| Summary: | 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 ...
|
|---|