Mesozoic and Cenozoic Stratigraphic Sequences and Basin Evolution in Wulaga Fault-Depression,Jiayin County,Heilongjiang Province

Based on discussing each unit of the lithostratigraphic rock composition,fossil assemblages and depositional environment from Mesozoic to Cenozoic in Wulaga fault-depression,Jiayin County,Heilongjiang Province,and comparison with other basins in Sunwu-Jiayin and Songliao basin,the authors divided the Mesozoic and Cenozoic strata into three tectonic layers and five lithostratigraphic units,and discussed their distribution and evolution,and made the regional geological map.The Wulaga basin shows three significantly different basin evolution stages,during which the two distinct unconformities are recognised,namely: the unconformity between upper Cretaceous and Lower Cretaceous and between the Upper Cretaceous and Neogene,thus made three different types of basin evolution stages in Wulaga from Mesozoic to Cenozoic;they are Early Cretaceous rift basin evolution stage,the Late Cretaceous large scale inland depression,and Neogene inland basin evolution stages.