Stratigraphic Subdivision And Sedimentary Facies Analysis Of Quaternary In Xinxiang City

The study area of Xinxiang locating in the hinterland of the Central Plain, is to the north of the middle and lower reaches of the Yellow River. It is in the transition zone between the piedmont fault zone of Taihang Mountain and the Estern Plain. The special position affects the geological environment of the study area. Both of the fault activity and the evolution of the Yellow River lead to the deposition environment of Xinxiang. Therefore,it is important to have a correct understanding of the Quaternary sedimentary environment of the disaster prevention and the urban construction.Based on the program of detection of city active fault in Xinxiang, stratigraphical classification and correlation have been done by a large number of test samples. By the analysis of sedimentary facies and grain-size characteristics, the article analysis the reason of sedimentary discontinuity reflected by the changes of sedimentary facies in studsy area.In addition,this paper discussed that the change of sedimentary environment and the impact of the neotectonic movement during Quaternary in the area.The results are as follows: 1 Based on a study of lithostratigraphy and chronostratigraphy of the drill core,Quaternary in Xinxiang City is subdivided into the Holocene Puyang Formation(Qhp),upper Pleistocene Huixingzhen Formation(Qp3h),middle Pleistocene Shanxian Formation(Qp2s),and lower Pleistocene Sanmenxia Formation(Qp1s). 2 There are three kinds of sedimentary facies in the study area, including alluvial facies,fluvial facies and delta facies. And the sedimentary environment of Xinxiang is affects by the evolution of the Yellow River. For example, the sand seam in the north area is much thicker than that in the sourth area. And the channel facies are more obvious. So the north area of Xinxiang is much closer to the Yellow River. 3 The evolution of paleogeography in study area reflects that the alluvial fan in the Yellow River expanded to the east. And courses of the Yellow River migrated from north to south along with the changes of the terrain. 4 By comparing the borehole data with other data collected, it shows that the stratum in the early period of the Quaternary is less stable than the one in the late period. This might because the deposition in study area is realated to the the characteristics of the neotectonic movement.