罗布泊地区第四纪岩石地层、磁性地层和气候地层

THE LITHOSTRATIGRAPHY, MAGNETOSTRATIGRAPHY, AND CLIMATOSTRATIGRAPHY IN THE LOP NUR REGION, XINJIANG

罗布泊地区的AK1孔,是目前为止该区唯一的、最深的钻孔,深465.55m。依据AK1孔的岩性特征、热释光年龄、古地磁极性倒转、磁化率变化和Fe2O3含量的研究,将该地区第四纪地层划分如下:全新世为灰色—浅灰绿色色系,与晚更新世的界线划在深8.80m处,年龄值为11.5kaBP;晚更新世为杂色色系,与中更新世的界线在牙买加反向极性亚带的底界面上,深66.25m,年龄值为0.20MaBP;中更新世为褐黄色—土黄色色系,与早更新世的界线划在布容正向极性带—松山反向极性带的界面上,深235.00m,年龄值为0.73MaBP;早更新世为灰色色系,与上新世的界线在松山反向极性带—高斯正向极性带的界面上,357.50m深,年龄值为2.48MaBP;上新世为土黄色与灰色交替色系,顶部为厚8.78m的土黄色粘土层,与下更新世底部厚25.27m的灰色粗砂和含砾粗砂层相接,界限清晰。本区第四纪岩石地层、磁性地层和气候地层的底界,完全一致。因此,它是一条具有全球等时性的界线,可用以与世界其他地区的第四纪地层进行对比。

The AK1 Borehole is the deepest drill hole in the Lop Nur Region, Xinjiang, reaching a depth of 465.55m. Based on the lithologic characters, the palaeomagnetic polarity reversement, the thermoluminescent dating, the magnetic susceptibility fluctuation, and the changes in the contents of the Fe2O3, the Quaternary strata can be divided as follows： the Holocene is grey to light grey green colour tones, the Holocene-upper Pleistocene boundary is at 8.80m, 11.5kaBP; the upper Pleistocene is variegated colour tones, the upper Pleistocene-middle Pleistocene boundary is placed at the base of the Jamaica Reversed Polarity subzone, at 66.25m depth, 0.20MaBP; the middle Pleistocene is brown yellow-brownish yellow colour tones, the middle Pleistocene-lower Pleistocene boundary is drawn between the Brunhes Normal Polarity Zone and the Matuyama Reversed Polarity Zone, at 235.00m depth, 0.73MaBP; the colour tones of the lower Pleistocene is grey, the lower Pleistocene-Pliocene boundary is put between the Matuyama Reversed Polarity Zone and the Gauss Normal Polarity Zone, at 357.50m depth, 2.48MaBP; the Pliocene colour tones is brownish yellow and grey alternating, there is a layer of brownish yellow clay, 8.78m in thickness at the top of the Pliocene, it links with the bed of grey coarse sand and the coarse sand containing gravel, 25.27m in thickness, at the bottom of the lower Pleistocene, the boundary between the lower Pleistocene and Pliocene is very distinct. These basal boundaries of the Quaternary lithostratigraphy, magnetostratigraphy, and climatostratigraphy in this region are in complete agreement with each other. Therefore, it is an isochronous boundary in the whole world and may be used for the international stratigraphic correlation of the Quaternary.