A multi-proxy reconstruction of depositional environment of a Late Pleistocene submerged site from the Central Coast of Chile (32°): Implications for drowned sites

Abstract

Site GNL Quintero 1 (GNLQ1), located on the central Chilean coast (32°S), remains the only submerged fini-Pleistocene landscape reported for the southeastern Pacific coast to date. This unique site is characterized by a high frequency and diversity of extinct terrestrial faunal remains supported within a fine-grained sedimentary matrix. Several studies have been performed on the faunal assemblage; however, the sedimentary environment in which the site was formed still remains unclear. In this work, stratigraphic, sedimentological and geochemical analyses conducted on two marine cores are combined with seismic data to determine the depositional conditions affecting the formation of this exceptional shallowly buried submerged landscape. Previous results indicated that site GNLQ1 formed, at least between 28 and 21 ka, in an aquifer-fed freshwater lagoon that developed on a fluvial plain. Here, we show a three-stage sedimentological evolution. In the first stage, a shallow restricted freshwater lagoon formed under relatively arid conditions. Subsequently, the lagoon expanded and deepened under the humid climatic conditions that affected central Chile during the Last Glacial Maximum (LGM). Finally, around 8.5-8 ka, the most recent post-glacial marine transgression (PMT) submerged the site, probably eroding the Late Pleistocene – Early Holocene part of the sequence. Currently, the site lies at ca. 13 m b.s.l. within the shoreface of present-day Quintero Bay, 650 m from the current shoreline. This enhanced understanding of GNLQ1's evolution offers a new perspective on resource availability on the coastal shelf of western South America during the Late Pleistocene, as well as highlighting the unexpected paleontological potential of this area and encouraging future archaeological research of potential prehistoric evidence within these drowned landscapes.