Coal Measures Group

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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 [1] 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.

Contents

Pennine Coal Measures Group

Within the Pennine Basin the Pennine Coal Measures Group is preceded (underlain) by the Millstone Grit Group which is of Namurian age. It is succeeded (overlain) by the Warwickshire Group which comprises a largely non-productive sequence of red beds. [2] It comprises the:

  • Pennine Upper Coal Measures Formation
  • Pennine Middle Coal Measures Formation
  • Pennine Lower Coal Measures Formation

The 'Pennine Basin' includes all of the coalfields of northern England and the English Midlands together with the Canonbie Coalfield of southern Scotland and the coalfields of northeast Wales and Anglesey.

Scottish Coal Measures Group

A similar scheme operates in the Midland Valley Basin of Scotland. These formations lie above the Namurian-age Clackmannan Group and below an unconformity.

South Wales Coal Measures Group

In those coalfields to the south of the former Wales-Brabant High i.e. the South Wales, Bristol, Somerset, Forest of Dean and concealed Oxfordshire and Kent coalfields, the corresponding group is the South Wales Coal Measures Group. It comprises the:

  • South Wales Upper Coal Measures Formation
  • South Wales Middle Coal Measures Formation
  • South Wales Lower Coal Measures Formation

In South Wales, the larger part of what had been the Upper Coal Measures now forms the Pennant Sandstone Formation in the overlying Warwickshire Group. [3] The South Wales Coal Measures Group is preceded (underlain) by the Marros Group.

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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.

<span class="mw-page-title-main">Millstone Grit</span>

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.

<i>Euproops</i> Genus of horseshoe crab relatives

Euproops Meek, 1867, is an extinct genus of xiphosuran, related to the modern horseshoe crab. It lived during the Carboniferous Period.

<span class="mw-page-title-main">Marros Group</span> Geological term for rock in south Wales

The Marros Group is the name given to a suite of rocks of Namurian age laid down during the Carboniferous Period in South Wales. These rocks were formerly known as the Millstone Grit Series but are now distinguished from the similar but geographically separate rock sequences of the Pennines and Peak District of northern England and northeast Wales by this new name.

<span class="mw-page-title-main">Pennant Measures</span> Geological term for rock in south Wales

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.

<span class="mw-page-title-main">Flintshire Coalfield</span> Coalfield in north Wales

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.

<span class="mw-page-title-main">Northumberland Coalfield</span>

The Northumberland Coalfield is a coalfield in north-east England. It is continuous with the Durham Coalfield to its south. It extends from Shilbottle in the north to the boundary with County Durham along the River Tyne in the south, beyond which is the Durham Coalfield.

<span class="mw-page-title-main">Cumberland Coalfield</span> Coalfield in Cumbria, England

The Cumberland Coalfield is a coalfield in Cumbria, north-west England. It extends from Whitehaven in the south to Maryport and Aspatria in the north.

<span class="mw-page-title-main">Canonbie Coalfield</span>

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 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.

<span class="mw-page-title-main">Coal measures</span>

In lithostratigraphy, coal measures are coal-bearing strata, with the term typically applied to European units of the Upper Carboniferous System.

<span class="mw-page-title-main">Sherwood Sandstone Group</span>

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 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 Pennine Coal Measures Group is a lithostratigraphical term referring to the coal-bearing succession of rock strata which occur in the United Kingdom within the Westphalian Stage of the Carboniferous Period. In formal use, the term replaces the Coal Measures Group as applied to the succession of coal-bearing strata within the Pennine Basin which includes all of the coalfields of northern England and the English Midlands. It includes the largely concealed Canonbie Coalfield of southern Scotland and the coalfields of northeast Wales and the minor Anglesey coalfield.

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 geology of Northumberland in northeast England includes a mix of sedimentary, intrusive and extrusive igneous rocks from the Palaeozoic and Cenozoic eras. Devonian age volcanic rocks and a granite pluton form the Cheviot massif. The geology of the rest of the county is characterised largely by a thick sequence of sedimentary rocks of Carboniferous age. These are intruded by both Permian and Palaeogene dykes and sills and the whole is overlain by unconsolidated sediments from the last ice age and the post-glacial period. The Whin Sill makes a significant impact on Northumberland's character and the former working of the Northumberland Coalfield significantly influenced the development of the county's economy. The county's geology contributes to a series of significant landscape features around which the Northumberland National Park was designated.

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 Scottish Coal Measures Group is a lithostratigraphic unit referring to the coal-bearing succession of rock strata which occur in Scotland during the Westphalian regional stage of the Carboniferous Period. It is the Scottish portion of the informal Coal Measures Group, which also includes the South Wales and Pennine coal measures. The Scottish coal measures are well-exposed across the Midland Valley. The group is also found within small grabens in the vicinity of Sanquhar and Thornhill.

References

  1. http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=CM BGS Lexicon of named rock units
  2. 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
  3. British Geological Survey 1:625,000 scale geological map Bedrock geology: UK South (5th edn) BGS, Keyworth, Notts