关键词: 地貌过程, 绿洲形成演变, 塔里木盆地

Abstract: Tarim Basin is the largest interior basin in China.Since the end of Tertiary,the violent uplift of the Tianshan Mountains and Kunlun Mountain has brought about a subsidence of the Tarim Basin,and the height difference between the mountains and the basin is great.From the alpine zones to the hinterland of the basin, the geomorphologic exogenic force action is in a devolution of glaciation → periglacial cold action → fluviatile action → arid action → alluvia-l dilluvial action → lacustrine action → sand drift action.The corridor-shaped, bead-string-shaped or fan-shaped oases form in the mountainous valley plains,alluvial fans on the plains,alluvial plains,lacustrine plains,etc.The shapes of the oases accord basically with the spatial distribution of the geomorphologic types befitting to form and develop oases.The temporal and spatial change and the rise and decline of the oases are caused4kinds of geomorphologic processes,i.e.,the neotectonic movement,fluviatile action, wind erosion and human activities.The main aspects are as follows：(1） The neotectonic movement results in the uplift of the alluvial fans in the piedmont zones,deep cut or course change of the streams,and desertification of the oases.(2） The oases are damaged by lateral fluviatile erosion,floods and debris flows,and the evolution of the oases is caused by the course change of the streams and the cut-off of the stream flow.(3） The desertification of the oases is aggravated by wind erosion and sedimentation.(4） The artificial geomorphologic processes make the enlargement of the artificial oases or the desertification of the natural oases.Desertification of the oases and the reverse of the deserts to oases are closely related to the geomorphologic processes.Making a comprehensive view on the developing trend of the geomorphologic processes in this region,it can be predicted that the three main geomorphologic processes,i.e.,fluviatile action,wind erosion and human activities,will be increased.The fluviatile erosion and wind erosion and sedimentation will result in the disadvantageous effects to the oases; the increase of fluviatile erosion process in the mountainous regions will result in the serious disasters of floods and debris flows in the piedmont oases,reduction of fluviatile action at the lower reaches of the plain rivers,the aggravation of wind erosion and sedimentation,and reverse of the oases to deserts.Human activities can stabilize the oases and even can reverse the deserts to oases,contrarily,can result in desertification of the oases.Therefore,it is an effective way for achieving the regional sustainable development to improve the geomorphologic processes in the important areas in the mountainous regions,piedmont zones,especially in the southern marginal zone of the Tarim Basin and the middle and lower reaches of Tarim River and to control desertification of the oases.

Key words: geomorphologic process, formation and evolution of oasis, Tarim Basin