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

The genus Gephyrocapsa, belonging to coccolithophores, has often been used in biostratigraphic and paleoceanographic studies of the late Cenozoic. This taxon exhibits a gradual increase in size during the Early Pleistocene which has been ascribed to evolutive and/or environmental processes and has been used for biostrati- graphic purposes. Here we show both biometric and relative abundance data of specimens of this genus between about 2.0 and 0.9 Ma, from sedi- ments of the Ionian Sea (eastern Mediterranean). Measurements on the long axis of placoliths highlight a gradual size increase between the upper part of MNN 19a and the top of MNN 19d biozones. On the basis of the comparison with paleoenvironmental proxy data acquired on the same site, we rule out the influence of climate and oceanographic phenomena due to glacial/interglacial oscillations, on Gephyrocapsa spp. size variations. However, we argue that the climate/environmental forcing may have acted by longer-scale phenomena, for instance the growth of ice sheets and the subse- quent sea surface cooling in the oceans. Finally, we suggest that the First Common Occurrence of Gephyrocapsa >4.5 mm and the First Occurrence of Gephyrocapsa >5.0 mm may approximate the Last Occurrence of Calcidiscus macintyrei in studies dealing with terrige- nous sediments affected by severe reworking.