东昆仑东段第四纪成山作用过程与地貌变迁

东昆仑山的现代地貌格局为一系列北西西向的山系和盆地(谷地) 相间列, 第四纪沉积和岩相分布与地貌格局存在良好的匹配性, 第四纪不同时代沉积反映了山系的成山作用过程.显著地貌分异首先出现于北部的布尔汗布达山, 即早更新世中晚期(1525ka), 表现为受布尔汗布达山地貌控制的其南部山脚的早更新世中期(1525ka) 左右冲洪积物的始现.南部马尔争—布青山的成型发生于早中更新世之交, 这次成山作用在整个青藏高原昆仑—黄河源地区具有广泛影响.更南部的查哈西里山在1113.9~979.6ka间的沉积特征也显示了这一事件的影响, 即由湖相转变为冲洪积相, 但在这一时期查哈西里山总体仍为沉积区, 山系并未形成, 山顶最高层位粗冲洪积物的砾石成分统计和砾石扁平面产状统计仍显示物源来自北部, 沉积与北部隆起的马尔争-布青山有关, 查哈西里山真正隆起高于两侧, 应发生在晚更新世.伸展断裂组合与地貌之间的良好耦合关系表明, 东昆仑地区山体的崛起与伸展断裂构造之间存在密切的成因关系.山系突出于高原面的成山作用主要受控于近南北向的伸展作用, 这一伸展作用应与青藏高原整体隆升后边缘的重力失稳垮塌及均衡作用相联系, 这种伸展垮塌随着时间的迁移向南发展. 

Mountain Building Process and Geomorphic Migration of Eastern Kunlun Mountains during Quaternary

The relief in the eastern Kunlun Mountains, northeast Tibetan plateau is characteristic of a series of NWW-SEE ranges alternating with basins or valleys. The distribution of Quaternary deposits and facies match well with the relief, exposing the mountain building process. The obvious relief differentia first appeared in the north of Buerhanbuda Mountain, represented by the first occurrence of the fluvial deposits at its south foot in the mid-late Early Pleistocene(after 1 525 ka). While the molding of the Maerzheng-Buqing Mountain happened in the later Early Pleistocene, when a so-called Kunlun-Yellow River movement affected an extensive area, the eastern Kunlun Mountains and the headstreams of the Yellow River. The Chahaxili Mountains in the south of our research area were also affected by this event which is inferred by the change from lacustrine deposits to pluvial or alluvial deposits at about 1 113.9-979.6 ka. However, the fact that there are still the deposition area in Chahaxili Mountain area shows that it didn't plump up at that time. Hence, the provenance of the pluvial or alluvial deposits, coming from the north and related to the uplift of the Maerzheng-Buqing Mountain, can be deduced by statistics of the gravel composition and the gravel array. It is concluded that the molding of the Chahaxili Mountains could have occurred in the Late Pleistocene. On the other hand, the good matching relationship between the Pleistocene extension fractures and the relief framework indicates that the mountain building process should be extension-controlled, mainly N-S. This N-S extension should be related to the collapse and equilibrium adjusting of the north edge of the Tibetan plateau caused by gravity unbalance after its being uplifted. The transfer of the mountains building process from north to south implies that the collapse developed from north to south.