Late Miocene deformation kinematics along the NW Zagros fold-thrust belt, Kurdistan Region of Iraq : constraints from apatite (U-Th)/He thermochronometry and balanced cross xections
Koshnaw, Renas I. (University of Texas at Austin. Department of Geological Sciences)
Stockli, Daniel F. (The University of Texas at Austin. Department of Geological Sciences)
Horton, Brian K. (The University of Texas at Austin. Department of Geological Sciences)
Teixell Cácharo, Antonio (Universitat Autònoma de Barcelona. Departament de Geologia)
Barber, Douglas R. (The University of Texas at Austin. Department of Geological Sciences)
Kendall, Jerome J. (University of New Mexico. Department of Earth and Planetary Sciences)

Data:	2020
Resum:	Apatite (U-Th)/He (AHe) thermochronometric results are integrated with geologic cross sections, structural relationships, and stratigraphic data to reconstruct the growth of the NW Zagros orogenic belt in the Kurdistan region of Iraq. Prolonged exhumation is documented across the belt with deformation advances and retreats from ~14 Ma onward. After in-sequence propagation of deformation during middle to late Miocene times, preserved growth strata and AHe data show a deformation retreat by latest Miocene time (~5 Ma). In the NW Zagros, the Phanerozoic succession contains two principal décollements in Lower Triassic and middle Miocene units. The Triassic strata are interpreted as the main décollement for a thin-skinned system that was dominant during most of the Cenozoic. By ~8-5 Ma, the fold-thrust belt shifted to basement-involved deformation in association with growth of the mountain front flexure and reactivation of frontal structures. The shift from thin-skinned to a hybrid thin- and thick-skinned mode of shortening may reflect variations in the mechanical behavior of the upper crust and the presence of inherited basement discontinuities. On the basis of two NE-SW balanced cross sections spanning the NW Zagros, the estimated total minimum horizontal shortening is ~18. 2 km (6%) in the central and ~16 km (7%) in the southern sectors of the Kurdistan region of Iraq. These findings suggest that the evolution of the NW Zagros orogenic belt was likely driven by the mechanical stratigraphy of the sedimentary cover, inherited basement discontinuities, and the dynamic and thermomechanical effects of potential slab breakoff and lithospheric mantle delamination events.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Zagros ; Fold-thrust belt ; Thermochronology ; Thin-skinned versus thick-skinned ; Out-of-sequence ; Slab breakoff
Publicat a:	Tectonics, Vol. 39, issue 12 (December 2020) , art. e2019TC005865, ISSN 1944-9194

DOI: 10.1029/2019TC005865

37 p, 13.9 MB

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