The evolution of the depositional environment along the Gaozhuang Formation Section in Yushe Basin, Shanxi Province

Abstract：Based on field geological survey and an analysis of such environmental indicators as grain sizes, magnetic susceptibility and carbonate content in combination with ESR age data provided by previous researchers, this paper discusses the variation of the depositional environment in the Gaozhuang Formation during the early Pliocene. The analytical results show that, in the early Pliocene (5.25～3.16 Ma), the Yushe Basin was mainly warm and wet in climate, with unsteady short-term drought, and its paleolake underwent three seasonal changes of the water level from steady increase to wavy increase. During 5.25～4.50 Ma, the basin evolved into the first strong rift stage, its paleolake underwent a change of its water level from steady increase to wavy increase, forming Taoyang Member strata. During 4.44～3.89 Ma, the basin evolved into the steady rift stage, its paleolake underwent a change of its water level from steady stabilization to wavy increase, forming Nanzhuanggou Member strata. During 3.81～3.16Ma, the basin evolved into the second strong rift stage, its paleolake underwent a change of its water level from steady increase to wavy balance, forming Culiugou Member strata, and the extreme dry climate occurred in 3.50～3.33Ma, after which the climate became warm and wet.