济阳坳陷西南端沙三段剥蚀厚度恢复及其区域构造意义

Estimation of eroded overburden and its tectonic significance of the third Member of Shahejie Formation in extreme southwest Jiyang Depression

基于地球物理、钻井等资料,运用地层对比、孔隙度拟合以及盆地模拟的原理与方法,恢复出济阳坳陷西南端沙三段(Es3)剥蚀地层厚度及原始地层厚度,进行构造沉降量和拉张系数计算,探讨沙三段沉积期盆地构造活动特征及主控应力场。结果表明:沙三段沉积期,济阳坳陷西南端沉积中心的延伸方向宏观上呈NE-SW向展布,局部表现为近SN向延伸;该时期盆地的伸展强度并不均匀,表现为中部强,向NW、SE方向减弱;伸展作用宏观上受控于NW-SE向伸展应力场,可能受基底断层走滑的影响,局部伸展受控于近SN向应力场;济阳坳陷沉积中心展布方位前后经历了不同阶段近EW向、近EW与NE向共存及NE向展布的递进演变过程,但最终受控于NW-SE向伸展应力场。

Using the physical geography and drilling well data, the eroded and original overbudens during the third Member of Shahejie Formation （Es3 ） in extreme southwest Jiyang Depression were estimated with a series of methods such as strati-graphic correlation, porosity fitting and the principle and methods of basin modeling. The tectonic subsidence and the exten-sion coefficient were then calculated, and the character of sedimentation and its main controlling factor were discussed. The results are as follows. First, the depocenter is NE-SW trending as a whole, but is locally nearly south-north trending during Es3 stage in the extreme southwest Jiyang Depression. Second, the extensional level is not uniform： the center is stronger and it weakens toward northwest and southeast. The extension is controlled by NW-SE trending stress field in general, and by south-north trending locally resulting from the slip of the basement faults. Lastly, the spatial distribution of the depocenter in Jiyang Depression has gone through the progressive development from east-west trending in the early stage, the coexistence of nearby east-west and north-east trending in the middle stage, and north-east trending finally during Es3 stage. The whole sys-tem is however controlled mainly by NW-SE trending extensional stress field.