塔里木盆地北部隆起负反转构造成因机制探讨

塔(里木盆地)北(部)隆起中生代以来经历了逆冲上隆,构造反转和再生前陆盆地斜坡带3个阶段,分别与库车前陆盆地构造运动强、弱、强的演化历史相对应。塔北隆起的大型负反转构造形成于白垩纪-中新世。白垩纪之前,塔北断隆作为库车前陆盆地和北部坳陷的相邻单元,发育两组背冲断裂以实现其缩短。在构造宁静期(白垩纪-新第三纪吉迪克期),岩石圈回跳,前缘隆起局部伸展,早期逆冲断块沿着原逆冲断层面下滑形成负反转构造。中新世以后,塔北地区成为库车再生前陆盆地的斜坡区,负反转构造得以保存且有进一步加剧之势。塔北隆起上伸展应力场的产生与深部岩石圈同步挠曲变形过程中波峰和波长的变化有关。

MECHANISM OF NEGATIVE INVERSION-STRUCTURING IN NORTH TARIM UPLIFT

From Mesozoic, evolution of the North Tarim Uplift underwent three phases: upthrusting, tectonic inversion and ramp of forebasin, corresponding to the strong, weak and strong tectonic evolution phases of the Kuche Foredeep respectively. The negative inversion structures in the North Uplift of Tarim basin formed during the Cretaceous Tertiary. In the stage of pre Cretaceous, the Kuche Foredeep and Northern Depression developed . Because of strong compression stress, the lithosphere bent and two groups of back thrusts formed to achieve shortening in the North Tarim Uplift. During tectonic tranquility period(K N 1j ), since the lithosphere adjusted and the former forebulge locally extended, two back\|thrusts slided along the former thrusts, the movement resulted in the negative inversion structures. After Miocene,because the lithosphere flexural rigidity increased, flexural crest migrated out of the Northern Uplift. Consequently, the Northern Uplift became a part of foredeep, so the negative structures not only still existed, but also had a tendency to become wider. The reason of the extensional stress field may be attributed to the chang of wave crest and wavelength of the lithosphere syn flexure.