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Partitionnement de la convergence oblique en zone de collision : Exemple de la chaîne du Zagros (Iran)

Abstract : This manuscript present the results of the tectonic analysis of two major dextral strike-slip faults in the Zagros fold-and-thrust belt of Iran : the Main Recent Fault (MRF) and the Kazerun Fault (KF). The MRF accommodates partitioning of a part of the obliquity of the convergence between Arabia/Eurasia at the rear of the northwestern Zagros. In the central Zagros, the KF, an inherited basement fault, affects the entire width of the belt. This fault, together with a series of N- to NNW-trending strike-slip faults, such the Karehbas fault, define an orogen-scale fan shaped fault pattern pointing towards the southeastern MRF tip.
Structural and kinematic study of these faults allows to consider a re-organisation of the structures and deformation modes of the Zagros in the Neogene. Between 9 and 5 Ma, distributed transpressional deformation operating at the rear of the Zagros belt became partitioned along the newly formed MRF. Around 3 Ma, the southeastern tip of the MRF connected to the northern tip of the KF. Through the fan shaped strike-slip faults pattern of the central Zagros, slip along the MRF became transmitted to the thrusts and folds of the eastern Zagros especially along the bent terminations of the three fault zones of the KF. This fault system corresponds to as an orogen-scale horse-tail termination of the MRF.
Geomorphic offset features analysis and dating (cosmogenic 36Cl exposure ages, U-Th dating) allow to determine the Quaternary horizontal slip rate of the two strike-slip faults. The MRF slip rate is of 6 ± 1 mm/yr. The slip rate along the strike of the KF varies from north to south, from 4 mm/yr to 0 mm/yr; and the Karehbas slip rate is of 6 ± 1.5 mm/yr. Considering the available GPS data over the study area, these results argue for a complete partitioning of the convergence along the MRF and support the hypothesis of the slip from along the MRF being transmitted to the eastern Zagros belt by the southern bent termination of the three fault zones of the KF and associated faults.
Right-lateral slip along this strike-slip fault system initiated as a consequence of the re-organization of the Arabia/Eurasia collisional domain at 5 ± 2 Ma. We suggest that the activation of the MRF was favoured by the slab break-off of the Arabian lithosphere subducting beneath central Iran.
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https://tel.archives-ouvertes.fr/tel-00071020
Contributor : Christine Authemayou <>
Submitted on : Monday, May 22, 2006 - 5:16:54 PM
Last modification on : Saturday, October 3, 2020 - 3:17:06 AM
Long-term archiving on: : Friday, November 25, 2016 - 10:42:17 AM

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  • HAL Id : tel-00071020, version 1

Citation

Christine Authemayou. Partitionnement de la convergence oblique en zone de collision : Exemple de la chaîne du Zagros (Iran). Tectonique. Université de droit, d'économie et des sciences - Aix-Marseille III, 2006. Français. ⟨tel-00071020⟩

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