High-resolution biometry and morphometric characterization of calcareous nannofossils during the Oceanic Anoxic Events 1a and 1d in a global context

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Based on their global distribution and their sensitivity to ecologicalchanges, calcareous nannofossils are ideal proxies for reconstructing past climatic conditions. Up to now, calcareous nannofossil assemblageshave been studied particularly to understand ecological parameters. Biometric studies of individual species in recent years have shown, that size variations of coccoliths can be associated with ecological changes. The understanding of the driving forces of size variation is, however, poor. We therefore plan to do a highresolution study on the size variation of the most-common coccolith species of the mid-Cretaceous with respect to the global and radical impact of the Oceanic Anoxic Events 1a and 1d (OAE 1a, 1d). In both cases, material from different latitudes and well defined settings will be used. The lower Aptian OAE 1a of the Boreal Realm will be represented by four localities (North Sea: North Jens-1 and Adda-2; Lower Saxony Basin: Alstätte 1 and Hoheneggelsen KB09). A comparison of the data obtained with the existing results from the Tethys will lead to a better and broader understanding of the climatic changes and the reasons for the coccoliths size variation. Material of the OAE 1d will be investigated from three localities spanning major parts of the globe: Germany (Kirchrode I / Anderten I), the Atlantic (ODP Site 1052E) and the Indian Ocean (ODP Site 763B). The study aims at a) understanding the reasons for size variations of coccoliths from different sites and settings, b) testing whether these size variations are globally synchronous and c) establishing size variation as an ecological proxy for OAEs.