Paleoclimatic implications of the spatial patterns of modern and LGM European land-snail shell δ18O

Abstract

The oxygen isotopic composition of land-snail shells may provide insight into the source region and trajectory of precipitation. Last glacial maximum (LGM) gastropod shells were sampled from loess from Belgium to Serbia and modern land-snail shells both record δ ¹⁸O values between 0‰ and − 5‰. There are significant differences in mean fossil shell δ ¹⁸O between sites but not among genera at a single location. Therefore, we group δ ¹⁸O values from different genera together to map the spatial distribution of δ ¹⁸O in shell carbonate. Shell δ ¹⁸O values reflect the spatial variation in the isotopic composition of precipitation and incorporate the snails' preferential sampling of precipitation during the warm season. Modern shell δ ¹⁸O decreases in Europe along a N–S gradient from the North Sea inland toward the Alps. Modern observed data of isotopes in precipitation (GNIP) demonstrate a similar trend for low-altitude sites. LGM shell δ ¹⁸O data show a different gradient with δ ¹⁸O declining toward the ENE, implying a mid-Atlantic source due to increased sea ice and a possible southern displacement of the westerly jet stream. Balkan LGM samples show the influence of a Mediterranean source, with δ ¹⁸O values decreasing northward.