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Daniela Crudeli, Elisabetta Erba:
High-resolution quantitative study of calcareous nannofossils of the Holocene eastern Mediterranean sedimentary record: response to paleoceanographic changes leading to sapropel S1 deposition
(Talk)

A high-resolution, quantitative analysis of calcareous nannofossil assemblages was applied to four box-cores from the eastern Mediterranean in order to evaluate their response to palaeoceanographic-palaeoclimatic changes related to Sapropel S1 deposition. Calcareous dinoflagellates cysts, Ascidiae and reworked coccoliths have been quantified as well as the non-biogenic fine-fraction, linked to eolian and river input. The presence of tiny and delicate species, both in oxic and anoxic sediments, indicate a general weak effect of dissolution with stronger diagenetic modifications in the deepest box-core. The abundance trends of Florisphaera profunda, Gladiolithus flabellatus and Algirosphaera robusta (characteristic of the lower photic zone) and of E. huxleyi 'low-calcified morphotype', E. huxleyi 'more-calcified morphotype', Reticulofenestra overcalcified s.l., Helicosphaera carteri sp.1 (sensu Castradori) and Rhabdosphaera spp. allow identification of four main intervals characterised by different assemblage composition. The abundance trend of Florisphaera profunda could suggest a decrease in phytoplankton productivity in the upper photic zone in the lower part of S1, related to an increase of terrigenous input, dissolved nutrients and water stratification. A better understanding of coccolithophore ecology will allow us to correctly interpret the coccolith sedimentary record of the eastern Mediterranean.

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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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