Stratigraphic Subdivision and Correlation of the Carboniferous Benxi Formation in Henan Province Using Paleontology

Henan Province is the second largest aluminum-producing province in China,where the bauxite occurs in the Carboniferous Benxi Formation.However,stratigraphic division of the Benxi Formation remains controversial for a long time.This paper presents a comprehensive analysis about lithological association,zoolite and plant fossil assemblage and sporo-pollen assemblage..The conclusions are as follows.(1) The Benxi Formation in Hebi of North Henan Province is a lithostratigraphic unit that spans across the Huashiban stage and Dalat stage.(2) The upper limit of the Benxi Formation in Jiaozuo City is near the upper limit of the Dala stage.(3) The Benxi Formation in West Henan Province is a lithstratigraphic unit cutting across the Huashiban stage,Dalat stage and Maping stage.(4) The biological group in the Benxi Formation of the North Songqi area is the product of the late Carboniferous epoch.(5) The biological group in the Benxi Formation of the central Songqi area is later than that in the north Songqi area.To sum up,the aluminiferous Benxi Formation in Henan Province is an obviously diachronous and typical lithostratigraphic unit.According to the current subdivision method of Carboniferous epoch,it formed both in the early and middle stage of the late Carboniferous.It is a lithostratigraphic assembly with homophase but different periods.