Holocene cuspate forelands in the Strait of Magellan southern Chile

Abstract

The eastern inlet of the Strait of Magellan is characterised by the presence of two truncate cuspate forelands, typically high-energy accretionary morphologies. Both forelands, Punta Catalina on the Fuegian side and Punta Dungeness on the Patagonian side, show similar features and accretionary trends and could have been formed and developed at the same time during the late Holocene regressive phase. On the basis of air-photo interpretation, together with field survey, almost nine different accretionary phases of Punta Catalina spit can be recognised. Each phase is marked by an extensive beach-ridge system, and subsequent back-barrier mud-flat and marsh development. The coastal retreat and erosion processes along the Atlantic side are responsible for the shifting and morphological readjustment of the spit, which tends to prograde towards the opposite direction. The strong eolian modelling over ancient beach-ridge systems, is marked by deflation furrows, hollows and nikes and subsequent construction of elongate parabolic dunes. Despite the lack of datings, a reconstruction of the system evolution was attempted, allowed by the evidence of a strong similarity with the Dungeness foreland and considering the evolutionary framework of analogous accretionary coastal forms in South America during late Holocene.