Environmental Characteristics And Paleoclimate Evolution Of Pucheng Shiyang In Weinan

The dust accumulation of loess is rich in continental paleoclimate and paleoenvironmental evolution information,which plays an important role in quaternary research.Among them,the weinan region where the study area ZK19 is located is located in the south margin of the typical loess plateau,and is located in the interaction zone of east Asian winter and summer monsoon,and has developed deep dust deposition and fluvial facies deposition.Therefore,the study on the environmental evolution law of this area is very sensitive and representative in the study of paleoenvironment.Geological survey geological survey projects in China based on the study of Chinese loess deposition record of climate change as the backing,weinan in pucheng shiyang drilling(ZK19)loess-paleosol sedimentary sequence strata as the research object,using the sedimentary stratigraphy,magnetostratigraphy,contrast and other ways to scale formation s framework,through climate proxies,such as granularity,further explore the environmental implications of sedimentary records.The main insights are as follows:The total footage of pucheng borehole in weinan is 128.91 meters,the upper part of which is 61.33 meters,and the particle size distribution is uniform.The probability accumulation curve is a fine two-section type,which is a typical feature of aeolian sedimentary composition,and is represented by 8 loess-paleosolm cycles(L9 / S8-L1 / S0).Fluvial facies began to appear below 61.33 meters,and the age was 0.927 Ma-2.611 Ma.The change of grain size in the lower part is more complex,and the content of each grain grade changes in high frequency and large amplitude.In particular,the average content of > 63 m particles was relatively large,during which there were about 5 obvious large range fluctuations,and the sand content even exceeded 50%.The location of the borehole was far from the desert,which proved that the lower part of the borehole was greatly affected by the running water of nearby luo river.Combined with the core description and other data such as magnetic susceptibility,it can be seen that there are 5 obvious silt-sand-silty clay sedimentary cycles,which reflect that the environment at that time belongs to the cold and warm alternations,and conform to the quaternary whole in the cold and dry conditions,a small range of cold and warm fluctuations.However,due to the limited data,the exact age,duration and magnitude of the flood still need to be further studied and discussed.