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洞庭盆地的形成与演化对长江中游乃至中国中部的地质环境变迁具有重要意义,但区内的第四纪年代地层研究一直不足.以洞庭盆地沉积中心——沅江凹陷的典型钻孔S3-7孔(孔深255.1m)为研究对象,在详细的沉积物岩性描述和岩石地层划分的基础上,系统地进行了古地磁、ESR、AMS~(14)C等测试,并建立了S3-7孔的年代地层序列.通过与其他两口典型钻孔的对比分析,初步建立了研究区的区域年代地层格架,结果显示洞庭盆地沉积中心下更新统底界位于各钻孔底部240~300m,中更新统底界位于90~95m,上更新统底界位于28~50m,全新统底界位于1.5~3.1m.平均沉积速率和分段线性方程的结果表明洞庭盆地覆盖第四纪区岩石地层单位的时代为:华田组的地质年龄为2 590~1 600ka BP,湘阴组的地质年龄为1 600~920ka BP,洞庭湖组的地质年龄为920~120ka BP,安乡组的地质年龄为120~11ka BP,全新统的地质年龄为11ka BP至今.
The formation and evolution of the Dongting Basin are of great significance to the geological environment changes in the middle reaches of the Yangtze River and even in central China, but the study of the Quaternary strata in the area has been inadequate.Taking the typical borehole S3-7 in the sedimentary center of Dongting Basin-Yuanjiang Sag (Hole depth 255.1m) as the research object. Based on the detailed description of sedimentary lithology and lithostratigraphic division, we systematically conducted the tests of paleomagnetic, ESR, AMS ~ (14) C, and established S3-7 The results show that the bottom of the Pleistocene in the sedimentary center of Dongting Basin is located at 240-300m at the bottom of each borehole The Pleistocene basement is located at 90-95 m, the upper Pleistocene lies at 28-50 m, and the Holocene bottom lies at 1.5-3.1 m. The results of the average sedimentation rate and the piecewise linear equation show that the Dongting Basin covers the Quaternary Quaternary lithostratigraphic unit The age of the Huatian Formation is 2 590 ~ 1 600 ka BP, the geological age of the Xiangyin Formation is 1 600 ~ 920 ka BP, the geological age of the Dongting Lake Formation is 920 ~ 120 ka BP, and the geologic age of the Anxiang Formation is 120 ~ 11ka BP, Geological age of Holocene 11ka BP so far.