Omani thrusts

Omani thrusts
Name	Omani thrusts
Location	Southeastern Oman, United Arab Emirates
Type	Thrust fault system
Age	Cretaceous, Tertiary
Orogeny	Oman ophiolite emplacement, Tethys Ocean closure

Omani thrusts

The Omani thrusts are major imbricate thrust systems associated with the emplacement of the Semail Ophiolite and related nappes across Oman, the United Arab Emirates, and adjacent parts of the Helmand Basin region. These thrusts record interactions between the Arabian Plate, Eurasian Plate, and remnants of the Tethys Ocean during the Late Cretaceous to Cenozoic tectonic evolution, and they link to classic field localities studied by researchers from institutions such as the University of Oxford, Imperial College London, and the Petroleum Development Oman exploration teams.

Geologic Setting and Regional Tectonics

The thrusts lie within the forearc and obduction framework of the Semail Ophiolite emplacement onto continental margin sequences including the Hawasina Complex, Sumeini Group, and shelf carbonates of the Cretaceous Arabian passive margin. Regional transport directions were controlled by convergence between the Arabian Plate and microplates including the Makran Arc and interactions with the Zagros Orogeny and Hindukush–Alborz deformation belts. The structural grain is superposed on stratigraphic units such as the Shuaiba Formation, Mishrif Formation, and Rus Formation, and the thrust network influenced sediment routing into basins like the South Oman Salt Basin and the Gulf of Oman depositional systems.

Structural Characteristics and Morphology

The thrust systems exhibit an imbricate stack architecture with out-of-sequence thrusts, duplexes, and roof thrust geometries observable in classic cross-sections near the Jebel Akhdar and along the Oman Mountains escarpment. Surface expressions include fault scarps, klippen, and hanging-wall anticlines that deform units such as the Haybi Formation and Hadhramaut succession. Kinematic indicators—slickenlines, asymmetric folds, and fault-propagation folds—record top-to-the-NE transport consistent with obduction models favored by field mapping campaigns from teams affiliated with the Natural History Museum, London, King Abdulaziz University, and the US Geological Survey.

Formation Mechanisms and Temporal Evolution

Mechanisms invoked include shallow-angle obduction driven by slab rollback and plate convergence, gravity sliding of ophiolitic sheets, and tectonic underplating during the Late Cretaceous to early Tertiary. Thermochronology and biostratigraphic constraints from foraminifera and ammonite assemblages tie major thrusting pulses to events correlated with the closure of the Neotethys and the onset of Arabian Plate northward migration. Work by teams from the University of Cambridge, Columbia University, and the Max Planck Institute has integrated seismic profiles, balanced cross-sections, and detrital zircon ages to reconstruct incremental emplacement stages, including an early obduction phase followed by syn- to post-obduction shortening and strike-slip partitioning related to the Red Sea rifting onset.

Petrology and Metamorphism

The thrust-related rocks encompass slices of mantle-derived peridotite, abyssal gabbro, sheeted dike complexes, and pelagic sediments juxtaposed against metamorphosed continental margin rocks within the Hawasina nappes. Metamorphic gradients across thrust contacts range from low-grade blueschist facies in localized shear zones to anchizone and greenschist facies recrystallization in adjacent sedimentary blocks, as documented in studies by researchers at the University of Tokyo, Swiss Federal Institute of Technology (ETH Zurich), and the Geological Survey of Oman. Geochemical fingerprints from researchers at the Geological Society of London and the Institute of Geology, U.A.E. indicate subduction-modified MORB affinities and forearc sediment mélanges that record fluid-rock interaction, serpentinite-hosted alteration, and metasomatic enrichment along thrust planes.

Economic Significance and Hydrocarbon Implications

The thrust architecture exerts first-order control on hydrocarbon reservoir distribution and trap formation within the South Oman Basin, Marmul Field, and stratigraphic plays tied to the Qahlah Formation and Shu'aiba carbonate systems. Thrust-related anticlines and duplex structures form structural traps exploited by operators including Petroleum Development Oman and international partners such as Shell and TotalEnergies. Moreover, thrust-bounded compartments influence fracture porosity, seal integrity, and migration pathways, factors assessed in exploration campaigns by the Society of Petroleum Engineers and the American Association of Petroleum Geologists technical conferences.

Research History and Key Studies

Key contributions began with regional mapping during the mid-20th century by teams from the British Geological Survey and the Trucial States Geological Survey, followed by seminal synthesis papers from investigators at the Plymouth University, California Institute of Technology, and the University of Leeds. Landmark works include structural cross-section reconstructions, ophiolite emplacement models advanced by researchers at the University of Oxford and Leiden University, and multidisciplinary datasets comprising seismic reflection, thermochronology, and geochemistry published in journals associated with the Geological Society of America and the Journal of the Geological Society. Ongoing research integrates high-resolution geodesy, paleomagnetic constraints from the Institut de Physique du Globe de Paris, and industry seismic campaigns to refine timing and mechanics of the thrusting episode.

Category:Geology of Oman