廊固凹陷构造演化史及其构造形成机制分析

TECTONIC HISTORY AND THE MECHANISM OF STRUCTURE GENESIS IN LANGGU DEPRESSION

廊固凹陷作为典型的箕状凹陷,其构造发育历史和成因具有一定代表性。本文根据该凹陷地震反射特征,结合地球物理测井和地质资料。对其构造演化史进行了研究,并划分出四个演化阶段,即(1)断陷发育的前第三纪背景期;(2)断陷发育早期(沙四段—孔店组沉积期);(3)断陷中期(沙三段沉积期)和(4)断陷改造期(沙二段—东营组沉积期),而最后两个阶段具有更重要的意义。另外,以构造地质学为基础,配合室内粘土模拟实验和相应的有限单元数值模拟,发现本凹陷的构造形成机制有两种,即南区块以重力滑动作用为主,北区块受右旋扭动和重力滑动的共同作用。

Based on a comprehensive analysis of data from large amount of seismic, well log and drilling in Langgu depression, this paper discusses the structural history of the depression and its evolution. In the period of sedimentation of the 3rd member of the Shahejie formation, the accompanying block faulting being tilted towards NW a series of structural zones developed with striks in NE direction, such as reverse drag fold, central graben zone...etc. By the end of the deposition of the Dongyin phase, because the tilting of fault blocks was changed from NW to north direction, structures trending in NWW direction were produced. Meanwhile, a distinct structure frame work with stack of those resulted in two periods had been formed. In order to expound and hold the origine of different structurAL zones and local structures, some simple and inexpensive laboratory simulation tests in clay models and correspounding numerical simulation by finite element method are carried out. The results from these two modelings show that structures in the southern part of the depression are mainly dominated by gravity slippage, while in the northern part, both gravity slippage and horizonta(?) right-hand torsion dominated the structural styles.