Monocline

A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence.

Monocline01
block diagram of a monocline
Grandview-Phantom Monocline
The Grandview-Phantom Monocline in the Grand Canyon, Arizona
Minor thrust monocline
Monocline formed at tip of small thrust fault, Brims Ness, Caithness, Scotland

Formation

MonoclineMonoclinalFr02
Possible modes of formation of monoclines

Monoclines may be formed in several different ways (see diagram)

  • By differential compaction over an underlying structure, particularly a large fault at the edge of a basin due to the greater compactibility of the basin fill, the amplitude of the fold will die out gradually upwards.[1]
  • By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence.[2]
  • As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence.[3]
  • As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence.[4]

Examples

See also

References

  1. ^ Skuce, A.G. (1996). "Forward modelling of compaction above normal faults: an example from the Sirte Basin, Libya". In Buchanan, P.G.; Nieuwland, D.A. (eds.). Modern Developments in Structural Interpretation, Validation and Modelling (PDF). Special Publications. 99. London: Geological Society. pp. 135–146. ISBN 978-1-897799-43-7. Archived from the original (PDF) on 2012-03-16.
  2. ^ Chadwick, R.A. (1993). "Aspects of basin inversion in southern Britain". Journal of the Geological Society. 150: 311–322. Bibcode:1993JGSoc.150..311C. doi:10.1144/gsjgs.150.2.0311.
  3. ^ Willsey, S.P.; Umhoefer, P.J.; Hilley, G.E. (2002). "Early evolution of an extensional monocline by a propagating normal fault: 3D analysis from combined field study and numerical modeling" (PDF). Journal of Structural Geology. 24: 651–669. Bibcode:2002JSG....24..651W. doi:10.1016/S0191-8141(01)00120-1.
  4. ^ Finch, E.; Hardy, S.; Gawthorpe, R. (2003). "Discrete element modelling of contractional fault-propagation folding above rigid basement fault blocks". Journal of Structural Geology. 25: 515–528. Bibcode:2003JSG....25..515F. doi:10.1016/S0191-8141(02)00053-6.
  5. ^ "Geology". Capitol Reef National Park. National Park Service. 23 December 2017. Retrieved 1 March 2018.
  6. ^ Abbott, Lon and Cook, Terri (2004). Hiking the Grand Canyon's Geology. Seattle: The Mountaineers Books. pp. 99–114. ISBN 978-0-89886-895-1.CS1 maint: Multiple names: authors list (link)
  7. ^ Murray, Frederick N. (1967). "Jointing in Sedimentary Rocks along the Grand Hogback Monocline, Colorado". The Journal of Geology. 75 (3): 340–350. doi:10.1086/627261. JSTOR 30071521.
  8. ^ Klausen, M.B. (2009). "The Lebombo monocline and associated feeder dyke swarm: Diagnostic of a successful and highly volcanic rifted margin?". Tectonophysics. 468 (1–4): 42–62. Bibcode:2009Tectp.468...42K. doi:10.1016/j.tecto.2008.10.012.
  9. ^ "L001 : Lapstone Monocline". Heritage places and items. Office of Environment and Heritage, Government of New South Wales. Retrieved 1 March 2018.
  10. ^ "61. Beaumaris Cliffs 3 - Monocline". Sites of Geological and Geomorphological Significance. Agriculture Victoria. 8 June 2017. Retrieved 1 March 2018.
  11. ^ Nowell, D.A.G. (1997). "Structures affecting the coast around Lulworth Cove, Dorset and syn-sedimentary Wealden faulting". Proceedings of the Geologists' Association. 108 (4): 257–268. doi:10.1016/S0016-7878(97)80011-9.
  12. ^ Kluska, B.; Rospondek, M.J.; Marynowski, L.; Schaeffer, P. (2013). "The Werra cyclotheme (Upper Permian, Fore-Sudetic Monocline, Poland): Insights into fluctuations of the sedimentary environment from organic geochemical studies". Applied Geochemistry. 29: 73–91. Bibcode:2013ApGC...29...73K. doi:10.1016/j.apgeochem.2012.09.010.
  13. ^ Memon, A.D.; Siddiqui, I.; Memon, A. (1999). "Tectonics of the Sindh monocline, Pakistan and their effects on hydrocarbons". Mehran University Research Journal of Engineering and Technology. 18 (2): 87–96.
  14. ^ Seth, H. (2018). Tectonic Deformation of Flood Basalt Provinces. Springer. ISBN 978-3-319-67704-0.

External links

Americium(III) chloride

Americium(III) chloride or americium trichloride is the chemical compound composed of americium and chlorine with the formula AmCl3. It forms pink hexagonal crystals.

In the solid state each americium atom has nine chlorine atoms as near neighbours, at approximately the same distance, in a tricapped trigonal prismatic configuration.The hexahydrate has a monocline crystal structure with: a = 970,2 pm, b = 656,7 pm and c = 800,9 pm; β = 93° 37'; space group: P2/n.

Box-Death Hollow Wilderness

Box-Death Hollow Wilderness is a 25,751 acres (104 km2) wilderness area located in south-central Utah, United States, on the Dixie National Forest. Vertical gray-orange walls of Navajo sandstone stand above two canyon tributaries of the Escalante River in Box-Death Hollow. The name Death Hollow gives reference to a number of livestock that plunged to their death trying to cross the steep canyon.

Running north-south through a steeply dipping monocline, Pine Creek forms the box canyon (a canyon accessible only at the lower end) known appropriately as "The Box." Death Hollow Creek, east of The Box, has carved its way through a gently dipping monocline. Raging waters often flood these canyon narrows after a rain. Pinyon and juniper cover many of the plateaus above the canyons. Brown and rainbow trout are plentiful in Pine Creek and in portions of Sand Creek. Along the creek banks, you may see mule deer, an occasional cougar, or even elk in winter. Three bird species listed by the Utah Division of Wildlife Resources as "sensitive" can be found in the wilderness - Lewis's woodpecker, the western bluebird, and the mountain bluebird. Nine miles of trail run the distance of "the Box", while hiking in the remainder of this wilderness requires following drainages or undesignated routes.

The larger Phipps-Death Hollow Outstanding Natural Area, a Bureau of Land Management wilderness study area, is adjacent to the wilderness on the south. Phipps-Death Hollow is part of the Grand Staircase-Escalante National Monument.

The Box-Death Hollow Wilderness briefly became the center of controversy during debate over the Utah Wilderness Act of 1984 due to a company that was interested in drilling exploration wells for carbon dioxide. The ridge-top well sites and routes leading to them were cherry-stemmed out of the north side of the legislated boundary, but the project never went into production.

Comb Ridge

Comb Ridge (Navajo: Tséyíkʼáán) is a linear north to south-trending monocline nearly 80 miles long in southeast Utah and northeast Arizona. Its northern end merges with the Abajo Mountains some eleven miles west of Blanding. It extends essentially due south for 45 km (28 mi) to the San Juan River. South of the San Juan the ridge turns to the southwest and is more subdued in expression as it extends for an additional 67 km (42 mi) to Laguna Creek 9 km (5.6 mi) east of Kayenta, Arizona.It was designated a National Natural Landmark in 1976 as the only North American location of tritylodont fossils. Parts of the ridge in Utah are protected as part of the Bears Ears National Monument.

Elk Mountains (South Dakota)

The Elk Mountains are a small range of mountains in western South Dakota, forming the southwest portion of the Black Hills as part of its west-dipping monocline. They are geologically distinct from the Black Hills, on the other side of a "racetrack" region of red stone. The ridge of the Elk Mountains is formed of harder sandstones. The east face of the Elk Mountains is a 300-to-800-foot (91 to 244 m) high escarpment, but the west portion falls slowly and features many canyons. Most of the Elk Mountains were protected in the Harney National Forest until 1954, when this protected area joined the Black Hills National Forest. Today the large South Dakota portion of the mountain range is in the Hell Canyon District of the Black Hills National Forest, while the much smaller Wyoming portion lies in the Bearlodge District. The Elk Mountains are one of three mountain ranges that comprise the Black Hills region and national forest, including the Black Hills itself and Wyoming's Bear Lodge Mountains.

Elk Mountain is the highest point of the range and has a lookout tower on its summit. Other peaks include Pilger Mountain and Sullivan Peak.Few people live in or near the Elk Mountains. The closest town is Edgemont, South Dakota, to the south. Tiny unincorporated Dewey and ghost town Burdock lie to the west. Ten miles to the northwest is Newcastle, Wyoming.

Explora Escarpment

Explora Escarpment (70°33′S 15°0′W) is an undersea escarpment named for the Antarctic science ship F.S. Explora. The name, proposed by Dr. Heinrich Hinze of the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, was approved by the Advisory Committee for Undersea Features in June 1997.The Explora Escarpment was aligned with the Lebombo monocline in southern Africa before the break-up of Gondwana.

Geology of Dorset

Dorset (or archaically, Dorsetshire) is a county in South West England on the English Channel coast. Covering an area of 2,653 square kilometres (1,024 sq mi); it borders Devon to the west, Somerset to the north-west, Wiltshire to the north-east, and Hampshire to the east. The great variation in its landscape owes much to the underlying geology which includes an almost unbroken sequence of rocks from 200 Ma to 40 Ma and superficial deposits from 2 Ma to the present. In general the oldest rocks (Early Jurassic) appear in the far west of the county, with the most recent (Eocene) in the far east. Jurassic rocks also underlie the Blackmore Vale and comprise much of the coastal cliff in the west and south of the county; and although younger Cretaceous rocks crown some of the highpoints in the west, they are mainly to be found in the centre and east of the county.Dorset's coastline is one of the most visited and studied coastlines in the world because it shows, along the course of 95 miles (153 km) (including some of east Devon), rocks from the beginning of Triassic, through the Jurassic and up to the end of the Cretaceous, documenting the entire Mesozoic era with well-preserved fossils. Throughout Dorset there are a number of limestone ridges. The largest and most notable is the band of Cretaceous chalk that runs from the south-west to the north-east of the county and forms part of the Chalk Group that underlies much of the south of England, including Salisbury Plain, the Isle of Wight and the South Downs. Between the bands of limestone and chalk are wide clay vales with flood plains.

South-east Dorset, around Poole, Bournemouth and the New Forest, lies on younger and less resistant beds: Eocene clays (mainly London Clay), sands and gravels. These rocks produce thin soils that historically have supported a heathland habitat. The chalk and limestone hills of the Purbecks lie atop Britain's largest onshore oil field. The field, operated from Wytch Farm, produces a high-quality oil and has the world's oldest continuously pumping well at Kimmeridge, which has been in use since the early 1960s. The source of this oil is the organic-rich shales found in the lower lias. Landslides along the coast have been known to ignite these shales causing cliff fires, the most recent of which occurred in 2000.

Geology of Sudan

The geology of Sudan formed primarily in the Precambrian, as igneous and metamorphic crystalline basement rock. Ancient terranes and inliers were intruded with granites, granitoids as well as volcanic rocks. Units of all types were deformed, reactivated, intruded and metamorphosed during the Proterozoic Pan-African orogeny. Dramatic sheet flow erosion prevented almost any sedimentary rocks from forming during the Paleozoic and Mesozoic. From the Mesozoic into the Cenozoic the formation of the Red Sea depression and complex faulting led to massive sediment deposition in some locations and regional volcanism. Sudan has petroleum, chromite, salt, gold, limestone and other natural resources.

Geology of the Isle of Wight

The geology of the Isle of Wight is dominated by sedimentary rocks of Cretaceous and Paleogene age. This sequence was affected by the late stages of the Alpine Orogeny, forming the Isle of Wight monocline, the cause of the steeply-dipping outcrops of the Chalk Group and overlying Paleogene strata seen at The Needles, Alum Bay and Whitecliff Bay.

Golden Throne (mountain)

The Golden Throne is a mountain located in Capitol Reef National Park, in Utah, U.S. It is a rock formation dome made of a gold color stained Navajo Sandstone, which is particularly special because normally the sandstone is creamy white or red. The presence of a small amount of the Carmel Formation on top of the Navajo Sandstone is the reason for this staining.

A two-mile-long (3.2 km) trail runs below the mountain. The summit is 7,042 feet (2,146 m) in elevation and is part of the Waterpocket Fold, a nearly 100-mile-long (160 km) monocline.

Grand Hogback

The Grand Hogback is a 70-mile long, curving, spine-like ridge in Western Colorado that extends from near McClure Pass in Pitkin County through Garfield County and then to near Meeker in Rio Blanco County. The hogback is significant because it marks part of the boundary between the Colorado Plateau to the west and the Southern Rocky Mountains to the east.The elevation of the ridge ranges from 7,710 ft (2,350 m) to 9,194 ft (2,802 m). The hogback appears as a series of serrated ridges and is easily discernable from Google Maps and other aerial views. It is visible from Interstate 70.

Grandview Mine

The Grandview Mine, also known as the Last Chance Mine, was operated by Pete Berry from 1892 until 1901 in what later became Grand Canyon National Park. The Grandview Mine Historic District includes what remains of the mine workings and machinery as well as the ruins of a stone house and sleeping shanty. Physical evidence, including low stone walls and construction debris, suggests that several wood structures were also originally present on the site.

Pete Berry established Last Chance Mine on Horseshoe Mesa in 1892. He constructed the four-mile Grandview Trail down to the copper mine, and in 1893 began hauling ore out by mule. Although the ore was over 70% pure copper and won a prize at the Columbian Exposition in Chicago, the mine did not prove profitable, and in 1901 Berry and his partners sold it to the Canyon Copper Company, who operated it until 1907. The mine was then acquired by William Randolph Hearst, who sold it to the National Park Service in 1940.The mineralization at the mine is secondary copper minerals in a breccia zone along a monocline flexure in Navajo Sandstone. Redwall Limestone is bleached, brecciated and marbleized. Grandview is the type locality for grandviewite, a copper aluminium silicate. Grandview produced exceptionally fine mineral specimens of cyanotrichite, brochantite, chalcoalumite, and many other copper and uranium minerals. These specimens are now rare, as mineral collecting is not permitted in the National Park.In 2009, the mines were gated to protect bat roosts, support on-going bat research, preserve historic mine resources, and promote visitor safety. The gating project was done by Mine Gates, Inc., with support from Grand Canyon National Park, Bat Conservational International, and Freeport-McMoRan. Details of the mine site, as well as manufacturing and installation of each bat gate are documented on the MineGates site.

Hampshire Basin

The Hampshire Basin is a geological basin of Palaeogene age in southern England, underlying parts of Hampshire, the Isle of Wight, Dorset, and Sussex. Like the London Basin to the northeast, it is filled with sands and clays of Paleocene and younger ages and it is surrounded by a broken rim of chalk hills of Cretaceous age.

Homocline

In structural geology, a homocline or homoclinal structure (from old Greek: homo = same, cline = inclination), is a geological structure in which the layers of a sequence of rock strata, either sedimentary or igneous, dip uniformly in a single direction having the same general inclination in terms of direction and angle. A homocline can be associated with either one limb of a fold, the edges of a dome, the coast-ward tilted strata underlying a coastal plain, slice of thrust fault, or a tilted fault block. When the homoclinal strata consists of alternating layers of rock that vary hardness and resistance to erosion, their erosion produces either cuestas, homoclinal ridges, or hogbacks depending on the angle of dip of the strata. On a topographic map, the landfroms associated with homoclines exhibit nearly parallel elevation contour lines that show a steady change in elevation in a given direction. In the subsurface, they characterize by parallel structural contour lines.Unicline and Uniclinal are obsolete and currently uncommon terms that are defined and have been used by geologists and geomorphologists in an inconsistent and contradictory manner. They are terms that have been used in a mutually exclusive manner as a synonym for either a homocline or monocline depending the author. The meaning of this term has been further confused by Grabau, who redefined uniclinal, not as a geological structure, but as a general term for ridges produced by erosion of anticlines.The erosion of tilted sequences of either stratified sedimentary or igneous rock, homoclines, of alternating resistance to erosion produce distinctive landforms that form a gradational continuum from cuestas through homoclinal ridges to hogbacks. Less resistant beds are preferentially eroded creating valleys that lie between ridges created by the erosion of more resistant beds. For example, the erosion of homoclines consisting of resistant beds of either limestone, sandstone, or both interbedded with weaker, less resistant beds of either shale, siltstone, marl, or combination of them will produce either cuestas, homoclinal ridges, or hogbacks depending on the angle of dip of the strata. The greater the difference in the resistance to erosion, the more pronounced the structural control and relief between valley and ridge crest.

Lebombo Mountains

The Lebombo Mountains, also called Lubombo Mountains (Portuguese: 'Montes Libombos'), are an 800 km-long (500 mi), narrow range of mountains in Southern Africa. They stretch from Hluhluwe in KwaZulu-Natal in the south to Punda Maria in the Limpopo Province in South Africa in the north. Parts of the mountain range are also found in Mozambique and Eswatini.

List of geological folds in Great Britain

This is a list of the named geological folds affecting the rocks of Great Britain and the Isle of Man.

Mount Augustus, Western Australia

Mount Augustus (Burringurrah) is located in the Mount Augustus National Park in Western Australia. The name is also given to the neighbouring pastoral lease, Mount Augustus Station. The local Wadjari people call it Burringurrah, after a Dreamtime figure, a young boy, who was speared and turned into a rock.It is a prominent inselberg that stands 1,106 metres (3,629 ft) above sea level, or approximately 860 metres (2,820 ft) above the surrounding plain, and covers an area of 4,795 hectares (18.51 sq mi). It has a central ridge which is almost 8 kilometres (5.0 mi) long.

Purbeck Monocline

The Purbeck Monocline is a geological fold in southern England. The term 'fold' is used in geology when one or more originally flat sedimentary strata surfaces are bent or curved as a result of plastic (i.e. permanent) deformation. A monocline is a step-like fold, in which one limb is roughly horizontal. The Purbeck Monocline was formed during the late Oligocene and early Miocene epochs, about 30 million years ago. It is the northernmost 'ripple' of the Alpine Orogeny.

The Purbeck Monocline gives rise to the prominent ridge of steeply dipping Cretaceous chalk which now forms the Purbeck Hills. This chalk band runs from Swyre Head via Flower's Barrow to Old Harry Rocks. From here the fold continues under the sea to The Needles and forms the central spine of the Isle of Wight. Here it is also known as the Purbeck-Isle of Wight Disturbance. The monocline continues under the English Channel as the Wight-Bray Monocline.

The Purbeck Hills run east–west through the small broad peninsula known as the Isle of Purbeck. The resistant beds of chalk and limestone form two ridges and the softer Wealden rocks between them have been eroded to form a valley.

Some visible features along the monocline include the disharmonic folds and faults, known as the Lulworth Crumple, at Stair Hole, Lulworth Cove, Arish Mell and at Peveril Point further east. These features also include the polygonal thrust ridges developed in the harder rock bands at Kimmeridge Bay and related to the growth of the monocline is the fault at Ballard Down.

Tanner Graben

Located directly downstream of the Little Colorado River confluence with the Colorado River, the Tanner Graben, in the Grand Canyon, Arizona, USA is a prominence and cliffside rock formation below the East Rim. Tanner Graben is located riverside, on the Colorado River, on a north-northwest bank at Mile 68.5, and lies opposite Tanner Canyon. The Tanner Rapid, created by Tanner Creek lies at the riverside foot of the graben. The graben is a pronounced feature because of the black Cardenas Basalt that forms the middle section of the graben, presumably free of debris accumulation by its cliff face steepness, and winds, and airflow drainage that course through the Colorado River's canyons; unprotected side canyons of Cardenas Basalt show accumulations as a slope-forming geologic unit, with little showing of black basalt.

The Tanner Graben sits on the Butte Fault which trends north-south up the Colorado River, and the west side of Temple Butte; it forms the east flank of Tanner Graben. The Butte Fault is connected to the East Kaibab Monocline which trends north-south up the Colorado River, and turns north-northwest forming the east perimeter of the Kaibab Plateau, which lies due-north of the Tanner Graben region.

Wrocław Valley

Wrocław Valley (Pradolina Wrocławska, Polish) (318.52) - a mesoregion of great length, located in the Silesian Lowlands, with a total west-to-east length of 100 km, and a width of 10-12 km, totalling a surface area of 1220 km². From the north and the north-east, the mesoregion borders the Rościsławska Upland, Oleśnica Plain and the Opole Plain, from the north-west with the Wrocław Plain, the Nysa Kłodzka Valley and Niemodlin Plain. On the very north-western tip, the Wrocław Valley borders the Ścinawski Lowland, Lubin Upland and Legnica Plain, whilst on the north-easternmost tip, it borders the Chełm Upland (Silesian Highlands), and Racibórz Basin.In geological terms, the Wrocław Valley is part of the Silesia-Kraków Monocline and the Sudetes Foreland Monocline, covered in Pleistocene and Holocene geological material, mainly sand, gravel and fluvisols.The left tributaries of the River Odra in the mesoregion are: Osobłoga, Nysa Kłodzka, Oława, Ślęza, Bystrzyca, Kaczawa; and right: Mała Panew, Stobrawa and Widawa.

Larger settlements located on the Wrocław Valley are: Krapkowice, Opole, Brzeg, Oława, Wrocław, Brzeg Dolny, and Prochowice.

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