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| Hajar Supergroup | |
|---|---|
| Name | Hajar Supergroup |
| Type | Supergroup |
| Period | Neoproterozoic–Cambrian |
| Lithology | Carbonate, shale, sandstone, volcanic |
| Region | Northeastern Oman, United Arab Emirates |
| Country | Oman; United Arab Emirates |
| Namedfor | Hajar Mountains |
Hajar Supergroup is the major Neoproterozoic to early Paleozoic succession exposed in the Hajar Mountains of northeastern Oman and the United Arab Emirates. The succession records deposition across the Arabian Plate margin during Rodinian breakup, the assembly of Gondwana, and early Pan-African orogeny–related events, and it is central to regional correlations with the Himalaya, Zagros Mountains, and the East African Orogen.
The Supergroup encompasses stacked sequences analogous to stratigraphic units recognized in the Nubian Shield, Siwa Oasis, and the Nilgiri Hills that record basin evolution from rift to passive margin settings during the Neoproterozoic. Key subdivisions correlate with global stratigraphic markers used in studies of the Cryogenian, Ediacaran, and early Cambrian successions and are compared to lithostratigraphic units in the Semail Ophiolite footwall, the Huqf Supergroup, and the Ad Dakhiliyah outcrops. Stratigraphers have tied sections to biostratigraphic data from the Edmond Formation and isotopic signatures comparable to the Niqab Formation and Ara Group in peninsular contexts. Regional mapping by the Ministry of Oil and Gas (Oman), Petroleum Development Oman, and academic teams from the University of Oxford, Imperial College London, and Sultan Qaboos University has refined contact relationships with overlying Phanerozoic cover.
Beds include platformal carbonates, dolostone, marl, siliciclastic turbidites, and volcaniclastic units reflecting alternating shallow-marine, tidal-flat, and deeper ramp conditions. Carbonate buildups show microbial textures akin to stromatolitic facies studied in the Doushantuo Formation and Morro do Chaves Limestone, while siliciclastic intervals contain sandstone, siltstone, and shale comparable to sequences in the Nubian Sandstone and the Molasse Basin. Volcanic layers and tuffs within the succession are geochemically tied to Neoproterozoic magmatism documented in the Arabian-Nubian Shield, the Semail Ophiolite margins, and arcs studied in the Eritrean Shield. Sedimentological analyses reference work from the British Geological Survey, US Geological Survey, and regional specialists at the University of Cambridge and King Fahd University of Petroleum and Minerals.
Deformation features include tight to open folding, thrust imbrication, and low- to medium-grade metamorphism related to Pan-African and Alpine events; these structures are linked to plate interactions involving the Neo-Tethys Ocean, the Arabian Plate rotation, and collision with Eurasia. Fault systems and shear zones are compared with structures in the Zagros fold-thrust belt, the Makran region, and the Hindu Kush in tectonic syntheses by groups at the Geological Society of London and the International Union of Geological Sciences. Structural studies employ techniques developed at institutions such as the ETH Zurich, University of California, Berkeley, and Massachusetts Institute of Technology to interpret fold kinematics, metamorphic P‑T paths, and exhumation histories.
The fossil record includes microbialites, acritarchs, and trace fossils that provide biostratigraphic ties to the Ediacaran biota and early metazoan assemblages similar to those in the Svanbergfjellet Formation and the Doushantuo Formation. Reported microfossils and organic-walled phytoplankton are compared with collections from the National Museum of Natural History (France), the Smithsonian Institution, and the Natural History Museum, London. Trace fossils and possible small shelly fossils enable correlation with Cambrian sections at Siberia and South China platforms, as discussed in paleontological reviews from Cambridge University Press and the Palaeontological Association.
Radiometric ages from volcanic ash beds using U–Pb zircon geochronology constrain deposition from the late Neoproterozoic (~Tonian–Cryogenian–Ediacaran) into the early Cambrian; isotopic studies (δ13C, δ34S) have been integrated with chemostratigraphic frameworks used in global correlations, including comparisons with the Marinoan glaciation records and the Shuram anomaly. Laboratories at University of Leicester, Lehigh University, and the ETH Zurich provided key analytical data. Chronostratigraphic models reference the International Commission on Stratigraphy timescale and regional syntheses by the GEOCHRON community.
The succession hosts hydrocarbon source and reservoir analogs pertinent to plays in the Persian Gulf and the Ghawar Field analogue studies, informing exploration by TotalEnergies, Shell plc, and ExxonMobil. Mineralization includes base-metal occurrences and potential ironstone horizons with comparisons to deposits in the Arabian-Nubian Shield and the Zagros foldbelt. Groundwater in fractured carbonates supplies oases and supports infrastructure in provinces governed by the Omani Ministry of Water Resources, with resource assessments by the World Bank and energy consultancies.
Geological work began with colonial-era surveys by the British Geological Survey and progressed through detailed mapping by national surveys, academic expeditions from the University of Oxford, Imperial College London, King Fahd University, and international collaborations with the US Geological Survey and the International Union for Quaternary Research. Key publications appeared in journals of the Geological Society of America, Journal of the Geological Society (London), and the Journal of African Earth Sciences, and mapping programs employed GIS methods from ESRI and stratigraphic schemes recommended by the International Commission on Stratigraphy.
Category:Geology of Oman Category:Neoproterozoic geology Category:Paleozoic geology