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

The Ioffe Drift, located in the western South Atlantic to the north-east to the Vema Channel, was discovered on cruise 32 of the R/V Akademik Ioffe in 2010. Analysis of the seismoacoustic, biostratigraphic, lithological, grain-size, geochemical, and X-ray fluorescence data made it possible to estimate the Pleistocene age of the upper part of the drift, as well as to confirm the contourite genesis of the sediments. Quantitative analyses of benthic foraminiferal assemblages were carried out in sediment core AI-2436 (26 degrees 51.6 ' S, 34 degrees 01.40 ' W, 3800 m water depth) collected near the drift summit. The results made it possible to reconstruct relative changes in the organic matter flux to the seafloor, its periodicity, and bottom current intensity, as well as to suggest the interplay of deep-water masses during the Pleistocene. Visual evaluation of benthic foraminiferal tests identified three groups of damage of presumably variable genesis. The first group includes damage possibly resulting from impacts of particles transported by bottom currents. The second group consists of damage that occurred due to movement of tests by strong bottom currents. The third group contains deformations caused by dissolution in the carbonate-corrosive bottom-water environment. Thus, the specific features of tests in combination with commonly used methods may potentially serve as a supporting technique for contourite diagnostics. However, this method demands a development of application criteria and should be verified on reliable material.