigraphic unit of the Upper Eocene. The section, described for the fi rst time in this paper, is continuously and spectacularly outcropping, well accessible, un-affected by structural deformation, rich in well-preserved planktic foraminifera and calcareous nannofossils, and contains six prominent crystal tuff layers, some of which seem amenable to isotopic dating.

A second output of our study is a much im-proved chronostratigraphic framework for the middle–late Eocene transition, which has been controversial in the literature. The high-resolu-tion and solid biomagnetostratigraphic frame-work established at Alano has been compared with the data already available (Wade, 2004) or was acquired specifi cally for this work in the deep-sea ODP Site 1052, straddling the middle–late Eocene. We have shown that the extinction of large muricate planktic foraminifera, a major step in the evolution of this group during the Cenozoic (e.g., Berggren, 1969), occurred in mid–chron C17n.3n and was probably a syn-chronous event over wide areas. Concomitant with this event, major changes are observed in the calcareous nannofossil assemblages, the most important of which is the acme beginning of the distinctive Cribrocentrum erbae. We have revised the biostratigraphic reliability and bio-chronology of calcareous plankton, pointing out that the LO of C. oamaruensis and the HO of C. grandis must be used with extreme caution for accurate correlations, the LO of I. recurvus is much older than in previous age estimates (e.g., Berggren et al., 1995), and the biochronol-ogy of the LO of T. cerroazulensis group likely

needs to be signifi cantly changed with respect to calibration reported in Berggren et al. (1995).

We have discussed the correlation potential of the proposed Priabonian GSSP at Alano. The extinction of muricate planktic foraminifera and the acme beginning of C. erbae are thought to be useful tools for approximating the base of the Priabonian in the marine stratigraphic records over large areas and depositional settings. The base of chron C17n is useful for correlation with continental records. Most probably, the fi rst ap-pearance of Nummulites fabianii would remain a useful criterion for recognizing the Priabonian in shallow-water marine settings, even if an im-proved correlation between the large forami nif-era biostratigraphy to the geomagnetic polarity time scale is in order.

If the proposed GSSP will be accepted, the Priabonian, the top of which is defi ned at Massignano (Premoli Silva and Jenkins, 1993), would have a duration of ~4.1 m.y., compared to the estimated duration of 3.5 m.y. of Berg-gren et al. (1995) and 3.3 m.y. of Ogg and Smith (2004).

Work is continuing on the Alano section in an attempt to establish an orbital tuning of the pro-posed GSSP and isotopic dating of the Tiziano bed, both of which would allow a much better time frame for the base of the Priabonian and improve the time scale of the late Eocene. How-ever, the data available and presented in this paper are considered adequate for formalizing the GSSP of the Priabonian at the base of the Tiziano bed in Alano section, thus contributing to the task of ratifying GSSPs and stabilizing the International Chronostratigraphic Scale ex-pected within the next International Geologic Congress in 2012.

ACKNOWLEDGMENTS

We would like to thank Eustoquio Molina, Simonetta Monechi, and the GSA Bulletin science editor, Christian Koeberl, for their reviews. This re-search was mostly funded by MIUR-PRIN grant 2007W9B2WE_004 to D. Rio (within a National Research Project coordinated by I. Premoli Silva). Additional funding was provided to P. Grandesso and

TABLE 4. EVENTS DURING THE BARTONIAN-PRIABONIAN TRANSITION

Position Position† Notation relative to chron top CK95 Age* GTS04 Age* Pälike et al. (2001) Age*)ak()aM()ak()aM()ak()aM()m()m(tnevE

C. erbae AE 75.01 11.44 C17n.1n 0.972 37.449 365 37.342 179 37.396 191G. semiinvoluta LO 68.37 4.8 C17n.2n 0.250 37.665 149 37.396 125 37.454 134Tiziano bed (base) 63.57 0 C17n.2n 0.861 37.814 0 37.521 0 37.588 0C. erbae AB 62.96 –0.61 C17n.2n 0.939 37.833 –19 37.537 –16 37.605 –17C. oamaruensis LRO 62.85 –0.72 C17n.2n 0.953 37.837 –22 37.539 –19 37.608 –20Morozovelloides HO 57.52 –6.05 C17n.3n 0.394 37.996 –182 37.673 –153 37.773 –185Large acarininids HO 57.32 –6.25 C17n.3n 0.418 38.001 –187 37.677 –157 37.778 –190Chron C17n.3n base 52.62 –10.95 C17n.3n 1.000 38.113 –299 37.771 –250 37.897 –309

Note: CK95—Cande and Kent, 1995; GTS04—Geological Time Scale 2004; LO—Lowest Occurrence; AB—Acme Beginning; LRO—Lowest Rare Occurrence; HO—Highest Occurrence. Age is calculated relative to the base of the Tiziano bed.

*Age (ka) relative to the Tiziano bed.†Position (m) relative to the Tiziano bed.



C. Stefani by the University of Padova, to L. Lanci by Urbino University, to G. Muttoni by the Univer-sity of Milano, to D.J.A. Spofforth by a Natural Environment Research Council studentship (NER/S/A/2005/13474), and to H. Pälike by Particle Physics and Astronomy Research Council - Science and Tech-nology Facilities Council grant PP/D002176/1.

The research project was promoted and coor-dinated by D. Rio, who supervised the organiza-tion and wrote the general parts of the manuscript; P. Grandesso, C. Stefani, C. Agnini, L. Giusberti, and D. Rio described the section and regional geology; D. Spofforth and H. Pälike produced the geochemical data; L. Giusberti studied benthic foraminifera and in-terpreted paleodepth; G. Muttoni and L. Lanci studied paleomagnetism; V. Luciani studied planktic forami-nifera; and E. Fornaciari and C. Agnini examined cal-careous nannofossils.

REFERENCES CITED

Agnini, C., Muttoni, G., Kent, D.V., and Rio, D., 2006, Eocene biostratigraphy and magnetic stratigraphy from Possagno, Italy: The calcareous nannofossil response to climate variability: Earth and Planetary Science Letters, v. 241, p. 815–830, doi: 10.1016/j.epsl.2005.11.005.

Alegret, L., Cruz, L.E., Fenero, R., Molina, E., Ortiz, S., and Thomas, E., 2008, Effects of the Oligocene climatic events on the foraminiferal record from Fuente Caldera section (Spain, western Tethys): Palaeogeography, Palaeo climatology, Palaeoecology, v. 269, p. 94–102, doi: 10.1016/j.palaeo.2008.08.006.

Aubry, M.-P., 1986, Palaeogene calcareous nannofossil bio-stratigraphy of northwestern Europe: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 55, p. 267–334, doi: 10.1016/0031-0182(86)90154-9.

Aubry, M.-P., Ouda, K., Dupuis, C., Berggren, W.A., Van Couvering, J.A., Ali, J.R., Brinkhuis, H., Gingerich, P.R., Heilmann-Clausen, C., Hooker, J.J., Kent, D.V., King, C., R.W.O.’B. Knox, Laga, P., Molina, E., Schmitz, B., Steurbaut E., and Ward., D.R., 2007, The global standard stratotype-section and point (GSSP) for the base of the Eocene Series in the Dababiya sec-tion (Egypt): Episodes, v. 30(4), p. 271–286.

Backman, J., 1987, Quantitative calcareous nannofossil bio-chronology of middle Eocene through early Oligocene sediment from DSDP Sites 522 and 523: Abhandlungen der Geologischen Bundesanstalt, v. 39, p. 21–32.

Backman, J., and Shackleton, N.J., 1983, Quantitative bio-chronology of Pliocene and early Pleistocene calcare-ous nannoplankton from the Atlantic, Indian and Pacifi c Oceans: Marine Micropaleontology, v. 8, p. 141–170, doi: 10.1016/0377-8398(83)90009-9.

Barbieri, R., Benjamini, C., Monechi, S., and Reale, V., 2003, Stratigraphy and benthic foraminiferal events across the middle–late Eocene transition in the western Negev, Israel , in Prothero, D.R., Ivany, L.C., and Nesbitt, E.A., eds., From Greenhouse to Icehouse: The Marine Eo-cene–Oligocene Transition: New York, Columbia Uni-versity Press, p. 453–470.

Bassett, M.G., 1985, Towards a “common language” in stra-tigraphy: Episodes, v. 8, p. 87–92.

Bassi, D., and Loriga Broglio, C., 1999, Alveolinids at the Middle–Upper Eocene boundary in northeastern Italy (Veneto, Colli Berici, Vicenza): Journal of Foraminif-eral Research, v. 29, p. 222–235.

Bassi, D., Cosovic, C., Papazzoni, C.A., and Ungaro, S., 2000, The Colli Berici, in Bassi, D., ed., Field Trip Guidebook. Shallow Water Benthic Communities at the Middle–Upper Eocene Boundary. Southern and North-Eastern Italy, Slovenia, Croatia, Hungary: Fer-rara, 5th Meeting of the International Geoscience Programme Annali dell’Università di Ferrara, Supple-ment 8, p. 43–57.

Beccaluva, L., Bianchini, G., and Wilson, M., eds., 2007, Cenozoic Volcanism in the Mediterranean Area: Geo-logical Society of America Special Paper 418, 335 p.

Benjamini, C., 1980, Stratigraphy and foraminifera of the Qezi’ot and Har‘Aqrav formations (latest middle to late Eocene) of the western Negev, Israel: Israel Journal of Earth Sciences, v. 29, p. 227–244.

Berggren, W.A., 1969, Rates of evolution in some Cenozoic planktonic foraminifera: Micropaleontology, v. 15, p. 351–365, doi: 10.2307/1484931.

Berggren, W.A., 1971, Tertiary boundaries and correlations, in Funnell, B.M., and Riedel, W.R., eds., Micro palaeon-tology of the Oceans: Cambridge, UK, Cambridge Uni-versity Press, p. 693–809.

Berggren, W.A., and Miller, K.G., 1989, Cenozoic bathyal and abyssal calcareous benthic foraminiferal zonation: Micropaleontology, v. 35, p. 308–320, doi: 10.2307/1485674.

Berggren, W.A., and Pearson, P.N., 2005, A revised tropical to subtropical Paleogene planktonic foraminiferal zona-tion: Journal of Foraminiferal Research, v. 35, p. 279–298, doi: 10.2113/35.4.279.

Berggren, W.A., Kent, D.V., Flynn, J.J., and Van Couver-ing, J.A., 1985, Cenozoic geochronology: Geological Society of America Bulletin, v. 96, p. 1407–1418, doi: 10.1130/0016-7606(1985)96<1407:CG>2.0.CO;2.

Berggren, W.A., Kent, D.V., Swisher, C.C., III, and Aubry, M.-P., 1995, A revised Cenozoic geochronology and chronostratigraphy, in Berggren, W.A., et al., eds., Geochronology, Time Scales and Global Stratigraphic Correlation: Society for Sedimentary Geology Special Publication 54, p. 129–212.

Bernoulli, D., 1972, North Atlantic and Mediterranean Meso-zoic facies: A comparison, in Hollister, C.D., Ewing, J.I., et al., Proceedings of Deep Sea Drilling Project, Initial Reports, Volume 11: Washington, D.C., U.S. Government Printing Offi ce, p. 301–871.

Bernoulli, D., and Jenkyns, H.C., 1974, Alpine, Mediter-ranean, and Central Atlantic Mesozoic facies in rela-tion to the early evolution of the Tethys, in Dott, R.H., Jr., and Shaver, R.H., eds., Modern and Ancient Geo-synclinal Sedimentation: Society for Sedimentary Geol ogy Special Publication 19, p. 19–160.

Bernoulli, D., Caron, C., Homewood, P., Kalin, O., and Van Stuijvenberg, J., 1979, Evolution of continental mar-gins in the Alps: Schweizerische Mineralogische und Petrographische Mitteilungen, v. 59, p. 165–170.

Besse, J., and Courtillot, V., 2002, Apparent and true polar wander and the geometry of the geomagnetic fi eld in the last 200 million years: Journal of Geophysi-cal Research, v. 107, no. B11, p. 2300, doi: 10.1029/2000JB000050.

Bignot, G., 1998, Middle Eocene benthic foraminifers from Holes 960A and 960C, Central Atlantic Ocean, in Mascle , J., Lohmann, G.P., Moullade, M., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Volume 159: College Station, Texas, Ocean Drilling Program, p. 433–444.

Bohaty, S.M., and Zachos, J.C., 2003, A signifi cant Southern Ocean warming event in the late middle Eocene: Geol-ogy, v. 31, p. 1017–1020, doi: 10.1130/G19800.1.

Bohaty, S.M., Zachos, J.C., Florindo, F., and Delaney, M.L., 2009, Coupled greenhouse warming and deep-sea acidifi cation in the middle Eocene: Paleoceanography, v. 24, no. 2, p. PA2207, doi: 10.1029/2008PA001676.

Bolli, H.M., ed., 1975, Monografi a Micropaleontologica sul Paleocene e l’Eocene di Possagno, Provincia di Treviso, Italia: Schweizerische Palaeontologische Abhandlungen, v. 97, 222 p.

Bonarelli, G., 1891, Il territorio di Gubbio. Norizie Geolo-giche: Roma, Tipografi a Economica, 38 p.

Bosellini, A., 1989, Dynamics of Tethyan carbonate platform, in Crevello, P.D., et al., eds., Controls on Carbonate Platform and Basin Platform: Society for Sedi mentary Geology Special Publication 44, p. 3–13.

Bosellini, F.R., and Papazzoni, C.A., 2003, Palaeoecological signifi cance of coral-encrusting foraminiferan associa-tions: A case-study from the Upper Eocene of north-ern Italy: Acta Palaeontologica Polonica, v. 48, no. 2, p. 279–292.

Bralower, T.J., and Mutterlose, J., 1995, Calcareous nanno-fossil biostratigraphy of Site 865, Allison Guyot, Central Pacifi c Ocean: A tropical Paleogene reference section, in Winterer, E.L., Sager, W.W., Firth, J.V.,

Sinton , J.M., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Volume 143: College Sta-tion, Texas, Ocean Drilling Program, p. 31–74.

Brinkhuis, H., 1994, Late Eocene to early Oligocene dino-fl agellate cysts from the Priabonian type-area (north-east Italy): Biostratigraphy and paleoenvironmental interpretation: Palaeogeography, Palaeoclimatology, Palaeo ecology, v. 107, p. 121–163, doi: 10.1016/0031-0182(94)90168-6.

Brinkhuis, H., and Biffi , U., 1993, Dinofl agellate cyst stra-tigraphy of the Eocene-Oligocene transition in central Italy: Marine Micropaleontology, v. 22, p. 131–183, doi: 10.1016/0377-8398(93)90007-K.

Canavari, M., 1894, I terreni del Terziario inferiore e quelli del Cretaceo inferiore nell’Appennino centrale: Pro-cessi Verbali Società Toscana, v. 8, p. 43–44.

Cande, S.C., and Kent, D.V., 1995, Revised calibration of the geomagnetic polarity time scale for the Late Creta-ceous and Cenozoic: Journal of Geophysical Research, v. 100, no. B4, p. 6093–6096, doi: 10.1029/94JB03098.

Channell, J.E.T., and Medizza, F., 1981, Upper Cretaceous and Palaeogene magnetic stratigraphy and biostratig-raphy from the Venetian (southern) Alps: Earth and Planetary Science Letters, v. 55, p. 419–432, doi: 10.1016/0012-821X(81)90169-2.

Channell, J.E.T., D’Argenio, B., and Horvath, F., 1979, Adria, the African promontory in Mesozoic Mediterra-nean palaeogeography: Earth-Science Reviews, v. 15, p. 213–292, doi: 10.1016/0012-8252(79)90083-7.

Channell, J.E.T., Doglioni, C., and Stoner, J.S., 1992, Jurassic and Cretaceous paleomagnetic data from the southern Alps (Italy): Tectonics, v. 11, p. 811–822, doi: 10.1029/92TC00212.

Cita, M.B., 1969, Le Paleocene et l’Eocene de l’Italie du nord, in Colloque sur l’Eocene, Paris (1968), France: Mémoires du Bureau des Récherches Géologique et Minières, v. 69, no. 3, p. 417–428.

Cita, M.B., 1975, Stratigrafi a della Sezione di Possagno, in Bolli, H.M., ed., Monografi a Micropaleontologica sul Paleocene e l’Eocene di Possagno, Provincia di Treviso , Italia: Schweizerische Palaeontologische Abhandlungen , v. 97, p. 9–33.

Coccioni, R., and Galeotti, S., 2003, Deep-water benthic foraminiferal events from the Massignano Eocene/Oligocene boundary stratotype, central Italy, in Prothero , D.R., Ivant, L.C., and Nesbitt, E., eds., From Greenhouse to Icehouse: The Marine Eocene-Oligocene Transition: New York, Columbia University Press, p. 438–452.

Coccioni, R., Monaco, P., Monechi, S., Nocchi, M., and Parisi , G., 1988, Biostratigraphy of the Eocene–Oligocene boundary at Massignano (Ancona, Italy), in Premoli Silva, I., et al., eds., The Eocene–Oligocene Boundary in the Marche-Umbria Basin (Italy): Ancona, Italy, Fratelli Anniballi, International Union of Geological Sciences Special Publication , International Subcommission on Paleogene Stratigraphy Report, p. 59–80.

Costa, V., Doglioni, C., Grandesso, P., Masetti, D., Pellegrini , G.B., and Tracanella, E., 1996, Carta Geo-logica d’Italia, Foglio 063, Belluno: Roma, Servizio Geologico d’Italia, scale 1:50,000, 1 sheet + 74 p.

Cowie, J.W., Ziegler, W., Boucot, A.J., Bassett, M.G., and Remane, J., 1986, Guidelines and statutes of the Inter-national Commission on Stratigraphy (ICS): Courier Forschungs-Institut Senckenberg, v. 83, p. 1–14.

Dallanave, E., Agnini, C., Muttoni, G., and Rio, D., 2009, Magneto-biostratigraphy of the Cicogna section (Italy ): Implications for the late Paleocene–early Eo-cene time scale: Earth and Planetary Science Letters, v. 285, p. 39–51, doi: 10.1016/j.epsl.2009.05.033.

D’Argenio, B., Channell, J.E.T., and Horwath, F., 1980, Paleotectonic evolution of Adria, the African Promon-tory: Mémoires du Bureau des Récherches Géologique et Minières, v. 115, p. 331–351.

Dercourt, J., Zonenshain, L.P., Ricou, L.-E., Kazmin, V.G., Le Pichon, X., Knipper, A.L., Grandjacquet, C., Sbortshikov, I.M., Geyssant, J., Lepvrier, C., Pecher-sky, D.H., Boulin, J., Sibuet, J.-C., Savostin, L.A., Sorokhtin, O., Westphal, M., Bazhenov, M.L., Lauer, J.P., and Biju-Duval, B., 1986, Geological evolution of the Tethys belt from the Atlantic to the Pamirs since

Agnini et al.


the Lias: Tectonophysics, v. 123, p. 241–315, doi: 10.1016/0040-1951(86)90199-X.

Di Napoli Alliata, E., Proto Decima, F., and Pellegrini, G.B., 1970, Studio Geologico, Stratigrafi co e Micropaleon-tologico dei Dintorni di Belluno: Memorie della So-cieta Geologica Italiana, v. 9, p. 1–28.

Doglioni, C., and Bosellini, A., 1987, Eoalpine and Meso-alpine tectonics in the southern Alps: Geologische Rundschau, v. 76, no. 3, p. 735–754, doi: 10.1007/BF01821061.

Edgar, K.M., Sexton, P.F., Norris, R.D., Wilson, P.A., and Gibbs, S.J., 2007, Evolutionary response of planktic foraminifera to a pronounced global warming event 40 Myr ago: Eos (Transactions, American Geophysi-cal Union), Fall Meeting supplement, v. 88, no. 52, abstract OS14A–03.

Fisher, R.A., 1953, Dispersion on a sphere: Proceedings of the Royal Society of London, v. A217, p. 295–305.

Fluegeman, R.H., 2004, Defi ning the Lutetian-Bartonian stan-dard Eocene Stage boundary and identifying a global stratotype section and point (GSSP): Geological Society of America Abstracts with Programs, v. 36, no. 5, p. 99.

Fornaciari, E., Agnini, C., Catanzariti, R., Rio, D., Bolla, E.M., and Valvasoni, E., 2010, Mid-latitude calcareous nannofossil biostratigraphy and biochronology across the middle to late Eocene transition: Stratigraphy, v. 7, p. 229–264.

Gibson, T.G., 1989, Planktonic/benthonic foraminiferal ratios : Modern patterns and Tertiary applicability: Ma-rine Micropaleontology, v. 15, p. 29–52, doi: 10.1016/0377-8398(89)90003-0.

Giusberti, L., Rio, D., Agnini, C., Backman, J., Fornaciari, E., Tateo, F., and Oddone, M., 2007, Mode and tempo of the Paleocene-Eocene thermal maximum in an ex-panded section in the Venetian pre-Alps: Geological Society of America Bulletin, v. 119, p. 391–412, doi: 10.1130/B25994.1.

Gonzalvo, C., and Molina, E., 1992, Bioestratigrafía y cronoestratigrafía del tránsito Eoceno–Oligoceno en Torre Cardela y Massignano (Italia): Revista Espanola de Paleontologia, v. 7, no. 2, p. 109–126.

Gonzalvo, C., and Molina, E., 1996, Bioestratigrafía y cronoestratigrafía del tránsito Eoceno medio-Eoceno superior en la Cordillera Bética: Revista Española de Micropaleontología, v. 28, no. 2, p. 25–44.

Gradstein, F.M., Ogg, J.G., and Smith, A.G., eds., 2004, A Geological Time Scale, 2004: Cambridge, UK, Cam-bridge University Press, 589 p.

Grandesso, P., 1976, Biostratigrafi a delle formazioni terziarie del Vallone Bellunese: Bollettino Società Geologica Italiana, v. 94, p. 1323–1348.

Grünig, A., and Herb, R., 1980, Paleoecology of late Eo-cene benthonic foraminifera from Possagno (Treviso—northern Italy): Cushman Foundation for Foraminiferal Research—Studies in marine micropaleontology and paleoecology: A memorial volume to Orville L. Bandy: Cushman Foundation Special Publication 19, p. 68–85.

Hardenbol, J., 1968, The “Priabonian” type section (a pre-liminary note): Mémoires du Bureau des Récherches Géologique et Minières, v. 58, p. 629–635.

Hedberg, H.D., ed., 1976, International Stratigraphic Guide: New York, John Wiley and Sons, 200 p.

Hilgen, F.J., 2008, Recent progress in the standardization and calibration of the Cenozoic time scale: News-letters on Stratigraphy, v. 43, no. 1, p. 15–22, doi: 10.1127/0078-0421/2008/0043-0015.

Hilgen, F.J., Schwarzacher, W., and Strasser, A., 2004, Con-cept and defi nitions in cyclostratigraphy (second report of the cyclostratigraphy working group), in D’Argenio, B., Fischer, A.G., Premoli Silva, I., Weissert, H., and Ferreri, V., eds., Cyclostratigraphy: Approaches and Case Histories: Society for Sedimentary Geology Spe-cial Publication 81, p. 303–305.

Holbourn, A.E., and Henderson, A.S., 2002, Re-illustration and revised taxonomy for selected deep-sea benthic foraminifers: Palaeontologia Electronica, v. 4, no. 2, 34 p., http://palaeo-electronica.org/paleo/2001_2/foram/issue2_01.htm.

Holland, C.H., 1984, Steps to a standard Silurian, in Stratig-raphy; Proceedings 27th International Geological Con-gress: Utrecht, VNU Science Press, v. 1, p. 127–156.

Hottinger, L., 1977, Foraminifères operculiniformes: Mém-oires du Muséum National d’Histoire Naturelle, v. 40, p. 1–159.

Huber, B.T., 1991, Paleogene and early Neogene planktonic foraminifer biostratigraphy of Sites 738 and 744, Ker-guelen Plateau (southern Indian Ocean), in Barron, J., Larsen, B., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Volume 119: College Sta-tion, Texas, Ocean Drilling Program, p. 427–449.

Jovane, L., Florindo, F., Coccioni, R., Dinarès-Turell, J., Marsili, A., Monechi, S., Roberts, A.P., and Sprovieri, M., 2007a, The middle Eocene climatic optimum event in the Contessa Highway section, Umbrian Apennines, Italy: Geological Society of America Bulletin, v. 119, p. 413–427, doi: 10.1130/B25917.1.

Jovane, L., Sprovieri, M., Florindo, F., Acton, G., Coccioni, R., Dall’Antonia, B., and Dinarès-Turrell, J., 2007b, Eocene-Oligocene paleoceanographic changes in the stratotype section, Massignano, Italy: Clues from rock magnetism and stable isotopes: Journal of Geo-physical Research, v. 112, p. B11101, doi: 10.1029/2007JB004963.

Katz, M.E., Tjalsma, R.C., and Miller, K.G., 2003, Oligo-cene bathyal to abyssal benthic foraminifera of the At-lantic Ocean: Micropaleontology, v. 49, p. 1–45, doi: 10.2113/49.Suppl_2.1.

Kent, D.V., and Tauxe, L., 2005, Corrected Late Trias-sic latitudes for continents adjacent to the North Atlantic: Science, v. 307, p. 240–244, doi: 10.1126/science.1105826.

Kent, D.V., Olsen, P.E., and Witte, W.K., 1995, Late Triassic–earliest Jurassic geomagnetic polarity sequence and paleolatitudes from drill cores in the Newark rift basin , eastern North America: Journal of Geophysi-cal Research, v. 100, p. 14,965–14,998, doi: 10.1029/95JB01054.

Kirschvink, J.L., 1980, The least-squares line and plane and the analysis of palaeomagnetic data: Geophysi-cal Journal of the Royal Astronomical Society, v. 62, p. 699–718.

Krijgsman, W., and Tauxe, L., 2004, Shallow bias in Medi-terranean paleomagnetic directions caused by inclina-tion error: Earth and Planetary Science Letters, v. 222, p. 685–695, doi: 10.1016/j.epsl.2004.03.007.

Larrasoaña, J.C., Gonzalvo, C., Molina, E., Monechi, S., Ortiz, S., Tori, F., and Tosquella, J., 2008, Integrated magnetobiochronology of the early/middle Eo-cene transition at Agost (Spain): Implications for defi ning the Ypresian/Lutetian boundary strato-type: Lethaia, v. 41, no. 4, p. 395–415, doi: 10.1111/j.1502-3931.2008.00096.x.

Lowrie, W., and Alvarez, W., 1977, Upper Cretaceous–Paleo-cene magnetic stratigraphy at Gubbio, Italy: III. Upper Cretaceous magnetic stratigraphy: Geological Society of America Bulletin, v. 88, p. 374–377, doi: 10.1130/0016-7606(1977)88<374:UCMSAG>2.0.CO;2.

Lowrie, W., and Lanci, L., 1994, Magnetostratigraphy of Eocene-Oligocene boundary sections in Umbria Italy: No evidence for short subchrons within chrons 12R and 13R: Earth and Planetary Science Letters, v. 126, p. 247–258, doi: 10.1016/0012-821X(94)90110-4.

Lowrie, W., Alvarez, W., Napoleone, G., Perch-Nielsen, K., Premoli Silva, I., and Toumarkine, M., 1982, Paleo-gene magnetic stratigraphy in Umbrian pelagic carbon-ate rocks: The Contessa sections, Gubbio: Geological Society of America Bulletin, v. 93, p. 414–432, doi: 10.1130/0016-7606(1982)93<414:PMSIUP>2.0.CO;2.

Luciani, V., and Lucchi Garavello, A.M., 1986, Biostratigra-fi a del Paleogene pelagico del Bacino del Sarca (Tren-tino meridionale): Studi Trentini di Scienze Naturali, Acta Geologica, v. 62, p. 19–70.

Luciani, V., Negri, A., and Bassi, D., 2002, The Bartonian-Priabonian transition in the Mossano section (Colli Berici, north-eastern Italy): A tentative correlation between calcareous plankton and shallow-water ben-thic zonations: Geobios, v. 35, no. 1, p. 140–149, doi: 10.1016/S0016-6995(02)00055-4.

Luterbacher, H.P., Ali, J.R., Brinkhuis, H., Gradstein, F.M., Hooker, J.J., Monechi, S., Ogg, J.G., Powell, J., Röhl, U., Sanfi lippo, A., and Schmitz, B., 2004, The Paleo-gene Period, in Gradstein, F.M., Ogg, J., and Smith,

A., eds., A Geological Time Scale: Cambridge, UK, Cambridge University Press, p. 384–408.

Lyle, M., Wilson, P.A., Janecek, T.R., et al., 2002, Pro-ceedings of Ocean Drilling Program, Initial Reports, Volume 199: College Station, Texas, Ocean Drilling Program, doi: 10.2973/odp.proc.ir.199.2002.

Lyle, M., Olivarez Lyle, A., Backman, J., and Tripati, A., 2005, Biogenic sedimentation in the Eocene equa-torial Pacifi c—The stuttering greenhouse and Eocene carbonate compensation depth, in Wilson, P.A., Lyle, M., and Firth, J.V., et al., Proceedings of Ocean Drill-ing Program, Scientifi c Results, Volume 199: College Station, Texas, Ocean Drilling Program, p. 1–35. doi: 10.2973/odp.proc.sr.199.219.2005.

Mancin, N., and Pirini, C., 2002, Benthic and planktonic foraminifera of the Paleogene Epiligurian succession (northern Apennines, Italy): A tool for paleobathy-metric reconstruction: Bollettino della Società Paleon-tologica Italiana, v. 41, p. 187–213.

Martini, E., 1971, Standard Tertiary and Quaternary calcare-ous nannoplankton zonation, in Farinacci, A., ed., Pro-ceedings of the 2nd Planktonic Conference, Volume 2: Rome, Tecnoscienza, p. 739–785.

Mayer-Eymar, K., 1857, Tableau Synchronique des For-mations Tertiaires d’Europe (3rd ed.): Zurich, Tecno-scienza, 250 p.

Miller, P.K.G., Kominz, M.A., Browning, J.V., Wright, J.D., Mountain, G.S., Katz, M.E, Sugarman, P.J., Cramer, B.S., Christie-Blick, N., and Pekar, S.F., 2005, The Phanerozoic record of global sea-level change: Sci-ence, v. 310, p. 1293–1298.

Mita, I., 2001, Data report: Early to late Eocene calcare-ous nannofossil assemblages of Sites 1051 and 1052, Blake Nose, northwestern Atlantic Ocean, in Kroon, D., Norris , R.D., and Klaus, A., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Vol-ume 171B: College Station, Texas, Ocean Drilling Program, p. 1–28.

Molina, E., Gonzalvo, C., Ortiz, S., and Cruz, L.E., 2006a, Foraminiferal turnover across the Eocene-Oligocene transition at Fuente Caldera, southern Spain: No cause-effect relationship between meteorite impacts and extinctions: Marine Micropaleontology, v. 58, p. 270–286, doi: 10.1016/j.marmicro.2005.11.006.

Molina, E., Gonzalvo, C., Mancheño, M.A., Ortiz, S., Schmitz, B., Thomas, E., and von Salis, K., 2006b, Integrated stratigraphy and chronostratigraphy across the Ypresian-Lutetian transition in the Fortuna Sec-tion (Betic Cordillera, Spain): News letters on Stra-tigraphy, v. 42, p. 23–41, doi: 10.1127/0078-0421/2006/0042-0001.

Molina, E., Alegret, L., Arenillas, I., Arz, J.A., Gallala, N., Hardenbol, J., von Salis, K., Steurbaut, E., Vanden-berghe, N., and Zaghbib-Turki, D., 2006c, The global boundary stratotype section and point for the base of the Danian Stage (Paleocene, Paleogene, “Tertiary,” Cenozoic) at El Kef, Tunisia—Original defi nition and revision: Episodes, v. 29, no. 4, p. 263–278.

Monechi, S., and Thierstein, H.R., 1985, Late Cretaceous–Eocene nannofossil and magnetostratigraphic correla-tions near Gubbio, Italy: Marine Micropaleontology, v. 9, p. 419–440, doi: 10.1016/0377-8398(85)90009- X.

Müller-Merz, E., and Oberhänsli, H., 1991, Eocene bathyal and abyssal benthic foraminifera from a South Atlantic transect at 20–30°S: Palaeogeography, Palaeoclimatol-ogy, Palaeoecology, v. 83, p. 117–171, doi: 10.1016/0031-0182(91)90078-6.

Munier-Chalmas, E., and de Lapparent, A., 1893, Note sur la nomenclature des terrains sédimentaires: Bulletin de la Société Géologique de France, v. 21, p. 438–488.

Muttoni, G., Kent, D.V., Garzanti, E., Brack, P., Abraham-sen, N., and Gaetani, M., 2003, Early Permian Pangea ‘B’ to Late Permian Pangea ‘A’: Earth and Planetary Science Letters, v. 215, p. 379–394, doi: 10.1016/S0012-821X(03)00452-7.

Nocchi, M., Parisi, G., Monaco, P., Monechi, S., Madile, M., Napoleone, G., Ripepe, M., Orlando, M., Premoli Silva, I., and Bice, D.M., 1986, The Eocene-Oligocene boundary in the Umbrian pelagic sequences, Italy, in Pomerol, C., and Premoli Silva, I., eds., Terminal Eo-cene Events: Amsterdam, Elsevier, p. 25–40.



Nocchi, M., Amici, E., and Premoli Silva, I., 1991, Plank-tonic foraminiferal biostratigraphy and paleoenvi-ronmental interpretation on Paleogene faunas from the subantarctic transect, Leg 114, in Ciesielski, P.F., Kristoffersen, Y., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Volume 114: College Station, Texas, Ocean Drilling Program, p. 233–279.

Nomura, R., and Takata, H., 2005, Data report: Paleocene/Eocene benthic foraminifers, ODP Leg 199 Sites 1215, 1220, and 1221, equatorial central Pacifi c Ocean, in Wilson, P.A., Lyle, M., and Fifht, J.V., et al., Proceed-ings of the Ocean Drilling Program, Scientifi c Results, Volume 199: College Station, Texas, Ocean Drilling Program, p. 1–34.

Norris, R.D., Kroon, D., Klaus, A., et al., 1998, Proceedings of the Ocean Drilling Program, Initial Reports, Volume 171B: College Station, Texas, Ocean Drilling Program, doi: 10.2973/odp.proc.ir.171b.1998.

Ogg, J.G., and Bardot, L., 2001, Aptian through Eocene magnetostratigraphic correlation of the Blake Nose transect (Leg 171B), Florida continental margin, in Kroon, D., Norris, R.D., and Klaus, A., et al., Proceed-ings of the Ocean Drilling Program, Scientifi c Results, Volume 171B: College Station, Texas, Ocean Drilling Program, p. 1–58.

Ogg, J.G., and Smith, A.G., 2004, The geomagnetic polarity time scale, in Gradstein, F.M., Ogg, J., and Smith, A., eds., A Geological Time Scale: Cambridge, UK, Cam-bridge University Press, p. 63–86.

Okada, H., and Bukry, D., 1980, Supplementary modifi -cation and introduction of code numbers to the low-latitude coccolith biostratigraphic zonation (Bukry, 1973; 1975): Marine Micropaleontology, v. 5, p. 321–325, doi: 10.1016/0377-8398(80)90016-X.

Ortiz, S., and Thomas, E., 2006, Lower-middle Eocene ben-thic foraminifera from the Fortuna Section (Betic Cor-dillera, southeastern Spain): Micropaleontology, v. 52, p. 97–150, doi: 10.2113/gsmicropal.52.2.97.

Pälike, H., Shackleton, N.J., and Röhl, U., 2001, Astronomi-cal forcing in late Eocene marine sediments: Earth and Planetary Science Letters, v. 193, p. 589–602, doi: 10.1016/S0012-821X(01)00501-5.

Parisi, G., Guerrera, G., Madile, F., Magnoni, M., Monaco, P., Monechi, S., and Nocchi, M., 1988, Middle Eocene to early Oligocene calcareous nannofossil and forami-niferal biostratigraphy in the Monte Cagnero section, Piobbico (Italy), in Premoli Silva, I., et al., eds., The Eocene–Oligocene Boundary in the Marche-Umbria Basin (Italy): Ancona, Italy, Fratelli Anniballi, Inter-national Union of Geological Sciences Special Pub-lication, International Subcommission on Paleogene Stratigraphy Report, p. 119–136.

Pearson, P.N., and Chaisson, W.P., 1997, Late Paleocene to middle Miocene planktonic foraminifer biostratig-raphy of the Ceara Rise, in Curry, W.B., Shackleton, N.J., Richter, C., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Volume 154: College Station, Texas, Ocean Drilling Program, p. 33–68.

Pearson, P.N., Olsson, R.K., Huber, B.T., Hemleben, C., and Berggren, W.A., eds., 2006, Atlas of Eocene Plank-tonic Foraminifera: Cushman Foundation Special Pub-lication 41, 514 p.

Perch-Nielsen, K., 1985, Cenozoic calcareous nannofossils, in Bolli, H.M., Saunders, J.B., and Perch-Nielsen, K., eds., Plankton Stratigraphy: Cambridge, UK, Cam-bridge University Press, p. 427–554.

Premoli Silva, I., and Jenkins, D.G., 1993, Decision on the Eocene-Oligocene boundary stratotype: Episodes, v. 16, no. 3, p. 379–382.

Premoli Silva, I., Coccioni, R., and Montanari, A., eds., 1988, The Eocene-Oligocene Boundary in the Marche-Umbria Basin (Italy): Ancona, Italy, Fratelli Anniballi, International Union of Geological Science Commis-sion on Stratigraphy, International Subcommission on Paleogene Stratigraphy Report, 268 p.

Proto Decima, F., Roth, P.H., and Todesco, L., 1975, Nanno-plankton calcareo del Paleocene e dell’Eocene della Sezione di Possagno, in Bolli, H.M., ed., Monografi a Micropaleontologica sul Paleocene e l’Eocene di Pos-

sagno, Provincia di Treviso, Italia: Schweizerische Palaeon tologische Abhandlungen, v. 97, p. 35–55.

Remane, J., Bassett, M.G., Cowie, J.W., Gohrbandt, K.H., Lane, H.R., Michelsen, O., and Naiwen, W., 1996, Revised guidelines for the establishment of global chronostratigraphic standards by the International Commission on Stratigraphy (ICS): Episodes, v. 19, no. 3, p. 77–81.

Rio, D., Raffi , I., and Villa, G., 1990, Pliocene–Pleistocene calcareous nannofossil distribution, patterns in the western Mediterranean, in Kasten, K., Mascle, J., et al., Proceedings of the Ocean Drilling Program, Scientifi c Results, Volume 107: College Station, Texas, Ocean Drilling Program, p. 513–533.

Roveda, V., 1961, Contributo allo studio di alcuni macro-foraminiferi di Priabona: Rivista Italiana di Paleonto-logia, v. 67, p. 153–224.

Salvador, A., ed., 1994, International Stratigraphic Guide: A Guide to Stratigraphic Classifi cation, Terminology, and Procedure (2nd ed.): Boulder, Colorado, Geological Society of America, and International Union of Geo-logical Sciences, 214 p.

Schmid, R., 1981, Descriptive nomenclature and classifi ca-tion of pyroclastic deposits and fragments: Recom-mendations of the International Union of Geological Sciences Subcommission on the Systematics of Ig-neous Rocks: Geology, v. 9, p. 41–43, doi: 10.1130/0091-7613(1981)9<41:DNACOP>2.0.CO;2.

Selli, R., 1954, Il Bacino del Metauro: Giornale di Geologia, v. 24, p. 1–268.

Serra-Kiel, J., Hottinger, L., Caus, E., Drobne, K., Ferràndez , C., Jauhri, A.K., Less, G., Pavlovec, R., Pignatti, J., Samsó, J.M., Schaub, H., Sirel, E., Strougo, A., Tambareau, Y., Tosquella, J., and Zakrevskaya, E., 1998, Larger foraminiferal biostratigraphy of the Tethyan Paleo cene and Eocene: Bulletin de la Société Géologique de France, v. 169, p. 281–299.

Setiawan, J.R., 1983, Foraminifers and Microfacies of the Type Priabonian: Utrecht Micropaleontological Bul-letins, v. 29, 173 p.

Sexton, P.F., Wilson, P.A., and Norris, R.D., 2006, Test-ing the Cenozoic multisite composite δ18O and δ13C curves: New monospecifi c Eocene records from a sin-gle locality, Demerara Rise (Ocean Drilling Program Leg 207): Paleoceanography, v. 21, no. 2, p. PA2019, doi: 10.1029/2005PA001253.

Spofforth, D.J.A., Agnini, C., Pälike, H., Rio, D., Bohaty, S., Fornaciari, E., Giusberti, L., Lanci, L., Luciani, V., and Muttoni, G., 2008, Evidence for the middle Eocene climatic optimum (“MECO”) in the Vene-tian Alps: Geophysical Research Abstracts, v. 10, p. EGU2008–A-9577.

Spofforth, D.J.A., Agnini, C., Pälike, H., Rio, D., Bohaty, S., Fornaciari, E., Giusberti, L., Lanci, L., Luciani, V., and Muttoni, G., 2010, Organic Carbon Burial follow-ing the Middle Eocene Climatic Optimum (MECO) in the central–western Tethys: Paleoceanography, v. 25, PA3210, doi: 2009PA001738.

Stefani, C., and Grandesso, P., 1991, Studio preliminare di due sezioni del Flysch bellunese: Rendiconti della So-cietà Geologica Italiana, v. 14, p. 157–162.

Stefani, C., Zattin, M., and Grandesso, P., 2007, Petrography of Paleogene turbiditic sedimentation in northeastern Italy, in Arribas, J., Critelli, S., and Johnsson, M.J., eds., Sedimentary Provenance and Petrogenesis: Perspec-tives from Petrography and Geochemistry: Geological Society of America Special Paper 420, p. 37–55.

Strougo, A., 1992, The Middle Eocene/Upper Eocene transi-tion in Egypt reconsidered: Neue Jahrbuch Paläontolo-gische Abhandlungen, v. 186, p. 71–89.

Sztrákos, K., 2005, Les foraminifères du Paléocène et de l’Éocène basal du sillon nord-pyrénéen (Aquitaine, France): Revue de Micropaleontologie, v. 48, p. 175–236, doi: 10.1016/j.revmic.2005.06.001.

Tauxe, L., 2005, Inclination flattening and the geocen-tric axial dipole hypothesis: Earth and Planetary Science Letters, v. 233, p. 247–261, doi: 10.1016/j.epsl.2005.01.027.

Tauxe, L., and Kent, D.V., 2004, A simplified statistical model for the geomagnetic field and the detection of shallow bias in palaeomagnetic inclinations:

Was the ancient magnetic fi eld dipolar?, in Channell, J.E.T., Kent, D.V., Lowrie, W., and Meert, J.G., eds., Timescales of the Palaeomagnetic Field: American Geophysical Union Geophysical Monograph 145, p. 101–115.

Thierstein, H.R., Geitzenauer, K.R., Molfi no, B., and Shackle-ton, N.J., 1977, Global synchroneity of late Quaternary coccolith datum levels: Validation by oxy gen iso-topes: Geology, v. 5, no. 7, p. 400–404, doi: 10.1130/0091-7613(1977)5<400:GSOLQC>2.0.CO;2.

Tjalsma, R.C., and Lohmann, G.P., 1983, Paleocene–Eocene bathyal and abyssal benthic foraminifera from the At-lantic Ocean: Micropaleontology, Special Issue, v. 4, p. 1–90.

Toumarkine, M., and Bolli, H.M., 1970, Evolution de Glo-borotalia cerroazulensis (Cole) dans l’Eocene moyen et supérieur de Possagno (Italie): Revue de Micro-paleon tologie, v. 13, p. 131–145.

Toumarkine, M., and Luterbacher, H.P., 1985, Paleocene and Eocene planktonic foraminifera, in Bolli, H.M., Saunders, J.B., and Perch-Nielsen, K., eds., Plankton Stratigraphy: Cambridge, UK, Cambridge University Press, p. 87–154.

Trevisani, E., 1997, Stratigrafi a sequenziale e paleogeo-grafi a del margine orientale del Lessini Shelf durante l’Eocene superiore (Prealpi Venete, provincie di Vi-cenza e Treviso): Studi Trentini di Scienze Naturali, Acta Geologica, v. 71, p. 145–168.

Tripati, A., Backman, J., Elderfi eld, H., and Ferretti, P., 2005, Eocene bipolar glaciation associated with global carbon cycle changes: Nature, v. 436, p. 341–346, doi: 10.1038/nature03874.

Ungaro, S., 1969, Étude micropaléontologique et strati-graphique de l’Éocène supérieur (Priabonien) de Mos-sano (Colli Berici), in Colloque sur l’Eocene, Paris (1968), France: Mémoires du Bureau des Récherches Géologique et Minières, v. 69, p. 267–280.

Van Couvering, J.A., and Berggren, W.A., 1977, Biostrati-graphical basis of the Neogene time scale, in Hagel, J.E., and Kauffman, E.H., eds., Concepts in Biostratig-raphy: Lawrence, Kansas, The Paleontological Society, p. 283–306.

Van der Zwaan, G.J., Jorissen, F.J., and Stigter, H.C., 1990, The depth dependency of planktonic/benthic forami-niferal ratios: Constraints and applications: Marine Geology, v. 95, p. 1–16, doi: 10.1016/0025-3227(90)90016-D.

Van Morkhoven, F.P.C.M., Berggren, W.A., and Edward, A.S., 1986, Cenozoic cosmopolitan deep-water benthic foraminifera: Bulletin Centre Research Exploration et Production, Elf-Aquitaine, v. 11, 421 p.

Verhallen, P.J.J.M., and Romein, A.J.T., 1983, Calcare-ous nannofossils from Priabonian stratotype and correlation with the parastratotype, in Setiawan, J.R, ed., Foraminifers and Microfacies of the Type-Priabonian : Utrecht Micropaleontological Bulletin, v. 29, p. 163–173.

Villa, G., Fioroni, C., Pea, L., Bohaty, S.M., and Persico, D., 2008, Middle Eocene–late Oligocene climate variability: Calcareous nannofossil response at Kerguelen Plateau, Site 748: Marine Micro paleon-tology, v. 69, no. 2, p. 173–192, doi: 10.1016/j.marmicro.2008.07.006.

Vonhof, H.B., Smit, J., Brinkhuis, H., Montanari, A., and Nederbragt, A.J., 2000, Global cooling accelerated by early late Eocene impacts?: Geology, v. 28, p. 687–690.

Wade, B.S., 2004, Planktonic foraminiferal biostratigraphy and mechanisms in the extinction of Morozovella in the late middle Eocene: Marine Micropaleontology, v. 51, p. 23–38.

Walsh, S.L., 2004, Solutions in chronostratigraphy: The Paleocene/Eocene boundary debate, and Aubry vs. Hedberg on chronostratigraphic principles: Earth-Science Reviews, v. 64, p. 119–155, doi: 10.1016/S0012-8252(03)00040-0.

Walsh, S.L., 2005a, The role of stratotypes in stratigra-phy: Part 1. Stratotype functions: Earth-Science Reviews, v. 69, no. 3–4, p. 307–332, doi: 10.1016/j.earscirev.2004.11.002.

Walsh, S.L., 2005b, The role of stratotypes in stratigraphy. Part 2: The debate between Kleinpell and Hedberg, and

Agnini et al.


a proposal for the codifi cation of biochronologic units: Earth-Science Reviews, v. 70, p. 47–73, doi: 10.1016/j.earscirev.2004.11.003.

Walsh, S.L., 2005c, The role of stratotypes in stratigraphy: Part 3. The Wood Committee, the Berkeley school of North American mammalian stratigraphic paleon-tology, and the status of provincial golden spikes: Earth-Science Reviews, v. 70, no. 1–2, p. 75–101, doi: 10.1016/j.earscirev.2004.11.004.

Wei, W., and Wise, S.W., Jr., 1989, Paleogene calcareous nannofossil magnetobiostratigraphy: Results from South Atlantic DSDP 516: Marine Micropaleontol-

ogy, v. 14, p. 119–152, doi: 10.1016/0377-8398(89)90034-0.

Winterer, E.L., and Bosellini, A., 1981, Subsidence and sedimentation on Jurassic passive continental margin, southern Alps, Italy: The American Association of Petro leum Geologists Bulletin, v. 65, p. 394–421.

Zijderveld, J.D.A., 1967, A.C. demagnetization of rocks—Analysis of results, in Collinson D.W., Creer, K.M, and Runcorn, S.K., eds., Methods in Paleomagnetism: New York, Elsevier, p. 254–286.

Živkovic, S., and Glumac, L., 2007, Paleoenvironmental re-construction of the middle Eocene Trieste-Pazin Basin

(Croatia) from benthic foraminiferal assemblages: Micro paleontology, v. 53, no. 4, p. 285–310, doi: 10.2113/gsmicropal.53.4.285.

MANUSCRIPT RECEIVED 22 AUGUST 2009REVISED MANUSCRIPT RECEIVED 22 OCTOBER 2009MANUSCRIPT ACCEPTED 29 OCTOBER 2009

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Plate I. 1–23: Planktonic foraminiferal scanning electron micrograph (SEM) images of selected zonal markers from the middle–late Eocene Alano section (northern Italy). “Large acarininids”: 1, 2—Acarinina topilensis. Sample COL 345 b (1. ventral view; 2. spiral view). 3, 4—Acarinina rohri (3. sample COL 40a, spiral view; 4. sample COL 600a, spiral view). “Small acarininids”: 5, 6—Acarinina medizzai. Sample COL 2799c (5. ventral view; 6. spiral view). 7, 8—Acarinina echinata. Sample COL 4845c (7. ventral view; 8. ventral view). 9—Morozo-velloides coro natus. Sample COL 2496c, ventral view. 10—Morozovelloides crassatus. Sample COL 732c, ventral view. 11–15—Turborotalia cocoaensis (11, 12, 13—sample COL 520a [horizon of lowest occurrence of the species], profi le; 14. sample COL 600 a, ventral view; 15—sample COL 1285b, profi le). 16, 17—Globigerinatheka semiinvoluta, sample COL 4605c. 18, 19—Sample COL 440a, Orbulinoides beckmannii. 20–23—Guembelitroides nuttallii (20. sample COL 240a, spiral side; 21. sample COL 3701c, spiral side; 22. sample COL 492c, ventral side; 23—sample COL 3281c, lateral side). Scale bar = 100 µm.

Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal for defi ning the middle-late Eocene boundaryAgnini et al.Plates I and II.Supplement to: Geological Society of America Bulletin, v. 123; no. 5/6; doi: 10.1130/B30158.S1© Copyright 2011 Geological Society of America

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

Plate II. Microphotographs of selected calcareous nannofossil taxa from the middle–late Eocene Alano section (north-ern Italy). 1, 2—Isthmolithus recurvus. Sample COL 4645c (1. parallel light; 2. crossed nicols). 3—Chiasmolithus oamaurensis. Sample COL 5225c. Crossed nicols. 4—Chiasmolithus grandis. Sample COL 40a. Crossed nicols. 5, 6—Cribrocentrum erbae (5. sample COL 3521c, crossed nicols; 6. sample 171B-1052B-10H-2w, 130 cm, crossed nicols). 7—Cribrocentrum reticulatum. Sample COL 10b. Crossed nicols. 8—Chiasmolithus solitus. Sample COL 40a. Crossed nicols. 9–11—Sphenolithus obtusus. Sample COL 1285b (9. crossed nicols 0°; 10. crossed nicols 45°; 11. crossed nicols 20°). 12—Reticulofenestra umbilicus. Sample COL 40a. Crossed nicols. 13—Dictyococcites bisectus. Sample COL 40a. Crossed nicols. 14—Dictyococcites scrippsae. Sample COL 40a. Crossed nicols. 15, 16—Sphenolithus furcatolithoides. Sample COL 0 (15. crossed nicols 0°; 16. crossed nicols 45°).

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