RAPID CLIMATE VARIABILITY RECORDED BY MOLLUSK ASSEMBLAGES IN THE LOESS PLATEAU DURING THE LAST GLACIAL MAXIMUM

A high-resolution terrestrial mollusk record from the Loess Plateau of China has been studied to characterize climate variability during the Last Glacial Maximum (LGM). The studied section is located at Weinan, Shaanxi Province, in the southern Loess Plateau. In this study, a total of 81 samples with a sampling interval of 3 cm were analyzed for fossil mollusks of the LGM. Fifteen species of terrestrial mollusk fossils were identified. Of them, six typical species with distinct ecological significance were selected to infer climate and environmental changes. The successions of mollusk species reflect the variability of the LGM climate in the Loess Plateau and relationships between temperature and precipitation. At least four times of sharp climate changes occurred at this period with the characteristic of millennia-scale fluctuations. The changes in temperature and precipitation were evidently not in phase during the LGM. Temperature decrease or increase is leading precipitation. Consequently, the climate in the Weinan region experienced cold-wet, cold-dry, temperate-dry, and temperate-humid condition during the last 22 kaBP., which is attributed to the effect of winter and summer monsoon interactions on the loess region. Our results also reveal that the East Asian summer monsoons could reach continuously the southeast part of the Loess Plateau during the whole LGM. The intensification of winter monsoons during the LGM led to short duration of summer monsoons annually impacting on the Loess Plateau, but the intrinsic intensity of summer monsoon would have not changed significantly, that ensured thermo-hydrological condition for temperate-humidiphilous mollusks to persistently grow and develop in the glacial age.