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Timing of Onset and Destruction of the Zagros Foreland Basin in Lurestan, Iran: New Magnetostratigraphic Data

Vergés, Jaume1, Stephane Homke1, Miguel Garces2, Ridvan Karpuz3, Ian Sharp4, Josep Serra-Kiel2, Hadi Emami1, Mohammad Goodarzi5 (1) Institute of Earth Sciences, CSIC, Barcelona, Spain (2) University of Barcelona, Spain (3) Norsk Hydro Zagros Petroleum, Tehran, Iran (4) Norsk Hydro Research Centre, Bergen, Norway, (5) National Iranian Oil Company, Tehran, Iran


The passage from passive margin to foreland in the Zagros Fold Belt as well as the onset of foreland deformation by folding and thrusting is investigated by means of AFTA and mag­netosptratigraphy together with biostratigraphy in the Push-e Kush Arc in Iran. The Amiran Fm. represents the first massive NE-derived clastic arrival to central parts of the basin in Lurestan. Composition of Amiran deposits reveals their provenance from the emplacement and subsequent erosion of ophiolitic tectonic slices. The large extent of the Amiran Fm. and its wedge geometry progressively thickening towards the NE suggest that deposition filled up a flexural basin formed as a response of thrust sheets emplacement. Results based on preliminary magnetostratigraphic analyses show a Maastrichtian age for Amiran deposits infilling this early foreland basin formed as a consequence of early-middle Late Cretaceous tectonic emplacement of ophiolites (~90 Ma based on detrital AFTA). Post-Asmari Fm. fore­land basin shows gentle thickening towards the Zagros hinterland in both Lurestan and Khuzestan provinces (Push-e Kush Arc and Dezful Embayment). Onset of Zagros foreland destruction started during deposition of fluvial Agha Jari Fm. based on reliable magne­tostratigraphic sections in the front of the Zagros Fold Belt. Initiation of folding in the Push­e Kush Arc is dated at 8.1-7.2 Ma. The Bakhtyari Fm. deposited conformably in growth syn­clines and above an angular unconformity elsewhere and thus constraining the end of major deformation in this region near the Pliocene-Pleistocene boundary.