CONICET | Buscador de Institutos y Recursos Humanos

The Argentine Continental Shelf (ACS) extends along a relatively stable continental margin at the intersection of the present Antarctic ice sheet and the relic of the former Patagonian ice sheet. This provides a preferential area to study the Quaternary sea-level fluctuations and to analyse the impact of ice extent variations on sedimentary processes on the shelf. In this context, we investigate Quaternary marine deposits from the Gulf of San Jorge (GSJ; central Patagonia) to characterize the last stage of the post-glacial transgression and related post-glacial sedimentation in the central part of the Argentine Patagonian margin. In 2014, during the MARGES (Marine Geology of the Gulf of San Jorge) expedition, ~2000 km of geophysical data (subbottom profiler and sparker) along with 15 sediment cores (gravity and piston cores) were collected in the GSJ and continental shelf. The post-glacial evolution of the sedimentary environments was reconstructed using CT imaging, geochemistry, mineralogy of the bulk and clay fraction, multi-sensor core logging and radiocarbon dating, coupled with the interpretation of seismic lines. We developed an age-depth model for 6 cores with the oldest sediments dated at 12.5 ka cal BP. Our data indicates higher-energy depositional environment at the bottom of the cores (~12.5-10.4 ka cal BP) and a gradual decrease of sedimentation rates toward the present. In addition, the base of two cores located in the Gulf is composed of a decimetric highly-indurated sediment layer seismically identified as a high amplitude and laterally continuous reflector extending through the entire GSJ, which most likely reflects both the sea-level lowstand and absence of water in this part of the GSJ during the LGM. Our results highlight a gradual flooding of the GSJ and central Patagonia?s ACS, which began ~12.5 ka cal BP and was completed by ~10.4 ka cal BP with a possible fitful sea-level rise during the last stage of the marine transgression.