Reconstruction of plate tectonic evolution and orogenesis of the Central Tethysides (Iran, Afghanistan) since the Permian

Nalan Lom, Douwe J.J. van Hinsbergen 

The Central Tethysides constitute the Iranian and Afghan section of the Alpine-Himalayan orogenic belt. Two large sutures in the north and south are widely considered to represent the closed Paleo- and Neotethys ocean, respectively, with a 'Cimmerian' continent in between that traveled from Gondwana-Land to Eurasia in the Permo-Triassic and reconnected with Arabia in the late Oligocene. However, the smaller Sabzevar-Nain-Baft and Sistan Sutures in Iran have not been kinematically reconstructed in detail before. Here, we review geological constraints on the architecture of the Central Tethysides and provide a GPlates-based reconstruction of its (plate) tectonic history. We show that the Sabzevar-Nain-Baft ocean basin opened by late Jurassic-early Cretaceous N-S back-arc extension that also formed the continental Central Basin, in tandem with opening of the South Caspian-Kopet Dagh basin to the north. The Sabzevar-Nain-Baft basin closed in late Cretaceous-Eocene time by westwards extrusion of the Central-East Iranian Microcontinent (CEIM) and its eastward extension, the Farah Rud Block. The Sistan Ocean closed simultaneously by faster westwards extrusion of the Helmand Block, originally part of the Tibetan Qiangtang terrane. Extrusion exceeded 1000 km and was likely initiated by Cretaceous shortening in the Tibetan Plateau. Early Cretaceous opening of the Sistan Ocean and simultaneous closure of the Waser Suture between Helmand and Farah Rud accommodated the final collision of the China Blocks with Eurasia. Whilst we reconcile known evidence with Tethyan plate tectonic history, key information remains hidden in the spectacular geology of Iran and Afghanistan, awaiting future detailed mapping and analysis.