Complex fault-fold interactions during the growth of the Jabal Qusaybah anticline at the western tip of the Salakh Arch, Oman

Abstract

The Jabal Qusaybah anticline is located at the western end of the Salakh Arch, a major salient in the foothills of the Oman Mountains. We performed a structural and petrographical-geochemical study of vein sets and fault zones associated with the development of this anticline. Our data illustrate a complex deformation pattern both in space and time, characterized by the unusual presence of widespread NE-SW left-lateral strike-slip fault zones trending oblique to the E-W fold axial strike, and of abundant and well-developed N-S fold-perpendicular extensional fault zones associated with axial bulging and dilation, well developed in the central region of the anticlinal crest. We propose a three-stage evolution for the Jabal Qusaybah anticline, starting with prefolding jointing in the foreland of the late Cretaceous Oman Mountains, and followed by development of extensional faulting in Campanian times. Positive inversion of the Qusaybah Fault, possibly in Miocene times, caused development of a layer-parallel shortening fabric and amplification the Jabal Qusaybah Anticline, in concomitance with the activity of NE-SW left-lateral strike-slip fault zones that triggered N-S, fold-perpendicular extensional faulting, particularly in the axial bump of the anticline. The final evolutionary stage was characterized by further amplification of the axial bump and related N-S extensional fracturing and by uplift and exhumation. To explain the complex noncylindrical fault-fold interactions in the study anticline, we tentatively propose that they were triggered by near foredeep-parallel tapering of the sedimentary/tectonic overburden of the Ara evaporites.

Syn‐Contractional Overprinting Between Extension and Shortening Along the Montagna Dei Fiori Fault During Plio‐Pleistocene Antiformal Stacking at the Central Apennines Thrust Wedge Toe

“…Offsets along these faults (Figure ) are consistently smaller than their downward continuations along the E‐W horst block boundary faults. Reactivation of these boundary faults striking perpendicular to the axial trend of the Montagna dei Fiori Anticline is favored in the late stages of fold growth, when underthrusting by younger structures in the footwall and/or mobilization of décollement material during fold tightening controlled extension parallel to the fold axis (e.g., Storti et al, ).…”

Understanding the Relationship between Large-Scale Fold Structures and Small-Scale Fracture Patterns: A Case Study from the Oman Mountains

“…They have partly controlled the distribution of the Paleozoic sediments. Among other fault systems, the Maradi fault system, Fahud fault, and Natih fault have been active in different tectonic episodes, including NW-SE Late Cretaceous compression and the NE-SW Late Cenozoic compression [27,32,37,38]. The NW-SE Late Cretaceous compression was probably contemporaneous or post-dates the obduction of the Semail Ophiolite.…”

Late-stage tectonic evolution of the Al-Hajar Mountains, Oman: new constraints from Palaeogene sedimentary units and low-temperature thermochronometry

“…2). After the obduction phase, a NE-SW-oriented extensional regime developed (Mann et al 1990;Fournier et al 2006;Storti et al 2015;Grobe et al 2018;Mattern & Scharf, 2018) and exhumation of the high-pressure, low-temperature autochthon of Saih Hatat (Fig. 1) was achieved by a ductile extensional detachment (Goffé et al 1988;Michard et al 1994;Searle et al 1994Searle et al , 2004Chemenda et al 1996;Gregory et al 1998;Searle & Cox, 2002;Fournier et al 2006).…”