Paleomagnetic constraints on paleogeography for the Kohistan-Ladakh arc and its surrounding terranes

Understanding the nature of the Kohistan-Ladakh arc before the India-Asia collision is crucial for reconstructing the Tethyan paleogeography, deciphering geodynamic process of the India-Asia collision, and restoring Asia's history of intracontinental deformation. However, there are two opposing views dealing with nature of the Kohistan-Ladakh arc: The continental marginal arc and intra-oceanic island arc. Based on the accumulated published paleomagnetic data for the Kohistan-Ladakh arc and its surrounding terranes during the Cretaceous-Paleocene, we reconstruct paleogeography of the Kohistan-Ladakh arc and its surrounding terranes, and explore the nature of the Kohistan-Ladakh arc. The Karakoram terrane was situated on the southern edge of Asia at a paleolatitude consistent with that of the western Lhasa terrane in the late Cretaceous. The Kohistan-Ladakh arc was situated in the equatorial Neo-Tethys Ocean (southern hemisphere) in the early Late Cretaceous (ca. 90 Ma) before drifting northward to reach the low-latitude northern hemisphere in the early Paleocene (ca. 64 Ma). The central and eastern parts of the Tethyan Himalaya, as the northern margin of India prior to the collision, were located at paleolatitudes of 16.7 degrees and 19.4 degrees S at ca. 75 Ma, respectively. The Kohistan-Ladakh arc was separated from the western Lhasa terrane by an ocean basin with a north-south extent of similar to 900 km at ca. 64 Ma. The above analyses suggest that the Kohistan-Ladakh arc demonstrated intra-oceanic characteristics prior to the India-Asia collision. Therefore, the Kohistan-Ladakh arc should be considered in the India-Asian collision system. Recently published paleomagnetic data obtained from the Tethyan Himalaya terrane, data obtained from the Kohistan-Ladakh arc, and the apparent polar wander path of India inspired us to propose a triple-stage India-Asia collision model. The first collision occurred at ca. 64 Ma between the Tibetan Himalaya terrane and the Kohistan-Ladakh arc. The second collision occurred at ca. 61 Ma between the Tibetan Himalaya terrane (including the accreted Trans-Tethyan subduction zone) and Asia. The final collision occurred during 53-47 Ma between India and the Tibetan Himalaya terrane, leading to diachronous suturing of the North India Sea from west to east. The proposed collision model reconciles multiple lines of geologic, geophysical, geochemical, and paleontologic evidence. Especially, we highlight that the new scenario well matches the history of the India-Asia convergence rates, which were documented by the relative plate motions between India-Africa and IndiaAntarctica. In addition, this new model provides important constraints for intracontinental deformation in Asia. For example, the second collision between the Tibetan Himalaya terrane and Asia occurred along the Shyok-Yarlung Tsangpo suture zone, rather than the Indus-Yarlung Tsangpo suture zone. The Shyok and Yarlung Zangbo suture zones have ever been connected, implying a total offset greater than 400 km for the Karakoram fault.