塔里木盆地西部喀什地区的新生代冲断构造

CENOZOIC THRUST STRUCTURES IN THE KASHI AREA,WESTERN TARIM BASIN

利用新近获得的地球物理资料并结合前人的研究成果研究了塔里木盆地西部喀什地区的冲断构造特征。天山南缘冲断带西段 (巴什布拉克构造带 )以倾伏的短轴背斜为特征 ,东段 (乌恰—阿图什—喀什构造带 )以 3排枢纽近平行的线性背斜为特征。西昆仑北缘冲断带中褶皱相对不太发育 ,西北段 (肖尔布拉克构造带 )的前锋不是原来普遍认为的乌帕尔断层 ,而是其北部隐没在克孜勒苏河之下的一条无名逆冲断层。在乌恰以西 ,由于南天山与西昆仑相距较近 ,肖尔布拉克构造带的前锋与巴什布拉克构造带的前锋相互交切改造 ,不显示明显的早晚关系 ;在乌恰以东 ,南、北两条冲断带基本被喀什深洼陷阻隔。两个冲断带都在上新世中 晚期成型 ,第四纪以来仍受到强烈改造。西昆仑北缘冲断带主要以无序的方式扩展 ,天山南缘冲断带则主要以后展的方式扩展。冲断带的前锋断层主要是盲冲断层 ,这使得冲断带内 ,特别是南天山南缘冲断带内的背斜圈闭得以比较好地保存下来 ,对油气勘探具有重要意义。

By use of recently geophysical data and predecessor's achievements, the Cenozoic thrust structure features in the Kashi area, western Tarim Basin, were studied. The western segment (named the Bashibrake structural belt) of the Southern Tianshan fold-and-thrust belt was characterized with plunging short-axis anticlines, and the eastern one (the Wuqia-Atushi-Kashi structural belt) of the belt was featured by three-row linear anticlines with nearly parallel striking. Comparatively, the folds in the north marginal fold-and-thrust belt of the Western Kunlun were poorly developed, and the frontier fault of the northwestern sector of the fold-and-thrust belt (named the Xiaoerbrake structural belt) might be an unnamed thrust lying beneath the Kuzilesu River, instead of the formerly Wuboer fault. To the west of Wuqia, both of the frontiers of the Xiaoerbrake and the Bashibrake structural belts overlappedand reformed each other, with the order of priority being not clear. To the east of Wuqia, the two fold-and-thrust belts were separated by the Kashi Depression. Both of the two fold-and-thrust belts created mainly in the middle-late Pliocene, and violently reformed in the Quaternary. The thrusting in the north marginal fold-and-thrust belt of the Western Kunlun expanded by out of sequence, however, the thrusting in the Southern Tainshan fold-and-thrust belt expanded in an order of overstep. Since the frontier faults in the both of the fold-and-thrust belts were mainly blind thrusts, which supported a condition for preservation of the anticlines, and had a great benefit to the anticlinal traps for the oil-gas exploration in both of the two fold-and-thrust belts, specially in the Southern Tianshan belt.