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The Eo-Cimmerian (Late? Triassic) orogeny in North Iran

Zanchi, A.; Zanchetta, S.; Berra, F.; Mattei, M.; Garzanti, E.; Molyneux, S.; Nawab, A.; Sabouri, J.. 2009 The Eo-Cimmerian (Late? Triassic) orogeny in North Iran. In: Brunet, M.-F.; Wilmsen, F.; Granath, J.W., (eds.) South Caspian to Central Iran basins. London, UK, Geological Society of London, 31-55. (Geological Society Special Publications, 312).

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Abstract/Summary

The Eo-Cimmerian orogen results from the Late Triassic collision of Iran, a microplate of Gondwanan affinity, with the southern margin of Eurasia. The orogen is discontinuously exposed along the northern side of the Alborz Mountains of North Iran below the siliciclastic deposits of the Shemshak Group (Late Triassic–Jurassic). A preserved section of the external part of the belt crops out in the Neka Valley (eastern Alborz) south of Gorgan. Here the Mesozoic successions (Shemshak Group–Upper Cretaceous limestones) overlay a pre-Jurassic Eo-Cimmerian thrust stack with a sharp unconformity. The stack includes the Gorgan Schists, an Upper Ordovician–Lower Silurian low-grade metamorphic complex, overthrusted southward above a strongly deformed Late Palaeozoic–Middle Triassic succession belonging to north Iran. In the Talesh Mountains (western Alborz), the Shanderman Complex, previously interpreted as an ophiolitic remnant isolated along the Eo-Cimmerian suture, is considered an allochthonous nappe of deeply subducted continental crust. The new evidence for this is the occurrence of previously unknown eclogites dating to the Carboniferous, and probably related to the Variscan history of Transcaucasia. South of the Shanderman Complex, Upper Palaeozoic slates and carbonates occurring below the Lower Jurassic Shemshak Group also record the occurrence of an Eo-Cimmerian metamorphic event. Based on our new data, the Eo-Cimmerian structures exposed in the Alborz appear to be remnants of a collisional orogen consisting mainly of deformed continental crust where no ophiolites are preserved.

Item Type: Publication - Book Section
Digital Object Identifier (DOI): 10.1144/SP312.3
Programmes: BGS Programmes 2009 > International Business Development
ISBN: 9781862392717
Additional Keywords: Iran, Triassic, Orogenesis
NORA Subject Terms: Earth Sciences
Date made live: 25 Jun 2009 14:21
URI: http://nora.nerc.ac.uk/id/eprint/7572

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