西藏边坝-洛隆地区下白垩统边坝组的建立及其意义

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

边坝组是新建立的一个岩石地层单位。该组与下伏下白垩统多尼组呈整合接触,与上覆上白垩统宗给组呈角度不整合接触关系。岩性以紫红色深灰色粉砂质泥岩夹薄层白云岩为特征,深灰色薄层粉砂质泥岩中产丰富的双壳类化石Trigonioides(Diversitrigonioides)xizangensis-Pleuromya spitiensis组合。边坝组的建立完善了该地区下白垩统地层系统,对冈底斯北缘弧后前陆盆地白垩纪岩相古地理研究具有重要意义。

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 beck-arc foreland basins on the northern margin of the Gangdise zone.