Geochemical Characteristics Of Borehole Sediments And Paleoclimatic Evolution Since The Middle Pleistocene In Rongcheng County,Hebei Province,China

Regional climate evolution is an important part of global change research.By restoring and reconstructing geological history,studying its evolution law and impact mechanism,it can scientifically and effectively predict future climate evolution and guide human beings to live in harmony with nature.In 2017,the Tianjin Geological Survey of the China Geological Survey and the Bureau of Geology and Mineral Exploration and Development of Hebei Province initiated the implementation of the engineering geological survey of the Xiong'an New District.In this paper,the G7159,G7160,and G7161 boreholes in the geological survey are selected.The main conclusions and achievements are as follows: the changes in the unit elements,element combinations,element ratios,and the relationship with the sediments in the history of the Rongcheng paleoenvironment since the Pleistocene.:(1)On-site observation and cataloging of cores,and in-situ measurement of three borehole cores using Portable X-Ray Fluorescent Spectroscopy(PXRF),including Ag,As,Au,Ba,Ca,Cd,Co,Cr,Cs,Cu,Fe,Hg,K,Mn,Mo,Ni,Pb,Pd,Rb,S,Sb,Sc,Se,Sn,Te,Th,Ti,U,V Component data of 33 elements such as W,Zn,and Zr.Based on the comparison with the laboratory analysis results and the reliability of the PXRF data,the data was screened in combination with the readout rate.(2)The vertical distribution characteristics of 11 main trace elements were analyzed.It was found that the high values of Fe,Ti,V,Rb,Zn and K were mainly found in fine particles such as clay,silty clay and silt.The elements such as Sr and Ba are mainly concentrated in coarse sediments such as coarse sand,medium sand,fine sand and silt.(3)Through the multivariate analysis method,Sr,Ba and other elements combinations reflecting coarse grain deposits,Rb,Fe,Ti,V,Zn and other element combinations reflecting fine grain deposits,and Mn,Ca,Zr,etc.A combination of elements with complex changes and no obvious rules.(4)Using the single element(Fe,Ti,V,Rb,Zn,K,Sr,Ba)and the element ratio(Rb/Sr)to restore the climate evolution since the middle Pleistocene in Rongcheng County,respectively,and obtained from the predecessors The results of the comparison show that the element is more reflective than the(Rb/Sr)climate change in the region.Finally,the climate change since the mid-Pleistocene is divided into eight stages(dry cold-warm wet-dry cold-warm wet-dry cold-warm wet-dry cold-warm and humid).(5)Using PXRF to measure sediment element content data in situ,it has certain application potential in paleo-climate rapid reduction.