Crustal-scale cross-sections across the NW Zagros belt: implications for the Arabian margin reconstruction

Abstract

-Quantified balanced and restored crustal cross-sections across the NW Zagros Mountains are presented in this work integrating geological and geophysical local and global datasets. The balanced crustal cross-section reproduces the surficial folding and thrusting of the thick cover succession, including the near top of the Sarvak Formation (∼ 90 Ma) that forms the top of the restored crustal cross-section. The base of the Arabian crust in the balanced cross-section is constrained by recently published seismic receiver function results showing a deepening of the Moho from 42 ± 2 km in the undeformed foreland basin to 56 ± 2 km beneath the High Zagros. The internal parts of the deformed crustal cross-section are constrained by new seismic tomographic sections imaging a ∼ 50 • NE-dipping sharp contact between the Arabian and Iranian crusts. These surfaces bound an area of 10 800 km 2 that should be kept constant during the Zagros orogeny. The Arabian crustal cross-section is restored using six different tectonosedimentary domains according to their sedimentary facies and palaeobathymetries, and assuming Airy isostasy and area conservation. While the two southwestern domains were directly determined from well-constrained surface data, the reconstruction of the distal domains to the NE was made using the recent margin model of Wrobel-Daveau et al. (2010) and fitting the total area calculated in the balanced cross-section. The Arabian continental-oceanic boundary, at the time corresponding to the near top of the Sarvak Formation, is located 169 km to the NE of the trace of the Main Recent Fault. Shortening is estimated at ∼ 180 km for the cover rocks and ∼ 149 km for the Arabian basement, including all compressional events from Late Cretaceous to Recent time, with an average shortening rate of ∼ 2 mm yr −1 for the last 90 Ma.

The seismogenic fault system of the 2017 <i>M<sub>w</sub></i> 7.3 Iran-Iraq earthquake: constraints from surface and subsurface data, cross-section balancing and restoration

“…The NW-SE striking Zagros mountain belt formed due to the continental collision between the Arabian and Eurasian plates (Vergés et al, 2011;Berberian and King, 1981;Alavi, 1994;2007;Argand et al, 2005;. The present-day northward motion of Arabia relative to fixed Eurasia is about 2 cm/yr (Vernant et al, 2004).…”

“…The Zagros FTB, to the SW of the suture, involves units originally pertaining to the Arabian continental margin (Ziegler, 2001;Blanc et al, 2003;Sepehr and Cosgrove, 2004;Ghasemi and Talbot, 2006;Mouthereau et al, 2012;English et al, 2015). Within the Zagros FTB, the High Zagros Fault, a major structure striking NW-SE, separates the Imbricate Zone to the NE, where intensely faulted and folded units are exposed, from the Folded Belt to the SW (Blanc et al, 2003;Karim et al, 2011;Vergés et al, 2011). The SW boundary of the Zagros FTB is the Mountain Front Flexure, corresponding to a basement and topographic step that divides the belt from its foreland basin to the SW (Falcon, 1961).…”

“…Folds and thrusts of the Folded Belt of the Kirkuk embayment and of the Lurestan arc are NW-SE-striking, becoming locally NNW-SSE-trending along the boundary between the two domains. There, a major bend of the Mountain Front Flexure occurs (Vergés et al, 2011;Sadeghi and Yassaghi, 2016) (Figs. 2,3).…”

“…In the Zagros FTB, many of the largest earthquakes are associated with major reverse faults affecting the Precambrian basement (e.g. Jackson, 1980;Berberian, 1995;Talebian and Jackson, 2004), which are included in almost all the published balanced cross-sections across the belt (Blanc et al, 2003;Molinaro et al, 2005;Mouthereau et al, 2007;Vergés et al, 2011). Despite being located more than 200 km away from the epicentral area, these cross sections suggest that the seismogenic structure of the Mw 7.3 earthquake could be related with the Mountain Front Flexure, which extends across the aftershock area of the November 2017 earthquake (Figs. 1,2).…”

Kinematics of Post-obduction Deformation of the Tertiary Ridge at Al-Khod Village (Muscat, Oman)

“…This started during the early Miocene (26)(27)(28)(29)(30)(31)(32)) and is an ongoing process as shown, for example, by present-day convergence rates, determined by GPS measurements, between Arabia and Eurasia with 36.5 mm/a near the Strait of Hormuz [20] (Figure 4), contributing to the Cenozoic and recent uplift of the Oman Mountains.…”