PALEOCENE LATITUDE OF THE KOHISTAN-LADAKH ARC INDICATES MULTI-STAGE INDIA-EURASIA COLLISION

The nature of the collision events involved in the Himalayan orogeny offers insight into the role of convergent margins in plate reconfigurations, global climate, and the evolution of biodiversity. We report paleomagnetic data showing that an intra-oceanic Trans-Tethyan subduction zone existed south of the Eurasian continent during Paleocene time. Our results demonstrate that this system was active at a paleolatitude of 8.1 ± 5.6 °N between 66 – 62 Ma, located 600 – 2,300 km south of the contemporaneous Eurasian margin. The location of this system at the same time as the first ophiolite obduction event onto the northern Indian margin confirms 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. Our results constrain the total post-collisional convergence accommodated by crustal deformation in the India-Eurasia system to 1,350 – 2,150 km, and the north-south extent of the northwestern part of Greater India to < 900 km.