The Songzhan region in northern Xujiaweizi Fault Depression of Songliao Basin is a small-scale faulted basin.The latest drilling data shows great gas potential in the basin and a possible replacement of the depleting deep gas zones in Daqing Oilfield.We chose the Shahezi Formation in the basin as a research object to analyze the stratigraphic sequences

sedimentary systems and filling-up history of small scale lake basins during intensive faulting based on previous studies as well as data of core

mud logging

conventional logging and 3D seismic survey.The result shows that the Shahezi Formation can be divided into one second-order sequence and four third-order sequences

with the latter being further subdivided into LST

TST and HST

according to lake flooding surfaces.Four kinds of sedimentary facies

including braided delta

fan delta

lacustrine and volcaniclastic facies

were recognized.The filling-up history of the Formation appears to be quite different from that of large-scale fault basins.Fan deltas dominated both steep and gentle slopes at the early stage of intensive faulting.And zonation of sedimentary facies was only distinctive with the expansion of the basin.How-ever

they were segmented into many shore-shallow lacustrine sedimentary zones with multiple depocenters due to a sediment supply shortage in the short axis of the basin.As a result

the thickness of layers in the basin varies greatly from one area to another.We proposed in the paper a sedimentary model for the continental narrow faulted lake basins based on the study of the filling-up history of the Shahezi Formation.