The formation and evolution of Sudeerte tectonic belt in Beier depression

The Sudeerte tectonic belt is one of the most important hydrocarbon accumulations in Beier depression of Hailar basin. From the detailed structural geometry and kinematics analysis of Sudeerte tectonic belt and peripheral Beixi subdepression and Beizhong subdepression using balanced section technique and herringbone truss method based on inclined shear model, the authors detected that the special structure style was caused by a series of extensions:the direction of extension in Nantun Formation was nearly NW-striking, forming an EW-trending rift basin group, then the direction changed to northwest in a short period of early Damoguaihe Formation stretching and continued thermal depression to the present. The boundary faults in the east of Beizhong subdepression were the major boundary faults of Beier depression in the extension of early Damoguaihe Formation, and show a ramp-flat listric feature. Sudeerte tectonic belt is "roll-over anticline" formed in the upper part of the first fault floor due to the combined effect of gravity and geometry of boundary fault. It is thus held that the mechanism of anticline type of Sudeerte tectonic belt is bending fold rather than buckle fold.