Establishment and significance of the Lower Cretaceous Banbar Formation in the Banbar-Lhorong region, Xizang

The Banbar Formation is a newly established lithostratigraphic unit in the Banbar-Lhorong region, eastern Xizang. It is in conformable contact with the underlying Lower Cretaceous Duoni Formation and in angular unconformable contact with the overlying Upper Cretaceous Zonggei Formation. The lithology is characterized by the purplish red and dark grey silty mudstone intercalated with thin-bedded dolostone. Abundant bivalve fossils Trigonioides (Diversitrigonioides) xizangensis-Pleuromya spitiensis assemblage occurs in the dark grey silty mudstone.The establishment of the Banbar Formation facilitates the improvement of the Lower Cretaceous stratigraphic systems in this region and has important implications for the examination of the Cretaceous sedimentary facies and palaeogeography in the back-arc foreland basins on the northern margin of the Gangdise zone.