天山山前主要推覆构造区的地壳缩短  

CRUSTAL SHORTENING OF MAJOR NAPPE STRUCTURES ON THE FRONT MARGINS OF THE TIANSHAN

作　　者：杨晓平[1] 邓起东[1] 张培震[1] 徐锡伟[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地震地质》2008年第1期111-131,共21页Seismology and Geology

基　　金：国家自然科学基金(40572126);国家科技支撑计划项目子专题(2006BAC13B01010102)资助

摘　　要：利用平衡地质剖面方法研究天山山前主要褶皱带的地壳缩短,其中3条平衡剖面分别横跨天山南簏的柯坪逆断裂-褶皱带和库车逆断裂-褶皱带,2条剖面横跨天山北簏的玛纳斯活动逆断裂-褶皱带,其余1条剖面横跨吐鲁番中央隆起逆断裂-褶皱带。柯坪活动逆断裂-褶皱带、库车逆断裂-褶皱带、玛纳斯逆断裂-褶皱带和吐鲁番盆地的地壳缩短量分别为40-45km、27-37km、8.5-10.5km和6-7km。天山山前活动逆断裂-褶皱带在EW向上互不重叠,它们的缩短量大致代表了该经度上新生代的最小地壳缩短量,反映出天山地壳缩短由西向东减小的趋势。假定天山山前活动逆断裂-褶皱带开始形成的时间为距今2.5Ma的西域砾岩沉积期,考虑到博阿断裂、塔拉斯-费尔干纳断裂在SN向上的缩短活动分量,上述4个地段的最小缩短速率分别为15.4-17.3mm/a、12.7-16.5mm/a、3.8-4.5mm/a和2.3-2.7mm/a。活动走滑断裂在天山内部特定位置向左偏转,走向由NW转为NWW,在断裂转折的部位走滑活动量转化为天山SN向的缩短变形。We present the results of selected balanced cross-sections across four active reverse fault-fold belts at the front margins of the Chinese Tianshan, an intracontinental mountain belt formed in response to the India-Eurasia continental collision. It consists of Paleozoic,Mesozoic and Cenozoic strata in active fold-and-thrust belts at two sides of Tianshan, and the stratum in active fold belt changes younger from west fold-and-thrust belt to east. The middle part＇s structure is complicated in Kalpin active fold-and-fauh belt,the width gradually diminishes towards east. At the west of Akesu city,the Kalpin active fold-and-thrust belt vanishes, but at the east part of Akesu city,the Kuche active fold-and-thrust belt emerges on the Tarim desert. In the middle section of the Kuche active fold-and-thrust belt near Baicheng County, the structure is most complicated, and the width is also maximal. The width of Kuche fold-and-thrust belt gradually decreases towards east,and disappears near 85° longitude line. But at the northern piedmont of Tianshan,the Manas active fold-and-thrust belt presents itself approximately at the same longitude. The longitude of the west end of Turpan centre uplift active fold-and-thrust zone is approximately the longitude of the east end of the Manas active fold-and-thrust belt. The four active fold-and-thrust belts which we studied are located at the north and south sides of Tianshan Mountains. Two balanced cross-sections traverse the Kalpin active fold-and-fault belt and one crosses the Kuche fold-and-fauh belt. Two balanced cross-sections cross the Manas active fold-and-thrust belt, and one balanced cross-section crosses the Turfan centre uplift zone. The crustal shortening of Kalpin fold-and-thrust belt is 40 - 45km, that of Kuche fold-and-thrust belt about 27 -37km, and of Manas,Turpan centre uplift active fold-and-thrust belt are 8.5 - 10. 5km and 6 -7km, respectively. The four active fold-and-thrust belts at south and north Tianshan are not superposed in longitude. So their crustal sh

关 键 词：天山 地壳缩短 逆断裂-褶皱带 缩短速率 第四纪 

分 类 号：P315.2[天文地球—地震学]