Douwe J.J. van Hinsbergen , Derya Gürer, Ayten Koç, Nalan Lom

Deformation in orogenic belts is typically widely distributed, but may localized to form discrete, fast-moving fault zones enclosing semi-rigid microplates such as the Anatolian microplate. This plate is extruding westwards from the East Anatolian Plateau in the Arabia-Eurasia collision zone along major North and East Anatolian Faults that cause devastating earthquakes, including the February 6, 2023 East Anatolian earthquakes. However, how distributed deformation became focused, and where it may still be active is less-well understood. Here summarise the kinematic history and orogenic tectonic development that preconditioned the orogen for development of the East Anatolian Plateau and the microplate. The orogen first formed in Cretaceous to Eocene time by subduction-accretion below oceanic lithosphere preserved as ophiolites. Then, while remaining oceanic crust was subducted in late Eocene-Oligocene time, it underwent regional extension causing crystalline crust exhumation and deep-marine basin formation. From Early Miocene time onwards, during and perhaps before the onset of Arabian continental underthrusting, the plateau shortened by ~350 km, making 45 km thick crust, and causing >3 km of uplift. Microplate extrusion since the onset of North Anatolian Fault formation around 13 Ma accounted for no more than 25% of Arabia-Eurasia convergence The remaining 75% (>200 km) must thus have been accommodated by continued ~N-S shortening. We highlight that new field studies of the East Anatolian Plateau, through an integrated geological-geomorphological approach to overcome the difficulties posed by a widespread young volcanic cover, are required to identify where and how this major shortening was accommodated and to better assess seismic hazards in eastern Anatolia, and to decipher the dynamics of microplate extrusion.