Presentation by Craig Martin.
Paleogeography of the southern Eurasian margin in the lead-up to the India-Eurasia collision
At the onset of the India-Eurasia collision the Eurasian margin was a complex system with extended back-arc basins and significant tracts of oceanic crust between the converging volcanic arc(s) and continental plates. Constraining the time of when Indian and Eurasian continental lithosphere began to accommodate India-Eurasia convergence is crucial to understand how continental plates behave during orogenesis. I will present field mapping, U/Pb zircon ages, and (U-Th)/He zircon cooling ages that constrain the tectonostratigraphic and structural development of the Shyok suture zone, which separates the Kohistan-Ladakh arc from the Karakoram terrane in north-western India and Pakistan. Our results show that the Shyok suture comprises a Jurassic fore-arc ophiolite overlain by Eurasia-derived sedimentary strata which accumulated in a Cretaceous back-arc basin that was under extension until the Paleocene onset of India-Eurasia collision. Closure of this back-arc basin post-dates the formation of the Indus suture zone between the Kohistan-Ladakh arc and India by as much as 15-20 million years. This suggests that before the Eocene, a significant portion of India-Eurasia convergence was accommodated by subduction rather than crustal thickening.
