西藏阿里札达盆地上新世—早更新世河湖相地层年代学研究

Chronology of Pliocene-early Pleistocene lacustrine strata in the Zanda basin, Ngari area, Tibet

通过对西藏阿里札达盆地河湖相地层实测剖面中的古地磁、ESR样品的测试分析,确定了札达盆地新近纪上新世—第四纪早更新世沉积地层的时间序列。测试结果表明:从剖面自下而上所做的古地磁测年数据为5.41～1.60Ma;而ESR测年数据为5.4～1.36Ma,两者大体吻合。根据古地磁、ESR测年结果,可将该套河湖相地层的时序划分为:上新世托林组(N21t)的形成时间为5.41～4.20Ma、上新世古格组(N22g)为4.20～2.57Ma、早更新世香孜组(Qp1-1x)为2.57～1.36Ma。为青藏高原新近纪上新世—第四纪早更新世地层时间序列标尺的建立,以及上新世、早更新世河湖相地层的划分与对比提供了重要依据。

Neogene Pliocene-Quaternary early Pleistocene strata have been determined through analyses of paleomagnetic and ESR samples from a section of fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet. The analytic results show that： the paleomagnetic ages obtained in ascending order from the section are 5.41-1.60 Ma, while the ESR ages are 5.40-1.36 Ma. The two analytic resuks roughly coincide. According to the results of the paleomagnetic and ESR datings, the time series of the fluvio-lacustrine strata is as follows： the Pliocene Tolin Formation （N2^1t） formed at 5.41-4.20 Ma, the Pliocene Guge Formation （N2^2g） formed at 4.20-2.57 Ma and the Quaternary early Pleistocene Qangze Formation （Qp^1-1x） formed at 2.57-1.36 Ma. This study provides an important basis for the establishment of the time scale of the Neogene Pliocene-Quaternary early Pleistocene strata on the Qinghai-Tibet Plateau and division and correlation of the Neogene Pliocene-Quaternary early Pleistocene fluvio-lacustrine strata.