新疆库车盆地东秋里塔格构造带新生代的构造演化

CENOZOIC TECTONIC EVOLUTION OF THE EASTERN QIULTAG STRUCTURAL BELT,KUQA FORELAND BASIN IN XINJIANG

东秋里塔格构造带位于库车前陆盆地的南缘,新生代经历了强烈的构造挤压和构造沉降。平衡剖面分析、生长地层识别和重点井沉降史的数值模拟表明:古新-始新世库姆格列木群沉积期间构造活动微弱并沉降缓慢。渐新世苏维依组沉积期间,构造活动开始加强,沉降速度加快,并形成了一些小断距的逆断层。中新世构造活动进一步加强,沉降加速,沉积了厚层的吉迪克组膏盐层;康村组沉积时期,构造挤压使得膏盐层发生塑性流动,形成盐枕,康村组发育生长地层。随后的上新世库车组沉积期间,研究区先发生快速沉降,然后,随着南天山急剧隆升,冲断作用迅速向南扩展。约在早更新世,库车褶皱冲断带前锋到达东秋里塔格构造带,并最终定型,使得该区发生强烈的构造变形,形成大量的逆冲断裂构造带,膏盐层表现出明显的塑性流动,形成盐推覆构造。

The eastern Qiultag structural belt, which was on the southern edge of Kuqa foreland basin, has occurred tense tectonic compression and subsidence during Cenozoic. The tectonic evolution history was analyzed by means of the balanced cross section, the growth strata and the numerical modeling of some key wells＇ subsidence history. The results showed that the tectonic movement was relatively weak and the subsidence rate was minimal during sedimentary stage of the Kumugeliemu Group in age of Paleocene to Eocene. The tectonic activity began to enhance and the subsidence rate increased, and therefore developed some thrusts with small fault displacement during sedimentary stage of the Suweiyi Formation in age of Oligocene. The tectonic movement enhanced further and the subsidence rate increased again during Miocene, so that deposited thick salt layer of the Jidike Formation, then the salt layer flowed by tectonic compression and formed salt pillow during the sedimentary stage of Kangcun Formation, when the growth strata occurred. Subsequently, the studied area subsided quickly during depositional stage of the Kuqa Formation in age of Pliocene. With the South Tianshan Mountains uplifted rapidly, the thrust expanded southwards rapidly, and the front of the Kuqa fold-and-thrust belt arrived the eastern Qiultag structural belt in Early Pleistocene when the regional tectonics fell into its pattern. To sum up, the tectonic deformation was tense in this area where developed many thrusts, and the salt layer flowed evidently and formed salt nappe.