Characteristics of grain size and magnetic susceptibility of Quaternary sediments in southeastern Changhu Lake,Jianghan Basin,and their environmental significance
Based on the analysis of grain size and magnetic susceptibility of ZK06 borehole in eastern Hunan,Jianghan Basin,the characteristics of grain size and mass magnetic susceptibility,hydrodynamic conditions and paleoclimate evolu-tion process of sediments in the study area since Quaternary were discussed.The study shows that the Quaternary environ-ment in eastern Hunan can be divided into five evolution stages:Stage Ⅰ(Early Pleistocene,depth of 34.9 to 51.15 m)was dominated by fluvial deposits,accompanied by inter-river depression sedimentary environment.The mass susceptibili-ty value was low and stable,and the climate was mild and humid,corresponding to the interglacial period after the fourth glacial period.Stage Ⅱ(Pleistocene,depth of 18.9 to 34.9 m),lake environment deposition,biological richness,low mass susceptibility value,occasional large fluctuations,the climate was generally mild and humid,corresponding to the in-terglacial period after the third glacial period.Stage Ⅲ(Late Pleistocene,depth of 14.4 to 18.9 m),the inter-river de-pression environment was deposited,the mass susceptibility value was generally stable and low,the hydrodynamic condi-tions were weak,and the climate changed from mild and humid to cold and dry,corresponding to the last interglacial period and the last glacial period.Stage Ⅳ(Early Holocene,depth of 5.45 to 14.4 m,lacustrine sedimentary environment,stable mass magnetic susceptibility remained at a low level,and hydrodynamic conditions were enhanced,indicating that the cli-mate began to change from cold to warm and entered the post-glacial period.Stage Ⅴ(Late Holocene,depth of 0 to 5.45 m),the lake and marsh sedimentary environment,the mass magnetic susceptibility value increased significantly,the hy-drodynamic conditions were weak,the climate was warm and humid,corresponding to the postglacial period.The results provide a new basis for the study of paleoclimate evolution in Jianghan Basin.
Quaternary sedimentsJianghan Basingrain size characteristicsmagnetic susceptibility characteristicsthe ancient environment
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