Abstract: Loess and loess-like sediments are vastly spread over the marginal mountains of the Tarim Basin and Zhungaer Basin in Xinjiang of northwestern China. Around the basins there are often two different aeolian sedimentation belts, which are separately covered by loess, and loess-like deposits. Generally speaking, the loess is more intensively developed in the southern margin of the basin than in the northern. On the northern flank of Kunlun Mountains, loess is mainly distributed between 2500 m and 3400 m a. s. l. (above see level), and its thickness is seldom over two dozen meters. Small loess patches with a thickness of about 1 m may occur even at the elevation over 5000 m a. s. l. But in the Tianshan Mountains, the loess is considerably restricted to 950 m and 2400 m a. s. l. on the southern flank, and 800 m and 2000 m on the northern side. The samples taken from Tashikuergan to Yütian of the northern flank of Kunlun Mountains show the grain size of loess tends to increase from West to East. Compared with Loess Plateau, the loess in Xinjiang is generally coarser probably owing to its shorter transport distance. The samples from Pulu in the upper reaches of Keriya River indicate that the percentage of heavy minerals in the loess is 5.5% on average. The content of stable and very stable minerals is only some 20%. One third of the heavy minerals is hornblende. Besides, the content of epidote, iron minerals and black mica is relatively high also. From the field investigation and laboratory analysis, it concludes that the preserved loess in the surrounding mountains of the Tarim Basin has been deposited mainly in Holocene. There the loess accumulation takes place principally during the intergalcial periods. Under the more severe climatic conditions of glacial times, the vegetation in the present loess zone would deteriorate considerably, and a stronger deflation and sand accumulation would replace the process of loess sedimentation. But in the northern flank of Tianshan Mountains, several layers of paleosol are present in the loess section, and both Holocene and late Pleistocene loess is observed.

Key words: Loess, environmental change, arid zone, Kunlun Mountains, Xinjiang