塔里木盆地库车坳陷中生代原型盆地分析

Analysis of Mesozoic Prototype Basin in Kuqa Depression, Tarim Basin

运用地震资料、地表露头、钻井和测井资料以及非地震物探等资料,对塔里木盆地库车坳陷中生代的盆地结构、构造样式、区域构造演化进行区域构造解析,采用地层趋势厚度法计算中生界剥蚀厚度,结合沉积学资料对库车坳陷中生代原型盆地进行成因分析。库车坳陷残留中生界总体上为北厚南薄、北剥南超的地质结构,北部强烈角度不整合在南天山海西运动期褶皱带之上,南部微角度不整合在寒武系—奥陶系之上。库车坳陷中生代原型盆地属于上覆于南天山海西运动期造山带和塔里木克拉通边缘过渡带的拗陷盆地,地壳均衡可能是盆地沉降的主要动力。海西运动使南天山褶皱隆升,早二叠世在塔里木克拉通和南天山有强烈的火山作用,在盆山过渡带形成了库车坳陷盆地雏形。三叠纪地壳开始均衡下沉,造山带塌陷,在盆山过渡带发育拗陷盆地。侏罗纪、白垩纪坳陷继承性发育,但是盆地轴线、沉降和沉积中心发生轻微的迁移,白垩纪晚期发生区域抬升剥蚀。

Using the data of seismic, surface outcrop, drilling, logging and non-seismic geophysics, the paper investigates the basin struc-ture, tectonic style and regional tectonic evolution of Mesozoic strata in Kuqa depression, Tarim basin. Stratum trend thickness method isadopted to calculate the Mesozoic denudation thickness and the genesis of the Mesozoic prototype basin is analyzed in Kuqa depressionwith sedimentary data. The residual Mesozoic strata in Kuqa depression are generally of a geologic framework characterized by thick in thenorth and thin in the south, denudating in the north and overlapping in the south, strong angular unconformity developed on the Hercynianfold belt of the southern Tianshan Mountain in the north and slight angular unconformity distributed on the Cambrian-Ordovician series.The Mesozoic prototype basin in Kuqa depression is a down-wrapped basin overlying the Hercynian orogenic belt of the southern TianshanMountain and the transitional zone at the margin of Tarim craton. The isostasy may provide the main force for the subsidence of the basin.The Hercynian movement resulted in the uplift of the southern Tianshan folds. Strong volcanism occurred in Tarim craton and southernTianshan Mountain during the early Permian allowed the formation of proto-Kuqa depression basin on the basin-mountain transitional zone.The balanced subsidence of the earthcrust started in Triassic period, the orogenic belt collapsed and the depression basin was developed onthe basin-mountain transitional zone. The successive development of the depression occured in Jurassic and Cretaceous, but the basin axis,sedimentation and depositional center slightly migrated and the regional uplift-denudation occurred in the Late Cretaceous.