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The geology of Shropshire is very diverse with a large number of periods being represented at outcrop. The bedrock consists principally of sedimentary rocks of Palaeozoic and Mesozoic age, surrounding restricted areas of Precambrian metasedimentary and metavolcanic rocks. The county hosts in its Quaternary deposits and landforms, a significant record of recent glaciation. The exploitation of the Coal Measures and other Carboniferous age strata in the Ironbridge area made it one of the birthplaces of the Industrial Revolution. There is also a large amount of mineral wealth in the county, including lead and baryte. Quarrying is still active, with limestone for cement manufacture and concrete aggregate, sandstone, greywacke and dolerite for road aggregate, and sand and gravel for aggregate and drainage filters. Groundwater is an equally important economic resource.
Millstone Grit is the name given to any of a number of coarse-grained sandstones of Carboniferous age which occur in the British Isles. The name derives from its use in earlier times as a source of millstones for use principally in watermills. Geologists refer to the whole suite of rocks that encompass the individual limestone beds and the intervening mudstones as the Millstone Grit Group. The term Millstone Grit Series was formerly used to refer to the rocks now included within the Millstone Grit Group together with the underlying Edale Shale Group.
The Pennant Measures is the traditional name for a sequence of sedimentary rocks of the South Wales Coalfield. They were also referred to as the Upper Coal Measures and assigned to the Westphalian 'C' and Westphalian 'D' stages of the Carboniferous Period. The Pennant Measures were divided into the Lower Pennant Measures and the Upper Pennant Measures, differing from the underlying Middle and Lower Coal Measures in being principally of sandstone units – known collectively as the Pennant Sandstone – with mudstone being the subsidiary rock type. Numerous coal seams occur within the Pennant Measures though they are less common than in the underlying Coal Measures.
The Flintshire Coalfield in north-east Wales is one of the smaller British coalfields. It is in the county of Flintshire and extends from the Point of Ayr in the north, along the Dee Estuary through Connah's Quay to Caergwrle in the south. A small part extends onto the Wirral i.e. English coast of the estuary at Neston, Cheshire which was the site of a coalmine for a period. The coal-bearing strata continue southwards of Caergwrle as the Denbighshire Coalfield. Together the two coalfields are known as the North Wales Coalfield.
The Canonbie Coalfield is a small and largely concealed coalfield at Canonbie in the south of Scotland. A comprehensive survey by Peach and Horne was published in 1903. Canonbie colliery was worked until 1920, and another mine at Archerbeck continued until 1942.
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 Manchester Coalfield is part of the South Lancashire Coalfield, the coal seams of which were laid down in the Carboniferous Period. Some easily accessible seams were worked on a small scale from the Middle Ages, and extensively from the beginning of the Industrial Revolution in the early 19th century until the last quarter of the 20th century. The Coal Measures lie above a bed of Millstone Grit and are interspersed with sandstones, mudstones, shales, and fireclays. The Lower Coal Measures occupy the high ground of the West Pennine Moors above Bolton and are not worked in the Manchester Coalfield. The most productive of the coal measures are the lower two thirds of the Middle Coal Measures where coal is mined from seams between the Worsley Four Foot and Arley mines. The deepest and most productive collieries were to the south of the coalfield. The coalfield is affected by the northwest to southeast aligned Pendleton Fault along the Irwell Valley and the Rossendale Valley anticline. The Coal Measures generally dip towards the south and west. Numerous other smaller faults affect the coalfield. The Upper Coal Measures are not worked in the Manchester Coalfield.
The Warwickshire Group is a lithostratigraphic unit of rock strata defined within the British Carboniferous system. Within the Pennine Basin it overlies the Coal Measures Group and is deemed to be of late Westphalian and Stephanian age. In the South Wales Coalfield it consists of the Pennant Sandstone Formation and overlying Grovesend Formation. It contains the youngest Carboniferous rocks in Britain. The name Warwickshire Group is a relatively recent one, replacing a variety of earlier names for the succession of coal-barren red-beds such as Barren Coal Measures and Red Measures which overlie the productive coal measures. It is derived from the Warwickshire Coalfield where they achieve their thickest development.
The Coal Measures Group is a lithostratigraphical term coined to refer to the coal-bearing succession of rock strata which occur in the United Kingdom within the Westphalian Stage of the Carboniferous Period. The succession was previously referred to as the 'Productive Coal Measures'. Other than in Northern Ireland the term is now obsolete in formal use and is replaced by the Pennine Coal Measures Group, Scottish Coal Measures Group and the South Wales Coal Measures Group for the three distinct depositional provinces of the British mainland.
In lithostratigraphy, coal measures are coal-bearing strata, with the term typically applied to European units of the Upper Carboniferous System.
The Sherwood Sandstone Group is a Triassic lithostratigraphic group which is widespread in Britain, especially in the English Midlands. The name is derived from Sherwood Forest in Nottinghamshire which is underlain by rocks of this age. It has economic importance as the reservoir of the Morecambe Bay gas field, the second largest gas field in the UK.
The Stretton Group is a group of rocks associated with the Longmyndian Supergroup of Ediacaran age, in Shropshire, England. The rocks are located within the tract between two elements of the Welsh Borderland Fault System, the Church Stretton Fault and the Pontesford-Linley Lineament.
The geology of Lancashire in northwest England consists in the main of Carboniferous age rocks but with Triassic sandstones and mudstones at or near the surface of the lowlands bordering the Irish Sea though these are largely obscured by Quaternary deposits.
The geology of Merseyside in northwest England largely consists of a faulted sequence of Carboniferous Coal Measures rocks overlain in the west by younger Triassic and Permian age sandstones and mudstones. Glaciation during the present Quaternary Period has left widespread glacial till as well as erosional landforms. Other post-glacial superficial deposits such as river and estuarine alluvium, peat and blown sand are abundant.
The geology of County Durham in northeast England consists of a basement of Lower Palaeozoic rocks overlain by a varying thickness of Carboniferous and Permo-Triassic sedimentary rocks which dip generally eastwards towards the North Sea. These have been intruded by a pluton, sills and dykes at various times from the Devonian Period to the Palaeogene. The whole is overlain by a suite of unconsolidated deposits of Quaternary age arising from glaciation and from other processes operating during the post-glacial period to the present. The geological interest of the west of the county was recognised by the designation in 2003 of the North Pennines Area of Outstanding Natural Beauty as a European Geopark.
The South Wales Coal Measures Group is a lithostratigraphical term referring to the coal-bearing succession of rock strata which occur in South Wales within the Westphalian Stage of the Carboniferous Period. The Group name is also applied to rocks of similar age across southern England from the Bristol Coalfield east to the concealed Oxfordshire, Berkshire and Kent Coalfields. In formal use, the term replaces the earlier Coal Measures Group The Group comprises the:
The Leitrim Group is a lithostratigraphical term coined to refer to the succession of rock strata which occur in Northern Ireland within the Visean and Namurian stages of the Carboniferous Period. The group disconformably overlies the Dartry Limestone of the Tyrone Group.
The geology of the Yorkshire Dales National Park in northern England largely consists of a sequence of sedimentary rocks of Ordovician to Permian age. The core area of the Yorkshire Dales is formed from a layer-cake of limestones, sandstones and mudstones laid down during the Carboniferous period. It is noted for its karst landscape which includes extensive areas of limestone pavement and large numbers of caves including Britain's longest cave network.
The geology of the Peak District National Park in England is dominated by a thick succession of faulted and folded sedimentary rocks of Carboniferous age. The Peak District is often divided into a southerly White Peak where Carboniferous Limestone outcrops and a northerly Dark Peak where the overlying succession of sandstones and mudstones dominate the landscape. The scarp and dip slope landscape which characterises the Dark Peak also extends along the eastern and western margins of the park. Although older rocks are present at depth, the oldest rocks which are to be found at the surface in the national park are dolomitic limestones of the Woo Dale Limestone Formation seen where Woo Dale enters Wye Dale east of Buxton.
The geology of the North York Moors National Park in northern England is provided largely by a thick southerly dipping sequence of sedimentary rocks deposited in the Cleveland Basin during the Jurassic Period. A series of ice ages during the Quaternary period has left a variety of glacial deposits, particularly around the margins of the National Park.
References
- ↑ http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=CM BGS Lexicon of named rock units
- ↑ http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=PLCM BGS Lexicon of named rock units: Lower Pennine Coal Measures Gp
- ↑ Powell, J.H. et al. 2000. Stratigraphical framework for Westphalian to early Permian red-bed successions of the Pennine Basin, British Geological Survey Research Report, RR/00/01
- ↑ British Geological Survey 1:625,000 scale geological map Bedrock geology: UK South (5th edn) BGS, Keyworth, Notts
- ↑ Aitkenhead, N. et al 2002 British Regional Geology: the Pennines and adjacent areas (Fourth edition) British Geological Survey, Nottingham p64-65, 71