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This Article Full Text (PDF) All Versions of this Article: B26035.1v1 121/7-8/963    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Homke, S. Articles by Goodarzi, M. H. Search for Related Content GeoRef GeoRef Citation

Late Cretaceous—Paleocene formation of the proto—Zagros foreland basin, Lurestan Province, SW Iran

¹ Group of Dynamics of the Lithosphere (GDL), Institute of Earth Sciences "Jaume Almera," Consejo Superior de Investigaciones Científicas, Lluís Solé i Sabarís s/n, Barcelona 08028, Spain and StatoilHydro Research Centre, Sandsliveien 90, Bergen, P.O. Box 7200, N-5020 Bergen, Norway
² Group of Dynamics of the Lithosphere (GDL), Institute of Earth Sciences "Jaume Almera," Consejo Superior de Investigaciones Científicas, Lluís Solé i Sabarí s/n, Barcelona 08028, Spain
³ Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, 08028 Barcelona, Spain
⁴ Department of Stratigraphy and Paleontology, Faculty of Science and Technology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
⁵ StatoilHydro Research Centre, Sandsliveien 90, Bergen, P.O. Box 7200, N-5020 Bergen, Norway
⁶ Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, 08028 Barcelona, Spain
⁷ Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, 08028 Barcelona, Spain
⁸ StatoilHydro Research Centre, Sandsliveien 90, Bergen, P.O. Box 7200, N-5020 Bergen, Norway and OMV Exploration and Production, Gerasdorfer Strasse 151, 1210 Vienna, Austria
⁹ National Iranian Oil Company, Exploration Directorate, National Iranian Oil Company Building, Taleghuni Avenue, Hafez Crossing, P.O. Box 1863, Tehran, Iran

Late Cretaceous emplacement of ophiolitic-radiolaritic thrust sheets over the Arabian passive margin was the first manifestation of the protracted closure of the Neotethys Ocean, which ended with the continental collision between Arabia and central Iran and the formation of the present Zagros fold belt. This tectonic stacking produced a flexural basin (the Amiran Basin: 400 x 200 km in size) in the northwest Zagros that was filled with a 1225-m-thick shallowing-upward detrital succession made up of the Amiran, Taleh Zang, and Kashkan Formations. This succession sits unconformably above the Late Cretaceous Gurpi Formation and is overlain by the Oligocene-Miocene Shahbazan-Asmari carbonate succession. Dating of the Amiran-Kashkan succession is based on detailed biostratigraphy using large foraminifera and calcareous nannoplankton. The Cretaceous-Tertiary (K-T) boundary is located within the uppermost 25-45 m of the Gurpi Formation. The overlying Amiran and Taleh Zang Formations have been dated as Paleocene in age. However, the base of the Paleocene within the Gurpi Formation lacks NP1 and NP2 zones, implying a hiatus of 2 m.y. at ca. 65.5 Ma, which is inferred to correspond to an early folding phase near the Cretaceous-Paleocene boundary. The upper part of the Kashkan Formation is dated to the earliest Eocene by palynostratigraphy. A large hiatus (or very slow deposition) lasting about 15 m.y. occurs between the Kashkan and Shahbazan Formations in the studied region. The base of the prograding Shahbazan platform deposits is dated by ⁸⁷Sr/⁸⁶Sr stratigraphy at ca. 33.9 Ma. The upper part of the Asmari Formation is dated as early-middle Miocene using foraminifera associations. Reconstruction of the Amiran-Taleh Zang-Kashkan succession of the Amiran Basin indicates a thickening of the basin fill from the southern pinch-out along the SE flank of the Kabir Kuh anticline to SW of the Khorramabad anticline, where the flexure is at least 900 m. In contrast, the NE part of the basin underwent coeval contraction and uplift of 1300 m. Superimposed smaller undulations onto the large-scale flexure are interpreted as Late Cretaceous-Paleocene folds. Regional comparisons (SE Zagros, Oman, and Turkey) indicate that Late Cretaceous-Early Tertiary deformation affected the entire NE margin of Arabia but that compression was not synchronous, being younger in Lurestan than in the NW Persian Gulf where inversion tectonics occurred from Turonian to mid-Campanian times. The long sedimentary hiatus spanning most of the middle and late Eocene must have been related to deep lithospheric processes linked to the initial events of the protracted closure of the Neotethys Ocean between Arabia and central Iran. The tectono-sedimentary history recorded in the Zagros Basin may help to understand early foreland basin growth in other orogens in which subsequent continental collision has obliterated these early events.

Key Words: Zagros orogeny • Lurestan Province • Paleocene • Amiran—Taleh Zang—Kashkan succession • flexural basin • biostratigraphy