Abstract:

The sedimentation features and its evolution since Cretaceous in the eastern Sanjiang basin play an important role for the oil and gas exploration in the outer Daqing area and also are essential for the research of evolution in NE Asia. Detailed studies on the rock cores, geo-loggings, well loggings, and seismic materials show that, fan delta and lake sediment system developed since Cretaceous. In the Early Cretaceous, it was a spreading back-arc basin, some shore-shallow lake and volcanic sediments developed in the residual stratums; in the Late Cretaceous, it was a NE displayed intra-plate flexure-squeezed basin with short axis sediment sources from the Suibin and Wandashan on the both sides of basin, conversed contemporary fault developed in the Hailang-Qixinghe Formation, area of the semi-deep lake shrinked after extension, followed by basin filling and disappearing in the Yanwo Formation. In the Cenozoic, this basin was a dextral strike-slip pull-apart basin with the main sediments from an inherited short-axis source. During Baoquanling period, a long-axis sediment source appeared in the direction of Huanan uplift. From Baoquanling to the Lower-Mid period of Fujin, the semi-deep lake area extended with the sedimentation center moving towards southeast. During the Late Fujin period, the water body became shallow and the basin extended with the sedimentation center moving northwestward.

Key words: east Sanjiang basin, Cretaceous, Cenozoic, sedimentology, back-arc spreading, intra-plate flexure, dextral strike-slip pull-apart