LAUSR

Abstract The internal architecture and processes involved in the development of paraglacial sandy-gravel beach ridges and barrier spits have been analyzed by interpretation of ground-penetrating radar (GPR) records, satellite images and detailed topographical sections on Holocene deposits in Rio Chico area, Tierra del Fuego, Argentina. These littoral deposits correspond to the infill of an extensive and shallow embayment facing the South Atlantic, and developed during the mid-Holocene. Radar facies were identified and characterized from both beach ridge plain and barrier spits. The radar facies in the beach ridge plain are interpreted as mainly progradational and regressive, associated with stages of high availability of sediment supply. On the contrary, barrier spits show a retrogradational pattern and occurred in transgressive conditions by rollover processes during periods of marked scarcity of sediment supply. Evolutionary models of the internal architecture of both beach ridge plain and barrier spits are developed for the southern hemisphere during stable sea level conditions.