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Skiddaw Group
''For the Skiddaw group of hills, see Skiddaw Group'' The Skiddaw Group is a group of sedimentary rock formations named after the mountain Skiddaw in the English Lake District. The rocks are almost wholly Ordovician in age ( Tremadoc through Arenig to Llanvirn epochs) though the lowermost beds are possibly of Cambrian age. This rock sequence has previously been known as the Skiddaw Slates, the Skiddaw Slates Group and the Skiddavian Series. Its base is not exposed but in its main outcrop area, it is considered to be in excess of thick though less elsewhere. It consists largely of mudstones and siltstones with subordinate wacke-type sandstones. Their main occurrence is within the northern and central fells of the Lake District, either side of the major ENE-WSW aligned Causey Pike Fault, but inliers are found at Black Combe in the south of the Lake District and at Cross Fell in the North Pennines. Stratigraphy In the Northern Fells of the Lake District, the Skiddaw Group com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skiddaw
Skiddaw is a mountain in the Lake District National Park in England. Its summit is the sixth-highest in England. It lies just north of the town of Keswick, Cumbria, and dominates the skyline in this part of the northern lakes. It is the simplest of the Lake District mountains of this height to ascend (as there is a well-trodden tourist track from a car park to the north-east of Keswick, near the summit of Latrigg) and, as such, many walking guides recommend it to the occasional walker wishing to climb a mountain. This is the first summit of the fell running challenge known as the Bob Graham Round when undertaken in a clockwise direction. The mountain lends its name to the surrounding areas of Skiddaw Forest and Back o' Skidda, and to the isolated Skiddaw House, situated to the east, formerly a shooting lodge and subsequently a youth hostel. It also provides the name for the slate derived from that region: Skiddaw slate. Skiddaw slate has been used to make tuned percussi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tremadocian
The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from to million years ago. The base of the Tremadocian is defined as the first appearance of the conodont species ''Iapetognathus fluctivagus'' at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland. Naming The Tremadocian is named after the village Tremadoc in Wales. The name was proposed by Adam Sedgwick in 1846 (as "Tremadoc group"). GSSP The GSSP for the beginning of the Tremadocian is the Greenpoint section () in Gros Morne National Park, in western Newfoundland. It is defined as the first appearance of the conodont species ''Iapetognathus fluctivagus''. This horizon can be found 101.8 m above the Greenpoint section datum within bed number 23. The boundary lies within the Broom Point Member, of the Green Point Formation which is part of the Cow Head Group. The first planktonic graptolites appear 4.8 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olistostrome
An olistostrome is a sedimentary deposit composed of a chaotic mass of heterogeneous material, such as blocks and mud, known as olistoliths, that accumulates as a semifluid body by submarine gravity sliding or slumping of the unconsolidated sediments. It is a mappable stratigraphic unit which lacks true bedding, but is intercalated amongst normal bedding sequences, as in the Cenozoic basin of central Sicily. The term olistostrome is derived from the Greek ''olistomai'' (to slide) and ''stroma'' (accumulation).Ernesto Abbate, et al., "Olistostromes and olistoliths", ''Sedimentary Geology'', 4 (1970), 521-557. See also *Submarine landslide Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting str ... References Sedimentary rocks {{Geology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, ''tuffaceous sandstone''). Tuff composed of sandy volcanic material can be referred to as volcanic sandstone. Tuff is a relatively soft rock, so it has been used for construction since ancient times. Because it is common in Italy, the Romans used it often for construction. The Rapa Nui people used it to make most of the ''moai'' statues on Easter Island. Tuff can be classified as either igneous or sedimentary rock. It is usually studied in the context of igneous petrology, although it is sometimes described using sedimentological terms. Tuff is often erroneously called tufa in guidebooks and in television programmes. Volcanic ash The material that is expelled in a volcanic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central Fells
The Central Fells are a group of hills in the English Lake District. Reaching their highest point at High Raise (2,500 ft or 762 metres), they occupy a broad area to the east of Borrowdale. The Central Fells are generally lower than the surrounding hills, the Lake District's dome-like structure having a slight dip in the middle. The range extends from the boggy ridge between Derwentwater and Thirlmere in the north, to the rock peaks of the Langdale Pikes in the south. Partition of the Lakeland fells The Lake District is a National Park in the north-west of the country which, in addition to its lakes, contains a complex range of hills. These are locally known as fells and range from low hills to the highest ground in England. Hundreds of tops exist and many writers have attempted to draw up definitive lists. In doing so the compilers frequently divide the range into smaller areas to aid their description. The most influential of all such authors was Alfred Wainwright, who ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northern Fells
The Northern Fells are a mountain range in the English Lake District. Including Skiddaw, they occupy a wide area to the north of Keswick. Smooth, sweeping slopes predominate, with a minimum of tarns or crags. Blencathra in the south-east of the group is the principal exception to this trend. Partition of the Lakeland fells The Lake District is a National Park in the north-west of the country, which, in addition to its lakes, contains a complex range of hills. These are known locally as fells and range from low hills to the highest ground in England. Hundreds of tops exist and many writers have attempted to draw up definitive lists. In doing so the compilers frequently divide the range into smaller areas to aid their description. The most influential of all such authors was Alfred Wainwright, whose ''Pictorial Guide to the Lakeland Fells'' series has sold in excess of 2 million copies, [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North Pennines
The North Pennines is the northernmost section of the Pennine range of hills which runs north–south through northern England. It lies between Carlisle to the west and Darlington to the east. It is bounded to the north by the Tyne Valley and to the south by the Stainmore Gap. Overview The North Pennines was designated as an Area of Outstanding Natural Beauty (AONB) in 1988 for its moorland scenery, the product of centuries of farming and lead-mining, and is also a UNESCO Global Geopark. At almost , it is the second largest of the 49 AONBs in the United Kingdom. The landscape of the North Pennines AONB is one of open heather moors between deep dales, upland rivers, hay meadows and stone-built villages, some of which contain the legacies of a mining and industrial past. The area has previously been mined and quarried for minerals such as barytes, coal fluorspar, iron, lead, witherite and zinc. Natural England maps Maps for North Pennines – Area of Outstanding Natural Beauty, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inliers And Outliers (geology)
An inlier is an area of older rocks surrounded by younger rocks. Inliers are typically formed by the erosion of overlying younger rocks to reveal a limited exposure of the older underlying rocks. Faulting or folding may also contribute to the observed outcrop pattern. A classic example from Great Britain is that of the inlier of folded Ordovician and Silurian rocks at Horton in Ribblesdale in North Yorkshire which are surrounded by the younger flat-lying Carboniferous Limestone. The location has long been visited by geology students and experts. Another example from South Wales is the Usk Inlier in Monmouthshire where Silurian age rocks are upfolded amidst Old Red Sandstone rocks of Devonian age. A similar outcrop pattern which results from movement on a thrust fault followed by erosion may be termed a window. Conversely an outlier is an area of younger rock surrounded by older rocks. An outlier is typically formed when sufficient erosion of surrounding rocks has taken place to s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Causey Pike Fault
The Causey Pike Fault or Causey Pike Thrust is a major WSW-ENE trending fault within the Lower Paleozoic rocks of the English Lake District. It is named for Causey Pike, where the fault was first recognised. Extent The Causey Pike Fault has been recognised across the entire outcrop of the Lake District inlier, extending about 35 km from near Ennerdale Bridge in the west, to near Troutbeck in the east. A possible continuation of the fault to the east has been recognised in the Cross Fell inlier, where it also juxtaposes two differing parts of the Skiddaw Group. Recognition It juxtaposes two successions dominated by mudrocks that are of similar age. To the north of the fault, the Ordovician Skiddaw Group is represented by the Kirk Stile Formation, to the south by the Buttermere Formation, both of Arenig age. The younger sequence of volcanic rocks overlying the Skiddaw Group also differs, with the Eycott Volcanic Group to the north and the Borrowdale Volcanic Group to the south. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wacke
Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found in Paleozoic strata. The larger grains can be sand- to gravel-sized, and matrix materials generally constitute more than 15% of the rock by volume. The term "greywacke" can be confusing, since it can refer to either the immature (rock fragment) aspect of the rock or its fine-grained (clay) component. The origin of greywacke was unknown until turbidity currents and turbidites were understood, since, according to the normal laws of sedimentation, gravel, sand and mud should not be laid down together. Geologists now attribute its formation to submarine avalanches or strong turbidity currents. These actions churn sediment and cause mi ... [...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] |
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] |
