Structure of the Cenozoic Cover of the Sanjiang-Middle Amur Sedimentary Basin (Russia, China)

Based on the map of the gravitational-field anomalies with respect to the existing structural data, a single structural scheme of the Sanjiang-Middle Amur sedimentary basin is constructed. It reflects the Paleogene rift-related stage of the basin's evolution, when numerous grabens oriented mostly to the northeast formed under the action of NW-SE tension forces. The regularities in the location of the grabens indicate that the basin formed under conditions of interaction of right-lateral northeastern and left-lateral sublatitudinal and west-northwestern strike-slip faults. The ancient northeastern faults activated in the Paleogene formed marginal Western and Eastern zones of right-lateral strike-slip faults. En-echelon series of grabens in the central part mark the position of the rudimentary zones of the left-lateral strike-slip faults. The internal structure of the grabens is analyzed using the materials of the previous and new seismic and well data. The common and individual features of their structures are revealed. The structure of the grabens of the western and eastern marginal zones is demonstrated. It is noted that some grabens are prospective for raw hydrocarbons. An analysis of the deep structure of the territory of East Asia, including the basin, assumes the presence of an upwelling zone by the results of geophysical studies of recent years, primarily seismotomography.