Depositional Model of Lowstand and Characteristics of Sequence Boundary in Deep-water Lake, Songliao Depression Basin

During the depositional stage of Cretaceous Qingshankou, Yaojia and Nenjiang Formation, Songliao basin was a depression lake with deep-water, the slope of the basin was gentle along the long-axis, and was steep along the short-axis. The migration of depositional facies is characteristics of the third-order sequence boundary in gentle slope, but the onlap and truncation in seismic profile is not clear. In the steep slope, the third-order sequence boundary displayed as migration of depositional facies, but the onlap and truncation in seismic profile is very clear. The LST, TST and HST can be recognized in the third-order sequence. Along the long-axis, the distributary channel of delta developed very well, but mouth-bar, distal-bar and lake-floor-fan sediments are thin. Along the short-axis, mouth-bar, distal-bar and lake-floor-fan sediments developed in order along the lake-direction, but lack of the sediments from distributary channel of delta.