- Renaudie, Johan
- Danelian, Taniel
- Saint Martin, Simona
- Le Callonnec, Laurence
- Tribovillard, Nicolas
The Middle Eocene diatom and silicoflagellate record of ODP Site 1260A (Demerara Rise) is studied quantitatively in order to throw light on the changes that siliceous phytoplankton communities experienced during a Middle Eocene warming event that occurred between 44.0 and 42.0 Ma. Both Pianka's overlap index, calculated per couple of successive samples, and cluster analysis, point to a number of significant turnover events highlighted by changes in the structure of floristic communities. The pre-warming flora, dominated by cosmopolitan species of the diatom genus Triceratium, is replaced during the warming interval by a new and more diverse assemblage, dominated by Paralia sulcata (an indicator of high productivity) and two endemic tropical species of the genus Hemiaulus. The critical warming interval is characterized by a steady increase in biogenic silica and a comparable increase in excess Ba, both reflecting an increase in productivity. In general, it appears that high productivity not only increased the flux of biogenic silica, but also sustained a higher diversity in the siliceous phytoplankton communities. The microflora preserved above the critical interval is once again of low diversity and dominated by various species of the diatom genus Hemiaulus. All assemblages in the studied material are characterized by the total absence of continental and benthic diatoms and the relative abundance of neritic forms, suggesting a transitional depositional environment between the neritic and the oceanic realms. (C) 2009 Elsevier B.V. All rights reserved.
- Middle Eocene
- Climate change
- Biogenic silica
- Tropical Atlantic
[Danelian, Taniel; Tribovillard, Nicolas] Univ Lille 1, CNRS, UMR Geosyst 8157, F-59655 Villeneuve Dascq, France; [Renaudie, Johan; Danelian, Taniel] Univ Paris 06, CNRS, UMR Paleobiodivers & Paleoenvironm 5143, F-75005 Paris, France; [Saint Martin, Simona] Univ Din Bucuresti, Fac Geol Geofiz, Bucharest, Romania; [Saint Martin, Simona] Museum Natl Hist Nat, Dept Hist Terre, F-75005 Paris, France; [Le Callonnec, Laurence] Univ Paris 06, ISTeP, UMR 7193, Lab Biomineralisat & Environm Sedimentaires, F-75005 Paris, France
Danelian, T (reprint author), Univ Lille 1, CNRS, UMR Geosyst 8157, Batiment SN5, F-59655 Villeneuve Dascq, France.
- Centre de recherche sur la paléobiodiversité et les paléoenvironnements (CR2P), UMR7207
- Géosystèmes, FRE3298
- Institut des Sciences de la Terre Paris (iSTeP), UMR7193