| The Western HeNan Area locates in the south of North China Platform,where proterozoic strata developed better.Owed to its stable deposits,thickness and complete outcrop,it has become one of the typical areas for Precambrian strata research.This paper focuses on RuYang group in Western HeNan Area and emphasizes the geological characteristics of Beidajian Formation.Ruyang group,as the first sedimentary stratum developed from volcanic formation of the three armed rift system in North China Platform in Proterozoic era,includes YuMengshan Formation,BaiCaoping Formation,BeiDajian Formation,CuiZhuang Formation,SanJiaotang Formation and LuoYukou Formation.Because of its large thickness and limited distribution,BingMagou group is included in some areas.Three profiles,LuShan,RuYang and MianChi,are selected for research.Another section from YongJi ShuiYougou in the south of ShanXi is chosen for comparing.The writer takes outcrop as research object,petrology,sedimentology and sequence stratigraphy as theory basis,previous research results as references to analyze the filed materials,then classifies the RuYang Group into 11 third-grade sequences and 4 second-grade sequences.The conclusion is the sea moved towards the north which is proved by the Ruyang Group sedimentary basin in taphrogenic trough lying on Shanxi,Henan and Shaanxi,and it forms a suit of sedimentary sequence that overlaps northward whose northern extremity extends to the Taihang Moutain in Shanxi and connects with Yanliao Trough.BeiDajian Formation forms a parallel unconformity with the stromatolite dolomite of the forth member of Gaoyuzhuang Formation.Thus,Beidajian Formation can be compared with Changgou Formation of the Jixian profile in Tianjin which agrees with WuTieshan's explanation on RuYang Group's age.The change that sandstone at the bottom and carbonate at the top layers suggests the deposit environment changed from muddy water to a clean one,which forecasts the RuYang Group's sedimentary environment will change. |
PDF Full Text Request