Pleistocene Paleoceanographic Conditions in the Ioffe Drift Area (South Atlantic) Based on Benthic Foraminiferal Assemblages

Abstract

The Ioffe Drift located in the western South Atlantic to the north-east to the Vema Channel was discovered in the 32nd cruise of the R/V “Akademik Ioffe” in 2010. The analysis of the seismoacoustic, biostratigraphic, lithological, grain-size, geochemical and X-ray fluorescence data allowed to estimate the Pleistocene age of the upper part of the drift as well as to confirm contourite genesis of the sediments. Quantitative analyses of benthic foraminiferal assemblages are carried out in the sediment core AI-2436 (26°51.6′ S, 34°01.40′ W, 3800 m water depth) collected near the drift summit. The obtained results allowed reconstructing relative changes of the organic matter flux to the seafloor, its periodicity and bottom current intensity as well as suggesting interplay of the deep-water masses during the Pleistocene. Visual evaluation of benthic foraminiferal tests allowed distinguishing three groups of damages of presumably variable genesis. First group includes damages possibly resulted from impacts of particles transporting by bottom currents. Second group consists of damages that appeared due to movement of the tests by strong bottom currents. Third group contains deformations caused by dissolution in carbonate-aggressive bottom-water environment. Thus, specific features of the tests in combination with traditional methods may serve as a supporting technique for diagnostics of contourites. However, this method demands a development of application criteria and should be verified on reliable material.