The Jal Az-Zor escarpment as a product of complex duplex folding and strike-slip tectonics; A new study in Kuwait, northeastern Arabian Peninsula

Abstract

The origin of Jal Az-Zor escarpment has been equivocal due to limited exposure and subsurface data. The escarpment was assumed to be a result of differential weathering and erosion. Most recently mapping of basement lineaments suggested a deep fault system as a most likely cause. The aim of this article is to use shallow seismic data acquired across various locations along the escarpment to investigate the underlying geology, structural elements and link these features to surface observations.To understand the near subsurface geology, post-stack time processing was applied to 2D seismic data acquired recently in the area. The objective was to focus on the shallow intervals, represented by the Rus, Dammam and Kuwait Formations. The analyses revealed a train of tight concentric folds that increase in stage development towards the escarpment in the Dammam Formation. The shallower Kuwait Formation shows early stages of fault propagation folding as a result of the Kuwait Arch uplift towards the south of the escarpment. We suggest that friction along the Dammam Formation upper contact detachment planes increased towards the south, thus promoting the propagation of the fold reaching the surface, resulting in the Jal Az-Zor escarpment that we see today. Structural kinematic analysis suggests that the Jal Az-Zor escarpment is also a principal displacement zone (PDZ) that is dominated by dextral strike-slip motion and exhibits a series of restraining bends, positive-flower structures, and a horsetail splay. 2D structural restoration and balancing suggest a total shortening magnitude of approximately 6.25 km. Considering the Arabian and Eurasian plates velocity vectors, along with the relatively large amount of shortening, this deformation initiated during the early Pleistocene (Calabrian). The presence of tight concentric and fault propagation folds combined with dextral strike kinematics introduce new complexities into the structural styles and assemblages of the area otherwise thought to follow the overall northern Arabian Peninsula tectonics.