Late Jurassic-Early Cretaceous strata and their sendimentary characteristics in the Qiangtang basin, northern Tibet

Abstract：The Late Jurassic-Early Cretaceous strata mainly include the Zhaworong Formation, Xueshan Formation, Bailongbinghe Formation and upper member of the Suowa Formation in the Qiangtang basin. Up to now there are different views about their division, correlation and mutual relation. This paper summarizes the definition and age evidence of each formation and points out that these formations are lithostratigraphic units. The available data are not enough to make a further chronological division. By the statistics of the distribution of various formations and analysis of the sedimentary characteristics of various formations, it is found that the Bailongbinghe Formation is of continental shelf facies and distributed in the northeastern part. Thus the authors think that these formations are contemporaneous and heteropic deposits, and that it is not advisable to consider their relationships to be overlying and underlying. According to this, the authors proposes a new scheme of stratigraphic correlation and think that the highest marine horizon in the basin should extend to the Lower Cretaceous and that seawater retreated from the basin gradually from southeast to northwest.