Geology of a suture zone

The Himalayan mountains formed as a result of the closure of the Neotethys Ocean and the continental collision between India and Eurasia. The two continents are now fused together along a complex geological boundary called a suture zone. The suture zone contains the fragmented remains of what was once an entire oceanic plate that has been subducted into the mantle.

We studied the Shyok suture zone in northwest India, which marks the boundary between the Kohistan-Ladakh arc and Eurasia. We measured the ages of the major lithologies and fault structures using the decay of uranium to lead in zircon crystals and crosscutting relationships between different rock types. Our detailed mapping and structural observations in the suture zone allow us to parse out the sequence of tectonic events that occurred during its formation.

Our work shows that the suture zone comprises complexly deformed and dismembered remnants of the ancient Eurasian continental margin. These tectonic slices span Jurassic to Oligocene time and were emplaced along major thrust faults that formed in the Eocene. Our results indicate the final continental collision between India and Eurasia is younger than previously thought.