Paleomagnetic results from the western Himalaya indicate multi-stage India-Eurasia collision

The classical model for the collision between India and Eurasia, which resulted in the formation of the Himalayan orogeny, is a single-stage continent-continent collision event at around 55 – 50 Ma. However, it has also been proposed that the India-Eurasia collision was a multi-stage process involving an intra-oceanic Trans-Tethyan subduction zone south of the Eurasian margin. We present paleomagnetic data constraining the location the Kohistan-Ladakh arc, a remnant of this intra-oceanic subduction zone, to a paleolatitude of 8.1 ± 5.6 °N between 66 – 62 Ma. Comparing this result with new paleomagnetic data from the Eurasian Karakoram terrane, and previous paleomagnetic reconstructions of the Lhasa terrane reveals that the Trans-Tethyan Subduction zone was situated 600 – 2,300 km south of the contemporaneous Eurasian margin at the same time as the first ophiolite obduction event onto the northern Indian margin. Our results confirm that the collision was a multistage process involving at least two subduction systems. Collision began with docking between India and the Trans-Tethyan subduction zone in the Late Cretaceous and Early Paleocene, followed by the India-Eurasia collision in the mid-Eocene. The final stage of India-Eurasia collision occurred along the Shyok-Tsangpo suture zone, rather than the Indus-Tsangpo. The addition of the Kshiroda oceanic plate, north of India after the Paleocene reconciles the amount of convergence between India and Eurasia with the observed shortening across the India–Eurasia collision system. Our results constrain the total post-collisional convergence accommodated by crustal deformation in the Himalaya to 1,350 – 2,150 km, and the north-south extent of the northwestern part of Greater India to < 900 km.