摘要
The Tertiary deposits of the Yongdeng section, the Lanzhou Basin were studied by means of magnetostrati-graphy. The magnetostratigraphic sequences from Paleocene to Miocene were established, and the time scale for the corresponding stratigraphy and mammalian faunas was also established by referring to their correlation to the GPTS of BKSA95 (The geomagnetic polarity time scale which was thoroughly revised and updated by Berggreen et al. in 1995). In the end the paleoenvironmental records and their relationship with the uplifting of the Tibetan Plateau were discussed. The results are as follows. The top boundary of the Xiliugou Formation is dated to be 51 Ma, i.e. Eocene. TheYehucheng Formation covers the time span of 51-31.5 Ma, i.e. from late Early Eocene to early Early Oligocene. The Xianshuihe Formation covers the time span of 31.5-15 Ma, i.e. from Early Oligocene to Middle Miocene. The lower member of the Xianshuihe Formation spans from 31.5 to 20.0 Ma, i.e. from Early Oligocene to early Early
The Tertiary deposits of the Yongdeng section, the Lanzhou Basin were studied by means of magnetostratigraphy. The magnetostratigraphic sequences from Paleocene to Miocene mere established, and the time scale for the corresponding stratigraphy and mammalian faunas was also established by referring to their correlation to the GPTS of BKSA95 (The geomagnetic polarity time scale which was thoroughly revised and updated by Berggreen et al, in 1995). In the end the paleoenvironmental records and their relationship with the uplifting of the Tibetan Plateau were dis cussed. The results are as follows. The top boundary of the Xiliugou Formation is dated to be 51 Ma, i.e. Eocene. The Yehucheng Formation covers the time span of 51-31.5 Ma, i.e, from late Early Eocene to early Early Oligocene. The Xianshuihe Formation covers the time span of 31.5-15 Ma, i.e. from Early Oligocene to Middle Miocene. The lower member of the Xianshnihe Formation spans from 31.5 to 20.0 Ma, i.e. from Early Oligocene to early Early Miocene. The middle member is from 20.0 to 16.5 Ma, i.e. in the middle Early Miocene.
基金
This work was supported by the National Natural Science Foundation of China (Grant Nos. 49472083, 49572133 and 49972004)
and the Institute Fund of ETH, Switzerland.
