Stable isotope composition of Late Pleistocene-Holocene Eobania vermiculata (Müller, 1774) (Pulmonata, Stylommatophora) shells from the Central Mediterranean basin: Data from Grotta d'Oriente (Favignana, Sicily)

This paper presents stable isotopic results (oxygen and carbon) from both modern and Late Pleistocene-Holocene shells of the land snail Eobania vermiculata (Muller, 1774) from Favignana Island (Sicily). It aims to contribute to the understanding of climate and vegetation history of this region during formation of Upper Palaeolithic, Mesolithic and Meso-Neolithic deposits of Grotta d'Oriente (ORT). Results from both an evaporative model (FBM) and an empirical regional isotopic model (i.e. linear relation between oxygen isotopic composition of shells (delta Os-18) and those of local precipitation (delta(18)Op)) indicate that the delta Os-18 values of modern specimens are mainly controlled by local temperature, relative humidity and delta(18)Op at the time of snail activity. Data also suggest that the modern snails are nocturnally active almost all-year round in the study area. The carbon isotopic compositions of shells (delta Cs-13) of the same specimens indicate a diet prevalently (or exclusively) composed of C3 vegetation. The delta Os-18 values of Late Pleistocene specimens suggest that climate conditions at similar to 14.2 ka cal BP were similar to the present day, in agreement with additional delta Os-18 records from southern Italy. By contrast, early-middle Holocene shells are notably O-18-depleted and suggest wetter conditions, possibly combined with a decrease in isotopic composition of precipitation source, compared to the present day. When compared with regional palaeoclimatic records a large-scale isotopic response to millennial-scale changes in atmospheric and hydrological conditions (e.g. enhanced rainfall) in the central-eastern Mediterranean is observed during the early-middle Holocene. The delta Cs-13 of Late Pleistocene and Holocene specimens are consistently higher than those of modern ones. For the Late Pleistocene, this could be reasonably explained in terms of water-stressed vegetation. On the other hand, this seems to be less valid for Holocene counterparts when the climate was wetter. Probably delta Cs-13 values result from the combination of distinct competing factors, involving atmospheric CO2 concentration, seasonal water budget, vegetation type-cover and other carbon sources. Results reveal coherent relationships between regional delta Os-18 and delta Cs-13, demonstrating that Late Pleistocene-Holocene land snail shell remains from archaeological sites may provide useful snapshots of past seasonal climate conditions. (C) 2011 Elsevier Ltd and INQUA. All rights reserved