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Flexural bending of the Zagros foreland basin

Pirouz, Mortaza and Avouac, Jean-Philippe and Gualandi, Adriano and Hassanzadeh, Jamshid and Sternai, Pietro (2017) Flexural bending of the Zagros foreland basin. Geophysical Journal International, 210 (3). pp. 1659-1680. ISSN 0956-540X. doi:10.1093/gji/ggx252.

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We constrain and model the geometry of the Zagros foreland to assess the equivalent elastic thickness of the northern edge of the Arabian plate and the loads that have originated due to the Arabia–Eurasia collision. The Oligo-Miocene Asmari formation, and its equivalents in Iraq and Syria, is used to estimate the post-collisional subsidence as they separate passive margin sediments from the younger foreland deposits. The depth to these formations is obtained by synthesizing a large database of well logs, seismic profiles and structural sections from the Mesopotamian basin and the Persian Gulf. The foreland depth varies along strike of the Zagros wedge between 1 and 6 km. The foreland is deepest beneath the Dezful embayment, in southwest Iran, and becomes shallower towards both ends. We investigate how the geometry of the foreland relates to the range topography loading based on simple flexural models. Deflection of the Arabian plate is modelled using point load distribution and convolution technique. The results show that the foreland depth is well predicted with a flexural model which assumes loading by the basin sedimentary fill, and thickened crust of the Zagros. The model also predicts a Moho depth consistent with Free-Air anomalies over the foreland and Zagros wedge. The equivalent elastic thickness of the flexed Arabian lithosphere is estimated to be ca. 50 km. We conclude that other sources of loading of the lithosphere, either related to the density variations (e.g. due to a possible lithospheric root) or dynamic origin (e.g. due to sublithospheric mantle flow or lithospheric buckling) have a negligible influence on the foreland geometry, Moho depth and topography of the Zagros. We calculate the shortening across the Zagros assuming conservation of crustal mass during deformation, trapping of all the sediments eroded from the range in the foreland, and an initial crustal thickness of 38 km. This calculation implies a minimum of 126 ± 18 km of crustal shortening due to ophiolite obduction and post-collisional shortening.

Item Type:Article
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URLURL TypeDescription
Pirouz, Mortaza0000-0002-7569-492X
Avouac, Jean-Philippe0000-0002-3060-8442
Gualandi, Adriano0000-0002-3100-8932
Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2017 June 7. Received 2017 June 5; in original form 2017 February 24. Published: 09 June 2017. This study was partially supported by the Swiss National Science Foundation (grant P2GEP2-148801). Schlumberger provided a free academic license of the Petrel software. The quality of the paper was greatly improved by editorial guidance and constructive reviews from Associate Editor J.C. Afonso, and two anonymous reviewers. Sylvain Bonvalot, Dan McKenzie, James Jackson, Keith Priestley and Nicky White are thanked for useful discussions.
Group:Seismological Laboratory
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)P2GEP2-148801
Subject Keywords:Numerical modelling, Continental margins: convergent; Crustal structure; Lithospheric flexure; Sedimentary basin processes
Issue or Number:3
Record Number:CaltechAUTHORS:20171005-083018196
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Official Citation:Mortaza Pirouz, Jean-Philippe Avouac, Adriano Gualandi, Jamshid Hassanzadeh, Pietro Sternai; Flexural bending of the Zagros foreland basin, Geophysical Journal International, Volume 210, Issue 3, 1 September 2017, Pages 1659–1680,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82109
Deposited By: Tony Diaz
Deposited On:05 Oct 2017 16:46
Last Modified:15 Nov 2021 19:48

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