Stable carbon isotope composition of land snail shells in Westerlies Asia and monsoonal Asia: paleoclimate implications

Paleoclimatic records of sub-annual to interannual resolution are valuable for the study of climatic forcing mechanisms but these records are rare in terrestrial settings. Here, we show that high-resolution stable carbon isotope data within shells of land snails (delta 13Cshell) living in a C3 plant-dominated community can be an indicator of growing season precipitation (GSP) amount. We collected modern land snails along two wet-dry climate gradients from northern Iran and the Chinese Loess Plateau (CLP), where the precipitation is mainly distributed in the boreal winter and boreal summer seasons, respectively. Our results indicate a common pattern of delta 13Cshell values increasing with aridity, driven by water stress in the local plant community. In contrast, temperature has a weak and inverse effect on delta 13Cshell values in these two regions, suggesting that rainfall amount is the primary control on delta 13Cshell for this modern comparison. Furthermore, we present a delta 13Cshell record covering the middle Holocene to the middle Pleistocene from the CLP. This record suggests that most of the average delta 13Cshell values from interglacial paleosol layers are lower than those from the adjacent glacial loess strata, suggesting higher GSP. However, the reconstructed glacial-interglacial difference in GSP is smaller than that estimated by other proxy indicators. This is likely due to the dietary preference of land snails and/or the sparse nature of this dataset, which might not be sufficient to capture the glacial-interglacial history of rainfall on the CLP. Large datasets with good taxonomic control and high stratigraphic resolution will be required to better describe the glacial-interglacial differences.