Beach ridge sequence evolution of Punta Verde, northern coast of the San Matías Gulf, Argentina

Abstract

The Villarino Peninsula, located in the San Matías Gulf, northern region of Argentine Patagonia, San Antonio Este, is characterized by Pleistocene and recent Holocene sedimentary deposits that provide a substrate for the accumulation of bioclastic sediments. The study of prograding paleo-beach ridges and the recent beach ridge at Punta Verde Beach, situated on the southern side of Villarino Peninsula, aimed to propose an evolutionary depositional model for the ridge sequence and to estimate the rate of progradation and relative sea level fall (RSL). The interpretation of the ridge sequence was conducted with field surveys using Ground Penetrating Radar(GPR) and GPS-RTK systems. Satellite imagery of natural resources and field data were employed in processing the radargrams and generating a Digital Elevation Model (DEM), leading to the identification of 33 beach ridges over a length of 681 m. Radiocarbon dating of shell samples from the crest of the beach ridge sequence yielded ages ranging from 5455 ± 28 cal Years BP to 2183 ± 123 cal Years BP, corresponding to the Middle to Recent Holocene, and the present day for the recent beach ridge. The average progradation speed of the system was estimated at 70 mm/year, and the average rate of relative sea level fall was estimated at 2 mm/year. Understandingcoastal processes, geometric parameters, and the shape of the beach ridges allowed for their characterization as prograding Holocene depositional systems, associated with fluctuations in relative sea level driven by glacio-eustatic events, components of astronomical tides, wave action, particularly storm waves, as well as antecedent topography and the positive or neutral sediment input balance.