Geology of the Shuwaihat 1:100 000 map sheet, 100-32 (and the Islands of Delma, Zirku, Qarnain and Arzana at 1:50 000), United Arab Emirates
0
Citation
0
Reference
20
Related Paper
Abstract:
This Sheet Description describes the solid and Quaternary geology of the Shuwaihat area and the salt islands of Delma, Zirku, Arzana and Qarnain (at 1:50 000 scale). The two small islands of Yasat Ali and Yasat Safli were also mapped. The mainland area shown is quite small (115 km2), but is geologically important in that it contains the Type Sections of the Miocene Shuwaihat Formation and the Barakah Member of the Baynunah Formation, on Shuwaihat Island and Jebel Barakah respectively. Some 300 observation points were made throughout the district.
The oldest rocks in the area are those of the Neoproterozoic Hormuz Complex, exposed on the four salt islands included on the map. The islands are cored by salt domes with excellent outcrops of the Hormuz breccias. These were mapped at 1:25 000 scale and large clasts >100 m across have been shown on the map as igneous, sedimentary and undifferentiated megaclasts. Two metamorphic rock clasts were recorded and detrital zircons from one of these, a layered marble from Delma, constrained the maximum age of deposition of the original sediments at 590 ± 2 Ma. The island of Zirku is unique in that it contains extensive outcrops of deformed turbiditic rocks, termed the Zirku Formation, which form a semi-continuous carapace over Hormuz breccia. U-Pb dating of detrital zircons of a sandstone unit in the formation determines a depositional maximum age of 560 ± 19 Ma. U-Pb zircon dating of a felsic volcanic igneous clasts from Qarnain yielded a Neoproterozoic (Ediacaran) crystallisation age of 561 ± 16 Ma, suggesting that volcanism was penecontemporaneous with sedimentation.
The salt domes are unconformably overlain by Quaternary pale cream-coloured carbonate grainstones and gravels of the Jebal Dhanna Formation, which are deposits unique to the salt domes. The salt domes were injected into Miocene strata which underlie most of the area. Recent movements of the salt diapirs are represented in numerous ‘salt blisters’ seen on many of the islands.
The oldest Miocene rocks in the district, marine sedimentary rocks of the Gheweifat Member of the Dam Formation, outcrop on the two small Gulf islands of Yasat Ali and Yasat Safli. Over the rest of the area, the oldest Miocene rocks belong to the Shuwaihat Formation, which consists of highly variable sequence of fluvial, aeolian, terrestrial playa and continental sabkha red-bed siliciclastic sediments, well exposed in a number of sections on Shuwaihat Island, Jebel Barakah and on Delma. The Shuwaihat Formation is unconformably overlain by the Barakah Member of the Baynunah Formation, also well exposed in sections on Shuwaihat Island and Jebel Barakah. It comprises a sequence dominated by fluvial sandstones, with channel lag conglomerates particularly common near the base, where fossilised bone, wood and egg shells are locally abundant. The topmost few metres of strata on Jebel Barakah are made up of greyish green carbonate siltstones of the succeeding Habshan Member.Keywords:
Breccia
Outcrop
Felsic
Cite
The eastern part of the northern Interior Plains is underlain by rocks of Cenozoic, Mesozoic, and Paleozoic age. The region is bounded on the east by the Coppermine arch, composed of lower Paleozoic and Precambrian rocks. The plains region is a northwest-dipping homocline, interrupted in its western part by the Kugaluk arch, a north-trending pre-Cretaceous uplift. Mesozoic rocks of the Interior Plains consist of Cretaceous sandstones, mudstones, and shales with a composite thickness of about 3,000 ft (900 m) along Anderson and Horton Rivers. The Lower Cretaceous units are correlated with similar rocks on Banks Island. On the mainland, these strata are disconformably overlain by varicolored clastic units of Late Cretaceous and early Tertiary age. Westward, in the region of the Mackenzie delta, the Tertiary Reindeer Formation consists of a northward-thickening sequence of poorly consolidated to unconsolidated cherty gravels, crossbedded sands, and coal and ash beds. Its maximum outcrop thickness is about 4,000 ft (1,250 m). In the nearby B.A.-Shell-I.O.E. Reindeer D-27 well, the Reindeer Formation is 3,970 ft (1,210 m) thick and underlies 790 ft (250 m) of Quaternary and recent sediments. Microfaunal studies show that the Reindeer Formation overlies 2,200 ft (670 m) of Late Cretaceous clastic rocks which, in part, may be equivalent to the Moose Channel Formation, which crops out on the west side of the delta adjacent to the Richardson Mountains. These Upper Cretaceous rocks in the Reindeer well lie unconformably on 5,690 ft (1, 50 m) of Lower Cretaceous sandstones and mudstones which can be correlated with similar units in the eastern Richardson Mountains. Offshore seismic profiles obtained during the 1969 Arcticquest survey indicate the presence of a thick sequence of sedimentary rocks, the lower part of which has been deformed into broad domal structures. These lower rocks are unconformably overlain by nearly flat-lying younger rocks. This unconformity may be the same as that separating the Lower and Upper Cretaceous rocks in the Reindeer well. Analyses of the profiles indicate that these younger rocks may have been intruded by diapiric structures.
Outcrop
Cite
Citations (4)
This Sheet Description describes the Quaternary and solid geology of the Ghantoot 1:100 000 scale geological map. Over 400 observation points were made throughout the district. The Ghantoot district covers about 1600 km2, including a number of low offshore barrier islands, reefs and sand flats. The region has seen great anthropogenic development over the past 30 years, which has radically changed the surface geology. The underlying pre-Quaternary bedrock comprises Miocene evaporitic mudstone and siltstone of the Gachsaran Formation (Fars Group) overlain by the Baynunah Formation sandstones (not exposed at surface) and the dolomitic conglomerates, sandstones and siltstones of the Barzaman Formation. The Miocene bedrock is poorly exposed, with relatively few surface outcrops, in east-northeast to west-southwest trending inter-dune areas and in a number of temporary excavations. In many areas, the Miocene rocks are only known from boreholes. The evidence from these suggests there is a marked facies change from the coarse dolomitic conglomerates of the Barzaman Formation in the east to interbedded siltstones and sandstones of the Baynunah Formation in the far southwest of the district. The Miocene rocks are locally overlain by fluvial sandstones and channel gravels of the Hili Formation. These represent Quaternary outwash from the Hajar Mountains in the east. The gravels contain ophiolite and chert clasts ultimately derived from the UAE-Oman ophiolite to the east. Much of the region is partially covered by pale carbonate-cemented aeolianites of the Ghayathi Formation, themselves often covered in a veneer of more recent aeolian sand. These are well exposed near the coast in spectacular zeugen. Inland these paleodunes forms a series of east-northeast trending fossil linear ridges. Along the coast, some of the Ghayathi Formation zeugen have a cap of the marine deposits of the Fuwayrit Formation. More recent, modern pale carbonate-dominated low dunes drape the Ghayathi Formation and the interdune bedrock exposures inland. The coastal zone is dominated by a range of Holocene to Recent littoral and marine deposits including beach ridges, algal mats, and intertidal sediments, all contained within the Abu Dhabi Formation. The Quaternary deposits are overlain by various modern dune sands (Rub al Khali Formation), mapped as Low Dunes. Interdune areas, floored either by Miocene or Quaternary rocks typically have continental sabkha veneers and, adjacent to the dune fields, thin sand veneers.
Much of the coastal strip consists of a variety of anthropogenic deposits including reclaimed ground, made ground and areas extensively landscaped for forestry and development.
Outcrop
Siltstone
Bedrock
Calcarenite
Cite
Citations (0)
Paleogene strata are exposed nearly the entire length of the Alaska Peninsula. They include continental and marine volcaniclastic rocks and a thick volcanic sequence. The strata are divided into the Tolstoi, Stepovak, Meshik, and Belkofski (in part) Formations in the southern part of the peninsula, and into the nonmarine clastic West Foreland Formation and the Hemlock Conglomerate in the northern part. The Tolstoi Formation (Paleocene and Eocene), 670-1,380 m thick, consists mainly of continental quartz- and chert-rich sandstone and conglomerate, siltstone, and coal. Volcanic clasts and tuffaceous detritus increase in abundance upward. Neritic strata are present as interbeds in the type area. The formation overlies, with a major unconformity, strata ranging in age from Late Jurassic to Late Cretaceous. Partly coeval strata at the north end of the peninsula (West Foreland Formation) are mainly volcanic sandstone and conglomerate. The Stepovak Formation, 1,800-2,000 m thick, represents two contrasting depositional environments--a lower dark siltstone and sandstone turbidite, about 975 m thick, and a shallow neritic sandstone and siltstone, rich in volcanic material, about 1,000 m thick. Locally, the upper part is deltaic sandstone, siltstone, and coal. An abundant megafauna of Eocene and Oligocene age is found in the neritic deposits. A thick coeval volcanic unit, the Meshik Formation, is present in the central part of the peninsula. Andesitic to basaltic lava, breccia, tuff, and lahars, as much as 1,500 m thick, have been K-Ar dated at 27-38 m.y. Similar rocks with interbedded sediment at the end of the peninsula are included with the Belkofski Formation. End_of_Article - Last_Page 661------------
Paleogene
Peninsula
Sequence (biology)
Cite
Citations (0)
The sedimentary and volcanic sequence of southeastern Guatemala is similar to that in bordering western Honduras. A metamorphic complex of probable Paleozoic age is overlain unconformably by red continental clastic rocks of the Late Jurassic-Early Cretaceous Todos Santos Formation, and carbonate rocks and shale of the Yojoa Group of Aptian?-Cenomanian? age. Both of these rock-stratigraphic units are relatively thick a few kilometers south of Jocotan, but only a few scattered outcrops remain north of the Jocotan-Chamelecon fault zone. The Subinal Formation, a sequence of interbedded terrestrial sedimentary and volcanic rocks, unconformably overlies the pre-Tertiary rocks. Red and olive-gray phyllarenites and calclithites are most common in the lower part of the formation. Locally, gypsum is interbedded. Rhyolitic tuff and volcanic arenite are found in the middle and upper parts. These rocks are ov rlain gradationally and concordantly by the Padre Miguel Group of Miocene?-Pleistocene? age, a series of basalt and felsitic ash-flow tuffs with local interbeds of volcanic arenite, tuff, and lahar.
Cite
Citations (19)
Imperial Valley is the southern part of a large northwesterly trending valley in southeastern California. This valley is a part of a large basin of deposition which existed during parts of Tertiary and Quaternary time. The stratigraphy discussed in this paper is based on a study of the exposed Tertiary and Quaternary sediments in the region bounded by the Santa Rosa Mountains on the north, Salton Sea on the east, Mexico on the south, and the crystalline rocks of the Coast Range on the west. The rocks exposed in this region may be divided as follows: Basement complex. Granite and metamorphic rocks Split Mountain formation--0 to 2,700 feet. Non-marine fanglomerates and sandstones intercalated with marine sandstones and shales unconformably overlying basement complex. Miocene? Alverson Canyon formation--0 to 700 feet. Non-marine unassorted sediments and associated basic igneous flows and tuffaceous sediments unconformably overlying all older rocks. Unfossiliferous End_Page 1781------------------------------ Imperial formation--0 to 3,600 feet. Marine mudstones, siltstones, and sandstones unconformably overlying all older rocks. Upper Miocene Palm Spring formation--0 to 6,100 feet. Non-marine mudstones, siltstones, and sandstones conformably overlying Imperial formation Borrego formation--0 to 7,600 feet. Non-marine mudstones, siltstones, sandstones, and conglomerates probably unconformably overlying all older rocks Terrace deposits--0 to 200 feet Lake Coahuila deposits--0 to 100 feet. Thin veneer of lake marls covering most of surface below ancient beach line Salton Sea deposits Recent alluvium The geology of the region surveyed indicates that the sediments are probably less than 14,000 feet thick due to the various unconformities within the sedimentary section. No data are available concerning the depth of the sediments in the central part of Imperial Valley. If the present topographic basin represents the central part of the basin of deposition, the sediments may extend to a depth of 22,000 feet or more. The principal microfossils represented in the succession are Foraminifera and Ostracoda. Sixty species of the small Foraminifera were found in the Imperial formation, and most of these are confined to the lower few hundred feet of strata. A gradual change to brackish-water conditions is indicated with the passage of Imperial time. This was followed by a comparatively abrupt change to fresh-water and slightly saline environments of the Palm Spring and Borrego formations. These locally contain Ostracoda, Chara, Rotalia beccarii, and a few species of Elphidium. The latter group of microfossils is represented in the deposits of Lake Coahuila, which covered the Salton Sink in relatively recent time. Some of the species are living in the Salton Sea, which now partially occupies the Salton Sink. The foraminiferal fauna of the Imperial formation is not found elsewhere in California. It is clearly related to Miocene faunas of the Gulf of Mexico and Caribbean borderlands and is considered to be upper Miocene in age. A meager fauna from the Split Mountain formation suggests Miocene age. The microfossils of the Palm Spring and Borrego formations have no apparent value at this time in determining geologic age, but they can be used in local correlation. End_of_Article - Last_Page 1782------------
Micropaleontology
Cite
Citations (13)
Two sedimentary formations are present in this area; the Modelo formation and the Mint Canyon formation. The latter sediments make up most of the rocks in this region while the former is confined to the southwestern one-fourth of the area. An angular unconformity separates the marine Modelo (Upper Miocene) from the non-marine Mint Canyon formation (Lower-Upper Miocene). The sediments are typical of those deposited under semi-arid conditions. Conglomerates, sandstones, and clays are abundant. There has been little local faulting, but folding is developed to a high degree, especially in the sediments of the Mint Canyon. Recurrent volcanic activity has taken place in Miocene time and several ash beds are interbedded in the sediments. The only other rocks present in the area are some uplifted terrace gravels of Quaternary age and the recent valley alluvium.
Terrace (agriculture)
Alluvial fan
Dome (geology)
Cite
Citations (0)
Commercial quantities of gas have been produced from several Miocene conglomerates in the southwestern part of the Veracruz basin. These conglomerates, with their associated sandstones and shales, make up a zone 1,000 m thick, all of which was deposited in a bathyal environment. The conglomerates consist of recycled Upper Cretaceous limestone clastic rocks containing minor amounts of igneous and metamorphic rock fragments. The clastic material was derived from the west, where a very thick section of carbonate and terrigenous rocks, Jurassic to Paleocene in age, was uplifted, folded, and thrust faulted during the Laramide orogeny. Erosion of the deformed source materials is indicated by two significant unconformities. One unconformity truncates sedimentary rocks from the Paleocene to the Upper Cretaceous, whereas the other is at the base of the Miocene. Most of the conglomerate beds are in the lower Miocene. A reconstruction of the pre-lower Miocene erosional surface serves to locate paleodrainage patterns and the areas of debouchment of deep-water fanglomerat s. Sediments derived from the source area west of Veracruz basin were transported in a general northeasterly direction by fluvial currents which fed into deep submarine canyons. Through these canyons most of the coarse clastic sediments were carried down to the basin floor and deposited as a series of prograding submarine fans.
Conglomerate
Terrigenous sediment
Cite
Citations (21)
The oldest rocks in the Southern Meyaneh basin area are a series of metasediments, dolomites, and quartzites probably Late Devonian in age, on top of which occur 126 meters of dolomitic limestone which contain well preserved productoid brachiopods of Carboniferous age. No Permian or Triassic rocks have been recognized in the area, but the Jurassic is represented by coal-bearing, gray, silty to argillaceous sandstones of Liassic age called the Ghaleh Bulagh Formation. Above these sandstones are 120 meters of a sandstone-limestone sequence of Sequanian to Lower Tithonian age, which the writer has called the Ouzeh Formation. No sediments of Cretaceous age have been found. Except for the Paleocene, the Tertiary is fairly complete in the area of investigation, and there is evidence of sporadic volcanic activity from Eocene to Early Miocene time. The only marine sequence in the area is about 270 meters of alternating calcareous shale and organodetrital reef limestone, the Marine member of the Qum Formation of Oligo-Miocene age. The Qum Formation is conformably overlain by 2,700 meters of continental redbeds known as the Upper Red Formation. Pliocene deposits exposed in the eastern part of the area are composed of a basal conglomerate and a sequence of light yellow to pinkish silts and clays. Structurally the area consists of three provinces. 1. The broad homocline at the south forms the southern plateau and dips northward into the basin. 2. A domal structure west of Mushampa is a sharp semi-elliptical upwarp containing a few subsidiary structures. Several faults are present in this province radiating from the core of the dome. 3. The north and central part of the basin is tightly folded and faulted by intense deformation of incompetent Upper Red deposits.
Cite
Citations (1)
Cretaceous marine and continental sedimentary rocks, of Albian and possibly Cenomanian ages, crop out in the south half of the Mitchell quadrangle in central Oregon. More than 70 sq mi of Cretaceous rocks is exposed along a northeast-trending, doubly plunging anticline. The sequence, 9,023 ft thick as described along three principal reference sections, lies with angular unconformity on Permian metasedimentary rocks, and is overlain unconformably by Tertiary lava flows and volcanic sedimentary rocks. In part, the rocks have been faulted complexly and there are numerous fault-controlled and randomly oriented intrusions of Tertiary age. These rocks are divided into two intertonguing formations. One, a widespread and thick sequence of marine mudstone with subordinate siltstone and sandstone, is defined herein as the Intertonguing intricately with the marine rocks are conglomerate and sandstone; these, predominantly of fluvial and deltaic origin, are defined herein as the Creek The total sequence consists of the Basal of the Hudspeth Formation, a thin sandstone and conglomerate unit lying unconformably on the Permian basement rock; a thick mudstone and siltstone unit referred to as the Main Mudstone member of the Hudspeth Formation; and 11 numbered conglomerate and sandstone members of the Gable Creek Formation intertonguing with a like number of mudstone and siltstone members of the Hudspeth Formation. Seven tongues of the Gable Creek Formation wedge out southward into the marine facies of the Hudspeth Formation; the four other tongues thin southward. Three Hudspeth Formation marine tongues wedge out northward into the Gable Creek Formation; the six other tongues thin northward. Shapes of tongues, textural and thickness variations, primary sedimentary structures, and current-flow directions indicate that during middle Cretaceous time there was a rising landmass on the north. Very large volumes of coarse sediment were delivered by a major river to a shallow-marine embayment, and extensive alluvial piedmont and delta plains projected into the sea. Swinging distributaries, episodic uplift of the source area, and intermittent subsidence of the basin caused the shoreline to fluctuate and produce a complex intertonguing of fluvial-deltaic sediments with marine sediments.
Quadrangle
Cite
Citations (20)
Paleogene strata are exposed nearly the entire length of the Alaska Peninsula. They include continental and marine volcaniclastic rocks and a thick volcanic sequence. The strata are divided into the Tolstoi, Stepovak, Meshik, and Belkofski (in part) Formations in the southern part of the peninsula, and into the nonmarine clastic West Foreland Formation and the Hemlock Conglomerate in the northern part. The Tolstoi Formation (Paleocene and Eocene), 670-1380 m thick, consists mainly of continental quartz- and chert-rich sandstone and conglomerate, siltstone, and coal. Volcanic clasts and tuffaceous detritus increase in abundance upward. Neritic strata are present as interbeds in the type area. The formation overlies, with a major unconformity, strata ranging in age from Late Jurassic to Late Cretaceous. Partly coeval strata at the north end of the peninsula (West Foreland Formation) are mainly volcanic sandstone and conglomerate. The Stepovak Formation, 1800-2000 m thick, represents two contrasting depositional environments - a lower dark siltstone and sandstone turbidite, about 975 m thick, and a shallow neritic sandstone and siltstone, rich in volcanic material, about 1000 m thick. Locally, the upper part is deltaic sandstone, siltstone, and coal. An abundant metafauna of Eocene and Oligocene age is found in the neritic deposits.more » A thick coeval volcanic unit, the Meshik Formation, is present in the central part of the peninsula. Andesitic to basaltic lava, breccia, tuff, and lahars, as much as 1500 m thick, have been K-Ar dated at 27-38 m.y. Similar rocks with interbedded sediment at the end of the peninsula are included with the Belkofski Formation.« less
Siltstone
Conglomerate
Paleogene
Breccia
Cite
Citations (0)