The Yanqi Basin is an important depression area of the Tianshan Mountains near the northeast margin of the Tarim Basin. The Hejing thrust-fold belt, a renascent thrust-fold belt with intense tectonic activity, is located on the north margin of the Yanqi Basin. We calculated the shortening and uplifting of the Hejing thrust-fold belt since Quaternary to analyze the tectonic activities of this region, then,made a preliminary estimation of the shortening and uplifting rate in the Yanqi Basin and compared the result with other areas to demonstrate the role of the Yanqi Basin in the tectonic deformation of Tianshan in late Cenozoic. With few seismic data but abundant attitude of stratum and fault, we restituted the geometry of the fold to calculate the shortening and uplifting of the fold and slip of the fault on the Hejing thrust-fold belt which has a simple and intact structural pattern,and obtained the shortening amount of 1. 79km, 0. 88km and 26m, respectively since early Pleistocene ( 1. 8Ma ), middle Pleistocene ( 780ka) and late Pleistocene ( 80ka). The respective shortening rate is estimated as 0. 99mm/yr, 1. 13mm/yr and 0. 33mm/yr. The intensity of tectonic activity is not constant on the Hejing thrust-fold belt since the beginning of deformation. Compared with the result of crustal deformation, Yanqi Basin,as a major depression on southeastern Tianshan Mountains,absorbs most of crustal shortening of this area(86° ~88°E)and exhibits strong deformation of the newborn thrust-fold belt on the northern margin of the basin.%焉耆盆地是塔里木盆地东北缘天山山间的重要坳陷区,盆地北缘发育的和静逆断裂-褶皱带是一条现今活动强烈的逆断裂-褶皱带,对其第四纪以来缩短量和隆升量的计算有利于分析该区域的构造活动情况,对缩短速率和隆升速率的估计可以与天山造山带其他区域的活动速率进行横向对比,从而反映出焉耆盆地在天山晚新生代构造变形的作用.在深部资料不足的情况下,对背斜形态完整、构造样式简单的和静逆断裂-褶皱带,利用地表可获得的地层和断层产状,通过恢复褶皱几何形态,计算褶皱的缩短量、隆升量和断层滑动量,得到逆断裂-褶皱带早更新世晚期(1.8Ma)、中更新世(780ka)和晚更新世中期(80ka)以来的缩短量分别为1.79km、0.88km和26m,初步估计的缩短速率分别为0.99mm/a、1.13mm/a和0.33mm/a.显示和静逆断裂-褶皱带自开始形成以来构造活动强度并不一致.与地壳形变观测结果对比,作为南天山东段最主要的坳陷区,焉耆盆地吸收了这一区域(86° ～88°E)的大部分地壳缩短,且主要表现为盆地北缘新生逆断裂-褶皱带的强烈变形.
展开▼
