INSIGHT INTO THE TECTONIC UNITS OF THE IRANIAN PLATEAU

The crust of the Iranian Plateau, stretching from the Persian Gulf up to the Caspian Sea, covers the complete width of the Alpine-Himalayan orogen and resembles the North American Cordillera. It encompasses extensive crustal deformation, complex tectonic history, and topographic contrasts with successive rifting and collision episodes between the converging Arabian and Eurasian plates. The present crust is an agglomeration of different continental core fragments with inherited structural trends that separated from the Gondwanian Passive margin, traveled thousands of kilometers, and accreted to the margins of Laurasia/Eurasia during different collisional orogenies since the Late Proterozoic Era. Palaeo- and active-deformations and topography are distributed irregularly over a very broad area. Pronounced deformation and topographic contrasts are mainly concentrated along the northern and southern marginal fold-and-thrust mountain belts (Talesh, Alborz, Binalud, Kopeh Dagh, and Zagros) surrounding relatively aseismic blocks with low topographic relief which is bisected by the Karkas Tertiary magmatic-arc with high topography. Areas with less internal relief (the Sirjan Mesozoic magmatic-arc; Abadeh Mesozoic backarc basin; Qom Tertiary backarc basin; Yazd, Tabas, and Bon-e Shuru blocks; Sistan, and Makran), and low relief (Central Desert, Gavkhuni, Sirjan, Lut, Jaz Murain depressions) are mainly located in central and east Iran. Tectonic evolution of the Plateau may be divided into two main phases, namely Pre-Tethyan (late Proterozoic to Permian) and Tethyan (Permian to Present). The Pre-Tethyan evolution was governed by the Late Neoproterozoic-Earliest Paleozoic orogeny, the Caledonian, and Variscan (Hercynian) movements. The Tethyan evolution took place during two partly overlapping events in time: the Paleo-Tethyan (Permian to Jurassic; Cimmerian), and the Neo-Tethyan (Jurassic to the Present; with the Late Cretaceous, Middle Eocene, and Late Neogene movements). The present Plateau consists of a composite system of collision-oblique transpressive fold-and-thrust mountain belts with active reverse and strike-slip faulting, range-and-basin terrains, active subduction zone, recent volcanic activities, variable crustal thickness and rigidity, and relatively stable blocks.