Mid-Holocene palaeohydrochemistry and palaeohydrology of Yamdrok Yumtso, southern Tibetan Plateau, reconstructed from δ18O and δ13C of fossil shells of the gastropod Radix auricularia

Palaeohydrochemical and palaeohydrological changes of lakes have seldom been reconstructed from the fossil shells of the gasropodRadix auricularia, which is a new, and potentially high-resolution environnmental archive. We conducted a geochemical and stable isotope study of the shells ofRadixfrom the exposed fluvio-lacustrine sediments near Lake Yamdrok Yumtso in the southern Tibetan Plateau. Our aims were to determine the sedimentary environment, palaeo-lake hydrochemistry and hydrological status. AMS(14)C and OSL dating indicates that a lake-level stage of Yamdrok Yumtso higher than that of today occurred during similar to 4.7-1.2 cal. kyr BP. Results of Sr/Ca, delta C-13 and delta O-18 analysis of the fossil shells ofRadix auriculariaindicate that the lake-level fluctuations were mainly controlled by changes of the Indian Summer Monsoon; decreasing evaporation during the mid- to late-Holocene was also responsible. In addition, based on the geochemical relationship betweenRadixsp. shells and the ambient water in lakes, the values of delta O-18(Palaeo-water) and Sr/CaPalaeo-water reconstructed using the fossil shells ofRadix auriculariaare -8.2 parts per thousand to -5.1 parts per thousand and 0.0012 to 0.0057, respectively. Further, based on the values of delta O-18(shell), together with geomorphological evidence, we infer that Yamdrok Yumtso was a closed lake system, and we estimate its possible extent during the interval of high lake-level. In addition, we speculate that the water level of Yamdrok Yumtso at this time exceeded 4448.9 m a.s.l., but was less than 4451 m a.s.l., and that the major separation of various components of the Yamdrok Yumtso system occurred after 1.2 kyr BP.