ZHAO Xi-tao, QU Yong-xin, LI Tie-song
Yulong Mountains (27°10′～27°40′N, 100°9′～100°20′E), situated in the north of Lijiang County, Yunnan Province and the southeast margin of the Tibetan Plateau, are the southernmost mountains with glaciers both in China and Eurasia Along their east, northeast and west feet, there is a series of relics of the Pleistocene glaciation Studying these glaciation relics and reconstructing their history of evolution have not only an important scientific implication for understanding the changes of glaciation, climate and environment and for discussing the uplift of the Hengduan Mountains and the Tibetan Plateau, as well as the development of the Jinsha River valley and the formation and development of Asian monsoon, but also major practical values for developing and protecting the tremendous resources of hydraulics and tourism in this area. The authors survey, research and map the Pleistocene glacial deposits along the eastern foot of the Yulong Mountains based on the topographic map with the scale of 1:10.000 and air-photographs, determining ESR dates of samples of calcareous cements from the glacial and fluvioglacial deposits as well as the calcareous glacio-lacustrine deposits, dividing them into four glaciations, i e the early Middle Pleistocene Yulong Glaciation (0.7～0.6 Ma BP), the middle Middle Pleistocene Ganhaizi Glaciation (0.53～0.45 Ma BP), the late Middle Pleistocene Lijiang Glaciation (0.31～0.13 Ma BP) and the Late Pleistocene Dali Glaciation, and correlating them with the glaciations on the Tibetan Plateau Results of study show that the Yulong Mountains area was a part of the united peneplain from the Tibetan Plateau to the Yunnan-Guizhou Plateau, 500～1.000 m a s l, during the Miocene. In the Pliocene and the Early Pleistocene, the Yulong Mountains uplifted and the Lijiang Basin, Daju Basin, Longpan Valley and other basins subsided due to the fault activities. In the early Middle Pleistocene, the Yulong Mountains had uplifted over the snowline, and giant piedmont glaciers of the Yulong Glaciation, the largest glaciation in this area, occurred at their east, west and northeast feet. The glaciers in the Ganhaizi Glaciation were also piedmont ones, but muchsmaller than the former During the following grand interglacial, the Longpan Valley and the Daju Basin became two lakes, and then cut by the modern Jinsha River In the late Middle Pleistocene and the Late Pleistocene, the larger-scale valley glaciers of the Lijiang and Dali Glaciations developed in the tributaries of the Jinsha River.
