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Tectonic evolution of Tian Shan and Kunlun Shan belts constrained by magnetostratigraphic and thermochronologic analyses

Abstract : In conclusion, this worl enabled to show that erosion of the Paleo-Tian Shan initiated in the Middle Triassic results in the general peneplanation of the Mesozoic Tian Shan dominated by a wide drainage system and long-lasting tectonic quiescence. The northern piedmont of the Tian Shan was characterized by a post-extensional thermally subsiding basin without much tectonic activity, and the southern piedmont also experienced a general flattening of topography. During the Early Jurassic, Early Cretaceous and Late Cretaceous, three identified minor tectonic inversions and adjustments of basin-range pattern in the Tian Shan, may potentially correspond respectively to the accretions of Cimmerian, Lhasa, and Kohistan-Dras in the southern margin of the Eurasian plate. Detrital zircon U-Pb and apatite fission-track data indicate an initial late Cretaceous – Early Tertiary basin reorganization and coeval renewed erosion along the southern Tian Shan piedmont. We interpreted this late Cretacesou to Paleogene activity in STS as the initial response of the distant effects of India-Eurasia collision as previously argued. During the Late Cenozoic, the major reactivation of the Tian Shan initiated around the Late Oligocene-Early Miocene times. This is evidenced mainly from the detrital zircon U-Pb geochronology in the northern piedmont of the Tian Shan, the apatite fission-track data suggesting a possible activation of the Talas Fergana Fault between 18 and 16 Ma, the major Oligocene depositional hiatus and conspicuous increase in accumulation rates at ~ 18.5 Ma revealed by the magnetostratigraphic results in the southern piedmont of the Tian Shan. Cenozoic uplift of the Tian Shan propagated northwards and evolved from local to regional effects during the late Cretaceous to Miocene times. This is also consistent with the northward propagation of far-field effects of the Indo-Asia collision. However, there is still plenty of unresolved related important scientific issues. Further research ought to be carried out in the northern piedmont of the Tian Shan in terms of low temperature thermochronology, especially for the Cenozoic series that are still constrained poorly in that aspect although they are already fairly well dated using magnetostratigraphy. This would enable to gain more insights on the exhumation history of NTS during the Early Cenozoic period. Along the southern Tian Shan piedmont it would be important to extend to the West and East correlative studies within the similar lithostratigraphic units by using similar geochronological approaches. This would provide opportunities to explore possible lateral propagation of the crustal shortening along the Tian Shan and understand further potential difference in tectonic deformation between the ETS and WST, across the Talas Ferghana Fault to the East, towards the Pamir salient to the West
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  • HAL Id : tel-01104374, version 1

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Wei Yang. Tectonic evolution of Tian Shan and Kunlun Shan belts constrained by magnetostratigraphic and thermochronologic analyses. Earth Sciences. Universite Rennes 1, 2014. English. ⟨tel-01104374⟩

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