Structures associated with nappe emplacement and culmination collapse in the Central Oman Mountains

Abstract

Abstract The Fanjah Saddle, in the Central Oman Mountains, forms a structural and topographic depression between two major culminations which expose parautochthonous rocks in windows through the overlying allochthon. Two styles of normal faulting are present in the culminations: high-angle faults which dip toward the saddle core and cut the plunging noses of the culminations, and low-angle faults around the culmination flanks which include bedding-parallel detachments, reactivated thrust planes and surge zones. This second set of faults verge down-dip radially away from the culmination flanks. The high-angle normal faults are interpreted to be accommodation structures resulting from the differential uplift of the parautochthon between the culminations and the saddle. The low-angle normal faults are interpreted to be gravity-driven culmination collapse structures resulting from oversteepening of the culmination flanks. Post-orogenic late Campanian to Maastrichtian sediments adjacent to the culminations indicate that the culminations were initialy emergent during this time, acting as a clastic source. These same sediments, and the underlying nappe pile, are folded by compression from displacements on the normal faults which implies culmination uplift was reactivated after the Maastrichtian, possibly during post-middle Eocene Zagros orogeny.