The Tethyan Himalayan detrital record shows that India-Asia terminal collision occurred by 54 Ma in the Western Himalaya

- Distinguishes between India-Asia vs India-island arc collision by arrival of Asian vs island arc detritus on Indian plate.
- Timing of terminal suturing between India and Asia documented at 54 Ma.
- 1st detrital zircon combined U-Pb & Hf study on Western Himalayan Tethyan rocks.

The Himalayan orogen is a type example of continent-continent collision. Knowledge of the timing of India-Asia collision is critical to the calculation of the amount of convergence that must have been accommodated and thus to models of crustal deformation. Sedimentary rocks on the Indian plate near the suture zone can be used to constrain the time of collision by determining first evidence of Asian-derived material deposited on the Indian plate. However, in the Himalaya, for this approach to be applied successfully, it is necessary to be able to distinguish between Asian detritus and detritus from oceanic island arcs that may have collided with India prior to India-Asia collision. Zircons from the Indian plate, Asian plate and Kohistan-Ladakh Island arc can be distinguished based on their U-Pb ages combined with Hf signatures. We undertook a provenance study of the youngest detrital sedimentary rocks of the Tethyan Himalaya of the Indian plate, in the Western Himalaya. We show that zircons of Asian affinity were deposited on the Indian plate at 54 Ma. We thus constrain terminal India-Asia collision, when both sutures north and south of the Kohistan-Ladakh Island arc were closed, to have occurred in the Western Himalaya by 54 Ma.