Characteristics and evolution of faults in the north-central Yin’e Basin and the effects on the coal-seam in the Cretaceous strata

Research on the characteristics of faults and their evolutionary history since the Cretaceous in the Suhongtu-Dagu depressions can provide a theoretical basis for geological evaluation of the coal seams in the Suhongtu Formation in the northern-central region of the Yin’e Basin. Using 3-D seismic-logging inversion techniques, seismic stratigraphic calibration, stratigraphic sequence delineation, and thickness calculations on the Suhongtu-Dagu depressions were carried out to clarify the planar and profile distributions of the faults, as well as the evolutionary history of these faults and the tectonic history of the depressions. The results of this study revealed that the distribution of the faults in the Suhongtu-Dagu depressions in the northern part of the Yin’e Basin varies with region, and the fault system was multi-period, orthotopic, north-east-trending, and north-north-east-trending, with a certain degree of inheritance in terms of the geological setting. Three types of faults were identified: Y-shaped fractures, reverse Y-shaped fractures, and parallel fractures, which can be classified as Paleozoic Cenozoic continuous syncline faults and intra-depression faults from the top of the Permian to the Upper Cretaceous series and inter-stratigraphic adjustment faults within the Cretaceous System, respectively. The evolution of these faults can be divided into three phases: the controlling faults were the faults that existed before the Early Cretaceous and had been active since then; synclinal faults that formed during the Early Cretaceous; and modified faults that formed since the Early Cretaceous. The development and modification of the coal seams in the Cretaceous Suhongtu Formation in the Hari, Kuanzihu, and Babei sags were strongly controlled and influenced by a multi-phase complex fault system.