Comparison Of Cenozoic Strata Between Qianhe Basin And Weihe Basin

The Weihe Basin is located at the junction of the southern margin of Ordos and the Qinling orogenic belt.It is the western part of the Qinhuang earthquake belt in China.It has been studied for more than a hundred years and has achieved a lot of results.Nowadays,the formation and evolution of the Weihe Basin are basically unified.It is known that the Weihe River began to rupture in the Eocene,and the river-lake-phase strata were deposited in the early period.To the Pliocene,the water body continued to shrink until it withdrew and began to accept wind-sedimentary sediments.At present,the research on the Weihe Basin,whether it is the wilderness section or the borehole,is concentrated in the east of Xi'an and the central part of the Weihe Basin.For the western part of the Quaternary system,only a small amount of hydrological drilling is involved,and the degree of research is low.Therefore,through the study of regional geological mapping,measured sections,and borehole data,this paper intends to clarify the Cenozoic strata in the western Qianhe-Rihe Basin,and to clarify the relationship between the Weihe Basin and the Qianhe Basin,and to carry out the Weihe Basin and Qianhe River.The comparison of the Cenozoic stratigraphy in the basin further delineated the boundary of the Weihe Basin,which has certain reference significance for the later study of the boundary of the Weihe Basin.The main points are as follows:1.Clarify the Qianhe-Xihe Basin in the western part of the Weihe Basin from the old to the new: the Upper Miocene Gansu Group,the Pliocene Sanmen Formation,the Lower Pleistocene Wucheng Formation,the Middle Pleistocene Lishi Formation,and the Upper Pleistocene Malan group,new system.2.The Qianhe Basin can be integrated with the strata of the western Weihe Basin(Fengxiang area),indicating that both the Qianhe Basin and the western part of the Weihe Basin are co-developed and evolved.The Upper Miocene and the Qianhe Basin sedimentary Gansu Group can be Comparison of the rivers in the Weihe Basin.The Pliocene accepted the sedimentation of the ancient Sanmen Lake.By the end of the Pliocene,the Sanmen Lake waters shrank,the Qianhe-Weihe Basin began to shrink,and then began to accept the Quaternary loess-paleosol deposition.Because the Sanmen Lake sedimentary center is in the middle and eastern part of the Weihe Basin,the Sanmen Lake in the western part of the Qianhe-Rihe Basin was the first to die,and the Loess-paleosol sedimentation was accepted in the Lower Pleistocene,while the basin continued to the Lower Pleistocene,and then began to accept Quaternary loess deposits.3.From the east to the west of the Weihe Basin,at the beginning of the Eocene,the Eocene Red River Formation,the Oligocene Bailuyu Formation,the Miocene Lengshuigou Formation,the Yanjia Village Formation,and the Late The Miocene Luhe Formation,the Late Miocene-Upper Xinhuan Youhe Formation,the Upper Pliocene Sanmen Formation,the Middle Renewal System,the Upper Rehabilitation Ganxian Formation and the Holocene Banpo Formation,within the basin In the center of several depressions,a thick layer is generally deposited.In the whole,the Cenozoic boundary of the middle and eastern sections of the Weihe Basin is relatively fully developed,and only the Neogene and the Quaternary are developed in the western part,and the sedimentary thickness is small.The western part of the Qianhe-weihe Basin is missing the Eocene-late Miocene strata in the eastern part of Xi'an,indicating that the western part of the Qianhe-weihe Basin continued to rise during this period and was subjected to denudation.