Related Research Articles
The London Basin is an elongated, roughly triangular sedimentary basin approximately 250 kilometres (160 mi) long which underlies London and a large area of south east England, south eastern East Anglia and the adjacent North Sea. The basin formed as a result of compressional tectonics related to the Alpine orogeny during the Palaeogene period and was mainly active between 40 and 60 million years ago.
The geological structure of Great Britain is complex, resulting as it does from a long and varied geological history spanning more than two billion years. This piece of the Earth's crust has experienced several episodes of mountain building or 'orogenies', each of which has added further complexity to the picture.
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.
The Welsh Borderland Fault System is a zone of faulting and associated folding which runs northeastwards through Wales from Pembrokeshire through Carmarthenshire and Powys into Shropshire in England. It comprises the Tywi Lineament, Pontesford Lineament and Church Stretton Fault Zone. The southern margin of the fault system is defined by the Church Stretton Fault and Dulas Valley Fault, amongst others whilst its northern margin is defined by the Garth-Llanwrtyd Fault Belt in Carmarthenshire. The Church Stretton Fault component of the system is deemed to form the terrane boundary between the Cymru Terrane to its northwest and the Wrekin Terrane to its southeast.
In geology, a disturbance is a linear zone of disturbed rock strata stretching for many miles across country which comprises a combination of folding and faulting. The British Geological Survey record a number of such features in South Wales including the Neath Disturbance, Pontyclerc Disturbance, Carreg Cennen Disturbance and the Cribarth Disturbance, the latter sometimes also known as the Tawe Valley or Swansea Valley Disturbance. The southwestward continuation of the Carreg Cennen Disturbance is known as the Llandyfaelog Disturbance.
The Bronnant Fault is a geological fault affecting the lower Palaeozoic rocks of the counties of Ceredigion and Pembrokeshire in West Wales. The feature is mapped over part of its length as the Bronnant Fault Zone and is closely associated with the Glandyfi Lineament, a similarly aligned zone of faulting and folding. The rocks of the Aberystwyth Grits Group dating from the Llandovery epoch of the Silurian period thicken markedly to the west of the fault suggesting it was active at the time of their deposition. North of Lledrod its alignment is affected by cross-cutting east–west faults, including the Ystwyth Fault Zone. Its alignment is sub-parallel to the coast of Cardigan Bay thus curving from a north–south alignment in the north through a northeast–southwest alignment until it merges with broadly east–west aligned faults in northeast Pembrokeshire.
The geology of Monmouthshire in southeast Wales largely consists of a thick series of sedimentary rocks of different types originating in the Silurian, Devonian, Carboniferous, Triassic and Jurassic periods.
The Warwickshire Coalfield extends between Warwick and Tamworth in the English Midlands. It is about 25 miles (40 km) from north to south and its width is around half that distance. Its western margin is defined by the 'Western Boundary Fault'. In the northeast it abuts against steeply dipping shales of Cambrian age. The larger part of the outcrop at the surface consists of the Warwickshire Group of largely coal-barren red beds. Until its closure in 2013, the Daw Mill mine near Arley within the coalfield, was Britain's biggest coal-producer in the 21st century.
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 Aberystwyth Grits Group is a Silurian lithostratigraphic group in mid Wales. The name is derived from Aberystwyth in northern Ceredigion where the strata are well exposed in coastal cliffs. The Group comprises the Trefechan Formation and the underlying Mynydd Bach Formation. The rocks of the Aberystwyth Grits Group have also previously been known as the Aberystwyth Grits Formation
The Portsdown Anticline is a north-facing geological fold of Tertiary age affecting rocks in Hampshire, southern England. This upfold of the local sedimentary rock sequence is paralleled by the Bere Forest/Chichester Syncline (downfold) about 2km to its north and a postulated deep fault to the north again. Further west, this major east-west structure adopts more of a NW - SE alignment. At the surface the Portsdown Anticline is seen to affect the Chalk rocks of Late Cretaceous age at Ports Down though it is known to also affect the underlying Jurassic strata.
The Exmoor Group is a late Devonian to early Carboniferous lithostratigraphic group in southwest England whose outcrop extends from Croyde in north Devon east across Exmoor to Minehead in west Somerset. The group comprises the following formations :
This article describes the geology of Dartmoor National Park in Devon, in south-west England. Dartmoor gained national park status in 1951 but the designated area of 954 km2 (368 sq mi) extends beyond the upland of Dartmoor itself to include much of the surrounding land, particularly in the northeast. The geology of the national park consists of a 625 km2 (241 sq mi) core of granite intruded during the early Permian period into a sequence of sedimentary rocks originating in the Devonian and Carboniferous periods. These rocks were faulted and folded, sometimes, intensely, during the Variscan orogeny. Thermal metamorphism has also taken place around the margins of the granite pluton altering the character of the sedimentary rocks whilst mineral veins were emplaced within the granite. A small outlier of Palaeogene sediments occurs on the eastern boundary of the national park.
The sedimentary basins of Britain and Ireland are numerous, occurring beneath both the land surface of these islands and the surrounding seas. Sedimentary basins have operated in this region over much of geological time from the Precambrian to the present day, typically accepting sediment from neighbouring areas where erosion is taking place, over timescales variously from millions to hundreds of millions of years. They may be referred to simply as basins or else as troughs, grabens or half-grabens, according to their mode of formation and morphology.
References
Maps
- 1:625,000 scale geological map 2007, Bedrock Geology UK South, British Geological Survey, Keyworth, Notts (UK (south) 625K)
- 1:250,000 scale geological map Mid Wales and the Marches, British Geological Survey, Keyworth, Notts (MW & M 250K)
- various of 1:50,000 scale geological maps of England and Wales, British Geological Survey, Keyworth, Notts (E & W no.)
- 1:25,000 scale sheet Usk - Cwmbran in Classic Areas of British Geology series, British Geological Survey, Keyworth, Notts (Usk-Cwm: 25K)
Books
- Barclay, W.J. 1989 Geology of the South Wales Coalfield Part II, the country around Abergavenny, 3rd edition. Mem Br. Geol. Surv. sheet 232 (England and Wales) (Mem E&W 232)
- Brenchley, PJ & Rawson, PF (eds) 2006. The Geology of England and Wales, (2nd edn) The Geological Society, London (Brenchley & Rawson 2006)
- Cave, R. & Hains, B.A, 2001 Geology of the country around Montgomery and the Ordovician rocks of the Shelve area Memoir of the British Geological Survey. Sheet 165 with part of sheet 151 (Welshpool) (England and Wales).(Mem E&W 165/151)
- Smith et al. 2005 Structure & Evolution of the south-west Pennine Basin and adjacent area. Subsurface memoir of the British Geological Survey. (Smith et al. 2005)
- Toghill, P 2006 Geology of Shropshire (2nd edn) Crowood Press, Wilts (Toghill P 2006)
- Warren et al. 1984, Geology of the country around Rhyl and Denbigh, Mem Br Geol Svy, sheets 95 and 107 (Mem E&W 95/107)
- Welch, FBA & Trotter, FM 1961 Geology of the Country around Monmouth and Chepstow, HMSO (explanation of 1" geol. sheets 233 & 250 (England and Wales) (Welch, FBA & Trotter, FM 1961)
| Counties |
|
|---|---|
| National parks |
|
| Other areas | |
| Other related topics | |
| Physical | |||||||
|---|---|---|---|---|---|---|---|
| Environment | |||||||
| Land use | |||||||
| Administrative |
| ||||||
| Social | |||||||
| Other | |||||||
