DEEP-SEA CONTOURITES IN THE WESTERN SOUTH ATLANTIC AS PALEOCEANOGRAPHIC AND PALEOCLIMATIC ARCHIVES
E.V. Ivanova, D.G. Borisov, I.O. E.V. Ivanova, D.G. Borisov, I.O. Murdmaa, E.A. Ovsepyan
Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
Keywords: contourite systems, hiatuses, bottom currents, Pliocene, Pleistocene, erosion, accumulation, drifts, sortable silt, Antarctic bottom water
Abstract
The paper reviews the results of comprehensive studies and dating of contourite deposits from the Southwest Atlantic. It focuses on sediment transport and depositional processes as well as sediment sources in the context of Pliocene-Quaternary environmental and climatic changes. The work primarily highlights investigations conducted over the past decade by the Laboratory of Paleoceanology of the Shirshov Institute of Oceanology RAS in collaboration with other research groups over the last decade. The study examines contourite systems along the Argentine Patagonian continental slope, on the Santa Catarina and São Paulo plateaus, the Ioffe contourite Drift and the gravitite-contourite system, at the foot of the São Tomé Seamount . These systems were identified using a comprehensive approach combining seismo-acoustic, lithological, geochemical, and magnetic susceptibility data. Specific features of contourites that distinguish them from other types of deep-sea sediments are considered. The sediment age was defined by biostratigraphy and/or oxygen isotope stratigraphy and confirmed by AMS-14C dates (within the last 50 ka). The depositional system formation was predominantly controlled by erosion-depositional activity of bottom along-slope currents of the Antarctic origin. These Antarctic waters are a key component of Atlantic meridional circulation and the global conveyor system. Consequently, the contourite systems formed under the influence of these waters preserve a geological archive of the region's climatic and oceanographic history. The Ioffe Drift contains the longest sedimentary record in the study area, spanning the last 3.2 Ma. This time interval captures the development of modern-type paleoceanographic variability following the closure of the Panama Gateway. Other studied systems preserve sedimentary sequences documenting glacial-interglacial stages and associated changes in sea level, climate, and bottom current circulation during the Late Quaternary.
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