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Tectonic evolution and growth of the Zagros Mountain Belt (Fars, Iran): constraints from magnetostratigraphy, sedimentology and low- temperature thermochronometry

Abstract : The distribution and precise timing of Cenozoic shortening as well as the degree of uplift and exhumation in the Zagros collision zone in Iran are keys to better understanding how the Arabia (AR) plate motion was accommodated during the collision with the overriding Eurasia (EUR) plate. This is particularly important if plate reconstructions are used to infer the connectivity between the Indo-Pacific Ocean, the Mediterranean Sea and the Para-Tethyan sea, to interpret the impact of the Arabia-Eurasia convergence on the regional aridification of Central Asia and on the Cenozoic global climate changes or to deduce the mechanisms of Iranian plateau uplift. In order to unravel the temporal evolution of uplift and exhumation patterns associated with the building of the Zagros in the Fars area from the Eocene period and the Miocene phase of shortening to the final regional uplift, we provide new magnetostratigraphic dating of Miocene detrital sediments. These new dating are combined with the provenance study of middle Miocene (19.7-14.8 Ma) detrital sediments in the northern Zagros foreland based on the analysis of petrological assemblages and clay mineralogy combined with new detrital apatite fission-track ages. The implications of the results are discussed in terms of plate geodynamics, landscape evolution and regional paleogeography. Combining all informations allowed proposing an original scenario for the building of the Zagros Mountains. After a protracted history of accretion and exhumation during the Jurassic and the Cretaceous on the Iranian plate, obduction occurred at ~70 Ma and a widespread thermal and extensional event affected the SSZ during the Eocene. Collision initiated ca. 35 Ma, several Myrs before first siliciclastic deposits were deposited in the foreland at 19.7 Ma. Until 12.4 Ma, exhumed source areas were dominated by the denudation of the suture domain including rocks from the High Zagros including the Neyriz ophiolites (ultramafic clasts and radiolarian cherts) and the adjacent Sanandaj-Sirjan metamorphic belt. Folding in the outer Zagros Folded Belt started between 15 and 14 Ma. However, the remarkable regional train of folds did not develop before 12.4 Ma. Since this time onwards both the Zagros Folded Belt and the Iranian plateau were uplifted as argued by the stratigraphy of the oldest marine sediments. This very fast accretion in the Zagros occurred probably in less than 5 Myrs and in association with weak erosion feedbacks as revealed by the arid climatic conditions that prevailed during the Miocene.
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Submitted on : Friday, November 18, 2011 - 12:01:15 PM
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  • HAL Id : tel-00642547, version 1


Shokofeh Khadivi. Tectonic evolution and growth of the Zagros Mountain Belt (Fars, Iran): constraints from magnetostratigraphy, sedimentology and low- temperature thermochronometry. Earth Sciences. Université Pierre et Marie Curie - Paris VI, 2010. English. ⟨tel-00642547⟩



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