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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.
Charles Lapworth FRS FGS was an English geologist who pioneered faunal analysis using index fossils and identified the Ordovician period.
The Howgill Fells are hills in Northern England between the Lake District and the Yorkshire Dales, lying roughly in between the vertices of a triangle made by the towns of Sedbergh, Kirkby Stephen and Tebay. The name Howgill derives from the Old Norse word haugr meaning a hill or barrow, plus gil meaning a narrow valley.
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 geology of India is diverse. Different regions of India contain rocks belonging to different geologic periods, dating as far back as the Eoarchean Era. Some of the rocks are very deformed and altered. Other deposits include recently deposited alluvium that has yet to undergo diagenesis. Mineral deposits of great variety are found in the Indian subcontinent in huge quantity. Even India's fossil record is impressive in which stromatolites, invertebrates, vertebrates and plant fossils are included. India's geographical land area can be classified into the Deccan Traps, Gondwana and Vindhyan.
The Wenlock Group (Wenlockian), in geology, is the middle series of strata in the Silurian of Great Britain. This group in the typical area in the Welsh border counties contains the following formations: Much Wenlock Limestone Formation, 90–300 ft.; Wenlock Shale, up to 1900 ft.; Woolhope or Barr Limestone and shale, 150 ft.
The geology of the Australian Capital Territory includes rocks dating from the Ordovician around 480 million years ago, whilst most rocks are from the Silurian. During the Ordovician period the region—along with most of eastern Australia—was part of the ocean floor. The area contains the Pittman Formation consisting largely of Quartz-rich sandstone, siltstone and shale; the Adaminaby Beds and the Acton Shale.
In geology, the Llandeilo Group is the middle subdivision of the British Ordovician rocks. It was first described and named by Sir Roderick Murchison from the neighborhood of Llandeilo in Carmarthenshire. In the type area it consists of a series of slaty rocks, shales, calcareous flagstones and sandstones; the calcareous middle portion is sometimes termed the Llandeilo limestone; and in the upper portion volcanic rocks are intercalated.
The Ludlow Group are geologic formations deposited during the Ludlow epoch of the Silurian period in the British Isles, in areas of England, Ireland, Scotland, and Wales.
The Windermere Supergroup is a geological unit formed during the Ordovician to Silurian periods ~450 million years ago, and exposed in northwest England, including the Pennines and correlates along its strike, in the Isle of Man and Ireland, and down-dip in the Southern Uplands and Welsh Borderlands. It underlies much of north England's younger cover, extending south to East Anglia. It formed as a foreland basin, in a similar setting to the modern Ganges basin, fronting the continent of Avalonia as the remains of the attached Iapetus ocean subducted under Laurentia.
The geology of Wales is complex and varied; its study has been of considerable historical significance in the development of geology as a science. All geological periods from the Cryogenian to the Jurassic are represented at outcrop, whilst younger sedimentary rocks occur beneath the seas immediately off the Welsh coast. The effects of two mountain-building episodes have left their mark in the faulting and folding of much of the Palaeozoic rock sequence. Superficial deposits and landforms created during the present Quaternary period by water and ice are also plentiful and contribute to a remarkably diverse landscape of mountains, hills and coastal plains.
Flexicalymene Shirley, 1936, is a genus of trilobites belonging to the order Phacopida, suborder Calymenina and Family Calymenidae. Flexicalymene specimens can be mistaken for Calymene, Gravicalymene, Diacalymene and a few other Calymenina genera. They are used as an index fossil in the Ordovician. Ohio and North America are particularly known for being rich with Flexicalymene fossils.
In geology, the Arenigian refers both to a time interval during the Lower Ordovician period and also to the suite of rocks which were deposited during this interval.
The Snowdon Volcanic Group is an Ordovician lithostratigraphic group in Snowdonia, north-west Wales. The name is derived from Snowdon, the highest peak in Wales where it outcrops. This assemblage of rocks has also been referred to as the Snowdon Volcanic Series.
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 Dent Group is a group of Upper Ordovician sedimentary and volcanic rocks in north-west England. It is the lowermost part of the Windermere Supergroup, which was deposited in the foreland basin formed during the collision between Laurentia and Avalonia. It lies unconformably on the Borrowdale Volcanic Group. This unit was previously known as the Coniston Limestone Group or Coniston Limestone Formation and should not be confused with the significantly younger Coniston Group.
The geology of England's Lake District is dominated by sedimentary and volcanic rocks of mainly Ordovician age underpinned by large granitic intrusions. Younger sedimentary sequences outcrop on the edges of the Lake District area, with Silurian to the south, Carboniferous to the north, east and west and Permo-Triassic to the west and east. The entire area was covered by a Mesozoic sequence that was eroded off during Paleogene uplift related to the opening of the North Atlantic. During the Quaternary the area was affected by repeated glaciations, which sculpted the current mountainous landscape.
The geology of Utah includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism and the formation of the basin and range terrain in the Cenozoic. Utah is a state in the western United States.
The geology of Uzbekistan consists of two microcontinents and the remnants of oceanic crust, which fused together into a tectonically complex but resource rich land mass during the Paleozoic, before becoming draped in thick, primarily marine sedimentary units.
References
This article incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Caradoc Series". Encyclopædia Britannica (11th ed.). Cambridge University Press.
- 1 2 One or more of the preceding sentences incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Bala Series". Encyclopædia Britannica . 3 (11th ed.). Cambridge University Press. p. 239.