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

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 lambda O-18 values between 0 parts per thousand and -5 parts per thousand. There are significant differences in mean fossil shell lambda O-18 between sites but not among genera at a single location. Therefore, we group lambda O-18 values from different genera together to map the spatial distribution of lambda O-18 in shell carbonate. Shell lambda O-18 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 lambda O-18 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 lambda O-18 data show a different gradient with lambda O-18 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 lambda O-18 values decreasing northward. (C) 2010 University of Washington. Published by Elsevier Inc. All rights reserved.