Group (stratigraphy)

A group in stratigraphy is a lithostratigraphic unit, a part of the geologic record or rock column that consists of defined rock strata. Groups are generally divided into individual formations. Groups may sometimes be divided into "subgroups" and are themselves sometimes grouped into "supergroups".

Some well known groups of northwestern Europe have in the past also been used as units for chronostratigraphy and geochronology. These are the Rotliegend and Zechstein (both of Permian age); Buntsandstein, Muschelkalk, and Keuper (Triassic in age); Lias, Dogger, and Malm (Jurassic in age) groups. Because of the confusion this causes, the official geologic timescale of the ICS does not contain any of these names any longer.

See also

External links

  • "Chapter 5. Lithostratigraphic Units". International Commission on Stratigraphy. 2013–2014. Retrieved 4 June 2014. - 6. Group
Edmontosaurus

Edmontosaurus ( ed-MON-tə-SAWR-əs) (meaning "lizard from Edmonton") is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago, while those of E. annectens were found in the same geographic region but in rocks dated to the end of the Maastrichtian stage of the Cretaceous, 66 million years ago. Edmontosaurus was one of the last non-avian dinosaurs, and lived alongside dinosaurs like Triceratops, Tyrannosaurus, Albertosaurus and Pachycephalosaurus shortly before the Cretaceous–Paleogene extinction event.

Edmontosaurus included some of the largest hadrosaurid species, measuring up to 12 metres (39 ft) long and weighing around 4.0 metric tons (4.4 short tons). Evidence does exist in the form of two fossilized specimens housed at the Museum of the Rockies for an even greater maximum size of 15 m (49 ft) and weighing 9.07 metric tons (10.00 short tons) for Edmontosaurus annectens. Several well-preserved specimens are known that include not only bones, but in some cases extensive skin impressions and possible gut contents. It is classified as a genus of saurolophine (or hadrosaurine) hadrosaurid, a member of the group of hadrosaurids which lacked large, hollow crests, instead having smaller solid crests or fleshy combs.The first fossils named Edmontosaurus were discovered in southern Alberta (named after Edmonton, the capital city), in the Horseshoe Canyon Formation (formerly called the lower Edmonton Formation). The type species, E. regalis, was named by Lawrence Lambe in 1917, although several other species that are now classified in Edmontosaurus were named earlier. The best known of these is E. annectens, named by Othniel Charles Marsh in 1892; originally as a species of Claosaurus, known for many years as a species of Trachodon, and later as Anatosaurus annectens. Anatosaurus and Anatotitan are now generally regarded as synonyms of Edmontosaurus.

Edmontosaurus was widely distributed across western North America. The distribution of Edmontosaurus fossils suggests that it preferred coasts and coastal plains. It was a herbivore that could move on both two legs and four. Because it is known from several bone beds, Edmontosaurus is thought to have lived in groups, and may have been migratory as well. The wealth of fossils has allowed researchers to study its paleobiology in detail, including its brain, how it may have fed, and its injuries and pathologies, such as evidence for tyrannosaur attacks on a few edmontosaur specimens.

Edmontosaurus regalis

Edmontosaurus regalis is a species of comb-crested hadrosaurid (duck-billed) dinosaur. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago.

E. regalis was one of the largest hadrosaurids, measuring up to 12 metres (39 ft) long and weighing around 4.0 metric tons (4.4 short tons). It is classified as a genus of saurolophine (or hadrosaurine) hadrosaurid, a member of the group of hadrosaurids which lacked large, hollow crests, instead having smaller solid crests or fleshy combs. The distribution of E. regalis fossils suggests that it preferred coasts and coastal plains. It was a herbivore that could move on both two legs and four. Because it is known from several bone beds, E. regalis is thought to have lived in groups. The wealth of fossils has allowed researchers to study its paleobiology in detail, including its brain, how it may have fed, and its injuries and pathologies.

Group

A group is a number of people or things that are located, gathered, or classed together.

Jerome, Arizona

Jerome is a town in the Black Hills of Yavapai County in the U.S. state of Arizona. Founded in the late 19th century on Cleopatra Hill overlooking the Verde Valley, it is more than 5,000 feet (1,500 m) above sea level. It is about 100 miles (160 km) north of Phoenix along State Route 89A between Sedona and Prescott. Supported in its heyday by rich copper mines, it was home to more than 10,000 people in the 1920s. As of the 2010 census, its population was 444.

The town owes its existence mainly to two ore bodies that formed about 1.75 billion years ago along a ring fault in the caldera of an undersea volcano. Tectonic plate movements, plate collisions, uplift, deposition, erosion, and other geologic processes eventually exposed the tip of one of the ore bodies and pushed the other close to the surface, both near Jerome. In the late 19th century, the United Verde Mine, developed by William A. Clark, extracted ore bearing copper, gold, silver, and other metals from the larger of the two. The United Verde Extension UVX Mine, owned by James Douglas, Jr., depended on the other huge deposit. In total, the copper deposits discovered in the vicinity of Jerome were among the richest ever found.

Jerome made news in 1917, when strikes involving the Industrial Workers of the World (IWW) led to the expulsion at gunpoint of about 60 IWW members, who were loaded on a cattle car and shipped west. Production at the mines, always subject to fluctuations, boomed during World War I, fell thereafter, rose again, then fell again during and after the Great Depression. As the ore deposits ran out, the mines closed, and the population dwindled to fewer than 100 by the mid-1950s. Efforts to save the town from oblivion succeeded when residents turned to tourism and retail sales. Jerome became a National Historic Landmark in 1967. By the early 21st century, Jerome had art galleries, coffee houses, restaurants, a state park, and a local museum devoted to mining history.

La Jolla Group

The La Jolla Group is a group of geologic formations in coastal southwestern San Diego County, Southern California. Its locations include the coastal La Jolla San Diego region.

The formation preserves fossils dating back to the Cretaceous period.

The Cretaceous aged formations of the La Jolla Group include the Point Loma Formation overlain by the Cabrillo Formation. Some incomplete dinosaur fossils have been discovered in the Point Loma Formation.

Most of the La Jolla Group Stratigraphy was deposited during the Eocene when sea level was higher than its present day elevation. Eocene aged formations of the La Jolla Group include the Del Mar Formation, Torrey Sandstone, Ardath Shale, and Scripps Sandstone (ascending order). There are only abundant fossils found in some sections of the Del Mar Formation, mostly bivalve shells.

An angular uncomformity separates the Eocene from the top section of the La Jolla Group.

The Pliocene Aged San Diego Formation is composed of interbedded silt and sand. Some fossil bivalve shell layers can be found in the San Diego Formation which were deposited from a transport.

The upper section of the La Jolla Group consists of Pleistocene aged marine terraces deposited during times of high sea level in between ice ages. The Linda Vista Formation, for example, is a reddish colored sandy marine terrace which is exposed throughout much of the Clairemont Area region of San Diego, and can be seen from Interstate 5 overlying the yellowish colored Torrey Sandstone in Del Mar Heights.

Madison Group

The Madison Limestone is a thick sequence of mostly carbonate rocks of Mississippian age in the Rocky Mountain and Great Plains areas of western United States. The rocks serve as an important aquifer as well as an oil reservoir in places. The Madison and its equivalent strata extend from the Black Hills of western South Dakota to western Montana and eastern Idaho, and from the Canada–United States border to western Colorado and the Grand Canyon of Arizona.

Muav Limestone

The Cambrian Muav Limestone is the upper geologic unit of the 3-member Tonto Group. It is about 650 feet (198 m) thick at its maximum. It is a resistant cliff-forming unit. The Muav consists of dark to light-gray, brown, and orange red limestone with dolomite and calcareous mudstone. The Muav is overlain in some areas by the Devonian Temple Butte Formation, but the major unit above are the vertical cliffs of Mississippian Redwall Limestone. The Muav is located in the lower elevations of the Grand Canyon, Arizona.The Muav is in-part younger than, and in-part grades into, the Bright Angel Shale which is less erosion resistant and is categorized as a slope-forming unit. The Muav is about 350 feet thick in the east and reaches about 600 feet thick in the western part of its exposure area in the Grand Canyon. The two units lie above the erosion-resistant cliff-forming Tapeats Sandstone. In the eastern canyon, the Tapeats creates the horizontal Tonto Platform. In west Grand Canyon, the north-south Toroweap Fault is the west perimeter of the Tonto Platform, and west Grand Canyon is dominated by the erosion resistant unit of the Esplanade Sandstone. The Tonto Trail is a mostly horizontal trail on the south side of Granite Gorge, on the platform.

The Tonto Group units were deposited on an ancient erosion surface (angular unconformity) on the Vishnu Basement Rocks. The Vishnu sequence has a dip of about 45 degrees. As this unconformity represents about 1,000 million years (1.0 billion years) of non–deposition, tectonic activity and erosion on the Vishnu Basement Rocks is called the Great Unconformity.

Beyond the Grand Canyon area the Muav occurs in southern Utah, southern Nevada and southern California. In the California occurrence it is known as the Muav Marble.

Olympic-Wallowa Lineament

The Olympic-Wallowa lineament (OWL) – first reported by cartographer Erwin Raisz in 1945 on a relief map of the continental United States – is a physiographic feature of unknown origin in the state of Washington (northwestern U.S.) running approximately from the town of Port Angeles, on the Olympic Peninsula to the Wallowa Mountains of eastern Oregon.

Stretton Group

The Stretton Group is a group of rocks associated with the Longmyndian Supergroup of Ediacaran age, in Shropshire, England. The rocks are located within the tract between two elements of the Welsh Borderland Fault System, the Church Stretton Fault and the Pontesford-Linley Lineament.The Stretton Group is a predominantly sedimentary group with a range of facies attributable to that of a closing ocean.

The Wentnor Group overlies the Stretton Group of rocks and although the units are separate, together they show a good geological progression. At the base of the Stretton Group the rocks are of basinal oceanic facies and as time goes a coarsening occurs with increased terrigenous input from the continent. Turbidites are observed and deltas form latterly with alluvial plains with occasional marine washovers.

This creeps up into the Wentnor Group where alluvial plains latterly with fluvial and alluvial deposits noted in the uppermost (youngest) Bridges Formation.

The information below is present oldest to youngest as it makes much more sense in this way. One should read the Wentnor Group stratigraphy as well in order to get a sense of continuity.

The progradational Longmyndian Sequence from oldest to youngest is:

Ragleth Tuff Formation; Stretton Shale Formation; Burway Formation; Synalds Formation; Lightspout Formation; Portway Formation; Bayston-Oakswood Formation; Bridges Formation. The latter two units belong to the Wentnor Group. Below we carry on from the underlying Portway Formation (Stretton Group).

Subgroup (disambiguation)

A subgroup is an object in abstract algebra.

Subgroup may also refer to:

a subdivision of a group

a subgroup of a galaxy group

a taxonomic rank between species and genus

a unit of language classification within a language family (see also subgrouping)

a subgroup of a group (stratigraphy)

TaskForceMajella

The TaskForceMajella (TFM) is an industry-funded geoscientific research project conducted between the years 1998 and 2005. The project involved numerous universities distributed worldwide, and was sponsored by a number of international major oil companies. The area of research was the Majella Mountain in Central Italy, regarded as an analogue of a faulted and fractured hydrocarbon reservoir as can be found in major provinces like the Middle East, Caspian Basin, Mediterranean Basin, and other areas. The scope was to obtain knowledge on the relation between fracture and fault generation, and all types of geological aspects of the evolution of the geological structure.

Tonto Group

The Cambrian Tonto Group is the three-member sequence of geologic formations that represent the basal section of Paleozoic rocks in the Grand Canyon. The group is about 1,250 feet (381 m) thick. The base unit, the Cambrian Tapeats Sandstone was deposited upon the erosion surface of the Vishnu Basement Rocks, which is found in Granite Gorge (the Inner Gorge). The erosion resistant Tapeats Sandstone forms the platform, called Tonto Platform, that the two less erosion resistant upper layers, the Bright Angel Shale and Muav Limestone, rest on.

The Tonto Trail is a mostly horizontal trail on the south side of Granite Gorge. The horizontal Tonto Group units are laid upon the Vishnu Basement Rocks above an angular unconformity as the Vishnu Basement Rocks have a dip of about 15 degrees. This erosion unconformity prior to the deposition of the Tapeats upon the tilted Vishnu Basement Rocks is about 1,000 million years (1.0 billion years), and is called the Great Unconformity.

Volcanic group

A volcanic group (or, equivalently, a volcanic complex) is a collection of related volcanoes or volcanic landforms. The term is also used in a different sense when it denotes a suite of associated rock strata largely of volcanic origin; see group (stratigraphy) for details.

Wentnor Group

The Wentnor Group is a group of rocks associated with the Longmyndian Supergroup of Precambrian age in present-day Wales, U.K.

The rocks are located within the confines between the Church Stretton Fault and the Pontesford-Lindley Lineament. The Wentnor Group is a predominantly sedimentary group with a range of facies attributable to that of a closing ocean. The Wentnor Group overlies the Stretton Group of rocks and although the units are separate, together they show a good geological progression. At the base of the Stretton Group the rocks are of basinal oceanic facies and as time goes a coarsening occurs with increased terrigenous input from the continent. Turbidites are observed and deltas form latterly with alluvial plains with occasional marine washovers. This creeps up into the Wentnor Group where alluvial plains occur latterly with fluvial and alluvial deposits noted in the uppermost (youngest) Bridges Formation.The information below is presented oldest to youngest as it makes much more sense in this way. One should read the Stretton Group stratigraphy first in order to get a sense of continuity. The progradational Longmyndian Sequence from oldest to youngest is:

Ragleth Tuff Formation; Stretton Shale Formation; Burway Formation; Synalds Formation; Lightspout Formation; Portway Formation; Bayston-Oakswood Formation; Bridges Formation. The latter two units belong to the Wentnor Group. Below we carry on from the underlying Portway Formation (Stretton Group).

Yakima Fold Belt

The Yakima Fold Belt of south-central Washington, also called the Yakima fold-and-thrust belt, is an area of topographical folds (or wrinkles) raised by tectonic compression. It is a 14,000 km2 (5,400 sq mi) structural-tectonic sub province of the western Columbia Plateau Province resulting from complex and poorly understood regional tectonics. The folds are associated with geological faults whose seismic risk is of particular concern to the nuclear facilities at the Hanford Nuclear Reservation (immediately northwest of the Tri-Cities) and major dams on the Columbia and Snake Rivers.

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