库车坳陷区西段拱拜孜活动逆断裂-背斜变形特征

DEFORMATION FEATURE OF GONGBAIZI REVERSE FAULT ANTICLINE IN WEST SEGMENT OF KUQA DEPRESSION

拱拜孜逆断裂-背斜为秋里塔格背斜带西延部分,由拱拜孜线状背斜构造及逆断裂组成.背斜北翼宽缓,南翼陡倾甚至倒转,为典型断层扩展褶皱构造.拱拜孜背斜变形方式和发展演化具阶段性变化特点,背斜强烈隆起,在中更新世末,为中晚第四纪背斜构造.拱拜孜断裂发育于背斜核部南翼,为拱拜孜逆断裂-背斜主要控制性断裂,其形成与发展控制着拱拜孜背斜形成与发展.断层造成背斜南翼上新统库车组直立甚至向北倒转,膝折现象明显.利用插分GPS测得断层两测Ⅱ级阶堆积底界不整合面高差为2.8 m,晚第四纪以来断裂垂直滑动速率为0.25 mm/a,地壳缩短速率为0.65 mm/a.

Gongbaizi reverse fault-fold belt is a region which develops from west segment of Qiulitage anticlinal belt and consists of Gongbaizi linear anticlinal structure and reverse fault with the same name.The north segment of Gongbaizi anticlinal belt is wide and gently,and the south is abrupt even reverse,which is a typical fault-Propagation fold.The type of distortion and development of Gongbaizi anticlinal belt shows phased characteristics.The anticlinal belt upheaves intensely at last stage of middle Pleistocene,which is a anticlinal belt at middle and late Quaternary.Gongbaizi fault locates at south of anticlinal core,which is mainly controlling fault of Gongbaizi reverse fault-fold belt.The formation and development of the fault controls that of Gongbaizi anticlinal belt.Furthermore,the fault brings terrane perpendicularity of Pliocene stratum at south of the anticlinal belt.At kekeyaer river,the second-lever terrace was offset along the fault,with a vertical displacement of 2.8m by differential GPS survey.Then,the average vertical slip rate of the Gongbaizi fault was calculated to be about 0.25mm/a since Late Pleistocene.The crustal shortening rate of Gongbaizi anticlinal belt was calculated to be about 0.65mm/a since Late Pleistocene.