A REASSESSMENT OF THE TIMING OF THE ARABIA-EURASIA COLLISION WITH REGIONAL AND GLOBAL IMPLICATIONS

The timing of the Arabia-Eurasia collision is controversial with recent estimates ranging from the Eocene to the Early Miocene. Resolving the timing of this event is critical because the onset of this collision resulted in the closure of the Mediterranean seaway, an increase in erosion rates, deformation of the Arabian cover sequence, and the cessation of subduction beneath eastern Turkey and Iran. These events affected the distribution of marine and terrestrial fauna, the flow of water between the Mediterranean and the Indian Ocean, weathering related CO2 drawdown, deformation across the Middle East, and the closure of a western free boundary to the Indo-Asia collision. Our detailed assessment of the available data suggests that break off of the Tethyan slab and the full onset of collision started in the late Oligocene. Full Closure of the Tethyan seaway and the establishment of the Gomphotherium landbridge was completed by Middle Miocene time. Major deformation and uplift started along the suture in Oligo-Miocene time and migrated to the Caspian by middle Miocene time. Some important implications of this analysis are: 1. Eocene Antarctic cooling is unlikely to be related to the Arabia-Eurasia collision, as it was not yet underway. The Eocene onset of Indo-Asia collision to the east seems a much better candidate for forcing the Eocene cooling event. 2. The development of the Eocene Urumieh-Dokhtar magmatic arc and the Oligocene Qom basin in central Iran occurred prior to the collision with Arabia and record subduction related rather than collision related processes. 3. The first ~20 Ma of the Indo-Asian collision proceeded with a free boundary to the west, permitting westward extrusion of continental fragments. 4. A marine connection between the Mediterranean and the Indian Ocean persisted for ~10 Ma after the onset of collision implying deeper marine conditions in the Zagros foreland basin during the early Miocene. 5. Full slab break off of the Tethyan slab probably occurred during the middle Miocene when the foreland basin shoaled and the Tethyan marine connection was severed. This is also the time when deformation and rapid exhumation and spreads throughout Iran and Turkey.