Oxygen isotopic composition of limpet shells from the Beagle Channel: implications for seasonal studies in shell middens of Tierra del Fuego

Shell middens distributed along the coastal areas of the Beagle Channel (Tierra del Fuego) testify the primary role of marine resources in the successful social dynamic of hunter gatherer fisher societies (HGF) in extreme high latitude environmental conditions. Intertidal and subtidal limpet species are frequently identified taxa of these archaeological deposits. We investigated whether shell delta O-18 of the limpet species Nacella deaurata is a valuable record of local sea surface temperature (SST) and ambient water delta O-18 (delta(18)Ow) fluctuations, and in turn can be tied to estimate the season of its exploitation by Holocene HGF. Sequential shell delta O-18 of modern species track seasonal changes of SST and delta(18)Ow. The comparison of shell delta O-18 profiles of N. deaurata and Nacella magellanica (a coexisting species) suggests the occurrence of distinct growth rate and physiological adaptations between species. Shell delta O-18 of zooarchaeological specimens of N. deaurata from Lanashuaia II suggests that animals were exploited predominantly in winter and that experienced similar environmental conditions of present day at similar to 1320 years BP. Results also indicate that N. deaurata is a valuable candidate for studying past seasonal changes in SST and delta(18)Ow in this southernmost part of South America. (C) 2012 Elsevier Ltd. All rights reserved.