Abstract

The Tian Shan Mountains constitute central Asia's longest and highest mountain range. Understanding their Cenozoic uplift history thus bears on mountain building processes in general, and on how deformation has occurred under the influence of the India-Asia collision in particular. In order to help decipher the uplift history of the Tian Shan, we collected 970 samples for magnetostratigraphic analysis along a 4571-m-thick section at the Jingou River (Xinjiang Province, China). Stepwise alternating field and thermal demagnetization isolate a linear magnetization component that is interpreted as primary. From this component, a magnetostratigraphic column composed of 67 polarity chrons are correlated with the reference geomagnetic polarity timescale between similar to 1 Ma and similar to 23.6 Ma, with some uncertainty below similar to 21 Ma. This correlation places precise temporal control on the Neogene stratigraphy of the southern Junggar Basin and provides evidence for two significant stepwise increases in sediment accumulation rate at similar to 16-15 Ma and similar to 11-10 Ma. Rock magnetic parameters also undergo important changes at similar to 16-15 Ma and similar to 11-10 Ma that correlate with changes in sedimentary depositional environments. Together with previous work, we conclude that growth history of the modern Tian Shan Mountains includes two pulses of uplift and erosion at similar to 16-15 Ma and similar to 11-10 Ma. Middle to upper Tertiary rocks around the Tian Shan record very young (5 Ma) counterclockwise paleomagnetic rotations, on the order of 15 degrees to 20 degrees, which are interpreted as because of strain partitioning with a component of sinistral shear that localized rotations in the piedmont. Citation: Charreau, J., et al. (2009), Neogene uplift of the Tian Shan Mountains observed in the magnetic record of the Jingou River section (northwest China), Tectonics, 28, TC2008, doi:10.1029/2007TC002137.