The Palaeogene system in the Southern west sag of the Dongpu Depression consists of riftlacustrine deposits and developed with fluvial, delta, alluvial, fandelta and lacustrine facies. The lithofacies paleogeographic features of the district are controlled by activity of two boundary faults, especially the Changyuan fault at the western side. A strong movement of the faults results in increasing in basin size and water depth, and developing fandelta, delta and deep-semideep lake facies. A weak movement of the faults results in shallowing and filling of the lake basin, and developing alluvial fan and fluvial facies.
