Jean-François Babinot

Paleobiogeography of Tethyan Cretaceous Marine Ostracods

During the Cretaceous, the geographic distribution of marine Tethyan ostracods always displays a dual trend: endemism and ubiquity. At the species level, major palaeogeographical entities can be defined. These are essentially the two main Southern and Northern provinces. With few exceptions, relations between both margins of the Tethyan Ocean are limited. Sub-provinces can also be recognized. At the genus level, the distinction between provinces is less apparent. Recent studies have reported identical generic associations on both sides of the Tethys during the Early Cretaceous. Some genera are synchronous, e. g., Protocythere s.1., in the western Tethys and Arculicythere and Majungaella in the eastern Tethys and the Proto-Indian Ocean. Other genera seem to be diachronous. Some “pioneer” genera, often without known ancestors, are reported later on the opposite continental margin. This may be the result of migrations controlled by factors such as climate, bathymetry and oceanic circulation. Faunal exchanges could have therefore happened during the Cretaceous. A north-south direction has often been suggested. This is the case for the genera Tethysia, Curfsina and Limburgina . Possible affinities between some genera in different provinces can also be advanced: Majungaella, Neocythere, Novocythere and Tickalaracythere Endemism can be observed at different taxonomic levels and in geographic areas of various extension. It is essentially controlled by the relative position of the continental blocks and the paleobathymetry. To conclude, knowledge of the dynamics of marine ostracod associations contributes to a better understanding of the structural and dynamic evolution of the Tethyan continental margins during the Cretaceous.

Marine ostracode provincialism in the Late Cretaceous of the Tethyan realm and the Austral Province

Abstract A synthetic analysis based on previous and new data allows the recognition of four main palaeobiogeographic units (palaeobioprovinces) for the Late Cretaceous of the Tethyan Realm and Austral Province of the South Temperate Realm: South European, North-Central American, Afro-Arabian, and Austral Bioprovinces. Another unit, the Dinaro-Hellenic Subprovince is located between the South European and the Afro-Arabian bioprovinces. Special emphasis is given to the spatial and temporal distribution of ostracode assemblages (at the specific level) and selected “key genera” within several geographic zones, from the Tethys (North- Central America, southern Europe, northern Africa, and the Middle East) to eastern Africa, India, South Africa, and Australia. Several factors are responsible for these palaeobiogeographic distributions (provincialism) and their evolution: the position and extension of continental margins, oceanic surface current patterns, paleobathymetry, eustatic sea-level changes, paleolatitudes, and their influence on paleoclimates. Other parameters are the biology, physiology, and ecology of the ostracodes. Therefore, ostracode provincialism has a high potential for further paleogeographic inferences, such as global tectonic reconstructions.

Ostracodes from the Early Cenomanian of Jordan.A preliminary report

Abstract Ostracode faunas have been identified for the firsttime in Early marine Cenomanian sediments of the Ajlun Group (Jordan) outcropping East of the Jordan Rift Valley. The faunal assemblages contain 14 genera and 17 species. Sediments indicate the internal part of a carbonate platform. The Ostracodes are closely related to those of neighbouring regions; accordingly, in the Tethyan context, Jordan belongs to the North Africa — Middle East bioprovince.

Integrated platform/basin biostratigraphy of the Upper Cenomanian-Lower Turonian in Provence (SE France)

Recent studies on Upper Cenomanian-Lower Turonian outcrops from Cassis area allow to build a biolithostratigraphic framework from platform (La Bedoule section) to basin deposits (Cassis section), based on ammonites, planktonic foraminifera, inoceramids, rudists and ostracods. Four ammonite Zones are documented: the Late Cenomanian Geslinianum and Juddii Zones; the Early Turonian Nodosoides and, possibly, the Middle Turonian Woollgari Zones. The latest Cenomanian Scottii and the earliest Turonian Coloradoense Zones have not been identified. At Cassis, all the three planktonic foraminifera zones of the Upper Cenomanian and the Lower Turonian are identified: the Cushmani, Archaeocretacea and Helvetica zones. For the first time in the study area, a biozonation based on inoceramids is established while the ostracod biozonation is improved. The rudist scale is calibrated with the ammonite one through stratigraphic correlation between platform and basin successions. A detailed study of facies geometry leads to a sequence stratigraphic interpretation of systems tracts both of carbonate platform and basin settings. Finally, the Cassis section is compared with the Pueblo section and proposed as a reference section for the Cenomanian/Turonian boundary.

Patterns of variability in ostracode species and communities from the late Cretaceous carbonate platforms: a report for ecozonal modelling and the study of ambient conditions

Abstract Previous palaeoecological and sedimentological analyses have demonstrated the marked variability of ostracode faunas in late Cretaceous environments. Such organisms are generally strongly related to their biotopes but deeply affected by fluctuations, even slight, of ambient conditions. Therefore, variations of both taxonomic units and communities may be used for a better knowledge and characterization of the main carbonate platform domains. An interesting method of investigation is provided by the study of anatomical and/or morphological variations within well defined taxonomic units, especially ornate species living in the more internal zones of platforms. They reflect with accuracy and reliability the impact of both ecological parameters and palaeogeographic settings. This is also the case for some genera and even families. Ostracode type-assemblages have been recently erected in the Tethyan Upper Cretaceous. Microfaunas develop characteristic features such as richness, diversity, morphological trends, according to their position on the carbonate platform system and sedimentary facies patterns. Furthermore, without any consideration of the stratigraphical position of carbonate formations, certain morphological variations concerning analogous taxa may be used for palaeogeographical interpretations. Trophic structures of ostracode communities versus nutrient flux are identifiable. Major changes occur through the sequences in the abundance, specific composition and quantitative ratio between two main sedimentological formations: carbonates (especially rudist limestones and calcareous marls with benthic foraminifers) and proximal terrigenous (siliciclastic, argillaceous) areas. Finally, this paper may be also considered as a useful attempt to synthesize present knowledge of late Cretaceous carbonate platform ostracodes, particularly intended for non-ostracodologists who are perhaps unaware of the potential contribution of these organisms for palaeoenvironmental reconstructions.

Zonocypris digitalis (Ostracoda, Crustacea), nouvelle espèce du Fuvélien (Campanien continental) de Provence (sud-est France)

Resume Des depots continentaux d’âge fuvelien (Campanien) de la region d’Auriol (Provence, sud-est France) ont livre de nombreux exemplaires d’une nouvelle espece d’Ostracode : Zonocypris digitalis nov. sp. C’est la premiere espece decrite de ce genre dans le Cretace de l’Europe meridionale ; elle est associee a des Charophytes et surtout des restes de Gastropodes qui confirment la datation proposee et l’âge des depots analyses. L’echelle biostratigraphique bâtie a l’aide des Ostracodes continentaux reconnus dans l’ensemble du Cretace superieur continental de cette region s’enrichit ainsi d’un nouvel element chronologique.