Late Pleistocene and Holocene transgression inferred from the sediments of the Gulf of San Jorge, central Patagonia, Argentina

This study presents the first detailed description of the upper sedimentary succession of the late Pleistocene and Holocene deposits in the Gulf of San Jorge (Patagonia) based on several hundred kilometers of high-resolution seismic (sparker) profiles and numerous sediment cores. High-resolution seismic stratigraphy confirms the existence of a paleo-fluvial network formed during sea-level lowstands and buried by central basin estuarine deposits during the last marine transgression. Analyses of lithostratigraphy and radiocarbon ages indicate the onset of subtidal sedimentation at ~14 cal ka bp. Before the onset of subtidal conditions, the first steps of marine incursion seem to have led to the development of lagoonal/wind–tidal flat environments, advocating for a sea-level stillstand. An abrupt increase in the log(Ti/Ca) ratio in a distinct multi-centimeter-thick layer and the identification of a wave-ravinement surface suggest rapid sea-level rise in the gulf prior to ~14 cal ka bp, consistent with Meltwater Pulse 1A. Overall, this study highlights the significant impact of sea-level rise on sedimentation in the gulf from the onset of marine incursions to the mid-Holocene, as well as the reduced contribution, as currently observed, of riverine inputs due to the progressive diminution and withdrawal of glacial drainage starting before the Holocene. -- Keywords : elemental geochemistry ; incised valleys ; MWP-1A ; Patagonia ; postglacial sea-level changes.