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Geology Of Mull
The geology of the Isle of Mull in Scotland is dominated by the development during the early Palaeogene period of a ‘ volcanic central complex’ associated with the opening of the Atlantic Ocean. The bedrock of the larger part of the island is formed by basalt lava flows ascribed to the Mull Lava Group erupted onto a succession of Mesozoic sedimentary rocks during the Palaeocene epoch. Precambrian and Palaeozoic rocks occur at the island's margins. A number of distinct deposits and features such as raised beaches were formed during the Quaternary period. Precambrian and Palaeozoic rocks The central complex is underlain by the Neoproterozoic age metamorphosed Moine rocks and is intruded into them. Moine Rocks of the Glenfinnan Group occur in places around the Mull Central Complex and others from the Glenfinnan and Morar groups occur on the Ross of Mull. Dalradian Semipelites and metalimestones of the Appin Group occur within the Loch Don Anticline in the east of the isl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isle Of Mull
The Isle of Mull ( gd, An t-Eilean Muileach ) or just Mull (; gd, Muile, links=no ) is the second-largest island of the Inner Hebrides (after Skye) and lies off the west coast of Scotland in the Council areas of Scotland, council area of Argyll and Bute. Covering , Mull is the fourth-largest island in Scotland and Great Britain. From 2001 to 2020, the population has gradually increased: during 2020 the populace was estimated to be 3,000, in the United Kingdom Census 2011, 2011 census it was approximately 2,800, and in 2001, it was measured at 2,667 people. It has the eighth largest Island population in Scotland. In the summer, these numbers are augmented by an influx of many tourists. Much of the year-round population lives in the colourful main settlement of Tobermory, Mull, Tobermory. There are two distilleries on the island: the Tobermory distillery, formerly named Ledaig, produces single malt Scotch whisky and another, opened in 2019 and located in the vicinity of Tir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pluton
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinemurian
In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian. In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias, in Great Britain known as the Blue Lias. Stratigraphic definitions The Sinemurian Stage was defined and introduced into scientific literature by French palaeontologist Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois, near Dijon. The calcareous soil formed from the Jurassic limestone of the region is in part responsible for the character of the classic Sancerre wines. The base of the Sinemurian Stage is at the first appearance of the ammonite genera ''Vermiceras'' and '' Metophioceras'' in the stratigraphic record. A global reference profile ( GSSP or golden spike) for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Lias
The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago. The Blue Lias is famous for its fossils, especially ammonites. Its age corresponds to the Rhaetian to lower Sinemurian stages of the geological timescale, thus fully including the Hettangian stage. It is the lowest of the three divisions of the Lower Jurassic period and, as such, is also given the name ''Lower Lias''. Stratigraphically it can be subdivided into three members: the Wilmcote Limestone, Saltford Shale and Rugby Limestone. Lithology and facies The Blue Lias comprises decimetre scale alternations of argillaceous limestone and mudstone. These alternations are caused by short-term climatic variations during the Early Jurassic attributed to orbital forcing (Milankovitch cycles). Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hettangian
The Hettangian is the earliest age and lowest stage of the Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ... Geological time scale, Period of the geologic timescale. It spans the time between 201.3 ± 0.2 annum, Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassic Period) and is followed by the Sinemurian. In European stratigraphy the Hettangian is a part of the time span in which the Lias Group, Lias was deposited. An example is the British Blue Lias, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from the Northern Limestone Alps where well-preserved but very rare ammonites, including Alsatites, have been found. Stratigraphic definitions The Hettangian was introduced in the literature by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Penarth Group
The Penarth Group is a Rhaetian age (Triassic) lithostratigraphic group (a sequence of rock strata) which is widespread in Britain. It is named from the seaside town of Penarth near Cardiff in south Wales where strata of this age are exposed in coastal cliffs southwards to Lavernock Point. This sequence of rocks was previously known as the Rhaetic or Rhaetic Beds. Stratigraphy It includes the Lilstock Formation and the underlying Westbury Formation. The Langport and Cotham Members, grey limestones of marine origin with associated mudstones, are recognised within the Lilstock Formation, itself named from Lilstock in west Somerset. The Westbury Formation is named from Westbury-on-Severn in Gloucestershire. Ireland In 1999, the discovery of an ichthyosaur from Langport Member mudstones exposed at Waterloo Bay, Larne provided the most complete example of this in Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New Red Sandstone
The New Red Sandstone, chiefly in British geology, is composed of beds of red sandstone and associated rocks laid down throughout the Permian (300 million years ago) to the end of the Triassic (about 200 million years ago), that underlie the Jurassic-Triassic age Penarth Group. The name distinguishes it from the Old Red Sandstone which is largely Devonian in age, and with which it was originally confused due to their similar composition. Its upper layers consist of mudstones, but most of the formation consists of reddish to yellowish sandstones, interbedded with rare evaporite minerals such as halite and gypsum. These indicate deposition within a hot and arid palaeo-environment, such as a desert or sabkha.Benton MJ and Walker AD. 1985. Palaeoecology, taphonomy and dating of Permo-Triassic reptiles from Elgin, North-East Scotland. Palaeontology 28:207–234. Geographical distribution The New Red Sandstone was originally identified in Scotland, at quarries in Elgin. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unconformity
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the sedimentary geologic record. The significance of angular unconformity (see below) was shown by James Hutton, who found examples of Hutton's Unconformity at Jedburgh in 1787 and at Siccar Point in 1788. The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents time during which no sediments were preserved in a region or were subsequently eroded before the next deposition. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Old Red Sandstone
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also extends northwards into Greenland and Svalbard. These areas were a part of the ancient continent of Euramerica, Euramerica/Laurussia. In Britain it is a lithostratigraphy, lithostratigraphic unit (a sequence of rock strata) to which Stratigraphy, stratigraphers accord Geological unit#Lithostratigraphic units, supergroup status and which is of considerable importance to early paleontology. For convenience the short version of the term, ORS is often used in literature on the subject. The term was coined to distinguish the sequence from the younger New Red Sandstone which also occurs widely throughout Britain. Sedimentology The Old Red Sandstone describes a suite of sedimentary rocks deposited in a variety of environments during the Devonian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gabbro
Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is chemically equivalent to rapid-cooling, fine-grained basalt. Much of the Earth's oceanic crust is made of gabbro, formed at mid-ocean ridges. Gabbro is also found as plutons associated with continental volcanism. Due to its variant nature, the term ''gabbro'' may be applied loosely to a wide range of intrusive rocks, many of which are merely "gabbroic". By rough analogy, gabbro is to basalt as granite is to rhyolite. Etymology The term "gabbro" was used in the 1760s to name a set of rock types that were found in the ophiolites of the Apennine Mountains in Italy. It was named after Gabbro, a hamlet near Rosignano Marittimo in Tuscany. Then, in 1809, the German geologist Christian Leopold von Buch used the term more restrictively in his descri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diorite
Diorite ( ) is an intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is intermediate in composition between low-silica (mafic) gabbro and high-silica ( felsic) granite. Diorite is found in mountain-building belts (''orogens'') on the margins of continents. It has the same composition as the fine-grained volcanic rock, andesite, which is also common in orogens. Diorite has been used since prehistoric times as decorative stone. It was used by the Akkadian Empire of Sargon of Akkad for funerary sculptures, and by many later civilizations for sculptures and building stone. Description Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene. The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic grani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granodiorite
Granodiorite () is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from granite to diorite, including granodiorite. Composition According to the QAPF diagram, granodiorite has a greater than 20% quartz by volume, and between 65% and 90% of the feldspar is plagioclase. A greater amount of plagioclase would designate the rock as tonalite. Granodiorite is felsic to intermediate in composition. It is the intrusive igneous equivalent of the extrusive igneous dacite. It contains a large amount of sodium (Na) and calcium (Ca) rich plagioclase, potassium feldspar, quartz, and minor amounts of muscovite mica as the lighter colored mineral components. Biotite and amphiboles often in the form of hornblende are more abundant in granodiorite than in granite, giving it a more distinct two-toned or overall darker appearan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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