The South Wales Coal Measures Group is a lithostratigraphical

term Term may refer to: * Terminology, or term, a noun or compound word used in a specific context, in particular: **Technical term, part of the specialized vocabulary of a particular field, specifically: ***Scientific terminology, terms used by scient ...

referring to the

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

-bearing succession of rock

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

which occur in South

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

within the Westphalian

Stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

of the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

. The Group name is also applied to rocks of similar age across southern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

from the

Bristol Coalfield The Bristol Coalfield is a geologically complex coalfield in the west of England. Comprising the coal-bearing rocks arranged around the Coalpit Heath Syncline and Kingsdown Anticline, it extends beneath the eastern parts of the city of Bristol ...

east to the concealed

Oxfordshire Oxfordshire is a ceremonial and non-metropolitan county in the north west of South East England. It is a mainly rural county, with its largest settlement being the city of Oxford. The county is a centre of research and development, primarily ...

Berkshire Berkshire ( ; in the 17th century sometimes spelt phonetically as Barkeshire; abbreviated Berks.) is a historic county in South East England. One of the home counties, Berkshire was recognised by Queen Elizabeth II as the Royal County of Berk ...

and Kent Coalfields. In formal use, the term replaces the earlier

Coal Measures Group 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. Other than in Northern Ireland the ...

The Group comprises the: :* South Wales Upper Coal Measures Formation :* South Wales Middle Coal Measures Formation :* South Wales Lower Coal Measures Formation The term 'Productive Coal Measures' was formerly used for this succession. Note that, other than a 0-30m thick sequence immediately above the ''Cambriense'' Marine Band, the South Wales rock sequence which had formerly been assigned to the 'Upper Coal Measures' (which was also referred to as the 'Pennant Measures') is no longer considered to be a part of the Coal Measures and is now designated as the

Warwickshire Group The Warwickshire Group is a lithostratigraphic unit of rock strata defined within the British Carboniferous system. Within the Pennine Basin it overlies (i.e. postdates) the Coal Measures Group and is deemed to be of late Westphalian and St ...

which is itself subdivided into the

Pennant Sandstone Formation Pennant may refer to: Flag or banner * Pennon (or pennant), a narrow, tapering flag ** Commissioning pennant, the traditional sign of a warship, flown from its masthead while the ship is in commission ** Broad pennant, flown from the masthead o ...

and overlying

Grovesend Formation Grovesend ( cy, Pengelli; ) is a village in the community of Grovesend and Waungron ( cy, Pengelli a Waungron), City and County of Swansea in Wales. The community has a population of 1,131.Marros Group 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 geographi ...

which is of

Namurian The Namurian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 326 and 313 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is ...

age though in southeast England, the Coal Measures directly overlies

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

strata. It is succeeded (overlain) by the

which comprises a largely non-productive sequence of

red bed Red beds (or redbeds) are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain th ...

s - the former 'Barren Coal Measures'.British Geological Survey 1:625,000 scale geological map ''Bedrock geology: UK South'' (5th edn) BGS, Keyworth, Notts The South Wales Coal Measures Group spans a time from the Langsettian to the

Bolsovian The Westphalian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 313 and 304 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Westphalia ...

sub-age.

References

{{reflist Coal in Wales Coal in England Geology of Wales Geology of England Geological groups of the United Kingdom Carboniferous Wales Carboniferous England Carboniferous System of Europe Geologic formations of England Stratigraphy of the United Kingdom