Chronological and geoarchaeological investigations on an anthropogenic shell accumulation layer in the Longotoma dune field (Central Chile)

Along the Chilean–Peruvian coast, numerous archaeological sites associated with shell accumulations provide evidence for the role of coastal environments as a natural corridor for the human occupation of South America. In particular, the semi-arid coastline of northern Central Chile (∼33–27° S) is a key area for investigating the relationship between human occupation history and past climate changes, as palaeoenvironmental studies record important climatic fluctuations in the area throughout the Holocene. In this study, we present a consistent chronology of an anthropogenic shell accumulation layer and an associated palaeosol, found in the stratigraphy of palaeodunes in the Longotoma dune system, northern Central Chile (32°24′ S, 71°23′ W). Infrared Stimulated Luminescence (IRSL) dating of feldspars is used, for the first time in this context, to establish the chronological framework together with radiocarbon dating. The consistency between IRSL- and radiocarbon ages demonstrates the potential of IRSL techniques for studies in comparable settings and at similar time scales, where Optically Stimulated Luminescence (OSL) dating of quartz is problematic. The chronostratigraphical results (i) allow to infer different phases of dune activity as well as an intermittent period of interdunal soil formation at the end of the 6th millennium BP, when the cultural layer and the palaeosol formed; (ii) allocate an age range of ∼4500–3500 a to alluvial deposits below the modern dune corridor; and thereby (iii) give further evidence for the presence of Archaic coastal hunter-gatherer populations in the La Ligua Bay and in northern Central Chile.