Paleoceanographic implications of a 17-mylong record of high-latitude Miocene calcareous nannoplankton fluctuations

Luc L Beaufort (1) , Marie-Pierre Aubry

1 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement

A record based on counts of the relative abundance of the dominant calcareous nannofossil taxa Coccolithus pelagicus and Reticulofenestra spp. in sediments recovered from Ocean Drilling Program Hole 747A (Kerguelen Plateau, Southern Indian Ocean) is established in this paper. This record (17 m.y. long) virtually spans the entire Miocene. Broad, steplike variations in the abundance of C. pelagicus range between 0% and 96%. Based on these variations, five stratigraphic units characterized by high abundance in C. pelagicus are delineated. We suggest that these variations are caused by water-mass movements (such as the north/south shifting of a front). This pronounced signal is compared with paleoceanographic events revealed by isotopic (δ18θ and δ13C) studies. The five defined units are tentatively correlated to well-known global isotopic events. In particular, Units A and D correlate respectively with the Oligocene/Miocene boundary glaciation and the middle Miocene cooling event. Time-series analysis indicates the presence of the three main periodic components of the eccentricity of the Earth's orbit. A 200-k.y. cycle is also present. The stratigraphic and paleoceanographic significance of this record is discussed.

Domaines: Paléontologie

Luc L Beaufort, Marie-Pierre Aubry. Paleoceanographic implications of a 17-mylong record of high-latitude Miocene calcareous nannoplankton fluctuations. Proceedings of the Ocean Drilling Program, Scientific Results, 130, pp.539--549, 1992. ⟨hal-01461274⟩