Constraints on the uplift mechanism of northern Tibet

- Fast motion along the ATF has terminated since ∼15 Ma.
- Widespread and simultaneous uplift of northern Tibet began at ∼15 Ma.
- The present tectonic configuration of northern Tibet initiated at ∼15 Ma.

Enhanced latest Oligocene to present uplift of northern Tibet is manifest in a variety of geological records. However, the main controversy is how the crust came to be thickened. Theories seeking to explain the growth of northern Tibet include removal of the mantle lithosphere beneath Tibet and the cessation of fast motion on major strike-slip faults. To address this issue, we conducted a detailed paleomagnetic study in the central Kumkol basin, south of the Altyn Tagh fault (ATF). Combined with our previous study from the Janggalsay area, north of the ATF, magnetic declination data suggest fast strike-slip motion for the left-lateral ATF between 22 and 15 Ma. However, the fast motion along the ATF terminated between 15 and <6.3 Ma. This change was accompanied by widespread and simultaneous uplift of northern Tibet at ∼15 Ma. Our results argue in support of a Mid-Miocene transition in tectonic regime from extrusion to distributed shortening in northern Tibet and emphasize the role of the ATF in governing widespread and simultaneous uplift of northern Tibet.