Influence of Quaternary sea level changes in the littoral of Chubut, Argentina

Abstract

Geomorphologic and stratigraphic studies accomplished in the littoral area between Cabo Raso and Punta Fabián, eastern Chubut Province, allowed the identification of different features and geomorphologic processes related to the modern dinamic, as well as a set of coastal units related to the different transgressive events occurred from the middle Pleistocene to the Holocene. The distribution and development of the littoral deposits displays a completely different situation from that of the area of Bahía Camarones, Bahía Bustamante, Cabo Raso and Bahía Vera (south and north of the study area), favored by a very hard substrate (Marifil Complex) at higher topographic positions. Abrasion platforms, cliffs, islands, capes and tómbolos form a broken coast in which the most relevant accumulation morphologies are gravel beaches. This situation prevailed as well in each of the high sea level event, forming beach crests in some places that corresponded to bays, wider than the modern ones. According to the altitud of these geoforms, respect to similar ones located to the south which have a significant number of numerical ages, the highest sea levels correspond to 500 k B.P., quite probably the Marine Isotopic Stage 11. This analysis includes a mean elevation of the continent of 0.12 ± 0.04 mm/yr. Although eight beach crests were clearly identified, not necessarily each of them responds to independent transgressive events. In fact, some of them may represent different positions of the same transgression during the regressive phase.