Geological evidence against the Shyok palaeo-suture, Ladakh Himalaya

Abstract

Evolution of the Ladakh Himalaya is related to the Cretaceous–Tertiary subduction of the Indian oceanic plate below the southern margin of the Eurasian plate along the Indus suture zone^1–11. The plate tectonic reconstruction suggests two stages of subduction due to the presence of a pre-Cretaceous suture along the Shyok valley^12,13. This hypothesis is based on there being ophiolite belts in the Indus and Shyok valleys. The Indus suture zone is well established but there have been insufficient data on the Shyok suture to confirm the existence of the palaeo-suture. I have studied the Saltoro hills, in the western part of the Shyok valley, and report here the salient geological features. With a few exceptions, the igneous and sedimentary rocks indicate that the Indus and Shyok sutures had the same Cretaceous–Oligocene history. However, the volcanic eruption during the deposition of post-Oligocene molasse in the Saltoro hills of the Shyok valley is the youngest igneous activity in the whole of the Ladakh Himalaya. Hence the geological evidence described here does not accord with the theory of palaeo-suture.