Middle-upper quaternary deposits of the northern sector of the Patagonian continental slope contourite system (Southwestern Atlantic)

Abstract

Lithological and micropaleontological (planktonic and benthic foraminifers, diatoms) studies in four sediment cores revealed major patterns of lithostratigraphy and biostratigraphy of contourites and gravitites in the uppermost sediment layer within the depth range 3500–4300 m of the northern sector of the Patagonian continental slope contourite system. It is ascertained that in conditions of low terrigenous material supply from the land and high, although variable bottom contour current velocities of waters of Antarctic origin, hemipelagic calcareous nanno-foraminiferal ooze deposited in the Holocene over middleupper Pleistocene contourites in the southern part of the study area (cores AI–2609, AI–2610). The Holocene calcareous surface layer is absent in the northern part of the study area (cores AI–2611, AI–2612). Middle-Upper contourites and gravitites are unevenly enriched in diatoms and radiolarians here, up to formation of slightly siliceous-terrigenous diatomaceous mud. Reworked Neogene foraminifers and diatoms evidence for erosion of Neogene deposits bottom currents and gravity flows.