The lofty Himalayas, which stretch nearly 3000 kilometers along the border between India and Tibet, mark the region where India collided with the Eurasian continent to create our planet’s highest mountains and largest plateau, which helped shape the surrounding region and influence global climate. However, the timing of the collision’s onset and details of how the continents deformed are still disputed.
To better constrain the collision zone’s history, Laskowski et al. integrate detailed analyses from the Lopu Range, located about 600 kilometers west of Lhasa, with regional studies to develop a new tectonic model of India-Asia collision and Tibetan Plateau development. On the basis of new mapping and chronological constraints from recently discovered metamorphic rocks that span the collision zone, the team reconstructed the geologic history from the Jurassic to the present.
Their results indicate that by about 97 million years ago, the southern margin of Eurasia had become a coherent Andes-style subduction system that later became “ground zero” for India-Asia collision. During the past 25 million years, two distinct episodes of extension were recorded by normal faults, sedimentary basins, and igneous intrusions. These events were interpreted to result from rollback of subducted Indian lithosphere and collapse of critically thick continental crust.
These and other key events in the researchers’ reconstructions are consistent with Mediterranean-style collisional tectonics, in which changes in episodic subduction zone—such as alternating intervals of slab rollback and underthrusting—control upper plate deformation. (Tectonics, https://doi.org/10.1002/2016TC004334, 2017)
—Terri Cook, Freelance Writer