This Thesis presents the results of a study of the "High Zagros", the most internal part of the Zagros-Fold-Thrust-Belt (ZFTB). On map view, the High Zagros is exposed in two separated domains (Western and Eastern High Zagros respectively) and partly hidden as an under-plated region beneath the Sanandaj-Sirjan Domain. The High Zagros is the only place in the ZFTB where the Paleozoic rocks are widely exposed.A primary objective was to reevaluate the structural style and kinematic evolution of the High Zagros. It is shown that the most significant geological elements within this area are large scale faulted detachment folds, associated with a complex system of thrust faults segmented by strike-slip faults. This work suggests that the existence of active Ordovician and/or Silurian décollements led to the development of duplex structures which are confined in the core of the anticlines. A two-step kinematic scenario, similar to the one already proposed elsewhere in the belt, is proposed for the High Zagros. Firstly, a thin-skinned phase led to establish detachment folding over the basal Hormuz salt. Then, a thick-skinned phase resulted in the basement thrusting and allowed the exhumation of Lower Paleozoic succession.After this presentation of the tectonic context of the High Zagros, the thesis focuses on the tectonic significance of the pre-Permian unconformity, which was known through a major hiatus between Cambro-Ordovicien to Early Permian and between Devonian to Permian rocks in the western and eastern High Zagros respectively. It is shown that (1) the High Zagros presents below the unconformity a large "Arch-and-Basin" geometry; and that (2) only extensional features such as normal faults and rotated blocks, without evidence of contractional deformation, can be observed below the unconformity. Thermal uplift of possible Late Devonian is proposed as a probable mechanism explaining both the uplift and the diffuse extensional deformation. This proposal strongly modifies the "classical" interpretation of the pre-Permian hiatus as a far effect of the Variscan Orogeny.Thermal modeling based on maturity data from potential source rocks cropping out in the High Zagros has been performed. The most probable modeled scenario suggests an important heat flow during the Devonian and the erosion of ~3900m of the sedimentary pile prior to the deposition of Permian sequence. This outcome reinforces our interpretation of a thermal uplift scenario responsible for pre-Permian vertical movements. On the other hand, a set of new (U-Th)/He ages obtained from the Lower Paleozoic, Devonian and early Permian clastic rocks show a partial reset of zircon grains. These two results are fairly consistent with the published data describing a major thermo-tectonic event during Late Devonian-Early Carboniferous in the Levant Arch (Israel, Jordan) and suggest a common mechanism at the scale of the Arabian Plate.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00824605 |
| Date | 19 December 2012 |
| Creators | Tavakolishirazi, Saeid |
| Publisher | Université de Cergy Pontoise |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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