Sedimentary geology of the Triassic-Paleogene strata in the Shading and Rongbo regions, Xizang

The Triassic-Paleogene lithostratigraphic units in the Shading and Rongbo regions, Xizang mainly consist of the Quehala Group (T₃), Xihu Group (J_1-2), Lhagongtang Formation (J_2-3), Duoni Formation (K₁), Jingzhushan Formation" (K₂) and Niubao Formation (F_2-3). The sedimentary facies show a depositional evolution from the deep-water sediments through shallow-water sediments to the continental sediments, including alluvial fan, river, lake, delta (tide-dominated), barrier coast, shallow sea, deep sea and volcanic debris flow deposits. The palaeogeographic research indicate that the palaeogeographic outline of the study area recorded the evolution from a sedimentary basin in which the shallow-water carbonate platform sediments and deep-water terrigenous elastic submarine fan developed from southeast to northwest and northeast during the Late Triassic through a submarine sheet-like model composed of deep-water sandy turbidite and fine-gained turbidite during the Early Jurassic to a terrigenous elastic barrier coast during the Middle and Late Jurassic and finally to the coal-bearing delta sediments during the Late Cretaceous.