Dynamique du nannoplancton calcaire au cours du Néogène : implications climatiques et océanographiques

Abstract : Variations in the composition of calcareous nannofossil assemblages of several Neogene series (from the North Atlantic and the Antarctic Ocean, Indian sector) were studied. Particular interest has been given to the quantification of data and high stratigraphic resolution. The analysis of the recordings obtained (due in particular to the mathematical treatment of the signals) made it possible to show the great sensitivity of the calcareous nannoplankton to the climatic variations: - the renewal of nannoplankton takes place during the last deglaciation (in the North Atlantic) by closely following the climatic changes. - all Miocene series studied contain periodic signals of frequencies identical to those of Milankovitch. It has been possible to study the modulation of eccentricity cycles and to see at what times they are particularly powerful. - many changes in nannoplankton composition observed in these Miocene series are directly correlated with paleoceanographic or palaeoclimatic events as evidenced by stable isotope studies of oxygen or calcium carbonate content in sediments. - the longest record (from 25 to 8.5 Ma) allows to trace the movements of the Antarctic polar front in the Miocene in a very detailed way (a sample every 18 000 years). Five major Miocene cooling phases could be identified.
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Luc Beaufort. Dynamique du nannoplancton calcaire au cours du Néogène : implications climatiques et océanographiques. Sciences de la Terre. Université Claude Bernard - Lyon 1, 1991. Français. ⟨tel-02307706⟩

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