Early-Middle Holocene land snail shell stable isotope record from Grotta di Latronico 3 (Southern Italy)

This paper compares stable isotope (delta O-18 and delta C-13) records of early-middle Holocene land snail shells from the archaeological deposits of Grotta di Latronico 3 (LTR3; southern Italy) with modern shell isotopic data. No substantial interspecific variability was observed in shell delta O-18 (delta Os-18) of modem specimens (Pomatias elegans, Cornu aspersum, Eobania vermiculata, Helix ligata and Marmorana fuscolabiata). In contrast, interspecific shell delta C-13 (delta Cs-13) variability was significant, probably due to different feeding behaviour among species. The delta Os-18 values of living land snails suggest that species hibernate for a long period during colder months, so that the signal of O-18-depleted winter rainfall in their delta Os-18 is lost. This suggests that delta Os-18 and delta Cs-13 values of Pomatias elegans from this archaeological succession provide valuable clues for seasonal (spring-autumn) climatic conditions during the early-middle Holocene. The delta Os-18 values of fossil specimens are significantly lower than in modern shells and in agreement with other palaeoclimatic records, suggesting a substantial increase of precipitation and/or persistent changes in air mass source trajectories over this region between ca. 8.8 cal ka BP and 6.2-6.7 ka ago. The delta Cs-13 trend suggests a transition from a slightly C-13-enriched to a C-13-depleted diet between early and middle Holocene compared to present conditions. We postulate that this delta Cs-13 trend might reflect changes in the C3 vegetation community, potentially combined with other environmental factors such as regional moisture increase and the progressive decrease of atmospheric CO2 concentration. Copyright (C) 2010 John Wiley & Sons, Ltd.