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RESEARCH PRODUCT

Size variations in the genus Gephyrocapsa during the Early Plaeistocene in the eastern Mediterranean

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The genus Gephyrocapsa, belonging to coccolithophores, hasoften been used in biostratigraphic and paleoceanographic studies ofthe late Cenozoic. This taxon exhibits a gradual increase in sizeduring the Early Pleistocene which has been ascribed to evolutiveand/or environmental processes and has been used for biostratigraphicpurposes.Here we show both biometric and relative abundance data ofspecimens of this genus between about 2.0 and 0.9 Ma, from sedimentsof the Ionian Sea (eastern Mediterranean). Measurements onthe long axis of placoliths highlight a gradual size increase betweenthe upper part of MNN 19a and the top of MNN 19d biozones. Onthe basis of the comparison with paleoenvironmental proxy dataacquired on the same site, we rule out the influence of climate andoceanographic phenomena due to glacial/interglacial oscillations,on Gephyrocapsa spp. size variations. However, we argue that theclimate/environmental forcing may have acted by longer-scalephenomena, for instance the growth of ice sheets and the subsequentsea surface cooling in the oceans. Finally, we suggest that theFirst Common Occurrence of Gephyrocapsa >4.5 mm and the FirstOccurrence of Gephyrocapsa >5.0 mm may approximate the LastOccurrence of Calcidiscus macintyrei in studies dealing with terrigenoussediments affected by severe reworking.