| Croisaphuill Formation Stratigraphic range: Ordovician (Tulean) ~488.3–472 Ma | |
|---|---|
| Type | Formation |
| Unit of | Durness Group |
| Lithology | |
| Primary | Limestone |
| Other | Chert |
| Location | |
| Region | Scotland |
| Country |  United Kingdom |
The Croisaphuill Formation is a geologic formation in Scotland. It preserves fossils dating back to the Ordovician period.
The Borrowdale Volcanic Group is a group of igneous rock formations named after the Borrowdale area of the Lake District, in England. They are Caradocian in age. It is thought that they represent the remains of a volcanic island arc, approximately similar to the island arcs of the west Pacific today. This developed as oceanic crust to the (present) north-west and was forced by crustal movement under a continental land-mass to the present south-east. Such forcing under, as two plates meet, is termed subduction. This land-mass has been named Avalonia by geologists. It is now incorporated into England and Wales and a sliver of North America.
The Hirnantian is the final internationally recognized stage of the Ordovician Period of the Paleozoic Era. It was of short duration, lasting about 1.4 million years, from 445.2 to 443.8 Ma. The early part of the Hirnantian was characterized by cold temperatures, major glaciation, and a severe drop in sea level. In the latter part of the Hirnantian, temperatures rose, the glaciers melted, and sea level returned to the same or to a slightly higher level than it had been prior to the glaciation.
The Caledonian orogeny was a mountain-building era recorded in the northern parts of Ireland and Britain, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 million years ago (Ma). It was caused by the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided.
The Andean-Saharan glaciation occurred during the Paleozoic from 450 Ma to 420 Ma, during the late Ordovician and the Silurian period. For the Ordovician/Saharan part, see the more extensive article on the Late Ordovician glaciation.
Tabulata, commonly known as tabulate corals, are an order of extinct forms of coral. They are almost always colonial, forming colonies of individual hexagonal cells known as corallites defined by a skeleton of calcite, similar in appearance to a honeycomb. Adjacent cells are joined by small pores. Their distinguishing feature is their well-developed horizontal internal partitions (tabulae) within each cell, but reduced or absent vertical internal partitions (septa). They are usually smaller than rugose corals, but vary considerably in shape, from flat to conical to spherical.
In the geologic timescale, the Rhuddanian is the first age of the Silurian period and of the Llandovery epoch. The Silurian is in the Paleozoic era of the Phanerozoic eon. The Rhuddanian age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma. It succeeds the Himantian Age and precedes the Aeronian age.
Cothurnocystis is a genus of small enigmatic echinoderms that lived during the Ordovician. Individual animals had a flat boot-shaped body and a thin rod-shaped appendage that may be a stem, or analogous to a foot or a tail. Fossils of Cothurnocystis species have been found in Nevada, Scotland, Czech Republic, France and Morocco.
The Ordovician Martinsburg Formation (Om) is a mapped bedrock unit in Pennsylvania, New Jersey, Maryland, Virginia, and West Virginia. It is named for the town of Martinsburg, West Virginia for which it was first described. It is the dominant rock formation of the Great Appalachian Valley in New Jersey (where it is called Kittatinny Valley and Pennsylvania.
The Ordovician Reedsville Formation is a mapped surficial bedrock unit in Pennsylvania, Maryland, Virginia, West Virginia, and Tennessee, that extends into the subsurface of Ohio. This rock is a slope-former adjacent to the prominent ridge-forming Bald Eagle sandstone unit in the Appalachian Mountains. It is often abbreviated Or on geologic maps.
Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and also the northwestern part of Scotland, known as the Hebridean Terrane. During other times in its past, Laurentia has been part of larger continents and supercontinents and itself consists of many smaller terranes assembled on a network of Early Proterozoic orogenic belts. Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today.
The Conococheague Formation is a mapped Appalachian bedrock unit of Cambrian age, consisting primarily of limestone and dolomite. It occurs in central Maryland, southern and central Pennsylvania, the Valley and Ridge of Virginia and easternmost West Virginia.
The Upper and Lower Fezouata Formations of Morocco are Burgess shale-type deposits dating to the Early Ordovician, filling an important preservational window between the common Cambrian Lagerstätten and the Late Ordovician Soom Shale. Found fossilized fauna were numerous organisms previously thought to have died out after the mid-Cambrian.
The Hebridean Terrane is one of the terranes that form part of the Caledonian orogenic belt in northwest Scotland. Its boundary with the neighbouring Northern Highland Terrane is formed by the Moine Thrust Belt. The basement is formed by Archaean and Paleoproterozoic gneisses of the Lewisian complex, unconformably overlain by the Neoproterozoic Torridonian sediments, which in turn are unconformably overlain by a sequence of Cambro–Ordovician sediments. It formed part of the Laurentian foreland during the Caledonian continental collision.
Similodonta is an extinct genus of early bivalve in the extinct family Praenuculidae. The genus is one of eleven genera in the subfamily Praenuculinae. Similodonta is known from Middle Ordovician through Middle Silurian fossils found in Europe and North America. The genus currently contains eight accepted species, Similodonta ceryx, Similodonta collina, Similodonta djupvikensis, Similodonta magna, Similodonta recurva, Similodonta spjeldnaesi, Similodonta wahli and the type species Similodonta similis.
Trinodus is a very small to small blind trilobite, a well known group of extinct marine arthropods, which lived during the Ordovician, in what are now the Yukon Territories, Virginia, Italy, Czech Republic, Poland, Denmark, Sweden, Svalbard, Ireland, Scotland, Wales, Iran, Kazakhstan and China. It is one of the last of the Agnostida order to survive.
The geology of the Isle of Skye in Scotland is highly varied and the island's landscape reflects changes in the underlying nature of the rocks. A wide range of rock types are exposed on the island, sedimentary, metamorphic and igneous, ranging in age from the Archaean through to the Quaternary.
The Maquoketa Formation is a geologic formation in Illinois, Indiana. Iowa, Kansas, Minnesota, Missouri, and Wisconsin. It preserves mollusk, coral, brachiopod and graptolite fossils dating back to the Ordovician period.
The Mount Simon Sandstone is the basal sandstone of the Potsdam Sandstone. It was deposited in a nearshore environment, unconformably overlying Precambrian basement.
Histiodella is an extinct genus of conodonts.
The Grampian orogeny was an orogeny mountain building event which affected Scotland in the middle of the Ordovician. At the time, Scotland was part of proto-North American continent Laurentia.
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