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Cymru Terrane
The Cymru Terrane is one of five inferred fault bounded terranes that make up the basement rocks of the southern United Kingdom. The other notable geological terranes are the Charnwood Terrane, Fenland Terrane, Wrekin Terrane and the Monian Composite Terrane.P. J. Brenchley, P. F. Rawson ''The Geology of England and Wales'', 2006, 2nd Ed In this article the definition of terrane is that implying rocks associated with the composition of the Precambrian basement. The Cymru Terrane is bounded to the northwest by the Menai Strait Fault System and to the southeast by the Pontesford Lineament. The geological terrane to the west is the Monian Composite Terrane and to the east is Wrekin Terrane. The majority of rocks in the area are associated with the outcrops that are evident at the faulted boundaries.Pharaoh, T.C., Gibbons, W., ''Precambrian Rocks in England and Wales south of the Menai Strait Fault System'', 1987 A Revised Correlation of the Precambrian Rocks in the British IslesJ. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geologic Timescale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardized international units of geologic time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely define gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twt Hill Granite
TWT may refer to: * Sanga-Sanga Airport (IATA code: TWT), an airport serving the general area of Bongao, the capital of the province of Tawi-Tawi in the Philippines * Ted Williams Tunnel, the third highway tunnel under Boston Harbor in Boston * Traveling-wave tube A traveling-wave tube (TWT, pronounced "twit") or traveling-wave tube amplifier (TWTA, pronounced "tweeta") is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs t ..., a specialized vacuum tube that is used in electronics to amplify radio frequency signals in the microwave range * ''The World Tomorrow'' (magazine), a defunct American political magazine * , a Tunisian television channel {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers, but which has only a weak tendency to fracture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granitoid
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites. As only two of the three defining mineral groups (quartz, plagioclase, and alkali feldspar) need to be present for the rock to be called a granitoid, foid-bearing rocks, which predominantly contain feldspars but no quartz, are also granitoids. The terms ''granite'' and ''granitic rock'' are often used interchangeably for granitoids; however, granite is just one particular type of granitoid. Granitoids are diverse; no classification system for granitoids can give a complete and unique characterization of the origin, compositional evolution, and geodynamic environment for the genesis of a granitoid. Accordingly, multiple granitoid classification systems have been developed such as those based o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parwyd Gneiss
Aberdaron is a community, electoral ward and former fishing village at the western tip of the Llŷn Peninsula in the Welsh county of Gwynedd. It lies west of Pwllheli and south west of Caernarfon, and has a population of 965. The community includes Bardsey Island ( cy, Ynys Enlli), the coastal area around Porthor, and the villages of Anelog, Llanfaelrhys, Penycaerau, Rhoshirwaun, Rhydlios, Uwchmynydd and Y Rhiw. It covers an area of just under 50 square kilometres. Y Rhiw and Llanfaelrhys have long been linked by sharing rectors and by their close proximity, but were originally ecclesiastical parishes in themselves. The parish of Bodferin/Bodverin was assimilated in the 19th century. The village was the last rest stop for pilgrims heading to Bardsey Island (Ynys Enlli), the legendary "island of 20,000 saints". In the 18th and 19th centuries it developed as a shipbuilding centre and port. The mining and quarrying industries became major employers, and limestone, lead, jasper an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the range of substitution in zircon is (Zr1–y, REEy)(SiO4)1–x(OH)4x–y. Zircon precipitates from silicate melts and has relatively high concentrations of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green. The name derives from the Persian ''zargun'', meaning "gold-hued". This word is corrupted into "jargoon", a term applied to light-colored zircons. The English word "zircon" is derived from ''Zirkon'', which is the German adaptation of this word. Yellow, orange, and red zircon is also known as "hyacinth", ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basement (geology)
In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The basement rocks lie below a sedimentation, sedimentary platform (geology), platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic rock, metamorphic or Igneous rock, igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover". Crustal rocks are modified several times before they become basement, and these transitions alter their composition. Continental crust Basement rock is the thick foundation of ancient, and oldest, metamorphic and igneous rock that forms the Crust (geology), crust of continents, often in the form of granite. Basement rock is contrasted to overlying sedimentary rocks which are laid down ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Padarn Tuff
Padarn ( la, Paternus, Padarnus; cy, Padarn; br, Padern; ? – 550 AD) was an early 6th century British Christian abbot-bishop who founded St Padarn's Church in Ceredigion, Wales. He appears to be one and the same with the first bishop of Braga and Saint Paternus of Avranches in Normandy. Padarn built a monastery in Vannes and is considered one of the seven founding saints of Brittany. Padarn's early ''vita'' is one of five insular and two Breton saints' lives that mention King Arthur independently of Geoffrey of Monmouth's ''Historia Regum Britanniae''. Life The ''Vita Sancti Paterni'', a major source for biographical details of Padarn, may be an epitome of a previous and more extensive source. According to the ''Vita Sancti Paterni'', Padarn is Armorican by race, born to "Petran, his father, and Guean, his mother". His parents "dedicated themselves to Christ" and Petran left Letavia (modern Brittany) for Ireland. Thomas Wakeman names Padarn a nephew of Hoel of Cornouaille. H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gwynedd
Gwynedd (; ) is a county and preserved county (latter with differing boundaries; includes the Isle of Anglesey) in the north-west of Wales. It shares borders with Powys, Conwy County Borough, Denbighshire, Anglesey over the Menai Strait, and Ceredigion over the River Dyfi. The scenic Llŷn Peninsula and most of Snowdonia National Park are in Gwynedd. Bangor is the home of Bangor University. As a local government area, it is the second largest in Wales in terms of land area and also one of the most sparsely populated. A majority of the population is Welsh-speaking. ''Gwynedd'' also refers to being one of the preserved counties of Wales, covering the two local government areas of Gwynedd and Anglesey. Named after the old Kingdom of Gwynedd, both culturally and historically, ''Gwynedd'' can also be used for most of North Wales, such as the area that was policed by the Gwynedd Constabulary. The current area is , with a population of 121,874 as measured in the 2011 Census. Et ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trawsfynydd
Trawsfynydd (; Welsh for "across hemountain") is a linear village in Gwynedd, Wales, near Llyn Trawsfynydd reservoir, and adjacent to the A470 north of Bronaber and Dolgellau and 10 km (6 miles) south of Blaenau Ffestiniog. The total community area is 12,010 hectares (46.4 square miles) with a population of only 973. The area is sparsely populated with each hectare (acre) inhabited by an average 0.07 (0.03) persons. The village is typical of many Welsh villages. There is one grocery shop, one public house, a newsagent, a chemist, garage, petrol service station, and a branch of a large agricultural merchants. The community includes Bronaber. History Prehistoric people lived in the area in scattered groups of circular huts near the river, Afon Crawcwellt, about two miles south of today's village. A substantial Romano-British fort and settlement was established at Tomen y Mur in the first century CE. The area continued to be inhabited during sub Roman Britain. An example ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pebidian Supergroup
The Pebidian Supergroup is an Ediacaran (i.e. late Precambrian) lithostratigraphic supergroup (a sequence of rock strata) in Pembrokeshire, west Wales. The term 'Pebidian' (along with Dimetian) was coined by geologist Henry Hicks in 1876 and published in a scientific paper in the Quarterly Journal of the Geological Society in the following year. It was named for ''Pebidiauc'', an ancient local name for the St Davids area. Outcrops These rocks are exposed in the St David's peninsula in northwestern Pembrokeshire. One outcrop stretches east from Treginnis, wrapping around the north of St David's to Treglemais. Another underlies Hayscastle Cross with scattered outcrops elsewhere in the area. Lithology and stratigraphy The supergroup comprises at its base the Treginnis, Treglemais and Penrhiw 'Groups' of the Lower Pebidian which include trachytic and andesitic tuffs and halleflinta. Overlying these are the tuffs, lavas and conglomerates of the Caerbwdy Group, Ramsey Sound Group ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
