Geological analysis and updating velocity model by restoration of a cross section in Zagros fold–thrust belt in the southwest of Iran

Abstract

The Zagros region (SW Iran) contains dominant parts of the remaining Iranian natural resources. Covering Abadan Plain, Dezful Embayment, and Izeh zone, this paper studies a structural cross section constructed across the Zagros belt using 2D and 3D seismic data, well data, surface and subsurface geological maps, satellite images, and field reconnaissance. Restoration assists us for validation and modification of the constructed cross section, better understanding of geology and stratigraphy of the Zagros basin, and computing an updated velocity model in seismic time to depth conversion. In the area of interest, Hormuz basal decollement and Gachsaran detachment play the most significant role in structural style and deformation of the Zagros. More complication links with interval decollements such as Triassic evaporites, Albian shales, and Eocene marls. Estimation of shortening is complex because of a variety of lithotectonic units and detachment surfaces. Here, we are about to introduce a new approach to update seismic velocity model by means of deduced balanced depth model by restoration and seismic two-way time. This is valuable in the case of thick sedimentary cover and steep dip of faults, where acquired seismic images are ambiguous and unreliable. The seismic velocity of Asmari and Gachsaran formations mainly depends on lateral facies and thickness variations within the overburden sediments and generally increases across the Zagros belt from foreland towards hinterland.