Stratigraphic sequence of the paleodunes and paleosols of Ventanas II in the coast of central Chile (32°) and its paleoclimatic implication

Abstract

The coast of central Chile maintains an extensive eolian sedimentary record that has remained without much attention and has potential as a paleoenvironmental record. In the Quintero Bay (32 degrees S), Ventanas sector, extensive paleodune fields have been described with a stratigraphy that includes sand sequences intercalated with paleosols, but details on the morphogenesis and pedogenesis of these records and their paleoenvironmental evolution remain unknown. This paper aims to determine the paleogeographic and paleoenvironmental implications of the Ventanas II stratigraphic site. By applying field, laboratory, statistical, and depositional environment descriptions we recognize sedimentary facies and pedogenetic intensity. In Ventanas II site, 13 sedimentary units were identified, which we classified into four facies: paleodune, paleosol, paleowetland, and paleobeach. The lower units of the sequence correspond to a coastal wetland and beach and the upper units (Units 10 to Unit 1) to five paleosols intercalated with paleodunes, denoting a change in the paleogeography within the stratigraphic sequence. The Unit 13 towards the base of the section is a paleosol developed on reworked sediments from the Horcon Formation. The paleosols and the paleodunes suggest similar and recurrent humid and dry conditions, respectively, caused by the latitudinal oscillation of the southern westerly winds during the last glacial period in central Chile.