Jurassic and Early Cretaceous platform margin configuration and evolution, central Oman Mountains

Abstract

Abstract The Hajar Supergroup is a Middle Permian to middle Cretaceous sequence dominantly composed of shallow-water carbonate rocks which veneer the eastern edge of the Arabian Platform in the Oman Mountains. The Jurassic and Early Cretaceous components of this package were deposited on the passive margin of Neo-Tethys which developed after initial rifting in the Late Permian and Triassic. Strata studied in Jebel Akhdar, Saih Hatat and neighbouring uplifts document low- and high-energy, shallow-water depositional environments punctuated by two drowning events when deeper water, slope conditions migrated onto the shelf margin. The mid-Jurassic event may have been precipitated by synsedimentary down-faulting of the Saih Hatat area as rifting continued. The latest Jurassic, earliest Cretaceous event, depositing the Rayda Formation, is ascribed to a regional decrease in carbonate production because of widespread evaporitic conditions in the Arabian Platform interior. The configuration of the Mesozoic platform margin in northern Oman conforms to a series of rift and transform segments inherited from the underlying crust when it separated in the Early Jurassic. The transform segments became the focus of major structural lineaments during subsequent thrusting and obduction. This provides an especially clearcut example of the structural control of passive margin geometry, as well as its effect on collision-related deformation. A new Jurassic lithostratigraphic unit, the Saih Hatat Formation, is formally described.