Evolution of the NW Zagros Fold-and-Thrust Belt in Kurdistan Region of Iraq from balanced and restored crustal-scale sections and forward modeling

Highlights

• Multidetachment folds above a Lower Triassic basal ductile level recorded around 19 km of shortening since Late Cretaceous.

• The structural steps below the Simply Folded Belt form above low-angle basement faults rooted at around 25 km of depth.

• Folding of the protoforeland basin initiated during Late Cretaceous obduction event as highlighted by growth strata.

Abstract

We present the first regional balanced and restored sections across the northwestern part of the Zagros Fold-and-Thrust Belt in Kurdistan Region of Iraq and a 2D kinematic model that illustrates the evolution of the belt since Late Cretaceous time. The balanced cross-section, based on surface and sub-surface data, is characterized by multi-detachment folds detached above a Lower Triassic basal ductile level, with intermediate detachment levels that induced internal complexities like accommodation thrusting and/or disharmonic folding. Our work suggests that the two main structural steps in the detachment level in the High Folded Zone may be related to low-angle thrusts rooted at the brittle/ductile transition. Growth strata of Late Cretaceous and Paleocene times have been recognized for the first time in the Kurdistan Fold-and-Thrust Belt. This allows us to constrain timing of deformation and to estimate the evolution of the shortening and the advance of the deformation front since Late Cretaceous. Deformation of the Zagros belt is characterized by a combination of thin- and thick-skinned tectonics that reactivated the Late Cretaceous-Paleogene obduction belt.