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A number of fossil mammals have been found in the very thick Cenozoic stratigraphy of the Guide Basin in the northeastern margin of the Tibetan Plateau.Some of these are of great significance in mammal evolution and stratigraphic correla-tion on and around the Tibetan Plateau and North China.However,the chronology of these mamals is poorly con-strained.Dating of the mammals will not only place precise age constraints on the mammals,but also provide much inlormation on the related stratigraphy that records the uplift process of the Tibetan Plateau.Detailed paleomagnetism of the upper part of the Cenozoic stratigraphy at He’erjia and Lajigai north of Guide County has revealed magnetic chrons that can be correlated to Ganss and 3An chrons.determining the section spanning about 3.16.5 Ma and the first.second and third layers of fossil mammals at about 5.25,5.1 and 4.4 Ma,respectively.Ages of the significant genus Gazella kueitensis and the Chinese elephant Anancus sinensis are firstly constrained at about 5.25 MaBP and 4.4 Ma,respectively.The mammalian evolution and the associated increase in coarse sediments and sedimentation rate may suggest that the northeastern Tibetan Plateau was uplifted rapidly at that time,and the eastern Tibetan Plateau with its neighboring regions was not high enough to stop mammal exchange between the northern and southern sides of the Tibetan Piateau.
A number of fossil mammals have been found in the very thick Cenozoic stratigraphy of the Guide Basin in the northeastern margin of the Tibetan Plateau. Home of these are of great significance in mammal evolution and stratigraphic correla-tion on and around the Tibetan Plateau and North China.However, the chronology of these mamals is poorly con- strained. Dating of the mammals will not only only precise age constraints on the mammals, but also provide inlormation on the related stratigraphy that records the uplift process of the Tibetan Plateau. Detailed paleomagnetism of the upper part of the Cenozoic stratigraphy at He’erjia and Lajigai north of Guide County has revealed magnetic chrons that can be correlated to Ganss and 3An chrons. stermining the section spanning about 3.16.5 Ma and the first. second and third layers of fossil mammals at about 5.25, 5.1 and 4.4 Ma, respectively. Ages of the significant genus Gazella kueitensis and the Chinese elephant Anancus sinensis are first c onstrained at about 5.25 MaBP and 4.4 Ma, respectively. mammalian evolution and the associated increase in coarse sediments and sedimentation rate may suggest that the northeastern Tibetan Plateau was uplifted rapidly at that time, and the eastern Tibetan Plateau with its neighboring regions was not high enough to stop mammal exchange between the northern and southern sides of the Tibetan Piateau