Holocene paleoenvironmental (~4.5-1.7 cal. kyr BP) conditions in central Argentina inferred from entire-shell and intra-shell stable isotope composition of land snails

YANEZ, Y.; IZETA, A.; CATTANEO, R.; COSTA, T.; ADAMI, M. Y GORDILLO, S.

Mendoza

Conferencia; 12th International Conference of Archaeozoology; 2014

International Council for Archaeological Studies

The isotopic composition of land snails is increasingly used as a paleoenvironmental proxy. The majority of published studies, however, has used this approach on mid-to-low latitude localities of the Northern Hemisphere, and principally provides data derived from entire-shell analyses. This study presents entire-shell and intra-shell isotopic data to deduce average and seasonal late Holocene environmental conditions in central Argentina (30°S). The species Plagiodontes daedaleus (Odontostomidae) was recovered from the Alero Deodoro Roca site, one of the few archeological sites in central Argentina that contains shelly accumulations associated with hunter-gatherer societies. Modern entire-shells exhibited an average δ13C and δ18O value of -11.9 ± 0.9? and -1.2 ± 0.6?, respectively. Fossil entire shells showed values that were ~2.5? higher in δ13C and ~1.8? higher in δ18O than modern specimens. This suggests that during 4.5-1.7 cal. kyr BP conditions were drier (lower relative humidity and/or higher rain δ18O) and C4 plants were more abundant than at present. These findings agree with published independent proxy data from the region. Intra-shell isotopic profiles suggest that modern and fossil individuals grew their shells throughout two-to-three summer/winter cycles. Intra-shell δ18O values varied ~5?, which matched with the range of rain δ18O values between seasons. The magnitude of seasonality was comparable during 4.5-1.7 cal. kyr BP and the present. The intra-shell δ13C values varied ~2-3? and did not show distinctive seasonal cycles, pointing to reduced seasonal variations in snail dietary habits. This study shows that snail shells from central Argentina, in southern America have great potential for paleoenvironmental inferences.