This paper presents the taphonomic and geoarchaeological study of a thin shell lens identified 3.2 km from the coast of San Sebastian Bay on the hilltop of the inland Cerro Bandurrias archaeological locality (Tierra del Fuego Province, Argentina). The biological assemblage of the shell lens comprises marine fauna (bivalves, gastropods, and fish) that may represent the remains of the occasional exploitation of littoral resources by hunter gatherers. However, since the lack of unequivocal anthropogenic signals, alternative non-anthropogenic hypotheses need to be also assessed. Indeed, the time frame of the shell lens (radiocarbon dated as ~6500 cal. years BP) indicates that the bioclast accumulation occurred during the Middle Holocene marine transgression with a different paleogeography, when the hill was part of a coastal landform (peninsula). The methodological design comprised the combination of different and independent sources of information and the techniques applied to assess competing genetic hypotheses. Based on compositional, taphonomic and sedimentological analyses, our research suggests that the most parsimonious explanation is that hunter gatherers were the primary agents of bioclast accumulation of the lens. Thus, this ephemeral archaeological evidence provides a new record for the human exploitation of littoral resources on the Atlantic coast of Isla Grande de Tierra del Fuego during the Middle Holocene. The conspicuous character of shells improves the archaeological visibility of short term, nonredundant past human occupations
