Tectonic evolution and its control over deposition infault basins: A case study of the Western Sag of theCenozoic Liaohe Depression, eastern China

The main petroliferous basins in eastern China are Cenozoic fault basins, most of which haveexperienced two-stage tectonic evolution, i.e., rifting subsidence in the Paleogene and post-rifting thermalsubsidence in the Neogene-Quaternary. The episodic tectonic evolution and syndepositional faulting hadsignificant influence on the fault basins in terms of accommodation space, deposition rate, and depositionalfacies zones. In this study, the tectonic deformation characteristics and the tectonic-depositional evolutionof the Western Sag of the Cenozoic Liaohe Depression were investigated by comprehensive analysisof the available geological and geophysical data using the modern theory of tectonic geology and thebalanced section technique. The tectonic deformation of the Cenozoic fault basin was characterized bysuperimposed faults and depression. In addition, there existed relatively independent but still relatedextensional tectonic systems and strike-slip tectonic systems. The tectonic evolution of the fault basininvolved five stages, i.e., initial rifting stage (E2s4), intense faulting stage (E2s3), fault-depressiontransition stage (E3s1-2), differential uplifting stage (E3d), and depression stage (N-Q). According to thecharacteristics of tectonic development and evolution of the Western Sag, the depositional evolution inthe Cenozoic fault basin was divided into two stages, i.e., multi-episodic rifting filling in the Paleogeneand post-rifting filling in the Neogene-Quaternary. The former rifting stage was further subdivided intofour episodes with different characteristics of depositional development. The episodic faulting controlledthe filling process and filling pattern of the Cenozoic Western Sag as well as the development and spatialdistribution of associated depositional systems, whereas the syndepositional faults that developed inmultiple stages in various tectonic positions controlled the development of depositional systems and sandbodies in the Western Sag. That is, the fault terraces on steep slopes controlled the development of sandbodies, the fault terraces on gentle slopes controlled the development of low-stand fan bodies, and thefault terraces or fault troughs in the central basin controlled the development of fluxoturbidite bodies.