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Somerset Coalfield
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The Somerset Coalfield in northern Somerset, England is an area where coal was mined from the 15th century until 1973. It is part of a larger coalfield which stretched into southern Gloucestershire. The Somerset coalfield stretched from Cromhall (Gloucestershire) in the north to the Mendip Hills in the south, and from Bath in the east to Nailsea in the west – a total area of about 240 square miles (622 km2). Most of the pits on the coalfield were concentrated in the Cam Brook, Wellow Brook and Nettlebridge Valleys and around Radstock and Farrington Gurney. The pits were grouped geographically, with clusters of pits close together working the same coal seams often under the same ownership. Many pits shared the trackways and tramways which connected them to the Somerset Coal Canal or railways for distribution.
The early pits were adits where coal outcropped or bell pits where coal was close to the surface. These methods were abandoned when deep seams were mined. The deepest shaft on the coalfield was at the Strap mine at Nettlebridge which reached 1,838 feet (560 m). Flooding and coal dust explosions in some mines required improved ventilation and pumping engines. Several pits closed in the 19th century as the coal was worked out. Those that survived until 1947 became part of the National Coal Board, but the expense of improving equipment and working conditions meant that these became uneconomical and the last pit closed in 1973. There is still evidence of the mine workings, with the remains of buildings, spoil heaps and tramways in the area.
The Somerset Coalfield covers a total area of about 240 square miles (622 km2). It consists of three synclines, informally referred to as 'coal basins'. The Pensford Syncline in the north and the Radstock Syncline in the south are separated by the east–west trending Farmborough Fault Belt. Further to the west is the smaller Nailsea Syncline. The Radstock Syncline in particular is cut by a series of east–west thrust faults and north–south trending normal faults.
The Coal Measures are divided into a Lower, Middle and Upper with coal seams found within each of these divisions. Lower and Middle Coal Measures are found at depths between 500 and 5,000 feet (150 and 1,520 m). Together the Lower and Middle Coal Measures are 1,600 feet (490 m) thick with the Middle Coal Measures averaging about 500 and 5,000 feet and the Lower Coal Measures about 600 feet (180 m).
Only in the southern part of the Radstock Syncline have coals of the Lower and Middle Coal Measures been worked, mainly at the Newbury and Vobster collieries in the southeast and in the New Rock and Moorewood pits to the southwest. Whilst in the eastern part of Pensford Syncline coals of the Lower and Middle Coal Measures have been worked, at the Globe Pit in the Newton St Loe area in the 19th century. The Variscan orogeny (also responsible for the emplacement of the granitic batholiths in Cornwall, and associated tin and copper mineralisation) involved lateral compression of the rock sequence resulting in the tight folding, fracturing and faulting of the sandstone and mudstone strata, and the associated Coal Measures. Along the Radstock Slide Fault the distance between the broken ends of a coal seam can be as much as 1,500 feet (457 m). The complex geology and thin seams gained the field notoriety and three underground explosions, in 1893, 1895 and 1908 were amongst the first attributable solely to airborne coal dust.
Exploratory surveys of the local geology were carried out by William Smith, who became known as the "father of English geology", building on work by John Strachey. Smith worked for the Stracheys who owned Sutton Court, at one of their older mines, the Mearns Pit at High Littleton. As he observed the rock strata at the pit, he realised that they were arranged in a predictable pattern that the various strata could always be found in the same relative positions and each particular stratum could be identified by the fossils it contained and the same succession of fossil groups from older to younger rocks could be found in other parts of England. Smith noticed an easterly dip in the beds of rock—small near the surface (about three degrees) then greater after the Triassic rocks which led to him a testable hypothesis, which he termed the principle of faunal succession, and he began to determine if the relationships between the strata and their characteristics were consistent throughout the country. During work as a surveyor (appointed by engineer John Rennie) for the Somerset Coal Canal Company and subsequently, he mapped the locations of geomorphological features, rock strata, and their vertical extent, and drew cross-sections and tables of what he saw and earned the name "Strata Smith".
The following coal seams are recognised within the coalfield. They are listed stratigraphically i.e. uppermost/youngest first. Note that not all seams are continuous across the coalfield and that correlation of some seams from one basin to another is uncertain.
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Somerset Coalfield
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The Somerset Coalfield in northern Somerset, England is an area where coal was mined from the 15th century until 1973. It is part of a larger coalfield which stretched into southern Gloucestershire. The Somerset coalfield stretched from Cromhall (Gloucestershire) in the north to the Mendip Hills in the south, and from Bath in the east to Nailsea in the west – a total area of about 240 square miles (622 km2). Most of the pits on the coalfield were concentrated in the Cam Brook, Wellow Brook and Nettlebridge Valleys and around Radstock and Farrington Gurney. The pits were grouped geographically, with clusters of pits close together working the same coal seams often under the same ownership. Many pits shared the trackways and tramways which connected them to the Somerset Coal Canal or railways for distribution.
The early pits were adits where coal outcropped or bell pits where coal was close to the surface. These methods were abandoned when deep seams were mined. The deepest shaft on the coalfield was at the Strap mine at Nettlebridge which reached 1,838 feet (560 m). Flooding and coal dust explosions in some mines required improved ventilation and pumping engines. Several pits closed in the 19th century as the coal was worked out. Those that survived until 1947 became part of the National Coal Board, but the expense of improving equipment and working conditions meant that these became uneconomical and the last pit closed in 1973. There is still evidence of the mine workings, with the remains of buildings, spoil heaps and tramways in the area.
The Somerset Coalfield covers a total area of about 240 square miles (622 km2). It consists of three synclines, informally referred to as 'coal basins'. The Pensford Syncline in the north and the Radstock Syncline in the south are separated by the east–west trending Farmborough Fault Belt. Further to the west is the smaller Nailsea Syncline. The Radstock Syncline in particular is cut by a series of east–west thrust faults and north–south trending normal faults.
The Coal Measures are divided into a Lower, Middle and Upper with coal seams found within each of these divisions. Lower and Middle Coal Measures are found at depths between 500 and 5,000 feet (150 and 1,520 m). Together the Lower and Middle Coal Measures are 1,600 feet (490 m) thick with the Middle Coal Measures averaging about 500 and 5,000 feet and the Lower Coal Measures about 600 feet (180 m).
Only in the southern part of the Radstock Syncline have coals of the Lower and Middle Coal Measures been worked, mainly at the Newbury and Vobster collieries in the southeast and in the New Rock and Moorewood pits to the southwest. Whilst in the eastern part of Pensford Syncline coals of the Lower and Middle Coal Measures have been worked, at the Globe Pit in the Newton St Loe area in the 19th century. The Variscan orogeny (also responsible for the emplacement of the granitic batholiths in Cornwall, and associated tin and copper mineralisation) involved lateral compression of the rock sequence resulting in the tight folding, fracturing and faulting of the sandstone and mudstone strata, and the associated Coal Measures. Along the Radstock Slide Fault the distance between the broken ends of a coal seam can be as much as 1,500 feet (457 m). The complex geology and thin seams gained the field notoriety and three underground explosions, in 1893, 1895 and 1908 were amongst the first attributable solely to airborne coal dust.
Exploratory surveys of the local geology were carried out by William Smith, who became known as the "father of English geology", building on work by John Strachey. Smith worked for the Stracheys who owned Sutton Court, at one of their older mines, the Mearns Pit at High Littleton. As he observed the rock strata at the pit, he realised that they were arranged in a predictable pattern that the various strata could always be found in the same relative positions and each particular stratum could be identified by the fossils it contained and the same succession of fossil groups from older to younger rocks could be found in other parts of England. Smith noticed an easterly dip in the beds of rock—small near the surface (about three degrees) then greater after the Triassic rocks which led to him a testable hypothesis, which he termed the principle of faunal succession, and he began to determine if the relationships between the strata and their characteristics were consistent throughout the country. During work as a surveyor (appointed by engineer John Rennie) for the Somerset Coal Canal Company and subsequently, he mapped the locations of geomorphological features, rock strata, and their vertical extent, and drew cross-sections and tables of what he saw and earned the name "Strata Smith".
The following coal seams are recognised within the coalfield. They are listed stratigraphically i.e. uppermost/youngest first. Note that not all seams are continuous across the coalfield and that correlation of some seams from one basin to another is uncertain.