Junggar Basin, Xinjiang Northern Margin Of The Tertiary Magnetostratigraphy

Dating the absolute time of mammalian fossils in the stratum is the tendency of stratigraphic research at present, identical research have been developed well in North American land facies and Europe sea facies. Since 1980s, dating studies such as magnetostratigraphy and isotope-stratigraphy have been carried out in many localities in China. For its coherence with global change and comparable with time scale, palaeomagnetism is mostly used by paleontologist to do the research in the Cenozoic land deposits.In this paper, we have researched 2 major sections and 2 assistant sections with mammalian fossils in north Junggar Basin by the means of magnetostratigraphy, analyzed its x-T curves and remnant magnetism, and thought that the hematite and magnetite were the main magnetic mineral and were the sign of hot climate. By virtue of main vectors analyzing, we have got the characteristic remnant magnetism of all the samples.Associated with some evidences from mammalian fossils, we correlate the geomagnetic results with the GPTS(Geomagnetic Polarity Time Scale). Tieersihabahe section (Ulungur district) had recorded the polarities C5Cn3n~C8r (26.6-16.6 Ma), from late Oligocene to early of middle Miocene, including the Tieersihabahe Formation (ie. 26.8-23.8 Ma, Late Oligocene), Suosuoquan Formation(23.8~18.5Ma, early Miocene), Halamagai Formation(23.8~18.5Ma, early Miocene), Kekemaideng Formation(<16.4 Ma, middle Miocene). The border of Oligocene and Miocene was in the continuous sediments between Tieersihabahe Fonnation and Suosuoquan Fonnation (23.8 Ma). The ages of the two faunas of late Oligocene in the bottom of the section were 26Ma and 25.5Ma. The short assistant section of Botamoyin was in the border of Oligocene and Miocene and had recorded the polarities C6r~C6Br (24.7-23.2Ma).Keziletuogayi section in the Burqin district had recorded the polarities C20n~C10r (43-13 Ma), from middle Eocene to early Oligocene, including the border of Eocene and Oligocene (33.6 Ma). The age of the mammalian fossils of lateEocene in the section was 34Ma.