Chaired by Isabella Premoli-Silva and Malcolm B. Hart Aim ... · The Cenomanian Dokan Formation...

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STUDIES ON MESOZOIC AND CENOZOIC FORAMINIFERA

Chaired by Isabella Premoli-Silva and Malcolm B. Hart

Aim of the Session is to discuss recent advances in the study of Mesozoic andCenozoic planktonic and benthic foraminiferal evolution, biostratigraphy,paleoecology, paleobiogeography and taxonomy.

Anuár io do Inst i tu to de Geociências - UFRJISSN 0101-9759 Vol. 29 - 1 / 2006 p. 307

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Foraminiferal assemblages of the Burdigalian andearly Langhian successions in Kirkuk Basin, NE Iraq

Ali Al-Juboury1; Abdulsalam Al-Tarif2 & Marwan Al-Esa3

1Research Center for Dams and Water Resources, Mosul University, [email protected]

2Applied Geology Department, Tikrit University, Iraq3Northern Oil Company, Kirkuk, Iraq

The study area is located in the Kirkuk area within the Zagros forelandbasin, which constitutes a rich petroleum province. The Burdigalian period ischaracterized by the deposition of the Serikagni, Euphrates and DhibanFormations. Planktonic foraminifera dominate throughout the entire SerikagniFormation in addition to few large benthonic foraminifera, echinoderms andred algae. Microscopic investigation revealed the presence of common planktonicforaminifera (Globigerinoides diminutus, Globigerinoides parawoodi,Globigerinoides primordius, Globigerinoides sacculifer, Globigerinoidesbullatus, Globigerinoides immaturus, Praeorbulina transitoria ,Catapsydrax stainforth). The dominance of globigerina-rich lime wackstonesand packstones microfacies may indicate the deep shelf margin or basinalmargins for the Serikagni environment of deposition.

The Euphrates Formation includes the benthonic foraminifera(Operculina, Borelis melo, Miliolidae, Peneroplidae, Rotalidae and Ammonia)as common skeletal components in addition to mollusca, bryozoans, echinoderms,algae and ostracods. The non-skeletal components include pellets and ooids.Diversity of bio-components in the Euphrates Formation indicate that thisformation was deposited in a spectrum of sedimentary marine environmentsranging from outer- to inner- shelf as shoals, open and semi-restricted, backlagoon shoals.

The presence of marine organisms in the limestone beds that alternatewith evaporites in the Dhiban Formation indicate the re-establishment andcontinuation of restricted marine environmental conditions between evaporativephases. Generally the intercalated limestone beds within the evaporites aredolomitic and are highly affected by anhydrisation and dissolution; therefore,only ghosts of the fossils are preserved. The observed fauna includes benthonicforaminifera (Borelis melo curdica) and relics of bivalves and gastropods aswell as echinoderms and ostracods.

Anuár io do Inst i tu to de Geociências - UFRJISSN 0101-9759 Vol. 29 - 1 / 2006 p. 315-316

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316Anuário do Instituto de Geociências - UFRJISSN 0101-9759 - Vol. 29 - 1 / 2006 p. 315-316

FORAMS 2006Foraminiferal assemblages of the Burdigalian and early Langhian successions in Kirkuk Basin, NE Iraq

Ali Al-Juboury; Abdulsalam Al-Tarif & Marwan Al-Esa

The nature and configuration of the sedimentary basin during the earlypart of the middle Miocene (Langhian) in the area of study reflects its featuresinherited from the earlier Burdigalian basin and was affected by the samestructural and environmental conditions that marked the older sequence. Thisbasin was formed after the transgressive phase that followed the seconddesiccation period (a regression that was responsible for the deposition ofDhiban Anhydrite Formation at the end of the earlier sequence). Thistransgression resulted in the formation of a spectrum of marine environmentsranging from nearly open marine conditions for the Jeribe Formation that iscomposed of marly limestone, rich in planktonic foraminifera, in the lower partof the formation passing upward into shallow marine limestones with benthonicforaminifera. This wide environmental range may be divided into several sub-environments similar to those observed in the Euphrates Formation and arerepresented by shoal, lagoonal and tidal flat sub environments.

Repeated periods of local tectonic movement, as well as world-widesea level variations, during the early middle Miocene (Langhian) resulted instratigraphic successions similar to those of the Burdigalian. These may havecontributed to a marine transgression and deeper environments rich in planktonic(Orbulina) foraminifera in the deep part of the basin that then changed to anopen lagoonal environment rich in miliolids throughout all of the Jeribe Formation.Perhaps due to the continuation of regional uplift, a third phase of drying appearsto have taken place and led to the deposition of Fat’ha successions (middleMiocene) of evaporites and limestones depending on the nature and time periodof tectonic stability.

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Foraminifera as paleoenvironmental indicatorsin Albian-Cenomanian carbonates, NE Iraq

Ali Al-Juboury1; Burkan Al-Zoobay 2 & Qais Al-Juwainy3

1Research Center for Dams and Water Resources, Mosul University, [email protected]

2 College of Science, Kirkuk University, Iraq3 Northern Oil Company, Kirkuk, Iraq

Albian and Cenomanian carbonate facies (Upper Qamchuqa and DokanFormations) are described from subsurface study in Kirkuk Basin within theZagros foreland basin of Iraq. In the Albian, carbonate (limestones, mainlydolomitic and partly marly) forms the main components of the Upper QamchuqaFormation. Among the dominant benthonic foraminifera, the genus Orbitolinais the main genus recorded throughout the present work, reaching to 50% ofthe skeletal components, and mainly represented by the oncoidal and concoidalorbitolinids. Miliolid-dominant facies is also recorded; other components include;planktonic foraminifera and calcispheres. In the Cenomanian Dokan Formation(mainly of marly limestone), the calcispheres are dominant, followed inabundance by foraminifera (planktonic and to a less extent benthonic), ostracodsand bioclasts. The biotic distribution was controlled largely by paleoenvironmentalchanges, such as trophic level, water energy and clay influx as well assedimentary factors controlled by variation in accommodation space. Inparticular, in the Albian the biotic components and their ecological requirementsindicate shallow-water carbonate facies characterized by shallow, warm andsaline water conditions with different degrees of water energy that change toa relatively deeper water in some parts of the area near the interfingering withthe basinal Balambo Formation. In the Cenomanian the biotic distribution refersto sub-basinal type facies. These facies changes subdivided the study arealaterally into three parts; the northwestern part in which neritic facies dominates,the central part in which the basinal influence is considerable; and thesoutheastern part that shows basinal mudstone type facies.

The association of orbitolinids with calcareous algae and echinoderms inslightly argillaceous limestones, as indicated from the present work, areinterpreted to have been deposited in relatively high trophic conditions(mesotrophic). Conversely, the grainy miliolid-dominated facies indicate lowertrophic conditions (oligotrophic). Changes in trophic level and clay input might


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FORAMS 2006Foraminifera as paleoenvironmental indicators in Albian-Cenomanian carbonates, NE Iraq

Ali Al-Juboury; Burkan Al-Zoobay & Qais Al-Juwainy

be related to variable humidity conditions during sea-level rise and fall. Theincreased weathering rates during early transgression induced the strongerrainfall and clay reworking during flooding of the exposed platforms and mayhave contributed to the onset of mesotrophic conditions favorable for thedevelopment of orbitolinids, whereas; the miliolid-rich facies developed in moreoligotrophic conditions, possibly caused by warmer and dryer climates duringperiods of eustatic highstand. Orbitolinid-rich facies occur generallycontemporaneously from inner to outer platforms and in intrashelf basins. Theoverall pattern of the Albian megasequence seems to indicate a regressiveshallow marine setting for the deposition of the Upper Qamchuqa succession.The Cenomanian Dokan Formation represents deeper shelf sequences that,being composed generally of marls and marly limestones rich in calcispheresassociated with planktonic foraminifera, may indicate an upper slope depositionalsetting. The transgressive depositional cycles of the Dokan Formation wereinterrupted by several local regressive cycles as indicated by the presence ofglauconite accumulation with common bioclastic and lithoclastic detritus.

319

Neogene foraminifera from Pelotas Basin, southern Brazil:Biostratigraphy and paleoceanography

G.S. Anjos-Zerfass1; A.L. Carreño2 & J.C. Coimbra3

1Programa de Pós-graduação em Geociências, Instituto de Geociências,Universidade Federal do Rio Grande do Sul (UFRGS), Cx.P. 15001, 91501-970 Porto

Alegre, RS, Brazil - [email protected] de Geología, Universidad Nacional Autónoma de México, Delegación de

Coyoacán, 04510 D. F. México3Departamento de Paleontologia e Estratigrafia, UFRGS, 91501-970 Porto Alegre, RS, Brazil

The Pelotas Basin has been intensively studied since the second half ofthe last century due to the Brazilian Atlantic margin oil possibilities; nevertheless,the biostratigraphy and paleoenvironments in the offshore portion of the basinare poorly known. Therefore, foraminiferal analyses in the Miocene-Pliocenesection of the basin made on 37 cutting samples between 270 and 1,350 m inthe 1SCS-2 well and between 360 and 1,320 m in the 1-SCS-3B drill-hole arehere discussed. The planktonic foraminiferal association allowed the recognitionin the 1-SCS-2 drill-hole of the Catapsydrax dissimilis, Catapsydraxstainforthi, Globorotalia fohsi robusta and Globorotalia mayeri Miocenezones, and the Globorotalia margaritae evoluta and Globigerinoides trilobusfistulosus Pliocene subzones. In the 1-SCS-3B well, the Catapsydraxdissimilis, Catapsydrax stainforthi, Globorotalia fohsi fohsi,Globigerinoides ruber, Globorotalia mayeri and Globorotalia acostaensis/Globorotalia menardii zones were identified in the Miocene and theGloborotalia margaritae evoluta and Globigerinoides trilobus fistulosussubzones in the Pliocene. All the above mentioned zones and subzones areaccording to Bolli & Saunders (1985) zonal scheme, otherwise indicating thepresence of four important hiatuses (at the Oligocene/Miocene boundary, lowerMiocene, lower Miocene-middle Miocene, and at the Miocene/Plioceneboundary). The planktonic foraminifers in both wells are quite similar to thoseassemblages reported from lower latitudes. Contrarily to the proposal of someauthors that suggested that the Pelotas Basin in the early Miocene was stronglyinfluenced by the Malvinas Currrent, a branch of the Antarctic CircumpolarCurrent, the abundant and constant presence of Globigerinoides species aswell the conspicuous occurrence of benthic species such as Amphistegina


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FORAMS 2006Neogene foraminifera from Pelotas Basin, southern Brazil: Biostratigraphy and paleoceanography

G.S. Anjos-Zerfass; A.L. Carreño & J.C. Coimbra

lessonii, Bolivina marginata, Cancris sagra, Siphonina reticulata andPoroeponides lateralis indicate a dominant warm water influx related to thewarm water Brazil Current. In the late Miocene the presence of rare andundersized specimens of Bucella peruviana campsi, a typical speciesassociated to the Malvinas Current, was observed. In both wells, the Plioceneinterval exhibits great diversity and abundant species typical of tropical tosubtropical waters such as Globorotalia menardii menardii, Globorotaliatumida tumida, Globigerinoides conglobatus, Globigerinoides ruber andNeogloboquadrina dutertrei dutertrei, whereas subantarctic water speciessuch as Globigerina bulloides, Globorotalia inflata and Globorotalia scitulascitula are scarce, an association suggesting that the Malvinas Currentreached the area, but it was not a primary controlling factor of thepaleoenvironmental conditions.

321

Variations in seafloor aeration during the late Campanian(Israel) based on foraminiferal assemblages

S. Ashckenazi-Polivoda1; A. Almogi-Labin2;Y. Edelman-Furstenberg2; Z. Lewy2 & C. Benjamini1

1Department of Geological and Environmental Sciences, Ben-Gurion University of theNegev, Beer-Sheva, Israel - [email protected]

2Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, Israel

During the late Campanian Israel lay beneath a wide belt of extensiveoceanic upwelling along the southern margin of the Tethys. This system wascharacterized by high productivity with temporal and spatial heterogeneity inbottom water conditions and consequently in sediment character. We here showhow organic matter content and degree of sea floor aeration affected benthicforaminiferal assemblages.

We examined organic rich carbonates (ORC), carbonate-porcelanitesand phosphate-rich carbonates from the carbonate-phosphate unit of thePhosphate Member, Mishash Formation (upper Campanian) from several basinsin southern and eastern Israel, in order to reconstruct bottom-water conditionsand especially the degree of pore-water ventilation. 76 samples from fourlocations were examined: The Saraf borehole in the Zin Basin represents themost restricted environment; the Qazra Basin to the southeast was somewhatless restricted, with the Nahal Omer section taken from the basin flank and theNahal Ashosh section from the central part of the basin; and the Wadi el Qiltsection to the northeast represents a more aerated basin better connected tothe open sea.

The abundance of benthic foraminifera is highly variable, varying fromnearly barren strata to intervals with floods of foraminifera (<146,000 specimens/gram dry sediment). Generally, the dominant forms are buliminids comprising90-100% of the benthic foraminiferal assemblage. Buliminid abundancedecreases from the most restricted environment of the Zin Basin to the moreaerated Wadi el Qilt Basin, indicating an increase in sea floor aeration. Speciesrichness is generally very low, usually of 5-6 species/sample in the Zin Basin,to a more diverse 10 - 17 species/sample in the other sections. The relativeabundance of benthic foraminifera out of the total foraminiferal assemblage isgenerally above 85%, except for some intervals from Wadi el Qilt.


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FORAMS 2006Variations in seafloor aeration during the late Campanian (Israel) based on foraminiferal assemblages

S. Ashckenazi-Polivoda; A. Almogi-Labin; Y. Edelman-Furstenberg; Z. Lewy & C. Benjamini

Five different oxygen levels were inferred for the ORC samples basedon benthic foraminiferal assemblages, percentage of benthic foraminifera andthe total organic carbon content (TOC). Based on the absence of macrobenthosall oxygen levels were inferred to be beneath 0.1 ml O2/l. The Wadi el Qiltassemblage with relatively high content of planktonic foraminifera characterizesthe best aerated location. The opportunistic species Praebulimina prolixaproliferated in dysoxic sediments containing 7-14% TOC. Neobuliminacanadensis, a more stress-tolerant species, is common mainly in intervals of14-21% TOC. The most restricted conditions are indicated by proliferation ofBolivian ‘porata’ in sediments with 24% TOC, probably characterizing almostfully anoxic pore-water conditions. This subdivision into five different levels ofoxygenation demonstrates that benthic foraminifera can be used as sensitiveindicators of degree of oxygen depletion, and in higher resolution than has beenpossible to date.

Water column productivity as inferred from calcareous nannofossils,dinoflagellate cysts and planktonic foraminiferal assemblages was found tocorrelate with oxygen depletion based on benthic foraminiferal assemblagechanges, showing an inverse relationship between water column primaryproduction and bottom or pore water aeration.

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3D-imaging of foraminifera by X-ray microtomography

Claudia Baumgartner-Mora; Peter O. Baumgartner & Lukas Baumgartner

Sciences de la Terre, Université de Lausanne, [email protected]

The low abundance of Heterostegina depressa in the Caribbean coastalreefs of Costa Rica have led us to use a new, non-destructive method to studythe internal structure of foraminifera. X-ray microtomography, in contrast totraditional transmission X-ray imaging, allows us to obtain non-destructive digital3D-image data (volume up to 1000 * 1000 * 1000 voxels) from geologicalobjects in which variations in mineralogy, chemical composition and/or porositycreate sufficient X-ray density contrasts.

We present here preliminary results of an application to the external andinternal morphology of Permian to Recent “larger” Foraminifera. We used aSkyScan-1072 high-resolution desk-top micro-CT system. The system has aconical X-ray source with a spot size of about 5 µm that runs at 20-100 kV, 0-250 µA, resulting in a maximal resolution of 5 µm. X-ray transmission imagesare captured by a scintillator coupled via fiber optics to a 1024 x 1024 pixel 12-bit CCD. The object is placed between the X-ray source and the scintillator ona stub that rotates 360° around its vertical axis in steps as small as 0.24 degrees.Sample size is limited to 2 cm due to the absorption of X-rays by geologicmaterials. The transmission images are back-projected using a Feldkampalgorithm into a vertical stack of up to 1000 1 Kpixel*1 Kpixel images thatrepresent horizontal cuts of the object. This calculation takes 2 to severalhours on a Double-Processor 4 GHz PC. The stack of images (.bmp) can bevisualized with any 3D-imaging software, such as Tview (Skyscan, Ltd), usedto produce axial and equatorial cuts of Foraminifera. Among other applications,the 3D-imaging software furnished by SkyScan can produce 3D-models bydefining a threshold density value to distinguish “solid” from “void”. Severalmodels with variable threshold values and colors can be combined, rotated andcut together.

The best results were obtained with microfossils devoid of chamber-filling cements (Permian, Eocene, Recent). However, even slight differencesin cement mineralogy/composition can result in surprisingly good X-ray densitycontrasts. We compared split specimens of Operculinoides ocalanus, andO. soldadensis from the Upper Eocene of the Southern Nicoya Peninsula(Costa Rica) with X-ray microtomographs of entire specimens. The split


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FORAMS 20063D-imaging of foraminifera by X-ray microtomography

Claudia Baumgartner-Mora; Peter O. Baumgartner & Lukas Baumgartner

specimens were cracked along the equatorial plane by heating and chilling inthe classical way (with a high risk of failure and destruction). They show irregular,chamber-filling glauconite aggregates separated by curved, narrow voids andcalcite cement. This structure could by perfectly imaged by X-ray tomographyof an entire specimens from the same locality. No risk was taken to destroythe specimen. The X-ray transmission images used for the calculation of theimage stack, already show a good contrast between chamber lumen and septa.Composite equatorial sections built from several cuts calculated in Tview, clearlyshow the foraminiferal structure and the chamber-filling mineral(s). To calculate3D-models of inner structures we defined a threshold value between theforaminiferal test and the cements.

X-ray microtomography may develop into a powerful tool for largermicrofossils with a complex internal structure, because it is non-destructive,requires no preparation of the specimens, and produces a true 3D-image dataset. We will use these data sets in the future to produce cuts in any direction tocompare them with arbitrary cuts of complex microfossils in thin sections.Many groups of benthic and planktic Foraminifera may become more easilydeterminable in thin section by this way.

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Upper Bathonian foraminifera from theNorth-Lusitanian Sub-Basin, Portugal

Maria Cristina Carapito-Krausshar

Department of Geosciences, University of Aveiro, P 3810-193 Aveiro, [email protected]

The main purpose of this paper is to present the biostratigraphy andenvironmental control on the distribution of benthic foraminifera in the UpperBathonian of the North-Lusitanian subbasin in two sections: the Brenha andthe Cabo Mondego sections.

Some recent works refer to the foraminifera of the Brenha Formation,Stam (1986. Utrecht Micropal. Bull., Netherlands, 34:168), Carapito & Ruget(1991. 3rd International Symposium on Jurassic Stratigraphy, Poitiers,23), Carapito (1994. Doctoral Thesis, University of Aveiro: 253) and Carapitoet al. (1998. 5th. International Symposium on the Jurassic System,Vancouver, 14).

These deposits are part of the Megasequence H (Soares et al., 1993.Comptes Rendus de l’Académie des Sciences, 2 (318): 1659-1666). DuringMegasequence H deposition (Cabo Mondego Fm., Upper Part; MiddleBathonian-Callovian), the hemipelagic sedimentation was limited to a westernresidual gulf in the Mondego area. Bituminous shales were deposited duringthe latest Bathonian (Soares et al., 1993).

The stratigraphic ranges of common species were compiled into adistribution chart for the Brenha and the Cabo Mondego sections.

Almost 56 species were identified and grouped in 6 assemblages. Thedominant species are Spirillina infima (Strickland), Lenticulina münsteri(Roemer), Reophax sterkii (Haeusler), Lenticulina quenstedti (Gümbel),Verneuilinoides mauriti (Terquem), Verneuilinoides minuta (Said & Barakat).

The Megasequence H is in general of regressive tendency (Carapito,1994). The analysis of the foraminiferal assemblages points to some probablechanges on the sea level.

The abundance of Spirillina spp. may indicate a relatively shallowerwater environment in an inner to middle shelf; but the diversity of species andthe amount of specimens identified points to a water depth, nutrients, oxygen,salinity and temperature sufficient to allow their existence (Carapito et al., 1998).


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Benthic foraminifera biofacies in UpperCretaceous Ceará Basin (Mundaú Sub-basin)

Denize Santos Costa & Marta Claudia Viviers

PETROBRAS-CENPES, Cidade Universitária, Quadra 7, Ilha do Fundão, 21941-598Rio de Janeiro, RJ, Brazil - [email protected]

The Ceará Basin is located in the Brazilian equatorial coast, whosetectonic compartment gave rise to various sub-basins, such as the MundaúSub-basin, in the easternmost region. The micropaleontological work carriedout in this area involves detailed analyses of foraminifera of the Cretaceousmarine section (upper Santonian–Maastrichtian). A composite sedimentarycolumn of 1200 m from two well sections, yielding abundant and well preservedmicrofossil assemblages, was studied.

A great number of benthic (calcareous-hyaline and agglutinated) andplanktic foraminifera species is recorded. Paleoecological analyses confirmthe presence of abundant and diversified assemblages, whose morphogroups,mainly composed by benthic foraminifera, allow to characterize eight biofacies.These contribute to the paleoenvironmental reconstruction of the basin, inferringpaleobathymetric oscilations that range from middle neritic to middlebathyal settings.

The integrated biostratigraphic (planktic foraminifera and calcareousnannofossils) and paleoecological interpretation indicate that the UpperCretaceous section can be divided into lower, middle and upper sub-units. Eachsub-unit is bounded by unconformities, as evidenced by biostratigraphic hiatuses,and characterized by abrupt changes in the microfossil assemblage compositionand in their corresponding paleobathymetry.


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Microfaunal analysis of an interval of the oil well Tiémié 1,Southwestern Côte d’Ivoire.

Paleoenvironmental implications

Digbehi Zéli Bruno & Ouffoue Kouamé Blaise

Université de Cocody, UFR of Sciences de la Terre et des Ressoures Minières, 22 BP 582Abidjan 22, Côte d’Ivoire - [email protected]

Microfaunal analysis of the interval 1350-1590 m of the well Tiémié 1leads to distinguish two facies:

1) a non-fossiliferous facies corresponding to the sub-interval 1350-1370m. Lithologically, the top (1350m) consists of clay while the lowerpart (1370 m) is mainly sandy.

2) a fossiliferous facies occurs in the interval 1390-1590 m which primarilyconsists of clay.

Planktonic foraminiferal assemblages are dominated by the generaWhiteinella, Hedbergella and especially Heterohelix, with rare Guembelitriaand Archaeoglobigerina.

In the interval 1390-1590 m the species identified are Whiteinellaarchaeocretacea, Whiteinella baltica, Hedbergella delrioensis, Hedbergellaplanispira, Hedbergella simplex, Heterohelix reussi, Heterohelix moremaniand Guembelitria cenomana.

This assemblage suggests a Turonian age. The abundance ofplanktonic foraminifera testifies to an external platform environment underoxygenated conditions.


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Use of benthic foraminifera with elongated tests (endofauna)in the determination of depositional environments.Case of the interval 1840-345 m of oil-well IVCO 25

off Côte d’Ivoire, West Africa

Zéli Bruno Digbehi1; Kouadio Affian1; Aka Kouamé1;Loukou Victor N’da2 & Thierry Tahe1

1Université de Cocody, 22 BP 582 Abidjan 22, Côte d’Ivoire2Société Nationale d’Opérations Pétrolières B.P . V 194, Côte d’Ivoire

Microfaunal analysis carried out on 120 samples of drilling cuttingsand cores from the interval 1840-345 m of oil well IVCO 25, located off-shoreCôte d’Ivoire, revealed:

o Dominance of benthic Foraminifera (92%) with respect to the plankticforms (8%). Among these benthic forms, foraminifera with elongatetests or endofaunas account for 43.3% against 56.7% of epifaunas;

o Characteristic assemblages of these benthic forms which allowedto attribute an age ranging from Campanian to mid Eocene to thestudied sediments;

o Four types of depositional environments namely:o A depositional environment ranging from slope to basin during the

Campanian and to external platform during the early Maastrichtian.This environment, oxygen deficient, is very rich in endofaunas;

o An environment of external platform during the late Maastrichtian,slightly oxygenated;

o An environment of inner to middle platform, slightly oxygenated, duringthe Paleocene;

o A depositional environment of inner platform gradually increasing tobe more littoral and oxygenated towards the top during the Eocene.


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329

Paleobathymetric and paleoenvironmental reconstruction ofthe Oligocene and Miocene deposits of

southern Caribbean (Carmen de Bolivar, Colombia)based on benthic foraminifera

Flavia Fiorini & Carlos A. Jaramillo

Smithsonian Tropical Research Institute, CTPA, Ancon, Panama,[email protected]

Foraminifera from an Oligocene-middle Miocene stratigraphic sectionwere used to interpret the depositional environments of these deposits. Thestratigraphic section (Carmen de Bolivar) located on the arroyo Alferez(Colombia) is 1950 m thick and mainly consists of shale and siltstone withsandstone layers belonging to the Carmen Formation, Oligocene-middleMiocene in age.

Paleobathymetric and paleoenvironmental interpretations were based onthe foraminiferal analysis of 160 samples collected every 10-15 m along theentire length of the section.

The foraminifera from the Carmen Formation have been previouslystudied by other authors for biostratigraphic purposes. In spite of being abundantin the section, specimens smaller than 120 µm have not been analyzed by otherauthors that previously worked on the Carmen Formation.

This study shows the results of a quantitative analysis of benthicforaminifera greater than 63 µm. Several foraminiferal associations havebeen identified:

1) Associations dominated by planktic foraminifera with variablepercentages of benthic foraminifera. The majority of the benthicassemblage consists of calcareous species mainly belonging to thegenera Uvigerina, Bulimina, Cibicidoides, Gyroidina and Bolivina.These associations are interpreted as belonging to normal marineenvironment from the middle neritic to the upper bathyal zone.

2) Association dominated or fully composed by agglutinated foraminifera.The calcareous foraminifera within this association are rare and poorlypreserved. The agglutinated foraminifera are abundant, finely to middleagglutinated and mainly small-sized (63-125 µm). This associationindicates a turbid water condition and suggests a depositionalenvironment receiving large amounts of land-derived clastic sediments.


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Taxonomic revision of coarsely ornamented UpperCretaceous trochospiral planktonic foraminifera

Marius D. Georgescu & Brian T. Huber

Department of Paleobiology, MRC 121, National Museum of Natural History,Smithsonian Institution, Washington D.C. 20013-7012, U.S.A.

[email protected]

Taxonomic revision of coarsely ornamented Upper Cretaceoustrochospiral planktonic foraminifera is proposed based on extensive SEMobservation of test ultrastructure, ornamentation, and porosity. This study wascarried out on very well preserved material from the Cenomanian-Maastrichtianof a number of DSDP/ODP holes. Our observations reveal considerablevariability of test morphology that nonetheless defines an evolutionary continuumwithin the Superfamily Alethogerinacea nov. sup., which is proposed herein toaccommodate tests with strong ornamentation of the Upper Cretaceous(Cenomanian-Maastrichtian). Iterative and parallel evolution commonly occursin the group’s evolutionary history.

The coarsely ornamented trochospiral planktonic foraminiferacommenced their evolutionary history in the middle Cenomanian with theevolutionary appearance of the genus Whiteinella, characterized by prominentpustulose test ornamentation, lack of peripheral structures, and a primaryaperture bordered by a poorly developed porticus (flap). A new genus,Alethogerina nov. gen. (type species: Archaeoglobigerina australis HUBER),is proposed to accommodate non-keeled tests with strongly pustulose testornamentation. It is the directly descendant from a:Whiteinella. This newlyemerged group morphologically diversified with development of plano-convex,single keeled genera (e.g., Helvetoglobotruncana, Bucherina), high-trochospired tests with papillose ornamentation (e.g., Kuglerina), and testswith meridional ornamentation on both sides (e.g., Costellagerina). Peripheralstructures, when present, are key features for the most specialized taxa (e.g.,Helvetoglobotruncana, Bucherina). This group is now formalized in the FamilyAlethogerinidae nov. fam. (Cenomanian-Maastrichtian).

The first major adaptive radiation of the Alethogerinacea occurred inthe Coniacian and resulted in the development of tests with peripheral structuresthat persisted throughout the evolutionary history of the Family


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FORAMS 2006Taxonomic revision of coarsely ornamented Upper Cretaceous trochospiral planktonic foraminifera

Marius D. Georgescu & Brian T. Huber

Archaeoglobigerinidae (Coniacian-Maastrichtian). Archaeoglobigerina is theoldest genus, presenting an imperforate peripheral band bordered by two rowsof pustules. Two lineages descended from Archaeoglobigerina in the latestCampanian-Maastrichtian, with development of tests having robust peripheralstructures (e.g., Gansserina, and Globotruncanella-Abathomphalus lineage).Notably, complex, asymmetrical test ornamentation that is meridional on theumbilical side and parallel to the periphery on the spiral side may be present inthis group (e.g., Abathomphalus mayaroensis).

The second adaptive radiation led to the evolutionary appearance oftests with meridional ornamentation on the dorsal and ventral sides and theprimary aperture bordered by a tegillum. The genus Rugoglobigerina is theoldest member of the Family Rugoglobigerinidae, its first evolutionaryoccurrence being dated as middle Campanian. This group underwentmorphological diversification, resulting in development of tests with a spinoseperiphery (e.g., Plummerita), a truncated single keeled periphery (e.g.,Trinitella), and a double-keeled test periphery with asymmetrical testornamentation (e.g., Rugotruncana).

The Superfamily Alethogerinacea nov. sup. is the sixth Mesozoicplanktonic foraminiferal superfamily, and the first one described according tothe principles of phylogenetic classification. The other five superfamilies include:Heterohelicacea (serial taxa), Planomalinacea (planispiral taxa), Favusellacea(primitive, globular-chambered trochospirals, probably with aragonite test),Rotaliporacea (trochospirals with supplementary apertures on the umbilical side),and Globotruncanacea (lightly ornamented trochospirals, with truncated andsingle- or double-keeled periphery).

332

The Wootton Bassett Mud Spings (Wiltshire, U.K.):An unusual Largerstatten for Jurassic foraminifera

Malcolm B. Hart1; Andrew S. Henderson2 & Timothy Frayling3

1School of Earth, Ocean & Environmental Sciences, University of Plymouth, Drake Circus,Plymouth PL4 8AA, U.K.I:[email protected]

2Palaeontology Department, The Natural History Museum, Cromwell Road,London SW7 5BD, U.K.

3English Nature (Wiltshire Team), Prince Maurice Court,Hambleton Avenue,Devizes, Wiltshire SN10 2RT, U.K.

On the January 6th, 1997, the mud springs at Templars Firs, WoottonBassett (Wiltshire) were designated a Site of Special Scientific Interest (SSSI)under Section 28 of the Wildlife and Countryside Act 1981 (as amended). Thesprings are notified as an SSSI on the basis of their hydrogeological interest.Water seeping through the Lower Calcareous Grit and Coral Rag (of Oxfordianage) liquefies the Ampthill Clay Formation (lowermost Kimmeridgian) whichthen migrates to the surface in a series of mud springs. Many of the fossilsbrought to the surface still display their aragonitic shells and are quite beautifullypreserved. In autumn 2003 and again in spring 2005 we collected a series ofsamples with the permission of English Nature (Wiltshire Team) and thesehave been washed for foraminifera and ostracods. The microfauna have beendescribed in a previous BGS report, although it is much more extensive andyields all the taxa associated with this stratigraphical interval. Many aragonitictaxa (epistominids) are present and beautifully preserved, including some ofthe stratigraphically significant taxa. Large agglutinated foraminifera appearto dominate one of the five active vents and are in an exceptional state ofpreservation. In the literature, many of these Jurassic taxa have been referredto modern, extant taxa, although this is almost certainly incorrect. The materialfrom Wootton Bassett should allow for a more appropriate determination ofthese taxa. Also recorded are small planktic foraminifera which extend ourknowledge of the early evolution of the poorly-known Jurassic plankton.


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333

Primary type specimens of some domestic speciesin Japan, and their taxonomic status

Shiro Hasegawa1; Kohei Abe2; Toyoho Ishimura3 & Jun-Ichi Uchida1

1Graduate School of Science and Technology, Kumamoto University,2-39-1, Kurokami, Kumamoto, 860-8555 Japan - [email protected]

2Graduate School of Life and Environmental Science, Tsukuba University,1-1-1, Tennodai, Tsukuba, 305-8572 Japan

3Graduate School of Science, Hokkaido University, N10 W8, Kita-ku, Sapporo, 060-0810 Japan

Since the first descriptive study of Paleogene species from Hokkaido byYokoyama (1890), more than 900 species of Cenozoic foraminifera have beenidentified from the Japanese Islands and surrounding seas of the NorthwestPacific. Two database sets, benthics by Hasegawa (2001) and planktonics byOda and Akimoto (2001), have been compiled as a project of the PaleontologicalSociety of Japan, and both are uploaded on a network from the GeologicalSurvey of Japan. Further, we are adding the image data of the primary typespecimens to those database sets.

During the research of the primary types of Cenozoic foraminifera inJapan, we sometimes notice that an image based on the description and figuresdo not correspond to the type specimens. It may be caused by insufficientdefinition and ambiguous figures given in the original description. For the samereason, many subsequent researchers may have illustrated those species withimages different from the type specimens. Therefore, only a small number ofspecies has been rightly referred to by workers from outside Japan. The restof species have not attracted notice, or erroneously identified. Such taxonomicconfusion is a big problem to solve for foraminiferal biogeography. An imagedatabase is important for it.

The species from Japan are frequently given the specific (or subspecific)name derived from any domestic geographic name. For example, there are 53species-group with the name given from “Japan” (i.e., nipponica, nipponensis,japonicus, -a, -um), even if it is limited to Cenozoic smaller foraminifera.

These species are classified into four categories, as follows:1) Type species of the genus: Discanomalina japonica Asano,

Discotruncana japonica Shirai, Dyofrondicularia nipponica


FORAMS 2006


FORAMS 2006Primary type specimens of some domestic species in Japan, and their taxonomic status

Shiro Hasegawa; Kohei Abe; Toyoho Ishimura & Jun-Ichi Uchida

Asano, Hanzawaia nipponica Asano, Nodobaculariella japonicaCushman and Hanzawa, Parafrondicularia japonica Asano ,Pseudoeponides japonicus Uchio, Pseudononion japonicum Asano.

2) Referred in the Northwest Pacific region: Bulimina nipponica Asano,Cassidulina japonica Asano and Nakamura, Cruciloculinajaponica Asano, Cyclammina japonica Asano, Discorbisnipponica Husezima and Maruhasi, Epistominella nipponicaKuwano, Lenticulina japonica Asano, Nonion japonicum Asano,Plectina nipponica Asano, Pseudoparrella japonica Asano,Rotalia japonica Hada, Rotalia nipponica Asano, Trochamminajaponica Ishiwada, Valvulineria japonica Asano.

3) Known only in Japan: Gyroidina nipponica Ishizaki, Sphaeroidinajaponica Asano etc.

4) Seldom used in Japan: Angulogerina japonica Asano, Bifarinajaponica Asano, Biloculinella japonica Asano etc.

Based on observation of primary type specimens, morphologicfeatures, and their taxonomic position will be discussed for several speciesparticularly within the categories 2, 3 and 4.

335

Micropaleontological investigations and sequence stratigraphyof the drilled strata of Qutb-Abad Well #1, Southwestern Iran

Seyed Abolfazl Hosseini

Exploration Directorate of National Iranian Oil Company , P.O.Box 11394, Tehran, [email protected]

The Qutb–Abad well # 1 locates at southwestern Iran in the ZagrosBasin. The total thickness of drilled sequence in the Qutb-Abad well # 1 is7500 ft.(2285.9m.). A total of 1808 thin-sections were prepared from the cuttingsamples of this well and investigated in order to differentiate the drilled rockunits and to determine their age relationships. The age relationships of thedrilled rock units have been determined based on the planktonic and benthicforaminifera. The electrical log data ( Gamma and Sonic) were used to separatethe rock units which were barren and their age relationships were identifiedbased on the stratigraphical position.

In this study, based on the paleontological and lithological data, the drilledsequence is divided in descending stratigraphic order into the Jahrum, Sachun,Tarbur, Gurpi, Ilam, Sarvak, Kazhdumi, Dariyan, Gadvan and Fahliyanformations, ranging from late Eocene to Early Cretaceous age. The aim of thisstudy was to identify the well known biozones of the Zagros basin within thedrilled sequence of the Qutb-Abad well # 1 and to make a better correlationwith the adjacent wells and also to separate the different sequence boundaries.The paleontological researches, allowed to distinguish a total of 16 biozonesthroughout the drilled rock units of this well. Based on the established biozones,there are two major hiata within the drilled sequence of the Qutb-Abad well#1.The first hiatus occurs between the Sachun and Tarbur formations andencompasses the uppermost Maastrichtian strata, seeing that the Elphidiellamultiscissurata subzone and also the Abathomphalus mayaroensis localoccurrence are not present. The second hiatus appears between the Sarvakand Ilam formations, which include strata of Turonian and Coniacian age, asthe Helvetoglobotruncana helvetica- Clavihedbergella-Hedbergella andalso the Marginotruncana schneegansi-Marginotruncana sigali assemblagezones are absent within the drilled strata.

The sequential interpretation suggests a total of 4 large scale (type 1)and also 16 medium scale (types 2 and 3) sequence boundaries and maximumflooding surfaces within the drilled formations. Based on the paleontologicaland sedimentological data, the depositional environments vary from the pelagic/hemipelagic facies to the ramp systems that consist of outer ramp to innerramp/platform and also supratidal environments.


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336

Tectonics, eustacy and climate: Foraminifera and thelate Cenozoic evolution of North-Central Chile

Scott Ishman1; Nicholas Pinter1; Timothy Reilly1; Jason Powell1;Anthony Stevens1; Hans Wilke2; Gary Wilson3 & Ruben Martinez-Pardo4

1Department of Geology, Southern Illinois University Carbondale,Carbondale, IL 62901 U.S.A. - [email protected]

2Department of Geological Sciences, Universidad Catolica del Norte, Antofagasta, Chile3Department of Geology, University of Otago, Dunedin, New Zealand

4Museo Nacional de Historia Natural, Santiago, Chile

The tectonic and eustatic history of northern and central Chile is importantto the understanding of its climatic evolution. The northwestern margin ofCentral Chile, in the Atacama Desert, includes uplifted marine sequences andterraced marine sediments that contain well preserved microfossil assemblagesand volcanic ash horizons. Preliminary micropaleontologic, geochemical,sedimentological and geospatial analyses of sedimentary sequences within theTiburon Basin of the Mejillones Peninsula and in the Caldera region to thesouth reveal significant late Cenozoic tectonic and eustatic events that provideadditional information towards our understanding of the climatic evolution ofnorthcentral Chile.

The generalized sedimentary sequence characterizing this region is abasal diatomite containing thin phosphatic horizons, marine vertebrates andabundant planktonic and benthic foraminifera. A progressive increase in clasticinput is observed up-sequence terminated by a coquina horizon of varying taxathat is capped with a cobble conglomerate with occasional boulders. Overlyingthe cobble conglomerate is a series of recurring foraminiferal volcaniclasticsands, mollusk horizons and thin ash beds. Ar/Ar dating of an ash horizon nearthe top of the sequence, and foraminiferal biostratigraphy indicate mid- to latePliocene deposition of the sediments. Preliminary analyses and interpretationof the foraminifera and sediments indicate an initial deep water (~500 m) basinwith high primary productivity related to upwelling of cold intermediate waterinterrupted by periods of little to no sediment input. Benthic foraminiferalassemblages from this interval are dominated by Bulimina and Bolivina taxa.This style of deposition was interrupted by a possible uplift event to the west-northwest resulting in the transport and deposition of the coquina and subsequentcobble conglomerate. This tectonic event resulted in subareal exposure to thewest and increased volcanism to the east. Foraminiferal data indicate shallowing


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FORAMS 2006Tectonics, eustacy and climate: Foraminifera and the late Cenozoic evolution of North-Central Chile

Scott Ishman; Nicholas Pinter; Timothy Reilly; Jason Powell;Anthony Stevens; Hans Wilke; Gary Wilson & Ruben Martinez-Pardo

of the basin to shelf depths (50-100 m), and sedimentological data indicates achange from biogenic sedimentation to volcaniclastic sedimentation. Geospatialdata on the sedimentary units support these interpretations.

Regional similarities in the above foraminiferal and sedimentologicalpatterns indicate an overall mid- to late Pliocene-Pleistocene shallowing withhigher frequency eustatic fluctuations occurring. This was followed by a regionaltectonic event resulting in further shallowing along the coast associated withincreased volcanism. This is corroborated in records recovered off-shore duringODP Leg 202. These marine sequences can be correlated to marine terracesequences observed on the Mejillones Peninsula in Northern Chile.

338

Deep-water agglutinated foraminifer from theFram Strait and Lomonosov Ridge:

Implications for the opening of the Fram Strait

Michael A. Kaminski1; Lóránd Silye2 & Sev Kender1

1Postgraduate Unit of Micropalaeontology, Department of Earth Sciences,University College London, Gower Street, London WC1E 6BT, U.K. - [email protected]

2Department of Geology, Babes-Bolyai University, Str. Kogalniceanu 1, 400084,Cluj-Napoca, Romania

Deep-water agglutinated foraminifera (DWAF) are investigated fromMiocene deposits recovered from the IODP Arctic Drilling Expedition (IODPLeg 302) cores and from ODP Hole 909C (ODP Leg 151) in the Fram Strait,Greenland Sea. We studied 90 samples from the Miocene of Hole M004 drilledon the Lomonosov Ridge in 2004, as well as 125 samples from Cores 909C-50R to –103R drilled on the Fram Straight.

At the Fram Strait site, we identified over 60 species of DWAF. Thefaunal succession in Hole 909C is subdivided into three assemblages based onthe stratigraphic ranges of characteristic cosmopolitan taxa. These are:

1) a diverse Reticulophragmium amplectens – Reophanus berggreniAssemblage in Cores 909C-100R-2 to -91R-1 (1040.71–952.78 mbsf);

2) a Reticulophragmium amplectens Assemblage in Cores 909C-87R-2, to -71R-3 (915.7–762.68 mbsf);

3) a low-diversity Reticulophragmium rotundidorsatum Assemblagein Cores 909C-71R-1 to -55R-1 (759.68-605.52 mbsf).

The DWAF assemblages are correlated to the standardchronostratigraphy using dinoflagellate cysts and magnetostratigraphy. Thestratigraphic ranges of some well-known Paleogene DWAF species extendfar into the Miocene at this locality, confirming the hypothesis that the Arcticand northern Norwegian Sea basins served as a refuge for these species longafter they disappeared from the North Atlantic stratigraphic record. Thetaxonomic affinity of the Miocene assemblages from Hole 909C with NorwegianSea assemblages supports the idea that an estuarine circulation pattern hasbeen in place between the Arctic Ocean and Greenland Sea basins since atleast the early Miocene. Changes in the benthic foraminiferal morphogroupswithin Hole 909C correlate with an increase in total organic carbon, indicatingan increase in oceanic productivity in the Fram Strait region during the late Miocene.


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FORAMS 2006Deep-water agglutinated foraminifer from the Fram Strait and Lomonosov Ridge:

Implications for the opening of the Fram StraitMichael A. Kaminski; Lóránd Silye & Sev Kender

Comparision with agglutinated foraminiferal assemblages recovered fromHole M004 suggest to us that the opening of the Fram Strait and the onset ofthe current fully-marine conditions in the Arctic took place during the earlyMiocene. Eocene sediments from the Lomonosov Ridge are largely biosiliceouswith indicators of brackish and fresh-water conditions, and are barren ofForaminifera. A hiatus or extremely condensed interval separates thesesediments from overlying marine sediments. The oldest fully marine sedimentswith cosmopolitan DWAF present on the Lomonosov Ridge are dated to theearliest middle Miocene (approx 15.2 Ma based on magnetostratigraphy). Sinceat least the mid-Miocene, the Arctic experienced open connections with theNorwegian-Greenland Sea to the south. The Arctic foraminiferal record fromthe mid-Miocene to Pliocene marine deposits consists entirely of agglutinatedbenthic species, largely sparse assemblages containing Cyclammina pusilla,Ammolagena clavata, and Alveolophragmium polarensis. By comparing theforaminiferal record of the new IODP Arctic Drilling holes with the recordfrom ODP Hole 909C in the Fram Strait, we now have better constraints onthe timing of the opening of the Fram Strait, and the establishment of the Arctic– Atlantic faunal connections.

340


FORAMS 2006

Gone but not forgotten – Casualties of the last global extinction

Shungo Kawagata; Bruce W. Hayward; Hugh R. Grenfell & Aswhaq T. Sabaa

Geomarine Research, 49 Swainston Rd, St Johns, Auckland, New [email protected]

The extinction of a group of elongate, cylindrical deep-sea (mid bathyal-midabyssal) benthic foraminifera occurred during the mid-Pleistocene Climatic Transition(MPT), between 1.2 and 0.55 Ma. It was first recognised ~25 years ago and untilrecently its full impact was undocumented. Our studies in twenty ODP cores fromthe North Atlantic, South Atlantic, Caribbean, Mediterranean, Southern Ocean,North Indian, South China Sea, North-east Pacific and South-west Pacific, showthat at least 76 species and 24 genera became extinct during this period of majorglobal climate and oceanographic change. A further 8 species and 3 genera declineddramatically during the MPT, but survived through in low numbers in geographically-restricted refugia. One complete family (Stilostomellidae – 23 species), characterisedby a distinct tooth structure in its necked aperture, became extinct at this time; anda second family (Pleurostomellidae – 24 species), also characterised by unusualelliptical or hooded apertures, was killed off except for three species that appear tohave just survived through. A further 32 species in the large Nodosariidae family(including all the Subfamily Plectofrondiculariinae) also died out and most of thesetoo, had unusual cribrate or narrow, constricted apertures.

Prior to the MPT, most of the extinct species had cosmopolitan distributionsat middle bathyal to middle abyssal depths (600-3500 m), although a minority hadgeographically-limited distributions. Our studies indicate that ~20% of the globaldiversity of benthic foraminifera at these depths (other than the diverse uniloculartaxa) became extinct during the MPT. This was an extinction rate of ~30% of themiddle bathyal-upper abyssal fauna/myrs, which is an order of magnitude greaterthan the background extinction rate for deep-sea benthic foraminifera of ~2-3%/ myrs.

Our studies are based on a taxonomic review of the Pliocene-Pleistocenemembers of the Stilostomellidae, Pleurostomellidae, Plectofrondiculariinae andNodosariidae with cribrate apertures. The review is being prepared for publicationas a monograph. The following genera of benthic foraminifera became extinct atthis time: Awhea, Chrysalogonium, Cribronodosaria, Ellipsoglandulina,Ellipsoidella, Ellipsoidina, Ellipsopleurostomella, Ellipsopolymorphina,Glandulonodosaria, Mucronina, Nodosarella, Orthomorphina,Parafrondicularia, Plectofrondicularia, Myllostomella, Siphonodosaria,Stilostomella, Strictocostella and several new genera yet to be described.Apparently surviving through in low numbers with restricted distribution wereNeugeborina, Pleurostomella, Proxifrons, Rectuvigerina and Vulvulina.

341

Micropaleontological characterization of Cenozoicdeep-sea fan deposits, Congo Fan, offshore Angola

Sev Kender1; Michael A. Kaminski1 & Bob W. Jones2

1Postgraduate Unit of Micropalaeontology, Department of Earth Sciences,University College London, Gower Street, London, WC1E 6BT, U.K.

[email protected] Exploration, Chertsey Road, Sunbury-on-Thames, London, TW16 7LN, U.K.

The Congo Fan is the second largest delta system in the world, spanningsome 3.7 x 106 km2 and draining most of central Africa through the CongoRiver and its associated tributaries. The Congo Fan is a terrigenous wedgelargely built of Oligocene and Miocene sands and shales organised into thicksedimentary packages containing paleocanyons, paleochannels, and overbankdeposits. The unique meandering paleochannels contain sands that have provedto be high quality traps for migrating hydrocarbons. In this study we analysethe foraminiferal microfauna from a well drilled in the distal section of the fanthrough Oligocene to middle Miocene deposits in an attempt to characterizethe sedimentological subfacies and the evolution of the fan.

The West African margin has been an active depocentre since initialrifting took place in the mid-Cretaceous. The earliest marine deposits consistof Aptian evaporites (<1000 m thick) that overlie lacustrine deposits and formthe complex of diapirs seen throughout the overlying strata. From the LateCretaceous to early Oligocene, aggradational carbonate/siliciclastic rampsediments formed ~200 m of deposits, which are the source rock for theoverlying hydrocarbon-bearing sands. These are directly overlain by a significantOligocene unconformity of several million years, followed by progradingterrigenous turbidite deposits that continue to the late Miocene forming up to2000 m of deposits. These consist of shale and sand overbank and channeldeposits, containing foraminifera in varying abundances. Sedimentation of theCongo Fan has continued throughout the late Miocene to Recent as aprogradational wedge.

The well in this study largely spans the Oligocene to middle Mioceneturbiditic fan. It has been sampled at 10 m intervals from about 2800 m to 4400m depth, has a water depth of ~2000 m, and is located ~170 km offshoreAngola (Block 31). The upper Oligocene section consists of predominantlyblack muds and silts with interbedded sandy horizons. This section continues


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FORAMS 2006Micropaleontological characterization of Cenozoic deep-sea fan deposits, Congo Fan, offshore Angola

Sev Kender; Michael A. Kaminski & Bob W. Jones

into the lower Miocene with little sedimentological change until reaching alarge sand/silt body that is interpreted as a submarine paleochannel. Theforaminifera are almost entirely agglutinated and are present in most samplesat medium to low abundances. Typical cosmopolitan Paleogene forms can beidentified (Nothia robusta, Ammodiscus latus , Reticulophragmiumamplectens), along with several dominating high productivity forms (e.g.,Portatrochammina alta n.sp. and Scherochorella congoensis n. sp.). Thediversity ranges from medium to low with significant faunal variation possiblyrelated to medium to high productivity fluctuations.

The overlying sand horizon becomes barren after foraminiferal diversityand abundance drops away leaving only rare specimens of Nothia andAmmodiscus. Above this, the sand abruptly gives way to lower and middleMiocene silts and muds containing gradually more calcareous and planktonicforaminifera as well as persistent agglutinated forms. The diversity andabundance are high, showing significant variation that could be related tofluctuations in the CCD during the middle Miocene or due to secondarygeochemical effects such as remobilised hydrocarbons. Faunas become morediverse with typical middle Miocene calcareous benthics (Eponides crebbsi)and Miocene agglutinated foraminifera (Cyclammina acutidorsata,Haplophragmoides carinatus) with some typical Paleogene forms persisting(Glomospira irregularis, Haplophragmoides excavatus). Planktonicforaminifera (Globigerinoides – Praeorbulina – Orbulina lineage andGloborotalia peripheroronda) have been used to assign the upper section ofthe well to the Langhian.

The fan underwent continuous progradation during the Oligocene toMiocene. Paleoenvironments changed from deep-sea (below the CCD) throughthe Oligocene and earliest Miocene, to progressively shallower environments(above the CCD) during the early and middle Miocene, showing a somewhatcontinuous rise to today’s depth of around 2000 m.

343

Neotectonic uplift of the Pacific Coast of Panamaand Costa Rica, based on benthic foraminifera

Lizette Leon-Rodriguez & Laurel S. Collins

Florida International University, Department of Earth Sciences, Miami, Florida 33199,U.S.A. - [email protected]

At the northeastern edge of the Cocos Plate there is an aseismic andanomalously light ridge known as the Cocos Ridge that is currently beingsubducted beneath the Central American volcanic arc. The initial stages ofthis subduction began in the early Pleistocene and were recorded by the marinesedimentary deposits of southwestern Panama and southeastern Costa Rica inthe Burica Peninsula region. In this Pacific coastal area it is possible to observehow the collision of the Cocos Ridge produced substantial alterations of thesedimentary regimes, which resulted in deposition of 2,600 m of turbidite depositsof the Burica Formation followed by 500 m of conglomerates, siltstones andlitharenites of the Armuelles Formation.

The current study consisted of analyzing 48 samples distributed overfour different locations on the Burica Peninsula. The foraminiferal assemblagescontaining species such as Stilostomella sagrinensis, Plectofrondiculariaadvena and Melonis pompiliodes indicate that the Burica Formation sedimentswere accumulated in bathyal depths (>2,000 m bsl). In contrast, the youngersediments of the overlying Armuelles Formation were mainly deposited at innerneritic depths (<50 m bsl) as indicated by Ammonia beccarii gr., Buliminellaelegantissima and Nonionella atlantica. These large bathymetric changesoccurred during the early to middle Pleistocene, and are seen as especiallyabrupt in the northern sections of the Burica Peninsula, which would indicatedifferential bottom water depths within the same basin when compared to thesouthern part of the area.

Overall, these results show high sedimentation rates and significantbathymetric changes due to the initial tectonic response to the collision of theCocos Ridge against the Central American Arc. The biochronology fromcalcareous nannofossils which reveals that the uplift process occurred duringthe early to middle Pleistocene indicates that this tectonic process occurredtwice as fast and late as previously thought.


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344

Bartonian to end-Rupelian reticulateNummulites of the Western Tethys

György Less1; Botond Kertész1 & Ercan Özcan2

1University of Miskolc, Department of Geology and Mineral Resources, H-3515,Miskolc-Egyetemváros, Hungary - [email protected]

2Department of Geology, Faculty of Mines, Istanbul Technical University,Ayazaða/Istanbul 34469, Turkey

Reticulate Nummulites can be found very often in rock-forming quantityin the Bartonian to Rupelian beds of the Western Tethys; however theirnomenclature is extremely complicated and rather controversial. Therefore,and since B-forms are quite rare and often missing, in the first phase of theresearch we have concentrated on the comparative morphometric study ofmegalospheric forms without prejudicing formerly introduced typological namesto particular populations. We used material from twenty-seven localitiesextending from SW France to Armenia and spanning from the early Bartonianto the Rupelian/Chattian boundary. Twenty-eight populations could beencountered, twenty-seven of which could be arranged safely into the well-known Nummulites fabianii-fichteli group. However, in the middle Bartonianlocality of Keçili 1 (eastern Turkey) another population of reticulate Nummulitesbearing about five times larger embryon than that of the population belongingto the N. fabianii-fichteli l-lineage from the same sample could be observed.This population has been identified with N. hottingeri (the end-member of theN. partschi-lorioli -lineage) on the one hand but also with the original descriptionof N. ptukhiani (later widely accepted as the precursor of N. fabianii) on theother. This means that the two names are synonymous and N. ptukhiani bearingpriority over N. hottingeri has to be applied for these forms. On the otherhand, it can by no means be used for the precursor forms of N. fabianii.

The twenty-seven populations belonging to the N. fabianii-fichteli grouphave been analyzed qualitatively by means of the surface characteristics andquantitatively by means of the internal features observable in the equatorialsection of A-forms. In order to distinguish the evolutionary trends from theecologically or ontogenetically affected phenomena we arranged the twenty-seven populations according to their supposed age based on the accompanyingfossils and/or stratigraphic position. The inner cross-diameter of the proloculushas been proven to be the most reliable evolutionary parameter. Beside, the


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FORAMS 2006Bartonian to end-Rupelian reticulate Nummulites of the Western Tethys

György Less; Botond Kertész & Ercan Özcan

evolution of surface characteristics (not detailed here) is also usable in thissense, although it shows great intrapopulational variation partly because of theontogeny. The increase of the average length of chambers (accompanied bygeneral flattening) in the third whorl is of secondary importance in recognizingthe evolution of the group because it is affected also by ecological factors.Finally, the tightness/laxity of the spire and the relative width of the spiral cordin the third whorl are clearly the functions of the actual paleoenvironment. Asa result, the N. fabianii-fichteli group is proven to form a single but rathervariable evolutionary lineage within which early Bartonian to end Rupeliandevelopment of six evolutionary stages (considered as species) could berecognized (we could not study the middle-late Lutetian precursor forms). Thesafety of identification of these evolutionary stages with particular species namesis of different degree. The six species are defined primarily on the basis of theaverage inner cross-diameter of the proloculus (Cmean) and secondarily bythe surface characteristics as follows: 1) N. bullatus (early Bartonian, earlySBZ 17 zone) with Cmean=65–100µm, granules, no reticulation. 2) N.garganicus (“middle” Bartonian, late SBZ 17) with Cmean=100–145µm, distinctgranules and reticulation. 3) N. hormoensis (upper Bartonian, SBZ 18) withCmean=145–200µm, distinct granules, polar knob and reticulation. 4) N. fabianii(Priabonian to early Rupelian, SBZ 19–21) with Cmean=200–320µm, distinctreticulation, optional granules and polar knob. 5) N. fichteli (late Priabonian toearly Rupelian, SBZ 20–21) with Cmean=200–320µm, dissolving reticulationto irregular mesh, no granules. 6) N. bormidiensis (late Rupelian, SBZ 22A)with Cmean=320–450µm, irregular mesh.

This research was realized in the frame of IGCP Project 393 havingfinanced also some of Less’ travels. The final phase of the work was sponsoredfor Less and Kertész by the National Scientific Fund of Hungary (OTKA,Grants ¹ T 037619, 042799 and 060645) while for Özcan by TÜBITAK (project¹ YDABAG–101Y060 and CAYDAG 104Y230).

346

Tempo and mode of planktonic foraminiferal evolution

Chengjie Liu

ExxonMobil Exploration Company, Houston, [email protected]

Planktonic foraminifera are among the most thoroughly studied fossilgroups because of their more complete fossil record and more intensiveinvestigation by a larger number of workers. A scrutiny of the tempo(s) andmode(s) of planktonic foraminiferal evolution will not only greatly enhancetheir biostratigraphic value but also significantly improve the theory of evolution.Since their initial appearance in the Jurassic, planktonic foraminifera haveundergone four major episodes of evolutionary radiation and suffered threemajor extinctions. All major extinctions wiped out morphologically advancedand complex forms and left a few survivors with simple, generalizedmorphologies. Each radiation begins with ecological expansion andmorphological diversification of survivors. Several morphological trends areiteratively shared by different radiations, such as the development of planispiraltests, clavate chambers, complex umbilical structures, supplementary apertures,increase in number of chambers, and enlargement in test size. These aremodifications of the simple morphology of survivors, which are characterizedin general by trochospiral tests, umbilical apertures, fewer chambers, smallersize, and globular chambers, and probably represent adaptation-related functionaladjustment as a result of natural selection. Even more important is the additionof progressively new characters in later radiations, such as the first occurrenceof peripheral keels in the Albian, double keels in the Cenomanian, multiserialtests in the Coniacian, spines in the Danian, spherical tests in the Ypresian, andcorticated tests in the Serravallian. The evolution of some new characters isprobably related to co-evolution. For example, the development of spines isvery likely related to the evolution of floating algal symbionts in the early Danian.Rate of speciation varies significantly and it accelerates after major extinctions.In addition, opportunist species have lower background speciation rate butrecover more rapidly following catastrophic extinction event. For example,during their entire >60 Ma range in the Cretaceous, only three species ofGuembelitria have been recognized, and they are all morphologically similarand probably represent the same biological species. In contrast, only ~30 kyrafter the K/T mass extinction, six new species with significantly distinct


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FORAMS 2006Tempo and mode of planktonic foraminiferal evolution

Chengjie Liu

morphologies evolved from the single survivor species Guembelitria cretacea.In contrast, the normal perforate Hedbergella clade has moderate speciationrate during background evolution and the rate of speciation accelerated onlyslightly after the K/T event. Approximately 50k years into the Danian, only sixnew species have evolved from the rest two K/T survivors (H. monmouthensisand H. holmdelensis). All of these early Danian normal perforate species canbe traced back to corresponding hedbergellid morphotypes in the Campanianand Maastrichtian. In addition, these two survivors had already undergonemorphological variation in the Late Cretaceous. Apparently, although the rateof speciation accelerated after the K/T mass extinction, the pace of speciationof the Danian normal perforate planktonic foraminifera from the Late CretaceousHedbergellids clearly reflects phyletic gradualism. The quick rise and demiseof the opportunists and rapid subsequent replacement by stable mainstreamnormal perforate planktonic foraminifera indicates that natural selection isoperative. Allopatric speciation and stasis are the two key elements ofpunctuated equilibrium theory (sensu Eldredge & Gould, 1972). While cases ofallopatric speciation exist, stasis is not apparent in planktonic foraminiferalevolution. The most important modes of planktonic foraminiferal speciationare cladogenesis, sympatric speciation, variable phyletic “gradualism”, andprobably phyletic transformation. This is more consistent with the speciationprocess presented by Charles Darwin, except that the rate of “gradual” changemay accelerate more rapidly than the traditional gradualism allows.

348

Eocene foraminiferal biostratigraphy and paleoenvironmentof Nagaland, Northeastern India

Kapesa Lokho

Wadia Institute of Himalayan Geology, GMS Road, Dehradun-248001, Uttaranchal, [email protected]

Nagaland state in the northeastern India is a part of Assam-ArakanBasin. Geodynamically the basin evolved through the convergence of Indian,Eurasian and Burmese plates. The Naga Schuppen Belt and Kohima-Patkaifolded zones are the major geotectonic units of Nagaland. The Naga SchuppenBelt is an imbricate thrust zone, in which Oligocene and younger sediments aremostly exposed, whereas the Kohima-Patkai Range comprises the anticlinaland synclinal reversals involving a huge exposed pile of sedimentary depositsof the Eocene Disang Group along with the Oligocene Barail deposits. Further,the eastern part of the Nagaland state comprises an epi-metamorphosed complexof ophiolite suite.

The Eocene Disang deposits are fossiliferous and considered to be thebasinal equivalents of the Jaintia Group of the Assam Shelf. In the presentpaper the foraminiferal biostratigraphy of the Disang and Barail Groups exposedin western and south-central parts is discussed along with itspaleoenvironmental significance.

In the western part, two assemblage zones, namely theCribrohantkenina inflata-Hantkenina alabamensis Zone and Nummulitespengaronensis-Pellatispira madaraszi-Discocyclina dispansa Zone, havebeen recognized, which are of middle to latest Eocene age (Zone P-16 andearly part of Zone P-17 of Blow, 1969). In the south-central part, three biozoneshave been recognized, namely the Globigerinatheka semiinvoluta Zone (ZoneP-15), Cribrohantkenina inflata Zone (Zone P-16) and Turborotaliacerroazulensis Zone (Zone P-17) of Berggren et al. (1995) of Priabonian(late Eocene) age.

The foraminiferal assemblages as recorded from the Disang and BarailGroups in the western area indicate deposition in shallow marine environmentwith oscillations in bathymetry. Inner shelf facies is inferred at Tehai Reu andLotsu Village sections in the western part based on reported occurrence ofPellastispira, Nummulites and Discocyclina. Middle to outer shelf setting isinferred by an association of larger benthic and planktonic foraminifera andsome uvigerinids (U. cf. jacksonensis) from the Heina Reu section.


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FORAMS 2006Eocene foraminiferal biostratigraphy and paleoenvironment of Nagaland, Northeastern India

Kapesa Lokho

In the south-central part the foraminiferal assemblage represents a deepermarine setting (lower part of upper bathyal) by the finding of Uvigerina faciesconsisting of U. cocoaensis, U. continuosa, U. eocaena, U. glabrans, U.jacksonensis, U. longa, U. moravia, U. steyeri and U. vicksburgensis fromthe localities of Pfutsero I, II, Chobama and Leshemi. If the foraminifera reportedfrom the western part are not transported by turbidity current, we may infer ashelf-slope setting from the western to south-central part of Nagaland.

Further towards eastern part, the basin seems to be shallower as supportedby the findings of scarce miliolids, bivalves, gastropods in the absence ofuvigerinids and planktonic foraminifera.

The morphological features of some cosmopolitan ‘species’ of uvigerinidsand their dominance and the presence of chiloguembelinids in south-centralNagaland suggest an anoxic environment. The foraminiferal criteria employedto infer anoxic conditions are based on localized occurrence of thick uvigerinids,presence of pteropods and pyritized tests. The Disang Sea may be termed as aconfined turbidite basin, sharing features common to many structurally complexcontinental slopes, that, in part was connected at times to the main Tethyan Sea.

350

Late Jurassic (Kimmeridgian) larger foraminiferafrom Santiago Coatepec, SE Puebla, Mexico

Lourdes Omaña; Celestina González Arreola & Ana Bertha Villaseñor

Departamento de Paleontología, Instituto de Geología, Universidad NacionalAutónoma de México, Ciudad Universitaria, 04510, México, D. F., México

[email protected]

The studied section crops out on the Santiago Coatepec stream, locatedin southeast Puebla, Mexico.

The sedimentary sequence consists of a reddish conglomerate, overliesby a rhythmic alternations of thin to thick beds of gray-greenish sandstone thatpassed upward to a fine grained calcareous sandstone, followed by alimestone deposit.

The reddish conglomerate could represent a continental deposit and thetransgression started with the sandstone deposit that contains an invertebratemarine faunal association composed of trigonids, ostreids, other bivalves,gastropods and echinoids.

The succession also provides a rich assemblage of larger foraminiferaas well as algae, that is reported for the first time in this site.

The larger agglutinated foraminiferal assemblage is composed ofAlveosepta jaccardi, Everticyclammina virguliana, Rectocyclamminachouberti, Pseudocyclammina lituus, Nautiloculina oolitica, Freixialinaplanispiralis and Glomospira sp, that were adapted to a special paleoecologicaland sedimentary conditions as a continuous terrigenous input.

A Kimmeridgian age is proposed based on the benthic foraminiferalassociation for the studied sequence. The widening of the Atlantic Ocean duringthe Jurassic and Early Cretaceous, permitted the colonization of its margins bythe larger foraminifera.

The presence of the larger foraminifera and the lithology suggest a warmshallow-water marine platform environment.

The identified benthic foraminifera species are cosmopolitan forms wellrepresented in the Tethys Realm.


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351

Upper Jurassic lituolids in the Sierra de Chiapas(Mexico) and their relation to the Tethys

Maria Ornelas-Sanchez1 & Lukas Hottinger2

1Instituto Mexicano del Petróleo, Gerencia de Geociencias. Edificio 6,Eje Central Lázaro Cárdenas, 152.San Bartolo Atepehuacán, C.P. 07730.

México D.F., México - [email protected] Natural History, CH 4001 Basel, Switzerland

Benthonic foraminifera from Upper Jurassic outcrops in the Sierra deChiapas are herein presented. These microfaunistic associations reflect majorgeologic and eustatic events. At the beginning of the Jurassic, a great marinetransgression flooded the continental margins; at the same time, the breakingof Pangea formed the Tethys Sea (Mc. Kenrrow, 1978). These events causedthe development of different communities to evolve along different phyleticlines. The Sierra de Chiapas Province in SE Mexico is intimately related tothese events, representing the most occidental region of the Tethys domain.

During mid Jurassic times, most of the region experienced hot weather,continental and fluviodeltaic environments (Todos Santos Fm.), covered byvegetation, probably of “chetine” type. Although some Callovian rocks recordfirst Tethyan invasions, it is until Oxfordian times when the first marineenvironments are registered by the sediments on an extensive carbonate shelf,the San Ricardo Formation (Oxfordian-Berriasian). Three large-scale eventsdetermine the succession of sedimentary environments and the evolution ofthe communities of organisms.

The first event corresponds to the formation of an inner shelf (Oxfordian-Kimmeridgian) as a consequence of a marine invasion with essentially subtidalcalcium carbonate deposits, deep enough to facilitate the proliferation ofdasycladacean algae and bivalves. The restricted environments mainlycorrespond to lagoons, with a dominant development of dasycladacean algaesuch as Clypeina, Cylindroporella, Zergabriella, Actinoporella, Apinella,Heteroporella, Deloffrella, Salpingoporella, Radoiciciella andKimmeridgian Likanella. As foraminifera, lituolids (Everticyclamminavirguliana, Pseudocyclammina lituus) and trocholinids (Trocholina sp.) are noted.


FORAMS 2006


FORAMS 2006Upper Jurassic lituolids in the Sierra de Chiapas (Mexico) and their relation to the Tethys

Maria Ornelas-Sanchez & Lukas Hottinger

The second event (Tithonian) corresponds to a sea level rise producinga marine flooding, with the deposition of calcareous-terrigenous sediments. Asa consequence, the facies changes, dasycladacean algae, trocholinids, andmiliolids are suppressed, only some lituolids and lagenids survive.

The third event refers to a sea level drop (Tithonian-Berriasian),permitting the extension of shallower environments on the open platform. Here,a terrigenous, sandy sedimentation permitted the lituolids to constitute thedominant element in the communities. Environments of deposition for theterrigenous open sea platform range from coastal facies with scarce fragmentsof lituolids to shallow subtidal facies characterized by limonite and biomicriteswith abundant larger lituolids. For this group, high specific and generic diversityis observed. The most common species are Anchispirocyclina lusitanicalusitanica, A. lusitanica minor, Pseudospirocyclina sp., P. maynci, andTimidonella (?). Most of these are large-sized and distinctly dimorphic, indicatinga double K-strategy of life similar to recent soritines. Dasyladacean algae suchas Draconisella genotii, Likanella and Radoiciciella are also reported. Thus,fauna and flora from Chiapas are similar to the communities registered on theother side of the Atlantic from coeval similar facies in Portugal (Cap Espichel)and Morocco.

353

The Late Cretaceous genus Omphalocyclus from Turkey:New stratigraphical data for the Mediterranean Tethys

Ercan Özcan

Department of Geology, Faculty of Mines, Istanbul Technical University,Ayazaga/Istanbul 34469, Turkey - [email protected]

Omphalocyclus is an orbitoidal benthic foraminifera, known from therelatively shallow-water paleoenvironments located in the outer parts of theLate Cretaceous Tethyan platforms. It is a relatively common taxon with ageographic distribution from Europe to north Africa, India and as far as Indonesiain the east, and to Caribbean in the west. Apart from its debatable diagnosisonly in the (late) Maastrichtian of western Tethys, the genus has been discoveredin Turkey in further much older beds in association with Orbitoides andLepidorbitoides having rather primitive developmental stages. Themorphometric analysis of A-forms in successive assemblages (based onseventeen populations in seven sections located in Sakarya, Eurasian andArabian plates), ranging in age from (late) Campanian to terminal Maastrichtian,enables the documentation of phylogenetic changes for the first time. Sincethese horizons contain a rather rich assemblage of accompanying specimensof Orbitoides and Lepidorbitoides, a correlation of the phylogenetic changesof the genus to that of Orbitoides and Lepidorbitoides, rather well-known inEurope, can also be made.

The most conspicuous phylogenetic change in the equatorial layer ofOmphalocyclus is found to be the general increase in the size of embryon,which on average doubles by the end of the Maastrichtian. This trend is followedby the increase in the number of epi-embryonic chamberlets, which is howevernot as significant as the former parameter. Omphalocyclus in thestratigraphically lowermost populations has mainly three to four primary epi-embryonic and no accessory epi-embryonic chamberlets. With the introductionof radial stolons, which seems to have taken place in horizons referable to theGansserina gansseri Zone, only several accessory epi-embryonic chamberletsarise from the tritoconch. Instead, epi-embryonic chamberlets become ratherlarger in size and also they cover a wider portion of embryon along its thickouter wall. Considering the suitable changes in embryon size, and also someother morphologic features in successive populations, two new species, O.anatoliensis sp. nov. and O. cideensis sp. nov. have been erected in late


FORAMS 2006


FORAMS 2006The Late Cretaceous genus Omphalocyclus from Turkey: New stratigraphical data for the Mediterranean Tethys

Ercan Özcan

Campanian and late Campanian-early Maastrichtian populations, respectively.The most advanced specimens in late Maastrichtian are attributed to the long-known species O. macroporus (Lamarck, 1816). Thus, a tentative subdivisionscheme comprising three successive species, O. anatoliensis- O. cideensis-O. macroporus, is proposed.

This evolution is supported by different assemblages of the co-occurringforaminifera. O. anatoliensis n. sp. is associated with Lepidorbitoidesbisambergensis, Orbitoides media-O . megaloformis, Siderolitescalcitrapoides and Loftusia spp. Omphalocyclus cideensis sp. nov. co-occurswith advanced developmental stage of Lepidorbitoides minor, primitive L.socialis, Orbitoides megaloformis (mainly advanced developmental stages),O. gruenbachensis, Siderolites calcitrapoides , S . denticulatus andPseudomphalocyclus blumenthali. Omphalocyclus macroporus, on the otherhand, associates with Lepidorbitoides socialis, Orbitoides gruenbachensis,O. apiculata, Siderolites calcitrapoides, S. denticulatus, Clypeorbismamillata, Hellenocyclina beotica and Cideina sözerii. SomeOmphalocyclus specimens are observed to develop rather weak lateralchamberlets. These specimens, first recorded in the Omphalocycluscideensis sp. nov. phylogenetic level, are attributed to Pseudomphalocyclus(Meriç, 1980).

355

The updated orthophragminid zonation and main turnoversbased on the late Paleocene to Priabonian record from Turkey

Ercan Özcan1 & György Less2

1Department of Geology, Faculty of Mines, Istanbul Technical University, Ayazaða/Istanbul34469, Turkey - [email protected]

2University of Miskolc, Department of Geology and Mineral Resources, 3515,Miskolc-Egyetemváros, Hungary

Orthophragmines constitute one of the major larger foraminiferal groupsof the shallow-water western Tethys spanning from the late Paleocene to theterminal Eocene. This group comprises two, phylogenetically independentfamilies, Discocyclinidae (with genera Discocyclina and Nemkovella) andOrbitoclypeidae (with genera Orbitoclypeus and Asterocyclina). Each genusyields several evolutionary lineages that are morphometrically segmented intochronosubspecies. Based on them Less (1998) encountered eighteen zones(marked by OZ) that are integrated into the shallow benthic zonation (SBZ)system by Serra-Kiel et al. (1998). An almost complete succession of Turkishorthophragmines have been morphometrically investigated focusing mainly onfeatures of the equatorial section. The about one-hundred samples come fromtwenty-one localities and sections of the Haymana-Polatli, Safranbolu,Kastamonu, Sivas, Elazig, Sarköy and Sile basins and cover the middle Thanetianto early Priabonian interval with a minor hiatus only in the middle Lutetian. Allthe major orthophragminid lineages of the more western parts of peri-Mediterranean realm could be detected with small differences only in theirproportions. Sporadic deviations from the typical forms and few endemic formscould only be recognized. The age of these orthophragminid assemblages iscontrolled by the associated nummulitids, planktic foraminifera and calcareousnannoplankton, too. The results confirm that the orthophragminid zonation ofthe western and central Mediterranean can be extended towards the easternMediterranean. Based mainly on the Turkish orthophragminid record theevolutionary track of several lineages could be completed and précised, havingerected thirteen new chronosubspecies, too. Four new (mainly endemic) speciesare introduced as well. As a result, the taxonomy of western Tethyanorthophragmines has been updated and the stratigraphic distribution of sometaxa is rearranged. Some of the previously assigned eighteen orthophragminidzones (OZ 2, 8A, 8B and 12 to 14) were redefined and simultaneouslyrecalibrated in the context of the shallow benthic zonation of the Tethyan Early


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FORAMS 2006The updated orthophragminid zonation and main turnoversbased on the late

Paleocene to Priabonian record from TurkeyErcan Özcan & György Less

Paleogene by Serra-Kiel et al. (1998). According to our recent knowledge sixmain steps can be encountered in the evolution of the western Tethyanorthophragmines as follows: 1) Two unribbed species of Discocyclina (D.seunesi and D. tenuis) and Orbitoclypeus (O. schopeni and O. multiplicatus)each appeared in the early Thanetian (SBZ 3, OZ 1A). 2) Ribbed Orbitoclypeus(O. munieri, O. bayani) and the genera Asterocyclina (A. taramellii) andNemkovella (N. evae) appeared around the Paleocene/Eocene boundary (SBZ5–6, OZ 2–3), simultaneously with specific changes within Discocyclina (D.archiaci and D. dispansa instead of D. seunesi). 3) The main diversificationof orthophragmines is observed to occur at about the Ilerdian/Cuisian boundary(SBZ 9–10, OZ 5–6) with the first appearance of such important lineages asD. augustae, D. fortisi, N. strophiolata, O. douvillei, O. varians, O.furcatus, A. stellata and A. alticostata simultaneously with the disappearanceof O. multiplicatus and other forms. 4) Characteristic early Eocene lineageslike D. fortisi, N. evae, O. schopeni, O. munieri disappeared gradually in theearly Lutetian (SBZ 13, OZ 8B–9), simultaneously with the appearance of D.pratti, D. pulcra and the ribbed D. radians and also with the replacement ofD. archiaci by D. discus. 5) The first main orthophragminid extinction event(with two sub-events) can be placed into the late Bartonian to earliest Priabonianinterval (SBZ 17 to the early part of SBZ 19, OZ 13–14) and characterized bythe disappearance of D. pulcra and O. douvillei first and then by the extinctionof D. discus, D. pratti, N. strophiolata and A. alticostata and also by thecommon appearance of D. t rabayens is . 6 ) . Al l surv ivororthophragmines disappeared at the very end of the Priabonian (SBZ20/21 boundary, end of OZ 16).

357

Recent advances in the study ofEocene planktonic foraminifera

Paul N. Pearson1; Richard K. Olsson2; Brian T. Huber3; Christoph Hemleben4;William A. Berggren5; Helen K. Coxall1; Vlasta Premec Fucek6;

Isabella Premoli Silva7 & Bridget S. Wade2

1School of Earth, Ocean and Planetary Sciences, Cardiff University,Main Building, Park Place, Cardiff CF10 3YE, U.K. - [email protected]

2Department of Geological Sciences, Rutgers University, New Brunswick, New Jersey 08903, U.S.A.3Department of Paleobiology, MRC NHB 121, National Museum of Natural History,

Smithsonian Institution, Washington, D.C., U.S.A.4Institute und Museum für Geologie und Paläontologie, Universität Tübingen, D-72076, Germany

5Department of Geology and Geophysics, Woods Hole Oceanographic Institution,Woods Hole, MA 02543, U.S.A.

6Laboratory Research Department, INA, NAFTAPLIN, HR/10000, Zagreb, Croatia7Dipartimento Scienze della Terra, University of Milan, Via Mangiagalli 34, 20133 Milano, Italy

We have recently completed a revision of the taxonomy, paleoecology,evolutionary relationships and stratigraphic distributions of planktonicforaminifera from the Eocene Epoch based on scanning electron micrographsof most of the type specimens and extensive illustration of exceptionally well-preserved material from around the world.

We recognize a total of 166 species in 36 genera, of which ten speciesand three genera are new. Analysis of wall structures forms the basis of ourhigher classification, dividing the group into microperforate, spinose andnonspinose groups. Revised biostratigraphic zonations for the Paleogene tropics/subtropics and high latitudes have been developed in parallel with this work.

Most of our studies have supported previous interpretations of thetaxonomy and phylogeny of the group, thereby establishing them on a firmerbasis. However the aspects of the taxonomy that are most novel are as follows:

1) Eocene Globorotaloides is revised following the assignment ofGloborotaloides suteri Bolli to Catapsydrax. Two new species ofGloborotaloides are described.

2) A new phylogeny for Eocene Parasubbotina is presented, in whichthe evolutionary relationship with Paragloborotalia is clarified.

3) The spinose genus Globoturborotalita is recorded from the Eocene.4) The modern genus Turborotalita is recognized as having originated

in the Eocene.


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FORAMS 2006Recent advances in the study of Eocene planktonic foraminifera

Paul N. Pearson; Richard K. Olsson; Brian T. Huber; Christoph Hemleben; William A. Berggren;Helen K. Coxall; Vlasta Premec Fucek; Isabella Premoli Silva & Bridget S. Wade

5) The rapid evolution of Hantkenina from Clavigerinella was via apreviously undescribed intermediate form.

6) The genus Morozovella is divided into two genera, whereby gracilemiddle Eocene species are included in a new genus.

7) Dentoglobigerina is nonspinose and may have descended from anonspinose ancestor such as Acarinina.

8) The genus Pseudohastigerina is divided into two genera, with anew genus and species named for compressed planispiral forms thatare believed to have arisen independently from Globanomalina.

9) The first species of Turborotalia, T. frontosa (Subbotina) is anonspinose form that evolved from Globanomalina.

10) Observations of a monolamellar wall structure and stable isotopedata from Eocene species of Tenuitella and Jenkinsina suggest thatthese genera may have evolved from a benthic ancestor.

The new data help clarify patterns of evolution and ecologicaldiversification in the group in relation to Paleogene climatic change. Someimplications for renewed study of Oligocene planktonic foraminifera are discussed.

359

Isotope records from Turborotalia cerroazulensis andTurborotalia pomeroli near the middle/late Eocene boundary

(North Adriatic Sea, Croatia)

Vlasta Premec-Fucek1 & Paul N. Pearson2

1INA-Industrija nafte d.d., Research and Development Sector,Biostratigraphy Department, Lovinciceva bb, 10 000 Zagreb, Croatia

[email protected] University, School of Earth, Ocean and Planetary Sciences, Main Building, Cardiff

CF10 3YE, Wales, U.K.

High-resolution biostratigraphic and isotopes analyses have beenconducted on 6m cored interval from Istra more-5 well (North Adriatic Sea,Croatia), which consists of hemipelagic marl with rare silty intercalations. Thesuccession studied was deposited on the eastern edge of the Venetian Basin ina slope to basinal environment. The sedimentation rate is estimated at 7.7cmper 1kyr enabling a high resolution record of geological events. A moderatelydiverse planktonic foraminiferal association indicates warm to temperateMediterranean bioprovince in the latest middle Eocene and lower part of theupper Eocene. Zone E13 (roughly equivalent to P14) is documented by G.index, G. tropicalis, C. unicavus, S. linaperta, Dentoglobigerina galavisi,A.. praetopilensis, M. crassatus and others. Zone E14 (roughly equivalent toP15) is characterized by S. linaperta, Globorotaloides sp., Catapsydraxspp., A. echinata. High dominance of two species of the T. cerroazulensislineage is documented for the whole interval by quantitative methods. T.cerroazulensis is more abundant than T. pomeroli, and T. cocoaensis is presentrarely in the fine fraction. Two extinction horizons of the muricate specieshave been observed. The first extinction level is at 1172.6m where all largeacarininids abruptly disappear, i.e. Acarinina praetopilensis, A. rohri andothers. Small acarininids, represented by A. medizzai, A. rugosoaculeata andA. echinata occur to the top of the study interval. M. crassatus occurs in thefine fraction (160-250µm) until 1171.80m, above which no specimens havebeen found. The 80cm interval between the extinctions corresponds toapproximately 10kyr, according to the long-term average sedimentation rate of7.7cm per 1 kyr. These data correspond very well to the investigations ofWade (2004). Isotopic analyses have been conducted on three size fractions oftests of T. cerroazulensis and T. pomeroli (160-250, 250-315 and >315µm.).


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FORAMS 2006Isotope records from Turborotalia cerroazulensis and Turborotalia pomeroli

near the middle/late Eocene boundary (North Adriatic Sea, Croatia)Vlasta Premec-Fucek & Paul N. Pearson

Samples are well preserved, exhibiting ‘glassy’ preservation suitable forquantitative isotope analysis. All samples studied for both species show similarδ13C values, although T. cerroazulensis (1.175-0.160‰) shows more variabilitythan T. pomeroli (1.065-0.136‰). All δ13C signals indicate a thermoclinehabitat. A shift in δ13C to heavier values is visible at the first extinction level(1172.6m) for both species. One possible explanation for this is a decrease insurface ocean productivity coincident with the Acarinina extinction, in whichthe transport of organic carbon to subsurface levels was reduced. Alternativelyit may be related to global changes in δ13C. The heavier δ13C values continueto the end of the interval studied. Oxygen isotope results from both speciesshow distinct variability close and between extinction levels and range from (-1.227) to (-1.627) ‰ for T. cerroazulensis and (-1.094) to (-1.713)‰ for T.pomeroli. Fluctuation in both δ18O and δ13C values near and between the twoextinction levels could imply changes of ocean circulation and instability of thewater column, possibly indicating a period of increased ecological stress for allgroup of planktonic foraminifera. After both extinction events the δ13C valuesshow less variability suggesting a period of stability in ocean circulation.According to the isotopic ratios, an ontogenic change in ecology or depth habitatmay have occurred in the turborotaliids. The finest fraction (160-250µm)consistently records the lightest δ13C, while the larger (> 315µm) fraction showsheavier values. These differentials are most pronounced during the more stabletemperature period in the upper cored interval, 1170.30-1171.55m, i.e. afterthe second extinction event, when finest fraction show deeper habitat than twolarger fractions for both species. All turborotaliid tests studied show relativelylight δ13C signals suggesting that they were not associating with large numbersof dinoflagellate symbionts as is believed to have occurred in the muricatespecies. However, the glassy, transparent tests of T. pomeroli and T.cerroazulensis may have hosted internal symbionts like some recentgloborotaliids which associate with some algae. Like the subbotinids theysurvived the extinction events which affected surface dwelling forms.

361

Classification of Early Cretaceous trochospiral andplanispiral planktonic foraminifera: An update

Isabella Premoli Silva & Davide Verga

Dipartimento di Scienze della Terra “Ardito Desio”, University of Milano, [email protected]

In the last twenty years several new genera of coiled planktonicforaminifera have been erected in the Early Cretaceous based on pore sizeand distribution, wall thickness and number and elongation of chambers in thelast whorl. Based on detailed SEM analysis, the wall texture of Valanginian-Aptian planktonic foraminifera can be assigned to three types, 1) microperforate(pore size <1 µm), confined to the heterohelicids, 2) finely perforate with poreranging in size from 1 to 3 microns observed in both the trochospiral andplanispiral groups, and 3) irregularly reticulate, confined to the species hoterivica.

The finely perforate wall of the trochospiral group wall is characterisedby rather randomly distributed, widely-spaced pores, ranging in size from 1 to 2µm on most of the species, and from 3-3.5 µm on the early outer whorl chambersof some Hedbergella trocoidea specimens; the surface is smooth at thebeginning of species range, acquiring volcano-like microstructures bearing poresat their top (perforation cones), which are more numerous in the early chambersof the outer whorl; these two types of wall cohexist in all species, formerlyattributed to the genera Hedbergella, Praehedbergella and Blefuscuiana,from small-sized H. sigali to larger-sized, many chambered H. trocoidea.Because the number of chambers in the last whorl is a criterion applicable onlyat species level, in the absence of other discriminating features of genus valuesthe genera Praehedbergella Gorbachik & Moullade 1973 and BlefuscuianaBanner & Desai 1988 are considered junior synonyms of the genus HedbergellaBroennimann & Brown 1958. Moreover, Moullade et al. (2002) stated that theshape (radial elongation) of the outer chambers is not a consistent feature indiscriminating at genus level; consequently, they invalidated the “clavate” generaLilliputianelloides Boudagher-Fadel et al. 1997 and Lilliputianella Banner& Desai 1988. It is worth mentioning, however, that all “clavate” species possessa smoth wall and never developed perforation cones. In agreement withMoullade et al. (2002), the species previously attributed to the “clavate” generaLilliputianelloides and Lilliputianella are also included in the genusHedbergella.


FORAMS 2006


FORAMS 2006Classification of Early Cretaceous trochospiral and planispiral planktonic foraminifera: An update

Isabella Premoli Silva & Davide Verga

Similarly to the trochospiral taxa, SEM analyses showed that all theValanginian-Aptian planispiral species described so far possess a finely perforatewall with pores 1 to 3 µm in diameter, including the larger speciesGlobigerinelloides ferreolensis and G. algerianus, the type species of thegenus Globigerinelloides Cushman & ten Dam 1948, as already noticed byBoudagher-Fadel (1995). These observations invalidate the fundamentalcriterion on which Banner & Desai (1988) emended the diagnose of the genusBlowiella Kretchmar & Gorbachik 1971 (type species Globigerinelloidesblowi). In fact, the other features used successively by several authors todiscriminate Blowiella from Globigerinelloides, such as low/higher numberof chambers in the last whorl, smaller/wider umbilical area, more/less developedrelict apertures, bilobate last chamber, and laterally compressed/inflated testoccur in species attributed to both genera and have a value only at specieslevel. A further feature for retaining the genus Blowiella was its smooth wall(lacking the perforation cones of Globigerinelloides). However, our SEMobservations indicate that the whole Aptian planispiral group is devoid ofperforation cones, while the wall roughness on the earliest outer chambersobserved in Globigerinelloides is simply due to pustules that may coalescegiving rise to ridges or plates, even though a few smooth morphotypes havealso been detected. Consequently, the genus Blowiella is not valid and must beconsidered as junior synonym of the genus Globigerinelloides.

363

Agglutinated foraminifera using coccoliths as buildingmaterial: Grain handling and wall structure

Erik Thomsen1 & Tine L. Rasmussen2

1Department of Earth Sciences, University of Aarhus, Building 1120, DK-8000Århus C, Denmark - [email protected]

2Department of Geology, University of Tromsø, Dramsveien 201, N-9037 Tromsø, Norway

Scanning electron microscopy of foraminifera from the lowermostBarremian (Lower Cretaceous) deposits at Speeton, eastern England, revealsthat about 4% of the agglutinated tests >36 µm are constructed almost exclusivelyof coccoliths of the species Watznaueria barnesae. This species makes upabout 5% of the total number of the grains <36 µm available for the agglutinatedfauna. The majority of the foraminifera utilizing coccoliths are smaller than125 µm in length. Most specimens are trochospiral showing resemblance toTrochammina depressa, but planispiral, unilocular, uniserial and biserial formshave also been observed. Specific identification is difficult due to compression,the small size of the tests, and the unusual building material. In the smallesttrochamminids, the walls are composed of a single layer of coccoliths. Theforaminifera were highly efficient in selecting and ordering the coccoliths, whichalways are placed with their distal surfaces facing outward. Apparently inorder to fit the coccoliths closer together and to diminish the amount of emptyspaces between them, the outline of the coccoliths - probably by a dissolutionprocess - was modified from oval to hexagonal. The dissolution was extremelyprecise affecting only the rims of the coccoliths leaving all other crystalsurfaces untouched.

In larger tests, the grain layer becomes layered as increasing amountsof cement covers the coccolith layer. The cement, which according to EnergyDispersive Spectroscopy (EDS) analyses consists of silica, was probablyoriginally organic. The silica contains relatively few grains. They are of mixedsedimentary and skeletal origin. In contrast to the inner coccolith layer, thegrains of the outer layer were apparently picked at random among the manysorts of grains available on the sea bottom. In 10-20% of the tests, the coccolithsare affected by a later dissolution phase, which attacked all the crystals of thecoccoliths and not only their rims as during the early phase. The late dissolutionmay result in almost total disintegration of the coccoliths. The timing of the latedissolution is uncertain. Some evidences indicate that it occurred while theforaminifera were still alive, whereas others suggest that it occurred post mortem.Some of the biserial tests show a distinct ontogenetic shift from an early partconstructed mainly of coccoliths to a later part constructed of sedimentarygrains and cement.


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364

Barremian-Turonian benthic foraminiferal assemblagesfrom the Great Valley Sequence, California

T. Tomosugi1; H. Nishi1; A. G. S. Fernando1; K Moriya1;K. Tanabe2 & M. A. Murphy3

1Graduate school of Science, Hokkaido University, Japan - [email protected] school of Science, Tokyo University, Japan

3Geology Department, Davis, University of California, CA, U.S.A.

The Budden Canyon Formation (BCF) is a thick sedimentary sequencecomprising the Great Valley Sequence (GVS) in the northwestern part of theSacramento Valley. The BCF consists mainly of mudstone, with intercalationsof thick sandstone and conglomerate units. Based on macrofossil (i.e. ammonitesand other mollusks), the age of the formation ranges from Hauterivian toTuronian. The studied sequence is located along the North Fork CottonwoodCreek (Shasta County) and is divided into the six units of the Ogo Member,Roaring River Member, Chickabally Member, Huling Sandstone, Bald HillsMember and Gas Point Member, in ascending order. The rocks contain abundantbenthic foraminifers except for the Huling Sandstone.

A total of 201 morphotypes of benthic foraminifers (>125 µm), consistingof 49 agglutinated and 152 calcareous species, were identified in the studiedsection. Agglutinated species are dominant throughout the sequence. Calcareousforms generally comprise less than 30% of total specimens. The total abundanceof benthic foraminifers decreases in the upper part of the Chickabally Memberand the Bald Hills Member, while planktic foraminifers commonly occur in theGas Point Member.

The benthic faunas were classified into three assemblages on the basisof species dominance. The Barremian Assemblages is characterized bydominance of Trochammina tehamaensis and common occurrence ofMarginulinopsis striatocostata and Astacolus pachynota. The Aptian-AlbianAssemblage is dominated by Recurvoides spp., with M. collinsi andUvigerinammina pacifica common in the Aptian, and Osangulariaschloenbachi and Plectorecurvoides alternans common in the Albian. TheCenomanian Assemblages are dominated by Haplophragmoides obesus,Bulbobaculites fragmentarius and Gyroidinoides infracretaceus in the earlyCenomanian, while Pleurostomella reussi and Quadrimorphinaallomorphinoides commonly occur in the late Cenomanian to Turonian.


FORAMS 2006


FORAMS 2006Barremian-Turonian benthic foraminiferal assemblages from the Great Valley Sequence, California

T. Tomosugi; H. Nishi; A. G. S. Fernando; K Moriya; K. Tanabe & M. A. Murphy

The results of the calcareous nannofossil biostratigrapy and carbon isotopeanalysis of wood fragments were used in the recognition of several intervals ofOceanic Anoxic Events (OAEs) in the studied sequence. The Early Albiansamples within Zone NC8A contain high total organic carbon (TOC) (2.5 wt.%),high abundance of radiolarians and dominance of Haplophragmoides spp.and Bathysiphon spp. Based on these observation, we correlate this intervalto the OAE1b. A positive shift of ~5‰ in´13Cwood, along with high TOC values(1.2 to 1.8 wt.%) were recognized near the Cenomanian/Turonian boundary,within Zone NC 12. Zone NC12 is characterized by the dominance ofValvulineria loetterlei and Hoeglundina chapmani, and by the high abundanceof radiolarians in the upper part of the interval. These results suggest that thishorizon corresponds to the OAE2. Both OAE 1b and OAE2 are characterizedby distinct extinctions of benthic species (OAE1b: 24.7%, OAE2: 27.3%).

OAE1c and OAE1d occur within Zones NC9A (early late Albian) andNC10A (late Albian), respectively. The samples corresponding to the OAE1ccontain abundant Bathysiphon spp. and are barren of nannofossils. Similar toOAE2, radiolarians are abundant above the interval. However, TOC andä13Cwood values do not show any significant change or excursion. The OAE1dinterval is marked by an increase of 0.6 wt.% in TOC and 2‰ of ä13Cwoodvalues, respectively. The samples in this interval are either barren of benthicfauna or only contain Bathysiphon spp. These two OAEs show low rates ofextinction (OAE1c: 2.3%, OAE1d: 6.4%).

These faunal turnovers and radiolarian abundance trends observed inthe OAEs of the Northern California are very similar to those observed in theYezo Group of Hokkaido, Japan. Based on these two areas, we suggest thatincreased organic carbon burial during OAEs resulted in impoverished benthicfaunas around the North Pacific continental margin.

366

Biostratigraphy and paleoecology of Qum Formation(Oligo-Miocene) of Kashan area, Iran

Mohammadreza Vaziri1 & Azam Mahanipour2

1Geology Department, Faculty of Sciences,Shahid Bahonar University of Kerman, Iran2College of Geology, Shahid Beheshty University, Tehran, Iran,

[email protected]

A detail study of Oligo-Miocene outcrops (Qum Formation) at Kashanarea has been done and 4 sections at Ghamsar, Vidoj, Maragh and Niasarwere logged in detail. Based on benthic foraminiferal analysis, the sectionsspan the middle Oligocene to middle Miocene interval. The unique appearanceof Nummulites fichteli in Ghamsar marks the Rupelian-Chattian? /Aquitanianboundary. Presence of Borelis melo curdica, Miogypsina globulus,Miogypsinoides sp., Lepidocyclina (Eulepidina) spp., in Niasar suggeststhe uppermost part of Qum Formation (Burdigalian). The two other sections,Vidoj and Maragh, comprise the lower Miocene strata (Aquitanian), althoughthe presence of Borelis melo curdica in the lower part of Maragh suggeststhe age of Burdigalian for this part. The stage boundaries are not well clearfrom the view point of lithological changes. The paleoecological analysis showsthat a shallow, warm and oligotrophic condition has been prevailed during thedeposition of the strata.


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367

A Cretaceous foraminiferal assemblage fromWest of Kerman area (Iran)

M. R. Vaziri1; A. Mahanipour2 & A. Arab

1Geology Department, Faculty of Sciences, Shahid Bahonar University of Kerman, Iran2College of Geology, Shahid Beheshty University, Tehran, Iran

[email protected]

The Cretaceous succession in West of Kerman city is represented bytwo discrete parts. The lower one consists of distinctive, correlatable greenmarls rich in macro and microfossils. These marls can be assigned a late Albianto early Cenomanian age based on the associated macrofossil assemblage,which is dominated by molluscs and echinoids. The marls are overlain bySantonian limestones rich in foraminifera such as:

Rotalia skourensis Henson, Antalyna sp., Nezzazata sp.,Trochamminoides sp., textulariids, Ophthalmidium sp., Cuneolina pavonia(d’Orbigny), miliolids, lituolids, Spiroplectammina sp., Dorothia sp., Gavelinellasp., Nezzazatinella picardi Henson, Pseudocyclammina sp., peneroplids,Spiroculina sp., Praechrysalidina sp., Dicyclina schlumbergeri Munier-Chamlas, Pseudolituonella reicheli Marie, Pseudocyclammina massiliensisMaync, Quinqueloculina sp., Minouxia lobata Gendrot, Archaeocyclus sp.,Subalveolina sp., Bolivinopsis sp., Nummofallotia apula Luperto Sinni,Reticulinella sp. and Lenticulina rotula Lamarck.

The fossil assemblage indicates a favorable condition during depositionof the green marls and limestones.


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368

Biozonation of Sinemurian and Pliensbachianlarger benthic foraminifera (Velebit Mt., Croatia)

Vladimir Veseli1; Ivo Velic2; Igor Vlahovic2; Josip Tisljar3 & Damir Stankovic1

1INA-Industrija nafte, d.d, Corporate Processes, Research and Development Sector, Rockand Reservoir Fluid Research Laboratory Department, Lovinèiæeva bb,

P.O.B. 555, HR-10002 Zagreb, Croatia - [email protected] Geological Survey, Sachsova 2, HR-10000 Zagreb, Croatia

3University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering,Pierottijeva 6, HR-10000 Zagreb, Croatia

Sinemurian and Pliensbachian shallow-marine carbonates of Velebit Mt.were deposited on a huge shallow marine carbonate platform which coveredvast areas of the Southern Tethyan realm. In the Toarcian, this disintegratedinto several smaller platforms (including the Apennineic, Apulian and AdriaticCarbonate Platforms), separated by deeper marine basins.

Detailed investigation of the continuous Sinemurian and Pliensbachiansuccession outcropping along the Gospiæ-Karlobag road (Kubus locality - Tišljaret at, 1991. Excursion guide-book, The Second Int. Symp. on the AdriaticCarbonate Platform, Zadar, 1991, Institute of Geology, Zagreb, 1-49.),allowed subdivision into 6 biostratigraphic zones, based on the distribution andstratigraphic ranges of Lower Jurassic lituolids:

o Biozone 1: Mesoendothyra sp. lineage zone, Early Sinemurian (=interval zone of Septfontaine, 1984. Rev. Micropaléont., 27 (3): 209-229) - bounded by the first appearance of Mesoendothyra sp. and thefirst appearance of Lituosepta recoarensis CATI.

o Biozone 2: Lituosepta recoarensis lineage zone, Late Sinemurian(Septfontaine, 1984.) – bounded by the first appearances of Lituoseptarecoarensis CATI and Orbitopsella primaeva Henson. Importanttaxa include: Mesoendothyra sp., Lituosepta recoarensis, Planiseptacompressa (Hottinger), Amijiella amiji (Henson), Haurania desertaHenson, Orbitopsella sp.

o Biozone 3: Orbitopsella primaeva lineage zone (Septfontaine, 1984)or Orbitopsella primaeva abundance zone, Early Carixian – boundedby the first appearances of Orbitopsella primaeva Henson andOrbitopsella praecursor (Gümbel). Important taxa include:Mesoendothyra sp., Lituosepta recoarensis, Planisepta compressa,Amijiella amiji, Haurania deserta, Orbitopsella primaeva.


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FORAMS 2006Biozonation of Sinemurian and Pliensbachian larger benthic foraminifera (Velebit Mt., Croatia)

Vladimir Veseli; Ivo Veliæ; Igor Vlahoviæ; Josip Tišljar & Damir Stankoviæ

o Biozone 4: Orbitopsella praecursor taxon-range zone, Late Carixian(Sartoni & Crescenti, 1962. Giorn. Geol. (2a) 29: 161–304) –corresponding to the stratigraphic range of Orbitopsella praecursor(Gümbel). Important taxa: Mesoendothyra sp., Paleomayncinatermieri (Hottinger), Lituosepta recoarensis, Planisepta compressa,Amijiella amiji, Haurania deserta , Orbitopsella primaeva,O. praecursor.

o Biozone 5: Orbitopsella praecursor–Pseudocyclammina liassicainterval zone, Early Domerian – bounded by the last appearance ofOrbitopsella praecursor (Gümbel) and the first appearance ofPseudocyclammina liassica Hottinger. Important taxa include:Mesoendothyra sp., Paleomayncina termieri, Planisepta compressa,Amijiella amiji, Haurania deserta, Agerina martana (Farinacci).

o Biozone 6: Pseudocyclammina liassica taxon-range zone, LateDomerian (Septfontaine, 1984) corresponding to the stratigraphic rangeof Pseudocyclammina liassica Hottinger. Important taxa include:Mesoendothyra sp., Paleomayncina termieri, Planisepta compressa,Amijiella amiji, Haurania deserta , Agerina martana,Pseudocyclammina liassica.

These established biozones correlate very well with contemporaneousdeposits of Velebit Mt. (e.g. Mali Halan profile), as well as with other areas ofthe Karst Dinarides. In the wider Mediterranean realm these results almostcompletely correspond with the biozonation proposed – and correlated withammonite zones – by Septfontaine (1984) in the High Atlas Mts. of Morocco.

Within the investigated Sinemurian and Pliensbachian shallow-marineinner platform carbonates of the Karst Dinarides, (completely lacking inammonites and planktonic foraminifera), the determined biozones of larger benthicforaminifera represent a most important tool for stratigraphic correlation.

370

The impact of orbitally forced upwelling on Oligoceneplanktic foraminifera δδδδδ13C and abundances

Bridget S. Wade; William A. Berggren & Richard K. Olsson

Department of Geological Sciences, Wright Geological Laboratory, Rutgers,The State University of New Jersey, 610 Taylor Road, Piscataway,

NJ 08854-8066, U.S.A. - [email protected]

Planktonic foraminifera from a continuous Oligocene sequence withclear magnetochronology, sediment cycles and abundant foraminifera at OceanDrilling Program Site 1218 (equatorial Pacific) were sampled in the intervalfrom 27 to 30 Ma at 10 cm resolution. Taxa of the genus Paragloborotaliaare particularly common through the interval studied and we examined thesize, relative abundance, stable isotopes and coiling direction ofParagloborotalia taxa.

Multispecies stable isotope data indicate Globoquadrina venezuelanaand Dentoglobigerina globularis were probable mixed-layer dwellers, withparagloborotaliids recording heavier δ18O signatures consistent with athermocline habitat. Cyclic variations in the abundances of Paragloborotalianana matching eccentricity (100 kyr) variations in percent carbonate and δ13C,suggest orbitally forced upwelling in the equatorial Pacific Ocean and that P.nana was a eutrophic species responding directly to changes in surface waterproductivity. Five chambered forms consistent with Paragloborotalia opimaare present throughout the section studied. An abrupt dwarfing (50% sizedecrease) in Paragloborotalia nana, P.opima and P. pseudocontinuosaoccurs within Chron 9n.

However, this dramatic change in size is not associated with any eventrecorded in the stable isotope records. The high resolution biostratigraphy hasbeen calibrated to the magnetochronology to constrain the extinction ofParagloborotalia opima (sensu strictu) which marks the top of planktonicforaminifera biozone O5 (P21b). In addition, we find the extinction ofChiloguembelina cubenisis within Chron 10n.1n is consistent with otherdeep-sea sections


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371

From grey to red pelagic sediments during the Turonian –A benthic foraminifera perspective

Ines Wendler1; J. Wendler1 & M. Wagreich2

1University of Bremen, Fachbereich 5 - Department of Geolocial Sciences,Postfach 330440, 28334 Bremen, Germany - [email protected]

2 University of Vienna, Department of Geolocial Sciences, Althanstrasse 14, A-1090 Wien, Austria

While the Early Cretaceous was characterized by periods of marineblack shale deposition, widespread deposition of marine red beds in pelagic aswell as in shallow water environments started in the Turonian, with apparentpeak abundances in the Santonian to early Campanian and late Campanian toMaastrichtian. Red colored marine sediments form when Fe is oxidized andbound in iron oxides. This chemical reaction is only possible under absence oflarger amounts of organic carbon, as organic matter degradation leads toreducing conditions precluding the formation of iron oxides. Oxidation of organiccarbon is mainly controlled by (1) the amount of available oxygen in the bottom-and sediment pore water, (2) the amount of organic carbon (Corg-flux) and (3)the oxygen exposure time (dependent on the sediment accumulation rate). Thus,the syn-sedimentary and early diagenetic redox conditions are the result of theinterplay of these three factors which, in turn, are modulated by the globalchanges of ocean circulation and climate. The general global cooling andreorganization of the ocean circulation in the Late Cretaceous certainly aremajor factors which must have had an influence on the oxygenation of thedeep water. However, detailed concepts for the explanation of the formationand distribution of marine red-beds in the Upper Cretaceous are still not available.

The studied Buchberg section is part of the Ultrahelvetic units of UpperAustria which represent sedimentation on the European passive continentalmargin during the Cretaceous. The 7 m long profile comprises a succession ofplanktonic foraminifera-rich marls and limestone with a transition from grey tored colors, and was studied at high resolution for the content on benthicforaminifera as well as the mineralogical composition. The section can beassigned to nannofossil standard zones CC10 to CC12 (UC3 – UC8a).Helvetoglobotruncana helvetica is present in the grey to red transitional intervaland gives evidence for an early to middle Turonian age of the marine red beds.Strontium isotope stratigraphy also confirms a Turonian age of the succession.The red sediment color is restricted to discrete beds pointing to a syn-depositionalto early diagenetic formation. It is interesting to note that the oxic conditionswhich lead to the red sediment color must have established in several steps.


FORAMS 2006


FORAMS 2006From grey to red pelagic sediments during the Turonian – A benthic foraminifera perspective

Ines Wendler; J. Wendler & M. Wagreich

The Buchberg section exposes alternations between red and grey marls aswell as between red and grey limestone, indicating that sedimentation rate andproductivity are most probably not the only factors controlling the colordistribution and that the oxygen content of the bottom water must have changedseveral times during this period. This can also be inferred from the changingvertical distribution patterns of benthic foraminifera in relation to the sedimentcolor. Very high abundance of species which are regarded to be typical forincreased organic matter flux rates to the sea floor and slightly reduced oxygenlevels such as Tappanina laciniosa and Praebulimina elata (Kuhnt &Wiedmann, 1995. American Association of Petroleum Geologists Studies inGeology, 40: 213-231; Friedrich & Erbacher, in press. Cretaceous Research)occurs just before the changes from grey to red colors and is followed bypeaks of pyrite, iron-hydroxides and iron-oxides. This indicates that the depositsreflect changing conditions at the sea floor which could have led to thepreservation of early diagenetic redox fronts in the sediments.

373

Depths, paleodepths and the percentage of foraminiferalassemblages comprising planktonics in Trinidad

Brent Wilson

Petroleum Geoscience Programme, The University of the West Indies,St. Augustine, Trinidad and Tobago, West Indies - [email protected]

The modern shelf sea around Trinidad is impacted by freshwater outflowfrom the Amazon, Essequibo and Orinoco rivers, which collectively deliver>20% of the global freshwater input to world’s oceans. This outflow, whichcommenced during late Miocene times, lowers salinities around Trinidad relativeto normal seawater, creating a surface layer 50 m deep with a salinity of <33.5ppt, and induces high phytoplankton primary productivity. This has been foundto impact on Recent benthonic foraminiferal diversities on the inner to middleshelf (1-100 m), which are low relative to assemblages at the same depths inoceans of normal marine salinities. However, there have not yet been anystudies of the Recent around Trinidad examining relationships between depth(D) and the percentage of the total foraminiferal assemblage comprisingplanktonics (P), although this would aid greatly in determining paleodepths inand, by extension, the sequence stratigraphy of the Neogene on the island.

Linear regression applied to a data set of 27 Recent sediment samplesfrom depths 1-102m around Trinidad indicates that:

D = 19.7 + 1.34P (r = 0.854, p <.0001) (1)

This expression, for which 95% confidence intervals are computed, isapplied to 36 samples from a 266 m section of the late Miocene San JoséCalcareous Silt (Manzanilla Formation, Globorotalia acostaensis Zone) ofNE Trinidad. Previous clustering of these samples using benthonic foraminiferahas indicated that they were deposited in six different biofacies. Planktonicforaminifera were recovered from five of these; the single sample representingthe sixth biofacies contained Haplophragmoides wilberti only and did notyield planktonics. Modern Haplophragmoides wilberti live among supratidalmangrove swamps. Of the remaining biofacies:

o Biofacies 1, dominated by Amphistegina gibbosa, comprises 1 sampleonly, for which P = 0.9%, corresponding to D = 2 m (95% confidencelimits, 0 – 37 m)


FORAMS 2006


FORAMS 2006Depths, paleodepths and the percentage of foraminiferal assemblages comprising planktonics in Trinidad

Brent Wilson

o Biofacies 2 comprises 1 sample only, dominated by Ammonia beccarii,for which P = 3.4%, corresponding to D = 24 m (4 – 40 m)

o Biofacies 3, dominated by Textularia sp. A, comprises 3 samples forwhich the mean P = 6.1% (standard deviation = 3.7%) corresponds toa mean D = 28 m (95% confidence limits on the mean, 8 – 44m)

o Biofacies 4 is dominated by Hanzawaia carstensi and comprises 17samples. These were deposited in two packages that, comprising theupper and lower parts of the sequence, enclose Biofacies 5. ForBiofacies 4 the mean P = 9.7% (maximum = 28.6%, minimum = 1.5%,standard deviation = 8.6%), corresponding to a mean depth of D = 32m (95% confidence limits on the mean, 10 – 50 m)

o Biofacies 5 comprises 10 samples in the middle part of the sequence inwhich the fauna is dominated by Pseudononion atlanticum withsubdominant Elphidium translucens. For this biofacies the mean P is17.5% (maximum 32.9%, minimum 7.4%, SD = 8.9%) correspondingto a mean depth of D = 42 m (95% confidence limits on the mean,26 – 62 m)

Student’s t-test indicates that there is no significant difference in themean D for Biofacies 3 and 4, but that the mean D in Biofacies 5 exceeds thatin Biofacies 3 and 4. From this it is concluded that the sequence was depositedin middle neritic and shallower water, but that water depths varied over time.Despite wide variations in the values of P within biofacies, it appears thatsamples from Biofacies 5, from the middle of the sequence, were depositedduring a sea-level highstand. In contrast those from Biofacies 4, the two packagesof which sandwich Biofacies 5, were deposited during relative lowstands. Theremaining biofacies, including that with Haplophragmoides wilberti, areintimately allied with those parts of the sequence deposited in the shallower-water Biofacies 4, and indicate times of shallowest water and riverine influence.

375

Hydrodynamic behavior of empty larger foraminiferal tests

Elza K. Yordanova & Johann Hohenegger

Institut für Paläontologie, Universität Wien, Althanstrasse 14, A-1090 Wien, [email protected]

Larger, symbiont-bearing benthic foraminifera are very importantproducers of carbonate sand in shallow environments of the marine tropics.Today, beach sand in the Indo-Pacific may consist up to 90% of foraminiferaltests and their proportion in the shallow subtidal also remains high peaking at50%. Because most of the sediments from the eu- and infralittoral are poorlypreserved in the geological record due to the extreme water energies acting inthese zones, the preservation and selected accumulation of larger foraminiferalshells from the shallowest region in the less dynamic circalittoral must beexplained through transport caused by currents or storm events.

Recent investigations of down-slope transport of foraminiferal tests bythe authors led to the assumption that differences in response of empty tests towater movement (especially transport by currents) cause accumulation atdifferent places although originating from the same shallow habitat.

Laboratory experiments with a settling tube were exemplified showingdifferences in sinking behavior (form and velocity). Entrainment from the bottomwas investigated using a flume tank with the 2 bottom-conditions ‘smooth’ and‘rough’ (medium sand) surface. Due to the lower density of foraminiferal testsfilled with seawater (~1.2 – 1.7) compared with broken pieces of skeletonsand shells consisting of compact calcium carbonate (bivalves, corallinean algaewith densities ~ 2.4), sinking velocity is lower than solid carbonate particles ofthe same size. Additionally, the test form reduces sinking, since spheres andthick discoids show faster sinking than flat discs and blades. Also the rod-likefusiform tests demonstrate slow sinking compared to spheres.

Entrainment of foraminiferal tests is opposite to the sinking behavior.Similar to siliciclastic grains, spherical tests are easier entrained compared toflat discoids and blades. According to differences in Reynolds numbers, sinkingvelocities, and entrainment, Hjulström diagrams combining sinking velocity andentrainment in relation to test size clearly separate regions with velocities, wheretests are entrained, from velocities leading to floating but too weak forentrainment. The third region characterizes velocities, where tests are not floating.

Lenticular peneroplids (Dendritina) with higher sinking velocities areeasier entrained than flat species (Peneroplis) with a lower sinking velocitiy.


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FORAMS 2006Hydrodynamic behavior of empty larger foraminiferal tests

Elza K. Yordanova & Johann Hohenegger

The flat soritids (Sorites, Parasorites, Amphisorus) show extremely low sinkingvelocities (high buoyancy) but weak entrainment. Similar behavior to thelenticular Dendritina can be experienced by the fusiform alveolinids(Alveolinella), where entrainment depends on the position of the longitudinalaxes to the current direction.

Amphisteginids and calcarinids with lenticular to spherical tests behavesimilar (high sinking velocity - easily entrained). The changing test-diameter/thickness ratio with growth in nummulitids leads to different behavior againsthydrodynamics. While settling velocity is reduced during growth, entrainmentis hampered. This explains differences in accumulation of Nummulites tests inthe geologic past. Because lenticular tests as they are significant for Nummulitesliving in the upper circalittoral (above the storm wave base) are easily entrainedand then depth transported, the flat forms (Planostegina) occupying the lowercircalittoral are less entrained. Therefore, a mixture of species, the oneallochthonous and the other semi-autochthonous can be accumulated at thesame depths.

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Paleoenvironmental reconstruction of themiddle Eocene Pazin Basin (Croatia)

Sanja Zivkovic

Department of Geology and Paleontology, Faculty of Science, University of Zagreb, [email protected]

Assemblages of benthic foraminifera from two clastic successions fromthe Pazin Basin (central Istria, Croatia) were investigated to reconstructpaleoenvironmental conditions during the middle Eocene time. Sections arecomposed of hemipelagic/Globigerina Marls which are conformably overlainby Flysch. The Graèišæe section is located in the southern part of the PazinBasin comprising E9 to E12 planktonic foraminiferal Zones whereas the Ipšisection, situated in the northern part of the Pazin Basin, includes E12 and E13Zones. Planktonic percentages are mostly high (80-98%). Benthic foraminiferalassemblages comprise calcareous and agglutinated taxa (up to 22%). Theprevalence of epifaunal foraminifera indicates good ventilation of the bottomwater caused by the morphology of the basin, which was elongated and openon both sides enabling the undisturbed flow of the water all the way through.The depth of deposition is inferred from the bathymetric distribution of theindividual taxa and estimated to be 200-300 m in the lowermost part of theGlobigerina Marls in the Graèišæe section where Lenticulina spp., Oridorsalisumbonatus, Cibicidoides spp. and Bulimina spp. prevail. Increasedabundances of Nuttallides truempyi, Anomalinoides capitatus, Cibicidoidesbarnetti, C. praemundulus, C. grimsdalei etc. in the lower part of Flyschdeposits indicate deepening to more than 500 m. Flysch from the upper parts ofboth sections was estimated to be even deeper environment, possibly middlebathyal, which is indicated by high abundances of tubular taxa (Bathysiphonsp. and Rhabdammina robusta), Uvigerina hispidocostata ,Haplophragmoides sp., and absence or very low abundances of Lenticulinaspp. Diversities of the benthic foraminiferal assemblages are high anddominances low in the most samples from the Graèišæe section (except for thelowermost part of the section). The abundances of the most commonforaminiferal taxa (Cibicidoides spp., Oridorsalis umbonatus, Bulimina spp.,Stilostomella spp., Osangularia spp., Nuttallides truempyi, etc.) within theGlobigerina Marls (E9-E10 Zones) from the Graèišæe section are quite variablewhile the proportions of Lenticulina species remain more or less constant.


FORAMS 2006


FORAMS 2006Paleoenvironmental reconstruction of the middle Eocene Pazin Basin (Croatia)

Sanja Zivkovic

Such assemblages imply generally mesotrophic environmental conditions withvariable organic flux. The transition to flysch-type sedimentation (E11 Zone) ismarked by a strong decrease in abundance of Lenticulina spp., Osangulariaspp., Bulimina spp., Bolivina spp. but increased numbers of tubular taxa,Dentalina spp. and Uvigerina spp. These composition changes were probablycaused by the input of irregular supply of more partially degraded and suspendedorganic matter carried from the shelf by turbidity currents. The assemblagesfrom the Ipši section are less diversified and show higher dominance with theprevalence of Cibicidoides spp. and juvenile or small specimens of epifaunalforaminifera. In the lower part of the Ipši section, within the GlobigerinaMarls (E12 Zone) and lower part of Flysch (lower E13 Zone), Buliminella sp.and Chilostomella spp. make up an important part of the assemblage (8-28%).These species reflect higher organic flux, although high percentages of epifaunalforaminifera don’t support the low oxygen conditions that might have developedas its result. Upwards (upper E13 Zone), abundances of Cibicidoides speciesdecrease while numbers of thin walled small specimens of epifaunal taxaincrease, as well as the abundances of infaunal Dentalina spp., Stilostomellaspp. and Uvigerina spp. These characteristics of foraminiferal assemblagesindicate decreased oxygenation that might have been a result of thereduced circulation caused by the beginning of the closure of the basinat the end of E13 Zone.

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