喀喇昆仑山-西昆仑山地区晚新生代隆起过程及自然环境变化初探

喀喇昆仑山、西昆仑山及其山前地区的上新统与下更新统之间虽然为整合连续沉积,但两者岩相上存在着巨大差异,由此推论本区强烈隆起的时代为上新世末至第四纪初。早更新世与中更新世之间的构造运动使山前地区的上新统和下更新统发生褶皱变形,并与中更新统呈不整合接触。中更新世山体强烈上升,本区山地发生第一次冰川作用。晚更新世发生两次冰川作用,其规模是晚期小于早期。晚更新世晚期气候强烈干旱化,湖面退缩、大湖解体,一些外流水系变为内流水系,高原植被出现半荒漠—草原—荒漠的演替过程,此时昆仑山北坡黄土发育。

A PRELIMINARY STUDY ON THE UPLIFTING AND ENVIRONMENT EVOLUTION OF THE KARAKORAM AND WEST KUNLUN MOUNTAINS AREA SINCE LATE CENOZOIC ERA

It can be confirmed that intensive uplifting of the Karakoram and West Kunlun Mountains occurred in the period from Late Pliocene epoch to Early Pleistocene, 'This is proved by the differences of Pliocene (Atushi formation) and Early pleistocene (Xiyue Conglomerate formation) stratigraphic features. Both in the interior of the Karakoram and West Kunlun Mts. and on thejnorthern side of the Kunlun Ms., the Atushi formation mainly composed of silts and fine sands is uniform. It means that the upheaval between the Kunlun Mts. and the Tarim Basin was gentle in Pliocene age. But the Xiyue Conglomeration, as a typical Ma-lasse deposit, is characterized by layered boulder conglomerates and coarse sands. It testifies that a great upheaval on the northern side of the Kunlun Mts. occurred in early Pleistocene age due to intensive uplifting. The climate was warm and humid during Pliocene age.A regional tectonic movement occurred between Early and Middle Pleistocene ages. This is proved by a series of folding, faulting and unconformity following the upheaval of the Plateau. Middle Pleistocene moraines have been found on of high peaks, That is the first gla-ciation on the Karakoram and west kunlun Mts. Two glaciations occurred in Pleistocene ape. The size of glaciation is less in the latter stage than in the former stage.Drying tendency .was progressing rapid ly since Late Pleistocene age. Levels of Plite;iu lakes were droping rapidly. The ancient lake of Tianshuihai was disintegrated and withered. Bangong Lake and other lakes changed from exterior drainage to interior drainage. Glaciers retreated. The vegetation changed from semi-desert throur stepps to desert. Loss on the northern slope of the Kunlun Mts. was formed at the same time.