The Sequence Stratigraphy And Dolomite Genesis Of Cambrian In Beijing Area

Beijing is located in the northern of China.The geological phenomenon of Cambrian outcropping is abundant.It is one of the classic geological sections in North China,but the study of the Cambrian dolomite in Beijing is relatively lack.Through outcrop observation and thin section identification,this study divides the Cambrian carbonate platform in Beijing into five sedimentary subfacies: tidal flat,limited platform,bank,open platform and shale shelf,and Cambrian carbonate platform is divided into 1 second Sequence and 9 third sequences,which are divided into SQ1(Changping Formation),SQ2(Mantou Formation),and SQ3(Maozhuang Formation),SQ4(Xuzhuang Formation),SQ5-SQ6(Zhangxia Formation,Gushan Formation),SQ7(Changshan Formation)and SQ8-SQ9(Fengshan Formation),each third sequence is composed of transgressive and high system tract.Through field outcrop observation,thin section identification,X-ray diffraction,carbon and oxygen isotopes,cathodoluminescence and inclusions,it is believed that the Cambrian dolomite in this area is caused by the dolomite of the evaporative pumping and seepage reflex dolomitization.The relationship between the genetic types and sequence stratigraphy of the dolomite in this area is explored,and the model of dolomitization in the sequence framework is established,that is,the late development of the evaporation pumping and seepage reflex dolomitization.This study will help to the further research on the relationship between Cambrian sequence stratigraphy and dolomitization in North China,and serve as reference for the study of dolomite of the same kind.