Deciphering late Quaternary land snail shell D18O and D13C from Franchthi Cave (Argolid, Greece).

This paper investigates the stable isotopic composition from late Pleistocene-Holocene (~ 13 to ~ 10.5 cal ka BP) shells of the land snail Helix figulina, from Franchthi Cave (Greece). It explores the palaeoclimatic and palaeoenvironmental implications of the isotope palaeoecology of archaeological shells at the time of human occupation of the cave. Modern shells from around the cave were also analysed and their isotopic signatures compared with those of the archaeological shells. The carbon isotope composition of modern shells depicts the consumption of C3 vegetation. Shell oxygen isotopic values are consistent with other Mediterranean snail shells from coastal areas. Combining empirical linear regression and an evaporative model, the D18Os suggest that modern snails in the study area are active during periods of higher relative humidity and lower rainfall D18O, probably at night. Late glacial and early Holocene ?18Os show lower values compared to modern ones. Early Holocene D18Os values likely track enhanced moisture and isotopic changes in the precipitation source. By contrast, lower late glacial D18O could reflect lower temperatures and D18Op, compared to the present day. Shell carbon isotope values indicate the presence of C3 vegetation as main source of carbon to late glacial and early Holocene snails.