Lithological and biogeochemical investigations of the North Atlantic sediment system (data from the 49th cruise of the R/V Akademik Ioffe)

Marine sediments and samples of suspended particulate matter from the North Atlantic were studied. It is shown that modern sedimentation in this area is controlled mainly by the efficiency of autochthonous marine phytoplankton and sediment supply by the system of near-bottom currents, as well as by means of the ice-rafting. The studied sediment sections were formed in the North Atlantic during the Middle Pleistocene to Holocene. The highest sedimentation rate, up to 58.3 cm/kyr, is established for AI-3359 core, collected in the area of the Gardar and Björn Drifts. This makes the core very interesting for detailed paleoreconstructions. AI-3378 and AI-3415 cores are characterized by low sedimentation rates. Nevertheless, they are of interest for spatial paleoreconstructions on a continuous timeline. The general pattern is established for the first time for the sediments from the central North Atlantic: biogeochemically significant processes are detected only in the thin surface layer (0–2 cm) and almost completely cease at depths of 90–180 cm. The processes are probably controlled by the position of the sampling stations and the composition of organic matter (OM) but not related to the age of the sedimentary layer. The low microbial activity in the sediments is most likely the result of a lack of OM.

Chemostratigraphy of the Snorry drift in the Northern Atlantic

On the basis of multi-element chemical analysis and oxygen isotopic data, for the first time the distribution of some geochemical indicators was investigated in the sediment core taken at the Western slope of the Snorry contourite drift (St. AI-3378, North Atlantic) in the 49th cruise of RV "Akademik Ioffe" in 2015. Down the core an asynchronous change in the terrigenous (IRD, Al, Si, Ti, Zr, Cr) and biogenic indicators (CaCO3, Corg) was recorded. Based on multi-element geochemical data, the rhythmic distribution along the core of terrigenous and biogenic sedimentary material has been revealed. Sedimentary matter entered the study area as a result of ice and iceberg unloading, as well as brought by near-bottom currents. The intensity and direction of the near-bottom contour currents seemed to change dramatically with the change of warming and cooling periods during the six marine isotope stages MIS 1–6 (the last 190 ka).