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53-793: The Huqf Supergroup is exposed in the Jabal Akhdar of the Al Hajar Mountains , and in the deformed and metamorphosed domal culmination of the Saih Hatat. Source rocks of the Neoproterozoic to Cambrian Huqf Supergroup are associated with most of the South Oman oils. However, the geochemical similarity of the organic matter across the Huqf sequence has impeded to assign oils to Huqf intervals. Huqf Supergroup preserves

106-407: A subaerial wedge is flanked with terrestrial or shallow marine foreland basins". The temperature underneath the orogen is much higher and weakens the lithosphere. Thus, the thrust belt is mobile and the foreland basin system becomes deformed over time. Syntectonic unconformities demonstrate simultaneous subsidence and tectonic activity. Foreland basins are filled with sediments which erode from

159-574: A subspecies of Wadi Kharrar rock gecko ( Pristurus gallagheri ) are found only in Oman while Musandam leaf-toed gecko ( Asaccus caudivolvulus ), Gallagher's leaf-toed gecko ( Asaccus gallagheri ), Oman rock gecko ( Pristurus celerrimus ), Jayakar lizard ( Omanosaura jayakari ) and Oman blue-tailed lizard ( Omanosaura cyanura ) are found only in the Hajar. The endangered Arabian leopard ( Panthera pardus nimr ) had been recorded here, particularly in

212-482: A SW-dipping subduction zone. The two culminations are separated by the Semail Gap. This is a prominent linear structure, trending NNE—SSW. However, it is still debated as to what this structure is. Different geologists claim that it is a left-lateral (sinistral) strike-slip fault , a normal fault , a lateral ramp, a monocline due to a blind thrust , or a fault with multiple phases of deformation. There

265-476: A complete sequence of Cryogenian , Ediacaran, and early Cambrian strata, becoming the group a reference in Earth history . This article about the geography of Oman is a stub . You can help Misplaced Pages by expanding it . Al Hajar Mountains The Hajar Mountains ( Arabic : جِبَال ٱلْحَجَر , romanized :  Jibāl al-Ḥajar , The Rocky Mountains or The Stone Mountains ) are one of

318-486: A much shallower depth to basement in the Hajar Mountains and a deeper depth to basement in the foreland basin to the west. This has implications on economic geology such as the mining for precious minerals and the extraction of oil and gas. The late Cretaceous obduction event created the proto-Hajar Mountains. However, this topography subsided and shallow marine sedimentation covered the region, beginning in

371-550: A number of endemic species. The vegetation changes with altitude, the mountains are covered with shrubland at lower elevations, growing richer and then becoming woodland, including wild olive and fig trees between 3,630 and 8,250 ft (1,110 and 2,510 metres), and then higher still there are junipers . Fruit trees such as pomegranate and apricot are grown in the cooler valleys and in places there are rocky outcrops with little vegetation. The flora shows similarities with mountain areas of nearby Iran , as well as with areas along

424-422: A process known as lithospheric flexure . The width and depth of the foreland basin is determined by the flexural rigidity of the underlying lithosphere, and the characteristics of the mountain belt. The foreland basin receives sediment that is eroded off the adjacent mountain belt, filling with thick sedimentary successions that thin away from the mountain belt. Foreland basins represent an endmember basin type,

477-607: A regime's tectonic origin and development as well as the lithospheric mechanics. Migrating fluids originate from the sediments of the foreland basin and migrate in response to deformation. As a result, brine can migrate over great distances. Evidence of long-range migration includes: 1) correlation of petroleum to distant source rocks , 2) ore bodies deposited from metal-bearing brines, 3) anomalous thermal histories for shallow sediments, 4) regional potassium metasomatism and 5) epigenetic dolomite cements in ore bodies and deep aquifers. Fluids carrying heat, minerals, and petroleum, have

530-447: A series of nappes ( allochthonous rocks) that were transported from the northeast to the southwest horizontally for more than 300 km (190 mi). This was a major tectonic event during the late Cretaceous . This process is called obduction , where Permian to middle Cretaceous continental slope-rise (shallow to deep marine) sedimentary rocks and late Cretaceous oceanic crust ( Semail ophiolite ) were thrust (obducted) above

583-454: A vast impact on the tectonic regime within the foreland basin. Before deformation, sediment layers are porous and full of fluids, such as water and hydrated minerals. Once these sediments are buried and compacted, the pores become smaller and some of the fluids, about ⁠ 1 / 3 ⁠ , leave the pores. This fluid has to go somewhere. Within the foreland basin, these fluids potentially can heat and mineralize materials, as well as mix with

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636-400: Is concern in the geological community that with the development of infrastructure these rocks that contain a great deal of information will be excavated and destroyed. The central section of the Hajar is the highest and wildest terrain in the country. Jabal Shams is the highest of the range, followed by Jebel Akhdar . The latter and the smaller Jebel Nakhl range are bounded on the east by

689-460: Is more geologically accurate within a specific region. Seismicity determines where active zones of seismic activity occur as well as measure the total fault displacements and the timing of the onset of deformation. Foreland basins form because as the mountain belt grows, it exerts a significant mass on the Earth's crust, which causes it to bend, or flex, downwards. This occurs so that the weight of

742-472: Is most rapid near the moving thrust sheet. Sediment transport within the foredeep is generally parallel to the strike of the thrust fault and basin axis. The motion of the adjacent plates of the foreland basin can be determined by studying the active deformation zone with which it is connected. Today GPS measurements provide the rate at which one plate is moving relative to another. It is also important to consider that present day kinematics are unlikely to be

795-596: Is named as "the stone" or "the rock". The Hajar Mountains extend for 700 kilometres (430 miles) through the UAE and Oman. They are located on the north-east corner of the Arabian Plate , reaching from the Musandam Peninsula through to the east coast of Oman . The range is about 100 km (62 mi) wide, with Jabal Shams being the highest peak at 3,009 m (9,872 ft) in the central region of

848-486: Is some debate over whether the topography of the Hajar Mountains is due to thin or thick-skinned tectonics (if basement rocks were faulted during collision to create uplift due to thrust faults). Recent Bouguer gravity and magnetotelluric geophysical data suggest deep basement faults that have been activated as thrust faults during the collisional event that obducted the Semail Ophiolite. This has resulted in

901-588: The Eocene Epoch around 45-40 Ma. This episode saw the reactivation of cretaceous thrust faults and the development of long and short wavelength folding of Paleocene marine sediments that infilled previous foredeep accommodation. Low temperature thermodchronometry of apatite grains has given ages to this deformation and subsequent exhumation of the mountain belt. Exhumation occurred in two states, first between 45 and 40 Ma and again from 20 to 15 Ma. This later unroofing could also be related to tectonic uplift in

954-690: The Makran subduction zone . The Hajar Mountains are the product of polyphase mountain building . Uplift and deformation of the Arabian passive margin began during the late cretaceous as the African-Arabian Plate began to subduct under the South Tethyan Oceanic Plate imitated at an intra oceanic subduction zone . This initiation may have been the result of plate rotation due to the breakup of Gondwana . Similar to

1007-535: The Paleocene . Paleocene to Eocene sedimentary rocks are found at 2,200 m (7,200 ft) above sea level within the Hajar, and are folded . This indicates that the present day topography formed after the late Eocene . The exact timing is debated, and various interpretations indicate the topography formed anywhere between the late Eocene through to the Miocene . The driving forces that formed

1060-677: The Red Sea in the Horn of Africa . For example, the tree Ceratonia oreothauma is found here and also in Somalia . A number of birds are found in the mountains including Egyptian and lappet-faced vultures ( Torgos tracheliotus ). Mammals include mountain gazelles ( Gazella gazella ) and the Arabian tahr ( Arabitragus jayakari ). Other endemic species include a number of geckos and lizards: Asaccus montanus , Asaccus platyrhynchus and

1113-542: The mantle , and then exhumed back to the surface. This exhumation event created possibly the largest megasheath fold on Earth, the Wadi Mayh megasheath fold. The common view is that these eclogites were originally basic volcanic rocks within the leading edge of the continental crust of the Arabian Plate . This leading edge was then subducted by a NE-dipping subduction zone . However, some geologists have interpreted that these eclogites were subducted through

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1166-500: The outlier of Jebel Hafeet , which measures 1,100–1,400 m (3,600–4,600 ft) in height. Due to its proximity to the main range, it may be treated as one of the Hajar Mountains, sensu lato . This mountain has ridges which stretch northwards to the city of Al Ain. The northernmost mountains of the Hajar range are found on the Musandam Peninsula. For this reason, the phrase Ru'us al-Jibal ("Heads of

1219-553: The Eastern Hajar, for the protection of Arabian tahr and mountain gazelle. For visitors, there is a road into the mountains from the town of Birkat al-Mawz (on the road to Nizwa from Muscat) and a walking route through Wadi al-Muaydin to the Saiq Plateau. There are 11 marked trails/routes of varying intensity (between Grade 1 to 3) and duration (between 1.5 hours to 18 hours) published by Ministry of Tourism, Oman along

1272-485: The Hajar is also debated. Many geologists relate the Zagros Collision as the reason for the uplift forming the mountains, as currently the Musandam Peninsula (northwest corner of the mountain range) is uplifting due to this collision. However, Jabal Shams , the highest peak of the central mountains is over 300 km (190 mi) away from this zone. In addition, there is no major seismicity within

1325-427: The Hajar range. Some areas are inaccessible, and requires special equipment, as shown in a Steve Backshall TV documentary. Other notes: Foredeep A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt . Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by

1378-643: The Hajar, the Semail ophiolite is still intact. Oman also has one of the best exposed mega-sheath folds ever discovered, the Wadi Mayh sheath fold. Additionally, the relatively small outcrop of eclogite is important. Eclogite is rare on the Earths surface, as it is a rock that forms at high pressures deep within the crust or mantle . Geologists can learn about what is occurring in the Earths interior and tectonic processes from these rocks. There are also various fossil localities in Oman that need to be protected. There

1431-585: The Mountains") is applied to them, or the peninsula itself. Despite being physically part of the western Hajar, they differ in geology and hydrology to the rest of the range. The highest point in the UAE is located at Jebel Jais near Ras Al Khaimah , which measures 1,911 m (6,270 ft) from sea level, but since the summit is on the Omani side, Jabal ar Rahrah , measuring over 1,691 m (1.051 miles), has

1484-534: The Western Hajar ( Arabic : ٱلْحَجَر ٱلْغَرْبِي , romanized :  Al-Ḥajar Al-Gharbī ), also known as the " Oman proper ". Since Jabal Akhdar and mountains in its vicinity are west of the valley, they may be regarded as Western Hajar. In the region of Tawam , which includes the adjacent settlements of Al-Buraimi and Al Ain , on the border of Oman and the UAE Emirate of Abu Dhabi , lies

1537-404: The adjacent mountain belt. In the early stages, the foreland basin is said to be underfilled . During this stage, deep water and commonly marine sediments, known as flysch , are deposited. Eventually, the basin becomes completely filled. At this point, the basin enters the overfilled stage and deposition of terrestrial clastic sediments occurs. These are known as molasse . Sediment fill within

1590-643: The area of Khasab in northern part of the Musandam . Like the Ru'us al-Jibal , the area of Jebel Hafeet is noted for hosting rare flora and fauna. For example, in February 2019, an Arabian caracal was sighted here, and in March, a Blanford's fox , which has also been reported in the mountains of Ras Al-Khaimah. In September 2024 it was reported that the rare white-edged rock brown butterflies were spotted in

1643-481: The area. The Hajar are extensively grazed by domestic goats, camels and donkeys and the landscape has been cleared in parts for urban areas and for mining, which has damaged both vegetation and water supplies and uprooted traditional rural land management behaviours. Poaching of wildlife is another issue. The Oman government has created the Wadi Sareen Reserve and an area of Jebel Qahwan-Jebal Sebtah in

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1696-480: The central mountains, indicating that the mountains are not currently deforming, even though the Zagros collision is. This indicates that the uplift that created the present day topography occurred in the past, possibly before the initiation of the Zagros collision , by a mechanism that is not fully understood. Oman's geological record is extremely valuable to geologists, and needs to be preserved . It contains

1749-421: The foredeep acts as an additional load on the continental lithosphere. Although the degree to which the lithosphere relaxes over time is still controversial, most workers accept an elastic or visco-elastic rheology to describe the lithospheric deformation of the foreland basin. Allen & Allen (2005) describe a moving load system, one in which the deflection moves as a wave through the foreland plate before

1802-524: The highest mountain ranges in the Arabian Peninsula , shared between northern Oman and eastern United Arab Emirates . Also known as "Oman Mountains", they separate the low coastal plain of Oman from the high desert plateau, and lie 50–100 km (31–62 miles) inland from the Gulf of Oman . Al ( اَلْ ) means "the", and Ḥajar ( حَجَر ) means "stone" or "rock". So al-Ḥajar ( اَلْحَجَر )

1855-685: The highest peak in the UAE. The mountains bordering the Shamailiyyah ( شَمَيْلِيَّة ) coast on the Gulf of Oman, forming parts of the northern UAE Emirates of Sharjah , Ras Al-Khaimah and Fujairah , may also be called the Shumayliyyah ( شُمَيْلِيَّة ). In this region is Jebel Al-Ḥeben ( جَبَل ٱلْحبن ; 25°7′33″N 56°9′33″E  /  25.12583°N 56.15917°E  / 25.12583; 56.15917 ). The mountains are rich in plant life compared to most of Arabia, including

1908-679: The lithosphere beneath the mountain range becomes ductile almost entirely, except a thin (about 6 km in the center) brittle layer near the surface and perhaps a thin brittle layer in the uppermost mantle." This lithospheric weakening underneath the orogenic belt may in part cause the regional lithospheric flexure behavior. Foreland basins are considered to be hypothermal basins (cooler than normal), with low geothermal gradient and heat flow . Heat flow values average between 1 and 2 HFU (40–90 mWm . Rapid subsidence may be responsible for these low values. Over time sedimentary layers become buried and lose porosity. This can be due to sediment compaction or

1961-424: The load system. The deflection shape is commonly described as an asymmetrical low close to the load along the foreland and a broader uplifted deflection along the forebulge. The transport rate or flux of erosion, as well as sedimentation, is a function of topographic relief. For the loading model, the lithosphere is initially stiff, with the basin broad and shallow. Relaxation of the lithosphere allows subsidence near

2014-457: The local hydrostatic head. Orogen topography is the major driving force of fluid migration. The heat from the lower crust moves via conduction and groundwater advection . Local hydrothermal areas occur when deep fluid flow moves very quickly. This can also explain very high temperatures at shallow depths. Other minor constraints include tectonic compression, thrusting, and sediment compaction. These are considered minor because they are limited by

2067-409: The low Samail Valley (which leads northeast to Muscat ). East of Samail are the Eastern Hajar ( Arabic : ٱلْحَجَر ٱلشَّرْقِي , romanized :  Al-Ḥajar Ash-Sharqī ), which run east (much closer to the coast) to the port city of Sur , almost at the easternmost point of Oman. The mountains to the west of Sama'il Valley, particularly those in Musandam Peninsula and the UAE, are known as

2120-534: The modern convergence of the Australian passive margin under Eurasian oceanic crust, Arabian passive margin sediments became highly deformed and shortened forming an imbricated thrust belt. This also coincided with the emplacement of the Semail Ophiolite . By the early Maastrichtian , deformation ceased, and stable continental shelf conditions resumed. A second episode of deformation began during

2173-438: The most complete ophiolite on Earth, of which it is most famous for among geologists. The ophiolite sequence has spectacular pillow basalt (Geotimes pillow lava), as well as exposures of the fossil crust-mantle boundary ( moho ). Generally, ophiolites are obducted prior to continental collision , which highly deforms the structure of the original oceanic crust . However, because continental collision has not occurred in

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2226-436: The mountain belt can be compensated by isostasy at the upflex of the forebulge. The plate tectonic evolution of a peripheral foreland basin involves three general stages. First, the passive margin stage with orogenic loading of previously stretched continental margin during the early stages of convergence. Second, the "early convergence stage defined by deep water conditions", and lastly a "later convergent stage during which

2279-503: The mountains. Currently, the Arabian Plate is moving north relative to the Eurasian Plate at 2–3 cm (0.79–1.18 in) per year. Continental collision is occurring at the Zagros fold and thrust belt west of the Musandam Peninsula . This collisional plate boundary transitions into a subduction zone , towards the east. Here, oceanic crust of the Arabian Plate is subducted northwards beneath Eurasia , called

2332-545: The moving thrust sheets and contains all the sediments charging from the active tectonic thrust wedge. This is where piggyback basins form. The foredeep is the thickest sedimentary zone and thickens toward the orogen. Sediments are deposited via distal fluvial, lacustrine, deltaic, and marine depositional systems. The forebulge and backbulge are the thinnest and most distal zones and are not always present. When present, they are defined by regional unconformities as well as aeolian and shallow-marine deposits. Sedimentation

2385-420: The nearby Zagros Mountains of Iran . The geology of the Hajar can be grouped into four major tectonostratigraphic groups. Group one are the pre- Permian basement rocks, a sedimentary sequence of clastics , carbonates and evaporites . Group two are a middle Permian to Late Cretaceous sequence of continental shelf carbonates , which were deposited unconformably above the basement. Group three are

2438-474: The other being rift basins . Space for sediments (accommodation space) is provided by loading and downflexure to form foreland basins, in contrast to rift basins, where accommodation space is generated by lithospheric extension. Foreland basins can be divided into two categories: DeCelles & Giles (1996) provide a thorough definition of the foreland basin system. Foreland basin systems comprise three characteristic properties: The wedge-top sits on top of

2491-511: The physical or chemical changes, such as pressure or cementation . Thermal maturation of sediments is a factor of temperature and time and occurs at shallower depths due to past heat redistribution of migrating brines. Vitrinite reflectance, which typically demonstrates an exponential evolution of organic matter as a function of time, is the best organic indicator for thermal maturation. Studies have shown that present day thermal measurements of heat flow and geothermal gradients closely correspond to

2544-424: The rheological structure of the lithosphere underneath the foreland and the orogen are very different. The foreland basin typically shows a thermal and rheological structure similar to a rifted continental margin with three brittle layers above three ductile layers. The temperature underneath the orogen is much higher and thus greatly weakens the lithosphere. According to Zhou et al. (2003), "under compressional stress

2597-479: The rocks from groups one and two. Lastly, group four are late Cretaceous to Miocene shallow marine and terrestrial sedimentary rocks that were deposited on top of all three previous groups. The high topography is around two major culminations: Jabal Akhdar and Saih Hatat, which are large scale anticlines . The Saih Hatat culmination contains eclogite in the northeast at As Sifah. These rocks were subducted to about 80 km (50 mi) depth into

2650-430: The same as when deformation began. Thus, it is crucial to consider non-GPS models to determine the long-term evolution of continental collisions and in how it helped develop the adjacent foreland basins. Comparing both modern GPS (Sella et al. 2002) and non-GPS models allows deformation rates to be calculated. Comparing these numbers to the geologic regime helps constrain the number of probable models as well as which model

2703-401: The slow rates of tectonic deformation, lithology and depositional rates, on the order of 0–10 cm yr , but more likely closer to 1 or less than 1 cm yr . Overpressured zones might allow for faster migration, when 1 kilometer or more of shaley sediments accumulate per 1 million years. Bethke & Marshak (1990) state that "groundwater that recharges at high elevation migrates through

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2756-441: The subsurface in response to its high potential energy toward areas where the water table is lower." Bethke & Marshak (1990) explain that petroleum migrates not only in response to the hydrodynamic forces that drive groundwater flow, but to the buoyancy and capillary effects of the petroleum moving through microscopic pores. Migration patterns flow away from the orogenic belt and into the cratonic interior. Frequently, natural gas

2809-444: The thrust, narrowing of basin, forebulge toward thrust. During times of thrusting, the lithosphere is stiff and the forebulge broadens. The timing of the thrust deformation is opposite that of the relaxing of the lithosphere. The bending of the lithosphere under the orogenic load controls the drainage pattern of the foreland basin. The flexural tilting of the basin and the sediment supply from the orogen. Strength envelopes indicate that

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