A Study On The Sedimentary Character And Paleogeography Of The Neoproterozoic Era In The West Of Henan Province

The West of Henan province locate at the south continental margin of the North China platform. The Neoproterozoic Era was 1000Ma– 540Ma years ago. The Neoproterozoic Era consists of three periods: Qingbaikou Period, Southern China Period and Sinian Period.This paper mainly deals with stratigraphic district, stratigraphic units distribution and correlation, the depositional characteristics and the depositional environment, the sedimentary paleogeographic evolution and tectonic background of Neoproterozoic. Futhermore, the tectonic– paleogeographic evolution characteristic of Neoproterozoic Era in the West of Henan province was discussed. The Neoproterozoic erathem of west of Henan province of mainly divided into three stratigraphic districts: the Mianchi– Queshan district, Song– Qi district and the Qinling– Luanchuan district. All of them was mainly a set of assembledge of terrigenous clastics carbonate rocks . The main conclusitions of the paper are as follows:Deposition of Neoproterozoic in Henan province was mainly occered in the southwest of Henan Province, The eastern area of Henan was old land which providing terrigenous clastics. The ancient geography outline was that the north was high and the south was low. And from north to south, the sea water was deeper gradually, the deep water deposition was occurred at the south of the Luonan– Luanchuan– Queshan fault zone, namely Qinling area. The transgression direction is from south to north, the direction of the sediments transposition was from north and east to south and west. The depositional environment of Neoproterozoic in the west of Henan province were mainly coastal to neritic environment.Sedimentary facies types in the area mainly involve beach facies, carbonate shore facies, limited carbonate bench terrace facies, neritic facies, continental glacial facies and glaciomarine facies. The Neoproterozoic strata's structure and the ingredient maturity of the clastic rock are high, the carbonate rocks grow abundant stromatolites. So the tectonic setting of the area should be stable type deposition in the passive continental margin shelf.The transgression scope was the greatest in the early Qingbaikou epoch in which Cuizhuang group was deposited, and the entire Henan province was nearly covered by sea water. Luoquan formation is only unit which was preserved as continental depositional environment in Neoproterozoic Era. Its depositional environments were moraine subfacies of the continental glacial facies and shallow water glaciomarine subfacies of the glaciomarine facies. The strata thickness of Neoproterozoic Era in Lushi and Luanchuan area is larger, which indicated that activity of earth crast in that area is stronger than that of other area, and which favorable to the accumulation of mineral deposit. Dahongkou formation of early Southern China epoch is alkali– trachyte volcanic eruption which is because of riffting of the passive continental margin. Neoproterozoic in the West of Henan province , specially the later period, had the environment of deposition turbulence to be changeable, accompanied by the volcanic eruption, indicated that the earth's crust activity had enhanced.