Near subsurface investigations of South Atlantic paleo beach processes at Bahía Laura, Patagonia, Argentina

Understanding coastal processes at work under past climates remains key to anticipating future scenarios. The Atlantic Coast of South America preserves records of Plio-Pleistocene and Holocene sea level in elevated marine deposits–especially along the coast of Patagonia in Argentina, where recent efforts have focused on compiling and refining Holocene sea level estimates. Here, we examine the internal structure of Holocene gravel beach deposits within an embayment at Bahía Laura, Argentina, to explore the dynamics at play over the past ~6 ka. Interpretation of over two kilometers of topographically-corrected Ground Penetrating Radar (GPR) profiles tells the story of generally consistent regression and progradation associated with falling or stable relative sea level (RSL) since a mid-Holocene highstand. Further, consistent supply of gravelly sediments likely stems from a combination of an eroded Pleistocene terrace perched immediately above the Holocene sequence, reworked near shelf sediments, and fluvial contribution from the south. Erosional surfaces and berm ridges visible within the profiles document high energy storm events and a shift in slope and spacing between radar reflectors along profiles may chronicle changing wave direction, accommodation space, sediment supply, and/or rate of sea level change.