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

Abstract

AbstractQuantified 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 10800 km2that 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-Daveauet 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−1for the last 90 Ma.