Controls on Faulted Sub-Depression Patterns in Continental Rifted Basins: The Beier Depression, Hailar Basin, Northeastern China

In contrast to well-studied rift basins in NE China, the Hailar Basin has received relatively less attention regarding the combined patterns of different types of grabens and half-grabens. This study aims to explore whether the combined patterns of grabens in the Hailar Basin exhibit similar characteristics to those in other NE China rift basins and to identify the underlying causes. To achieve this, a comprehensive analysis of the major fault systems and the combined patterns of faulted sub-depressions, as well as their controlling mechanisms, was conducted. This analysis utilized the latest 3D seismic data that cover nearly the entire Beier Depression. Three groups of pre-existing fault systems were observed in the basement of the Beier Depression, and they are the NEE-EW-trending fault systems, the NE-trending fault systems, and the NW-trending fault systems. The NEE-EW-trending fault systems were distributed in the central part of the Beier Depression and primarily controlled the sedimentary filling of the Tongbomiao and the Lower Nantun Formations. The NE-trending fault systems were distributed in the southwestern part of the Beier Depression and primarily controlled the sedimentary filling of the Upper Nantun Formations. The NW-trending fault systems were distributed rarely in the Beier Depression. Five kinds of combined patterns of the sub-depressions were developed in the Beier Depression, and they are the parallel, en echelon, face-to-face, back-to-back, and S-shaped combined patterns. They were controlled by the NEE-EW-trending and the NE-trending fault systems with different orientations, arrangements, and activation sequences.