Molecular Fossils and Sedimentary Environment of the Cretaceous Lower Qingshankou Formation in Eastern Songliao Basin, Northeast China

摘要

INTRODUCTION The Songliao basin in Northeast China is one of the largest Cretaceous continental rift basins in the world. The black shale and oil-bearing shale in the lower Qingshankou Formation were considered to be the record of a lacustrine anoxic event (Huang et al., 1998), forming a primary source for the basin's hydrocarbon reserves (Li et al., 1995). More studies were conducted on the central zone of Songliao basin (Feng et al., 2007; Yang et al., 1985), leaving the eastern zone largely unknown. The maturity index of the lower Qingshankou Formation is commonly very high in the central zone (Zhong et al., 2009), which is not conducive to the preservation of molecular fossils. The study area is located in the Qingshankou Village, southeastern Songliao basin (Fig. 1), where the lower Qingshankou Formation crops out along the southern bank of Second Songhua River (Wang et al., 2001).