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Coniston Limestone
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 (uppermost Silurian) Coniston Group. Distribution The Dent Group is exposed in four areas, the southern Lake District as a narrow strip across the whole width of the outcrop, in the Cautley and Dent inliers, the Cross Fell inlier and the Craven inliers. Lake District outcrop In the main Lake District outcrop, the group consists of calcareous siltstones and mudstones of the basal Kirkley Bank Formation, micritic limestones of the Broughton Moor Formation and dark blue-gray shales of the Ashgill Formation. Locally v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, W. H. Freeman, 2nd ed, 529 pp. The term ''mudstone'' is also used to describe carbonate rocks (limestone or dolomite) that are composed predominantly of carbonate mud. However, in most contexts, the term refers to siliciclastic mudstone, composed mostly of silicate minerals. The NASA Curiosity rover has found deposits of mudstone on Mars that contain organic substances such as propane, benzene and toluene. Definition There is not a single definition of mudstone that has gained general acceptance,Boggs 2006, p.143 though there is wide agreement that mudstones are fine-grained sedimentary rocks, composed mostly of silicate grains with a grain size less than . Individual grains this size are too small to be disting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Craven Fault System
The Craven Fault System is the name applied by geologists to the group of crustal faults in the Pennines that form the southern edge of the Askrigg Block and which partly bounds the Craven Basin. Sections of the system's component faults which include the North, Middle and South Craven faults and the Feizor FaultBritish Geological Survey 1:50,000 scale geological map (England and Wales) sheet 60 ''Settle'' are evident at the surface in the form of degraded faults scarps where Carboniferous Limestone abuts millstone grit. The fault system is approximately coincident with the southwestern edge of the Yorkshire Dales National Park and the northeastern edge of the Bowland Fells. Location The Craven Faults are major crustal fractures across the Pennines. These faults constitute a zone crossing the backbone of England from west to east commencing near Leck, Lancashire at then branching three ways: * The North Craven Fault extends about to . * The Mid Craven Fault extends about ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anticline
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold that dip away from the hinge. Anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. Therefore, if age relationships between various rock strata are unknown, the term antiform should be used. The progressing age of the rock strata towards the core and uplifted center, are the trademark indications for evidence of anticlines on a geologic map. These formations occur because anticlinal ridges typically develop above thrust faults during crustal deformations. The uplifted core of the fold causes compression of strata that preferentially erodes to a deeper st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroclastic Rock
Pyroclastic rocks (derived from the el, πῦρ, links=no, meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroclasts. Pyroclastic rocks are a type of volcaniclastic deposit, which are deposits made predominantly of volcanic particles. 'Phreatic' pyroclastic deposits are a variety of pyroclastic rock that forms from volcanic steam explosions and they are entirely made of accidental clasts. 'Phreatomagmatic' pyroclastic deposits are formed from explosive interaction of magma with groundwater. Unconsolidated accumulations of pyroclasts are described as tephra. Tephra may become lithified to a pyroclastic rock by cementation or chemical reactions as the result of the passage of hot gases (fumarolic alteration) or groundwater (e.g. hydrothermal alteration and diagenesis) and burial, or, if it is emplaced at temperatures so hot that the soft glassy pyrocl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dent Fault
The Dent Fault is a major fault zone on the boundary between the counties of Cumbria and North Yorkshire in northern England. It is named after the village of Dent in Dentdale, on the western margin of the Yorkshire Dales. The fault, or rather the 'Dent Fault System' – a collection of closely associated faults and folds, defines the western edge of the Askrigg Block, a geological structure that underlies the Yorkshire Dales. The fault is associated with the Taythes Anticline to its west and the Fell End Syncline to its east. Other than vertical movement on the fault, there has also been an element of strike-slip movement. To the north, the fault links with the Pennine Fault System in the vicinity of Brough and with the Craven Fault System near Kirkby Lonsdale to the south.Stone et al. 2010 ''British Regional Geology: Northern England'' (5th edition) Keyworth, Notts, British Geological Survey Regional setting The Carboniferous geology of northern England consists of a series ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petrology: Igneous, Sedimentary and Metamorphic'', 2nd ed., Freeman, pp. 281–292 Shale is characterized by its tendency to split into thin layers ( laminae) less than one centimeter in thickness. This property is called '' fissility''. Shale is the most common sedimentary rock. The term ''shale'' is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock. Texture Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable beddin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life. About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. The remaining carbonate rock is mostly dolomite, a closely related rock, which contains a high percentage of the mineral dolomite, . ''Magnesian limestone'' is an obsolete and poorly-defined term used variously for dolomite, for limes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micrite
Micrite is a limestone constituent formed of calcareous particles ranging in diameter up to four μm formed by the recrystallization of lime mud. Flügel, Erik, ''Microfacies of Carbonate Rocks: Analysis, Interpretation and Application,'' Springer, pp 74-94, 2004 The term was coined in 1959 by Robert Folk for his carbonate rock classification system. Micrite is derived from MICRocrystalline calcITE. In the Folk classification micrite is a carbonate rock dominated by fine-grained calcite. Carbonate rocks that contain fine-grained calcite in addition to allochems are named ''intramicrite'', ''oomicrite'', ''biomicrite'' or ''pelmicrite'' under the Folk classification depending on the dominant allochem. Micrite is lime mud, carbonate of mud grade. Micrite as a component of carbonate rocks can occur as a matrix, as micrite envelopes around allochems or as peloids Peloids are allochems that are composed of micrite, irrespective of size, shape, or origin. The two primary types of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, pp.381-382 Although its permeability and porosity is relatively low, siltstone is sometimes a tight gas reservoir rock, an unconventional reservoir for natural gas that requires hydraulic fracturing for economic gas production. Siltstone was prized in ancient Egypt for manufacturing statuary and cosmetic palettes. The siltstone quarried at Wadi Hammamat was a hard, fine-grained siltstone that resisted flaking and was almost ideal for such uses. Description There is not complete agreement on the definition of siltstone. One definition is that siltstone is mudrock ( clastic sedimentary rock containing at least 50% clay and silt) in which at least 2/3 of the clay and silt fraction is composed of silt-sized particles. Silt is defined a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Craven In The Domesday Book
The extent of the medieval district of Craven, in the north of England is a matter of debate. The name Craven is either pre-Celtic Britain, Britonnic or Romano-British in origin. However, its usage continued following the ascendancy of the Anglo-Saxons and the Normans – as was demonstrated by its many appearances in the Domesday Book of 1086. Places described as being ''In Craven'' in the Domesday Book fell later within the modern county of North Yorkshire, as well as neighbouring areas of West Yorkshire, Lancashire and Cumbria. Usage of Craven in the Domesday Book is, therefore, circumstantial evidence of an extinct, British or Anglo-Saxon kingdom or subnational entity (such as a shire or earldom). The modern local government district of Craven – a much smaller area entirely within North Yorkshire – was defined in 1974. Background Although historic Craven extended a little further southeast in Yorkshire, as it still does with the Church of England's Deanery of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross Fell
Cross Fell is the highest mountain in the Pennines of Northern England and the highest point in England outside the Lake District. It is located in the North Pennines Area of Outstanding Natural Beauty. It lies within the county of Cumbria and the historic county boundaries of Cumberland. The summit, at , is a stony plateau, part of a ridge running north-west to south-east, which also incorporates Little Dun Fell at and Great Dun Fell at . The three adjoining fells form an escarpment that rises steeply above the Eden Valley on its south-western side and drops off more gently on its north-eastern side towards the South Tyne and Tees Valleys. Cross Fell summit is crowned by a cross-shaped dry-stone shelter. On a clear day there are excellent views from the summit across the Eden Valley to the mountains of the Lake District. On the northern side of Cross Fell there are also fine views across the Solway Firth to the Southern Uplands of Scotland. The fell is prone to dense hil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
