Paleoenvironments of Tibetan Plateau Viewed from Glacial Fluctuations in the Northern Foot of the West Kunlun Mountains

Abstract

Map reading and field observation of the glaciers around Mt. Kongur, West Kunkun, Xinjiang Provice, Western China revealed that the present ELA (Equilibrium Line Altitude) of the glaciers is much lower in the side of Tarim Basin (about 4, 200-4, 300m) than in the Tibetan Plateau side (about 4, 750-5, 200m). The Last Glacial ELA reconstructed by the AAR method indicates a similar steep gradient of ELA (about 4, 050-4, 200m in Tarim side, about 4, 600-4, 950m in Tibetan side). ELA of the penulitimate glaciation (just before the Last Interglacial) shows a similar situation (about 3, 500-3, 700m in Tarim side, about 4, 400-4, 700m in Tibetan side). Depression of ELA was much larger in the penultimate glaciation (about 350-700m) than in the Last glaciation (about 100-120m). Depression of ELA was larger in Tarim side than in Tibetan side, especially in the penultimate glaciation.The age control of the moraines was attempted by the carbon and AMS datings for the Little Ice Age and Late Glacial moraines. Measurement of the magnetic susceptibility of loess covering the outwash terrace surface which connects topographically to the moraines upstream was used for the age determination of older moraines. The result supports the idea that the Tibetan Plateau was not covered by a single and uniform large ice cap even in the penultimate glaciation.