末次盛冰期黄土高原蜗牛化石记录的气候快速变化及其影响机制

本文通过对渭南黄土剖面末次盛冰期地层较高分辨率的蜗牛化石记录研究，发现这一时期特征蜗牛种类峰值的演替反映了古气候的演化过程和温，湿度的组合关系。气候变化显示出百年-千年尺度波动的特征，温度的变化明显地要早于湿度（降水）的变化1000-2000a，表现为变冷-冷湿-冷干-温干-温湿的气候过程，研究认为造成这一气候特点的原因是东亚冬，夏季风共同作用的结果，可喜温湿蜗牛种类的研究，揭示出东亚夏季风在这一时期至少能够持续地影响到黄土高原的东南部地区，这个时期冬季风强化的结果之一是影响了夏季风在这一地区滞留的时间，加大了季节性的差异，分析表明尽管夏季风在这一地区滞留的时间缩短，但维持了它固有的强度，提供了适量的水热条件供喜温湿蜗牛种类在这一寒冷阶段持续地生长和发育。

RAPID CLIMATE VARIABILITY RECORDED BY MOLLUSK SPECIES ON THE LOESS PLATEAU DURING THE LAST GLACIAL MAXIMUM

A high resolution terrestrial mollusk record from the Chinese Loess Plateau has been studied to study 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. Each sample weights about 15 kg, which was washed and sieved through a 0.5 mm mesh in the field. 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 variations of the LGM climate in the Loess Plateau and the 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 decreases or increases 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?000aB.P., which is attributed to the effect of winter and summer monsoon interactions on the loess region. Our results also suggest that the East Asian summer monsoons could reach 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 conditions for temperate humidiphilous mollusks to persistently grow and develop in the glacial age.