Tectonic uplift of the Tianshan Mountains since Quaternary: evidence from magnetostratigraphy of the Yili Basin, northwestern China.

Under the influence of the far-field effect of the India-Asia convergence, the Tianshan Mountains have become a typical area of Cenozoic resurrection orogeny, a natural laboratory for continental geodynamics. However, the study of its uplift exhumation history is still controversial. Based on a detailed magnetostratigraphic study of sediments in a 501.29 m deep drill core, located in the Yili Basin that is sandwiched between the Northern and Southern Tianshan Mountains, a total of 202 samples were used to establish magnetostratigraphy. Characteristic remnant magnetization with both normal (N1–N7) and reversed (R1–R7) polarity was isolated by thermal demagnetization. The maximum age can be obtained at the bottom of the borehole profile is 1.95 Ma. Our results show that a significant increase in sedimentation rate as well as notable shift in depositional environment occurred at ~ 0.99–0.78 Ma, which represents the uplift of the northwest Tianshan Mountain and one subsequent rapid uplift event in early Pleistocene time. [ABSTRACT FROM AUTHOR]