GCR block - Namurian of England & Wales (NAM-E-WL)

Namurian of England & Wales

Block Description

UK map showing distribution of GCR sites of GCR block NAM-E-WL
Distribution of GCR sites of GCR block Namurian of England & Wales

The GCR sites selected for this GCR Block represent the British geological record of Earth history from about 327 to 310 million years ago (Ma) as represented by rocks in England and Wales. This interval is the middle part of the Carboniferous Period, which itself spans from about 354 to 292 Ma. Underlying rocks formed during Dinantian time (see, for example, DIN-N-E-WL) constitute the Dinantian Subsystem, which comprises the Tournaisian and Visean series. Overlying rocks formed during the Westphalian Epoch (see WPH). In the GCR, the Dinantian Subsystem plus Pendleian and Arnsbergian stages (the lowest two stages of the overlying Namurian Series of the Silesian Subsystem) are equated with Lower Carboniferous (or Mississipian) Subsystem. Therefore British Namurian strata include rocks either side of the Lower–Upper Carboniferous boundary.

There has been much confusion as to the exact meaning of the term ‘Upper Carboniferous’. In northern Europe, it has been taken to include all of the Namurian, Westphalian and Stephanian series, as this represents an interval of largely fluvio-deltaic clastic rocks, which can be readily separated from the mainly marine shelf limestones of the underlying Viséan. It is placed just above the base of the Chokierian Stage in the European classification. For convenience, the base of the Chokierian Stage is used in the GCR as an approximation to the lower limit of the Lower Carboniferous subsystem.

Now, all of the eight stages of the Upper Carboniferous, from the Chokierian, Alportian, Kinderscoutian, Marsdenian, Yeadonian, Langsettian, Duckmantian and Bolsovian are defined by stratotypes in this country.

Namurian rocks in Britain can be roughly equated to the informal term ‘Millstone Grit’, which is overlain by the ‘Coal Measures’ and underlain by the Dinantian ‘Carboniferous Limestone’.

Outcrop pattern

Britain has some of the best-exposed sequences of non-marine Upper Carboniferous strata anywhere in Europe. Nowhere else has such extensive coastal exposures of these beds, as can be seen in Pembrokeshire, Northumberland, Cumbria and Fife. Even outside of Europe, one would struggle to find comparable coastal exposures, at least within the palaeoequatorial belt, with the possible exception of Nova Scotia in Canada (e.g. Joggins Bank, Point Aconi). Britain is also unusually well endowed with natural, inland exposures. For instance the Pennines is a classic area for Namurian studies, with their extensive exposures of Millstone Grit.

There is considerable variation in the lithostratigraphical development of the Upper Carboniferous strata of Britain, and different areas often have their own set of formations. Only ‘the Productive Coal Formation’ (the mainly Westphalian, grey, coal-bearing deposits) has a reasonably wide distribution. However, there is an underlying pattern of lithofacies recognizable over much of the country, and this is recognized here as five groups listed as follows.

• Culm Group

• Yoredale Group

• Millstone Grit Group

• Passage Group

• Coal Measures Group

Palaeoenvironment and palaeogeography

The Upper Carboniferous of Britain was formed in an elongate belt of deposition lying between Poland and Ireland, that marks the contact-zone between the Gondwana and Laurasia continental plates. Originally separated by deep ocean (the ‘Proto-Tethys’), the Gondwana plate progressively drifted north relative to the Laurasia plate during Late Palaeozoic times. By Late Carboniferous time, the deep ocean had totally disappeared, and eventually the collision caused significant uplift and deformation of the Laurasian foreland. This tectonic episode is termed the ‘Variscan (or Hercynian) Orogeny’ (see VAR-STR-SW; VAR-STR-WM). However, between the times of ocean closure and basin inversion, a complex set of localized, synorogenic basins developed on the foreland.

There are four main mechanisms that have been proposed for how these basins were generated: (1) the northwards subduction of Gondwana under Laurasia, (2) transtension due to east–west mega-shear along the Gondwana-Laurasia plate boundary, (3) nappe loading due to the northwards migration of the Variscan front, and (4) north–south rifting and ocean spread due to the opening of a ‘Proto-Atlantic’ Ocean.

The result has been five discrete areas of deposition, separated by areas of non-deposition and sometimes erosion. These are, from south to north, Sabrina, the Wales–Brabant Barrier and the Southern Uplands Massif.

(1) The Culm Trough in south-west England. This was a shallow marine basin that was progressively filled during the Namurian by northerly derived deltaic sediments. Basin inversion and tectonic deformation here was rather earlier than in the rest of Britain, probably sometime in the middle part of the Westphalian Epoch.

(2) The Kent Coalfield, which is effectively a western extension of the Franco-Belgian Basin. This coalfield is known only through boreholes and underground mine workings, therefore as there is no exposure.

(3) The area immediately south of the Wales–Brabant Barrier, including principally South Wales, the Forest of Dean and the Bristol–Somerset coalfields. Like the Culm Trough, the Namurian strata are characterized by the progressive infill of a shallow marine basin by deltaic sediment, although it seems to have been ‘less marine’ than the Culm deposits. During the early and middle Westphalian times (up to the middle Bolsovian), deposition was characteristically in a fluvio-delatic regime, with extensive peat deposits. In late Westphalian times, however, uplift mainly to the south resulted in the influx of mainly arenaceous fluvial deposits (the Pennant Formation).

(4) The area between the Wales–Brabant Barrier and the Southern Uplands Massif, and including the northern English Midlands, the Pennines, and northern England. Again, the Namurian is characterized by mainly northerly-derived deltaic deposits filling a shallow marine basin, and the lower and middle Westphalian by fluvio-deltaic deposition. Unlike further south, however, there is no evidence of major fluvial deposits in upper Westphalian strata, except in the southern margins of the area. Instead, the progressive development of Variscan movement resulted in the formation of red beds such as the Etruria Formation.

(5) The Midland Valley of Scotland. The general facies development here is similar to the area south of the Southern Uplands Massif, with predominantly arenaceous deposits in the Namurian, coal-bearing deposits in the lower Westphalian and red beds in the upper Westphalian. However, marine influence was significantly reduced, with the result that marine bands are fewer and less well developed. Also volcanicity was a much greater influence, both as an influence on basin configuration, and on sedimentation itself (e.g. the Ayrshire Bauxitic Clay Formation).

GCR site selection

For the Upper Carboniferous stratigraphy of Britain sites were selected according to palaeogeographically defined GCR networks

• Culm Trough

• South Wales

• Forest of Dean and Severn coalfields

• Bristol-Somerset Basin

• English Midlands

• North Wales

• Millstone Grit of the Central Province

• Coal Measures of the Pennine Basin

• Northern England

• Scottish Basin

Although the relatively common invertebrate fossils do not have a separate selection category in the GCR in their own right, the scientific importance of many stratigraphy sites lies in their fossil content. Therefore, some of the GCR sites are selected specifically for their fossil fauna, which facilitates stratal correlation and enables the interpretation of the environments in which the animals lived. Moreover, some sites have international significance because they have yielded fossils that are the ‘type’ material for a taxonomic group.

Palaeontology

Five main groups of fossils have been used for biostratigraphical work in the British Upper Carboniferous strata: ammonoids (goniatites), conodonts, non-marine bivalves, microspores and plant macrofossils.

Most stratigraphical correlations in the British Upper Carboniferous are based on biostratigraphical criteria. However, there are two types of ‘marker horizon’ available in these strata that provide valuable, abiotic means of establishing time-planes.

The most widely used are the marine bands. During the Late Carboniferous, Britain saw a progressive change from predominantly marine to predominantly non-marine conditions, and the preserved sedimentary sequence can be interpreted in terms of the interplay between these two broad environments.

The second type of ‘marker horizons’ consists of cineritic tonsteins, which were the result of volcanic ash-falls.


Volume Introduction

Namurian of England & Wales


Site List

Your selection found 49 GCR sites. Sites are sorted alphabetically by country, local authority and then by site name -
CodeNameCountryLocal AuthorityGrid RefGCR Site Account
335Yeadon Brickworks and Railway CuttingEnglandBradfordSE193407Not available
340Crimsworth DeanEnglandCalderdale, Kirklees and WakefieldSD988292Not available
339Derby Delph QuarryEnglandCalderdale, Kirklees and WakefieldSE017160Not available
776Park CloughEnglandCalderdale, Kirklees and WakefieldSE030125Not available
336Pule HillEnglandCalderdale, Kirklees and WakefieldSE032102Not available
396Rake DikeEnglandCalderdale, Kirklees and WakefieldSE094048Not available
322Pot Bank QuarryEnglandCheshire CCSJ869593Not available
331Widemouth to CrackingtonEnglandCornwall and Isles of ScillySX139967Not available
329Bickleigh Wood QuarryEnglandDevon CCSS944180Not available
330Bonhay Road CuttingEnglandDevon CCSX914926Not available
347Botany HillEnglandDurham CCNY955204Not available
348Crag GillEnglandDurham CCNZ026235Not available
349Rogerley QuarryEnglandDurham CCNZ019375Not available
346Sleightholme BeckEnglandDurham CCNY965116Not available
333Mousegill BeckEnglandEast CumbriaNY825129Not available
323Harewood GrangeEnglandEast DerbyshireSK311683Not available
332Ladcastle And Den QuarriesEnglandGreater Manchester NorthSD994059Not available
338Standedge Road CuttingEnglandGreater Manchester NorthSE018095Not available
318Cockwood GorgeEnglandLancashire CCSD746345Not available
319Harper Clough, Smalley Delph and Close Brow QuarriesEnglandLancashire CCSD717317Not available
3024Heys Britannia QuarryEnglandLancashire CCSD872202Not available
315Hodge CloughEnglandLancashire CCSD785193Not available
881Light CloughEnglandLancashire CCSD752376Not available
316Little Mearley CloughEnglandLancashire CCSD779415Not available
317River DarwenEnglandLancashire CCSD608291Not available
337Great Dib WoodEnglandLeedsSE199443Not available
879Gill BeckEnglandNorth Yorkshire CCSD947433Not available
345School ShareEnglandNorth Yorkshire CCSD845623Not available
344Brunton Bank QuarryEnglandNorthumberlandNY928698Not available
342Corbridge Limestone QuarryEnglandNorthumberlandNY995653Not available
341Greenleighton QuarryEnglandNorthumberlandNZ034917Not available
343Howick to Seaton PointEnglandNorthumberlandNU262173Not available
395Hathersage MoorEnglandSheffieldSK255820Not available
327Alport CastlesEnglandSouth and West DerbyshireSK142914Not available
328Blackden BrookEnglandSouth and West DerbyshireSK115884Not available
324Jumble CoppiceEnglandSouth and West DerbyshireSK268721Not available
326Mam TorEnglandSouth and West DerbyshireSK130836Not available
325River NoeEnglandSouth and West DerbyshireSK091858Not available
775Blake BrookEnglandStaffordshire CCSK063612Not available
321Cauldon Railway CuttingEnglandStaffordshire CCSK075495Not available
320Gib TorrEnglandStaffordshire CCSK012643Not available
880Orchard FarmEnglandStaffordshire CCSK023691Not available
409Neath, Mellte and SychrydWalesBRIDGEND AND NEATH PORT TALBOTSN890093Not available
1858Lower House Stream SectionWalesGWENT VALLEYSSO104102Not available
308Llammarch DingleWalesMONMOUTHSHIRE AND NEWPORTSO218122Not available
311Marros SandsWalesSOUTH WEST WALESSN183073Not available
312Smarts QuarryWalesSOUTH WEST WALESSN434084Not available
310Tenby BeachWalesSOUTH WEST WALESSN135005Not available
309Barland CommonWalesSWANSEASS576897Not available
Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access. Search Again