Accommodation of the different structural styles in the foreland fold-and-thrust belts: northern Dezful Embayment in the Zagros belt, Iran

Abstract

Structural styles in the Zagros foreland fold-and-thrust belt vary spatially. Differential lateral propagation of folds causes to create tear faults in this belt. In this research, tear faults are studied in northern Dezful Embayment. Tear faults have been accommodated the different structural styles in sedimentary cover during the compressional regime in the Zagros fold-and-thrust belt. Different structural styles indicate a difference in intensity deformation. These faults originated as the pre-existing inverted reactive deep-seated faults or which activate in the sedimentary strata during the compressional regime. Investigation of the structural style of folds in the sedimentary cover is a key point to recognize tear faults. In this research, the structural style of the Kabood, Qale Nar, Bala Rud and Lab-e-Safid subsurface anticlines in the northern Dezful Embayment has been studied. The interpretation of seismic profiles, balanced cross sections, restoration, and 3D structural modeling is investigated to study the structural style of mentioned anticlines. The area of the studied region is 92 × 20 km2. Two tear faults with NNE trending have been separated Qale Nar and Bala Rud anticlines (in the central part) from Lab-e-Safid and Kabood anticlines in eastern and western parts, respectively. The intensity of deformation in the Lab-e-Safid anticline is less than the Qale Nar and Bala Rud anticlines on its western side. Displacement and deformation of the Kabood anticline are more than the Qale Nar anticline in its eastern side. Kabood anticline is multi-bend fault bend fold, Qale Nar and Bala Rud are fault bend folds and Lab-e-Safid is detachment fold. Tear faults have been accommodated by these different structural styles in this region.