| Slip history determination of the Altyn Tagh fault, a 1600 km long left-slip fault which defines the northern edge of the Tibet Plateau, is essential for testing if Asian tectonics is dominated by lateral extrusion or distributed crustal thickening. This study concerns the extent, timing of initiation, slip rate variation, and magnitude of slip of this fault.; Petrotectonic correlation of the Beishan and Inner Mongolia orogens demonstrates that the Alxa-East Mongolia fault, which is in the NE extension of the Altyn Tagh fault, is a left-lateral fault with an offset of ∼400km. This indicates that although the Altyn Tagh fault currently terminates at the North Qilian Shan, it propagated into the Far East Asia during its early stage of evolution. A two-stage model, which combines lateral extrusion and distributed crustal thickening, is developed for fault evolution: From Oligocene to ca. 16–13 Ma, ∼400 km lateral extrusion toward the Sea of Okhotsk occurred along a continuous Altyn Tagh-Alxa-East Mongolia fault. At ca. 16–13 Ma, the Alxa-East Mongolia fault became inactive, and since then, slip on the Altyn Tagh fault has been accommodated by distributed shortening and thickening in northern Tibet. This model predicts 400 ± 50 km of Cenozoic cumulative offset near the eastern end of the Altyn Tagh fault, slow post-Early Miocene slip rate, and mid-Miocene exhumation of northern Tibet.; Provenance analysis of the Tertiary Xorkol basin deduced three sequentially younging Oligocene-Miocene piercing points along the Altyn Tagh fault on the basis of cross-fault source-sediment matches. These piercing points indicate (1) Oligocene-earliest Miocene initiation of the Altyn Tagh fault, (2) 375 ± 25 km cumulative left-lateral slip on the fault, and (3) the post-Early Miocene slip rate can not exceed 10 mm/year.; Basin analysis of Xokol, Subei and Aksay basins demonstrates that these basins were formed as small foreland-like basins in the Oligocene. All these basins underwent a change from fluvial environment in the Oligocene and earliest Miocene to alluvial environment in the Early Miocene, suggesting Miocene exhumation of northern Tibet. This is consistent with apatite fission-track data and supports the two-stage model, which predicts an Early/Middle Miocene age for the exhumation. |
