According to geological survey

well log

seismic information and rock assemblages combined with the interpretation of log and seimic information

Shiwu Dehui region in Songliao Basin could be divided into four types of sedimentary systems such as alluvial fan system

fluvial delta system

subaqueous fan fan delta and lacustrine systems and nine kinds of sedimentary facies and a number of subfacies.The study shows that different sedimentary systems developed in different developing stages of the basin.Alluvial fan facies developed in the initial fault depressed stage;lacustrine and subaqueous fan fan delta systems developed in the early middle fault depressed stage.In the lacustrine system

deep semideep lacustrine facies and subaqueous gravity flow facies developed well

in the late peried of faulted depression

water depth was shallower

the dominant deposits were those of shallow lake and fluvial delta facies.Two major water transgressive and regressive cycles formed in depression stage can be recognized.The Quantou Formation and Yaojia Formation are mainly of fluvial and shallow lake deposits while lacustrine system is the dominant facies of Qingshankou and Nunjiang Formations.