Tectonic uplift of mountains in northwestern Junggar since late cenozoic: evidences from sedimentology and magnetic fabric in Heshituoluogai basin

Through the results of detailed sedimentological and magnetic fabric study, on the Heshituoluogai basin, northwestern Junggar, we discussed the tectonic evolution since 7 Ma ago in the northwestern Junggar. The Baiyanghe section can be divided into Taxihe Formation, Dushanzi Formation and Xiyu Formation from bottom to up, corresponding to the lacustrine facies, fan delta facies and gravelly braided river facies. Paleocurrent and provenance analysis shows that the provenance of the section comes from the northern mountains nearby the basin. On the basis of the sedimentterological and magnetic fabric results, we divided the tectonic-sedimentary evolution of northwestern Junggar into three stages since 7 Ma ago: I(6.80-3.50 Ma), lacustrine facies, lowest magnetic susceptibility and magnetic fabric parameters with small changes, indicating a stable tectonic environment, small topographic elevation difference or far provenance area; II(3.50-2.58 Ma), fan delta facies, significant increase of the sedimentation rate, magnetic fabric parameters and magnetic susceptibility all suggest that the northwestern Junggar mountains underwent intense tectonic uplift; Ⅲ(<2.58 Ma), gravelly braided river facies, magnetic fabric parameters and magnetic susceptibility increases further, which coused by tectonic uplift and climate change together. The tectonic uplift of the northwestern Junggar mountains occured at 3.50 Ma is almost synchronous with the uplift of the Tianshan Mountains and the Tibetan plateau occurred at 3.00-4.00 Ma, which is influenced by the far-filed effects of the India-Asia intracontinental subduction extrusion. ©, 2015, China University of Geosciences. All right reserved.