Abstract

Aeolianites (chemically cemented wind-blown dune deposits) are relatively rare in tectonically active and rapidly uplifting coastal environments such as the Pacific rim in northern Chile, but where preserved can provide invaluable insights into past changes in wind regime, moisture availability and marine-onshore sediment fluxes. This paper presents the preliminary results of an investigation at Llano Agua de los Burros (27°54‟22” S, 71°04‟56” W) to the southwest of Copiapó, Atacama region, where carbonate-cemented aeolianite deposits outcrop over an area of approximately 2.6 km2 . The deposits appear to have developed as a result of the deflation of marine sediments by onshore winds, with subsequent accumulation at an elevation of between +230 and +280 m asl against the coastal Sierra del Carrizo range. Reconnaissance mapping suggests that the most likely sediment source for the aeolianites was a raised shoreline at an elevation of approximately +175 to +185 m asl. Stratigraphic logging of the main aeolianite outcrop was undertaken in order to ascertain variations in past wind direction and identify major units of accumulation. At least eight distinct phases of sediment accumulation (or redistribution) were identified, with each accumulation unit subsequently sampled for stable C and O isotopic analysis, thinsection analysis and optically-stimulated luminescence (OSL) dating. The main results of the OSL dating programme are presented here and discussed in relation to published climatic and sea level change records.