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Book Chapter

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

By
Andrea Zanchi
Andrea Zanchi
Dipartimento Scienze Geologiche e Geotecnologie, Università di Milano-Bicocca, Piazza della Scienza 4, Milano, 20126Italy
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Stefano Zanchetta
Stefano Zanchetta
Dipartimento Scienze Geologiche e Geotecnologie, Università di Milano-Bicocca, Piazza della Scienza 4, Milano, 20126Italy
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Fabrizio Berra
Fabrizio Berra
Dipartimento di Scienze della Terra, Università di Milano, Via Mangiagalli 34, 20133 Milano, Italy
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Massimo Mattei
Massimo Mattei
Dipartimento di Scienze Geologiche, Largo San Leonardo Murialdo 1, 00146 Roma-I, Università Roma TRE, Italy
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Eduardo Garzanti
Eduardo Garzanti
Dipartimento Scienze Geologiche e Geotecnologie, Università di Milano-Bicocca, Piazza della Scienza 4, Milano, 20126Italy
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Stewart Molyneux
Stewart Molyneux
British Geological Survey, Kingdom Kingsley Dunham Centre Keyworth, Nottingham NG12 5GG, UK
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Amir Nawab
Amir Nawab
Geological Survey of Iran, Azadi Square, Meraj Avenue, 13185-1494, Tehran, Iran
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Jafar Sabouri
Jafar Sabouri
Geological Survey of Iran, Azadi Square, Meraj Avenue, 13185-1494, Tehran, Iran
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Published:
January 01, 2009

Abstract

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.

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Contents

Geological Society, London, Special Publications

South Caspian to Central Iran Basins

M.-F. Brunet
M.-F. Brunet
CNRS-INSU and Université Pierre et Marie Curie, France
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M. Wilmsen
M. Wilmsen
Senckenberg Naturhistorische Sammlungen Dresden, Museum für Mineralogie und Geologie, Germany
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J. W. Granath
J. W. Granath
Granath & Associates Consulting Geology, USA
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Geological Society of London
Volume
312
ISBN electronic:
9781862395602
Publication date:
January 01, 2009

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