Abstract
This paper presents a detailed provenance analysis of the 6.5 km thick Oligocene–Pliocene foreland succession in the north Dezful embayment in Zagros, Iran. Using petrography, geochemistry and palaeoflow analysis, we determined three provenance shifts during the exhumation of the Zagros orogen. Above the Ahwaz sandstones, sourced from the Arabian craton, a sharp decrease in SiO2/Al2O3, Zr/Sc, Th/Sc, Th/Co and Th/Cr within the Gachsaran Fm. and the appearance of first-cycle sands derived from metamorphic and volcanic rocks at the base of the Aghajari Fm. characterize the onset of exhumation, rising topography and denudation of the Zagros orogenic system during the latest Oligocene and constitute the first shift. The second shift, in the middle Aghajari Fm., is marked by a distinct increase in radiolarian cherts and compatible/incompatible elements, indicating the exhumation of Neotethyan radiolarite–ophiolite allochthonous slices in the High Zagros Zone during the Tortonian (c. 9 Ma). Large quantities of carbonate clasts derived from the nearby growing Izeh Zone anticlines characterize the Messinian (c. 7 Ma) Bakhtyari conglomerates marking the third shift. In conclusion, a detailed hands-on provenance analysis of the clastic sedimentary sequences in the north Dezful embayment enabled us to determine catchment areas and shifts hitherto unstudied, thus contributing to the exhumation history of the Central Zagros orogenic system. Supplementary material: Details of the petrography and geochemistry results are available at https://doi.org/10.6084/m9.figshare.c.4905558
Highlights
Provenance evolution of Oligocene– Pliocene foreland deposits in the Dezful embayment to constrain Central Zagros exhumation history
Two major issues are addressed in this study: a) Recycling and past weathering conditions, and b) Provenance evolution of the foreland sediments and its implications for the exhumation history of the central Zagros Mountains
T Recycling and past weathering conditions IP Prior to any tectonic interpretation of the Zagros orogen, the influence of recycling and R paleo-weathering on the sediment composition must be assessed
Summary
This is a PDF of an unedited manuscript that has been accepted for publication. The manuscript will undergo copyediting, typesetting and correction before it is published in its final form. They were unconformably covered by the Paleogene sedimentary successions, and started to expose again with the folding of the High Zagros zone during Neogene. AN The current study area is located in the footwall of the Mountain Frontal Fault, in the north M Dezful embayment (Figs 2a and b) in which a thick and continuous syntectonic succession is well-preserved This large sedimentary succession was deposited during both active shortening and as salt tectonics developed over the 1.5-km thick Gachsaran salt-bearing deposits in the Azanak growth syncline-minibasin. In the present study we used the Sr-isotopic ages determined for the Asmari Formation in the Ahwaz and Marun oil fields (Ehrenberg et al 2007), and magnetostratigraphic ages determined for the Mishan–Bakhtyari formations in the Jarik anticline (Lashgari et al 2020) (Fig. 2a for locations)
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