Glacial-interglacial climate controls on sediment supply along the southern Argentine margin
Creators: name: Shamus, Timothy Gary
Publisher: name: No Publisher Supplied
Year: 2022

description: The TN372-1909 Research Cruise sailed along the southern Argentine margin September through October 2019. The Piedra Buena terrace is a constructional terrace between 2200 and 2800 m water depth. A south to north transect of cores was collected to study changes along this terrace. Multi-sensor core logger (MSCL) data profiles of magnetic susceptibility (MS) and density show similarities to other jumbo piston cores (JPCs) that were taken along the Piedra Buena terrace. Core 27 GC was collected from the mid-point of the transect and chosen for initial analysis. Five Lithostratigraphic Units were identified in Core 27 GC that consist of alternating layers of biogenic carbonate oozes and quartz-glauconite sands. Starting from the top, Lithostratigraphic Units I (0-25cm), III (45-165 cm), and V (255-360cm) are identified by high biogenic CaCO₃, low MS and density, and light color. The coarse fractions of these units have abundant planktonic foraminifera with minor abundances of radiolaria and diatoms. The terrigenous components of these units consists of quartz and glauconite sands. Lithostratigraphic Units II (25-45 cm) and IV (165-255cm) are characterized by terrigenous sediments and glauconite, high MS and density, and a dark color. Quartz and glauconite dominate the sediments deposited in Lithostratigraphic Units II and IV with minor contributions of radiolaria and diatoms. Planktonic foraminifera were absent in Units II and IV. Stable isotopes were performed on Neogloboquadrina pachyderma (s) showing low δ¹⁸O values for Units I and V, intermediate values for Unit III and high values going into II and IV where planktonic foraminifera became absent. Therefore, the first-order control on depositional facies is sea level changes driven by glacial-interglacial cycles. The presence of radiolarians and diatoms in Units II and IV indicate that surface water hydrography also influenced the composition of the sediments with biosiliceous fauna and flora replacing the calcareous counterparts during glacial intervals. The dominance of terrigenous material during the glacial Units II and IV with low to moderate contribution to Units I, III, and V indicates that sediments are trapped on the shelf during sea level highstands and delivered to the canyon system during sea level lowstands. Any age model will need verification from cores to the north. The MSCL profiles were correlated across the Piedra Buena terrace coring transect. The five established lithostratigraphic units can be correlated to all but one core on the terrace. Differences among core logger profile result from large sediment delivery on the terrace related to proximity to submarine canyon systems that transport and redeposit material. Based on correlation of the Lithostratigraphic units, the northernmost cores on Piedra Buena (58 JPC and 43 JPC) record the highest sedimentation rates because of their proximity to large canyon systems. The southernmost core (25 GC) is distinct and provides only tenuous correlation, which may indicate bottom currents are stronger and/or sediment supply was lowest.