Quaternary Sedimentary Environment Documented by Borehole Stratigraphical Records in Eastern Jianghan Basin

In order to explore the further relationship among the Quaternary neotectonic movement, climate change and sedimentary response in the Jianghan basin, a systematic study of lithology, geochronology and sedimentology was carried out using typical Quaternary boreholes in the Mianyang depression in the eastern part of the basin. A comparable sequence of Quaternary borehole strata was first established in the deposition center of the eastern Jianghan basin. A complete sedimentary evolution history of the river facies, alternation of river and lacustrine facies, lacustrine facies, alternation of river and lacustrine facies, lacustrine facies and floodplain facies was reconstructed in turn in the past 140 ka based on lithology, grain size and magnetic fabric analysis. The integrated analysis of regional tectonic movement, sedimentary evolution and climatic change shows that there occurred 3 periods of lacustrine deposition including the transition of Qp₂/Qp₁, Qp₃, and mid-late Holocene (ancient Yunmeng lakes), respectively. Our results demonstrate that the development of paleolake since the MIS3 is related to the coupling of neotectonic subsidence and extremely strong summer monsoon. The unique environment of lacustrine deposition provides important material conditions for the formation of high-arsenic groundwater in the basin. This study not only provides reliable basic data for the stratigraphic division and correlation of Quaternary boreholes in the Jianghan basin, but also provides an important reference for underground resources investigation and environmental planning and protection.