基于新钻井对柴达木盆地东部石炭系分布及控制因素的再认识

通过钻井、野外地质考察、地震精细解释等资料,重新确定柴达木盆地东部石炭系残余地层的分布范围,并根据平衡剖面恢复和印支期应力场数值模拟分析柴达木盆地东部构造演化特征,探讨石炭系分布的影响因素。结果表明:石炭系主要分布于大柴旦凹陷、德令哈凹陷、霍布逊凹陷和大红沟凸起等地区,鱼卡凹陷、欧南凹陷基本无石炭系残留;石炭系残余分布受古地理格局和后期构造运动共同控制,古地理格局造成了东西方向石炭系分布的差异,柴达木盆地东部地区印支期褶皱抬升,形成近东西走向背斜凸起,造成石炭系抬升剥蚀;柴达木盆地东部在印支期以逆冲断裂和与之相关的断展褶皱为主要构造变形模式,在不均匀分布的最大主应力与右旋剪应力共同作用下,石炭系在各地区遭受不同程度的剥蚀。

New study on Carboniferous stratigraphic distribution and controlling factors in the eastern Qaidam Basin based on new drilling data

Based on drilling data, field geological investigation, fine interpretation of seismic data, the distribution of the residual Carboniferous strata in the eastern Qaidam Basin was determined. According to the balanced section and the numerical simulation of tectonic stress field in Indosinian, the characteristics of basin tectonic evolution were analyzed and the impacts of Carboniferous strata distribution factors were explored. The results show that Carboniferous is mainly distributed in Dachaidan sag, Delingha sag, Huobuxun sag and Dahonggou salient. There is almost no Carboniferous residual in Yuqia sag and Ounan sag, the Carboniferous residual strata distribution is controlled by the ancient geographical pattern and the late tectonic movement. The palaeogeographic pattern may explain the Carboniferous residual differences between the east and west. And the eastern Qaidam Basin folded and uplifted in Indosinian, forming a series of nearly east-west anticlinal bulge, which resulted in Carboniferous uplift and erosion. Thrust faults and fault propagation folds are the major tectonic deformation modes of the eastern Qaidam Basin in Indosinian. Affected by the uneven distribution of the principal stress and dextral shear of Indosinian, Carboniferous suffered different degrees of erosion in various regions.