COMPARISON OF δ18 O RECORD DURING MIS 5 IN WANXIANG CAVE STALAGMITE, GANSU PROVINCE OF WESTERN LOESS PLATEAU AND THOSE OF SOUTHERN CHINA STALAGMITES
中国黄土高原西缘甘肃万象洞MIS 5石笋δ18 O记录与南方地区石笋记录的对比研究*

Speleothem, which is suited for precise U-series dating and contains many climate proxies, is widely used in paleoclimate reconstruction. In China, it has been proved that speleothem δ18 O is suitable for paleomonsoon reconstruction in the south and east regions. But in the northwest region few studies have been done. Here, we report high resolution δ18 O records of MIS 5 (from 118kaB.P. to 79kaB.P.) from two stalagmites (WXSM51 and WXSM52) collected form the Wanxiang Cave, Gansu Province (33°19'N, 105°00'E).The Wanxiang Cave is located at the transition zone between the Qinghai-Tibetan Plateau and the Loess Plateau. The location is close to the northern limit of the summer monsoon. The results indicate that δ18 O of stalagmite at this site is inversely related to the East Asian summer monsoon intensity. δ18 O of the Wanxiang Cave closely resembles the D3 record from the Dongge Cave, and also agrees well with the NGRIP record and the 65°N summer isolation curve. These indicate that δ18 O of the Wanxiang Cave is a valid and robust proxy for paleomonsoon intensity analysis. These also suggest that the East Asian monsoon varies in step with global climate change and is largely controlled by solar variations in the Northern Hemisphere.The Wanxiang record presents similarity to the Mediterranean speleothem records, and presents an inverse pattern compared with the Brazilian stalagmite BT2 record on the millennial timescales. These indicate that there are climate links among the East Asian monsoon, the Mediterranean and the Brazil summer monsoon regions, and further prove that the north-south climate seesaw did exist.It should be pointed out that the pattern of the transition from MIS 5b to MIS 5a recorded in the Wanxiang records differs from that in the Shennongjia stalagmite records. This difference, which does not seem to be caused by sampling resolution difference, may indicate that δ18 O of the precipitation in the Wanxiang Cave region is more sensitive to changes in monsoon intensity due to its close location to the northern limit of the monsoon region.