Stable isotope composition of Helix ligata (Müller, 1774) from Late Pleistocene-Holocene archaeological record from Grotta della Serratura (Southern Italy): Palaeoclimatic implications

Carbon and oxygen isotope ratios were measured in fossil and recent shells of the land snail Helix ligata. Fossil shells were recovered from the archaeological excavations of Grotta della Serratura and recent specimens collected adjacent to the cave. The record is discontinuous and spans from ca 14 to 7 ka cal BP. The oxygen isotope composition of the fossil shells suggests they were grown from environmental waters (e.g. precipitation) isotopically similar to the present during the recorded part of the Late Glacial. A notable exception is represented by a layer at ca 13.4 ka cal BP, with shells characterised by 18O-enriched values, suggesting drier conditions, with rainfall perhaps reduced by 25% compared to the present day. This layer could correspond in part with the GI-1b event of the Greenland ice-core records. The onset of the Holocene was marked by a decrease of delta18O, suggesting an increase in humidity. Significantly lower delta18O values occur at ca 7.4 ka cal BP, in agreement with other stable isotope records, which suggests enhanced rainfall over the Mediterranean region at that time.