Research On Lithofacies Palaeogeography Of Cretaceous In Songliao Basin

This paper stuied lithofacies palaeogeography of the Cretaceous in Songliao basin,by using seismic, well logging, paleontology and other methods. The research shows that the basin developed volcanic rocks, rivers, shallow lake, delta and alluvial fan deposits in Early Cretaceous, and semi-deep to deep lake, shallow lake, delta, river and alluvial fan deposits in late Cretaceous. In the further study, also shows tectonic controls the basin evolutionary and regional tectonic is the main factor causing the subsidence center and depocenter of the westward movement. NNE and NW-trending basement faults controlled the distribution of the early rift basin, but also because of its effect on the control basin, the sedimentary axis is nearly NNE, source and river systems along these faults.Base on this foundation, combined with the sediment source, paleoclimate, and lake level changes, lithofacies palaeogeography of the Cretaceous in Songliao basin is described. in the Early Cretaceous from Yingcheng Formation to Huoshiling Formation is mainly developed pyroclastic rocks and deposited in small lakes.The basin merged into one sedimentary basin area and formed a suit of sand and mud stone. Untill the Quantou Formation,it has formed a unified lake sedimentary system except for a few areas. The basin is subsidenced and the lake is expaned during Qingshankou Formation, and developed fan delta system and braided delta system along basin axis.During Yaojia Formation, it is uplifted. It turned into smaller from Nengjiang Formation. Depocenter moved to west and center depression deposited fine clastic durning Sifangtai Formation to Mingshui Formation. The basin has experienced the fault activity from fierceness to light, the paleo-lake from small to large, the basin from the division to the unity, and sedimentary facies were divied into east and west part, distribution shows pattern of asymmetry.