THE TIMING OF THE OLDEST GLACIATIONS IN THE MOUNTAINS OF THE QINGHAI-TIBETAN PLATEAU

The Qinghai-Tibetan Plateau consists of broad planation surfaces, basins, and mountain ranges. Research in the past several decades has argued that Quaternary glaciations developed only around the high mountains on the Plateau. In recent years we and other researchers have dated the oldest moraines in several mountain ranges using ESR. The relative age of these moraines was first confirmed based on their geomorphologic position and degree of weathering. The results show that the oldest glaciation, the Zhonglianggan Glaciation, in the Qilian Mountains, occurred at about 462.9ka BP (Zhou Shangzhe et al, 2002), and the high Wangfeng glaciation, the oldest one in the Tianshan Mountains, was dated at 477.1 and 459.7 ka BP (Zhou Shangzhe 2002). These ages imply that the earliest glaciation in Qilian and Tianshan Mountains probably occurred during MIS-12. The oldest glaciation in the Hengduan mountains, the Daocheng Glaciation, which is characterized by moraines with deeply weathered red soils having a SiO2/Al2O3 ratio of about 2.42 and a SiO2 /R2O3 ratio of about 2.35, was dated 571.2ka BP. This was also reconfirmed by the ages 592.6ka BP (Zheng Benxing, 2000) and 500-600ka BP (Yao Xiaofeng, 2000) on the oldest moraine at Yulong Shan in the southern Hengduan Mountains. The Wangkun glaciation, the oldest in the Kunlun Mountains, was dated 710ka BP by Cui Zhijiu (1995) using ESR. This was similar to the Cl36 age of bottom ice layer of a 309m ice core of Guliya Ice Cap (Shi Yafeng, 1998).

These dates of the oldest moraines in several mountain ranges suggest that the glaciers began to develop during MIS-12 in Qilian and Tianshan Mountains, MIS -14 in Hengduan Mountains and perhaps MIS-16 in Kunlun Mountains. Cui Zhijiu and Li Jijun suggest that wide spread, rapid uplift of Qinghai-Tibetan Plateau (Kunlun-Huanghe Tectonic Movement) occurred between 1.1-0.6Ma BP. We suggest that uplift of mountain ranges on the Plateau during this time initiated widespread mountain glaciation, but not widespread ice sheets.