Alluvial deposit stratigraphy from the Salto de Piedra Paleontological Locality (Argentine Pampas): evidence from last glacial- interglacial cycles

Abstract

The Salto de Piedra Paleontological Locality is located in the upper basin of the Tapalqué Creek (Buenos Aires Province, Argentine Pampas). Stratigraphic, sedimentological, and pedological studies were carried out in two exposed sections of the stream bank, corresponding to the late Quaternary (early/middle Pleistocene to Holocene). Six depositional units (allounits) were recognized, separated by discontinuities. These discontinuities correspond to both erosive discordances indicating fluvial reactivation and pedological horizons indicating stability intervals; among the latter, the development of a thick calcrete stands out. The facies and lithofacies identified in the depositional units correspond to sedimentation sub- environments having different attributes with respect to the preservation of the fossil record. This consists mainly of bone remains of mammals and snails of freshwater gastropods. The main vertebrate fossil- bearing units in Salto de Piedra correspond to channel facies and secondly to swampy floodplain facies, in accordance with taphonomic expectations. The stratigraphy shows changes in fluvial dynamics during the last glacial- integlacial cycles in the upper basin of the Tapalqué Creek and constitutes a good frame of reference for the paleontological, chronological and paleoenvironmental studies that are being carried out in this locality.