GCR block - Carboniferous - Permian Igneous (C-P-IG)

Carboniferous - Permian Igneous

Block Description

UK map showing distribution of GCR sites of GCR block C-P-IG
Distribution of GCR sites of GCR block Carboniferous - Permian Igneous

This GCR Block encompasses the British volcanic rocks and associated intrusions that were emplaced north of the Variscan Front (see VAR-STR-SW and VAR-STR-WM) during the Carboniferous and Permian periods (from about 354 to 251 million years ago (Ma)). At this time the geological basement of Great Britain was part of the supercontinent of Pangaea, which was drifting slowly northwards through tropical latitudes, sequentially developing semi-arid river flood-plains, shallow tropical seas with carbonate reefs, thickly vegetated coastal deltas with coal-forming swamps and finally, deserts (for details of stratigraphy see DIN-DV-CW; DIN-N-E-WL; DIN-SC; MAR-PER; NAM-E-WL; PER-TRI; WPH). Stretching and thinning of the Earth’s outer layers, well to the north of the nearest zone of continental collision, facilitated melting of the underlying mantle. Rifting provided weaknesses along which the resulting magmas could reach the surface or near-surface and volcanoes erupted across the wide range of geographical and climatic settings. Their products are dominantly basaltic but during Early Carboniferous time in central Scotland, the ascent of the magmas was interrupted locally, allowing a wide range of more-evolved compositions to form.

Outcrop pattern

The Carboniferous and Permian igneous rocks are widely scattered along the length of Great Britain, from the Bristol Channel in the south to the Orkney Islands in the north.By far the greatest concentration of outcrops is in and around the Midland Valley of Scotland, with significant but less extensive outcrops around the Solway Firth, along the England–Scotland border, and in Derbyshire. Small outcrops occur in the West Midlands of England, in the western Mendip Hills and in south-east Wales). In addition, a concealed widespread volcanic field underlies younger rocks in the East Midlands, a sill-complex crops out and extends beneath a large area of north-east England and dyke swarms extend across parts of the Highlands of Scotland.Igneous rocks to the south of the Variscan Front, that is, south of the Mendip Hills, are included in the Igneous Rocks of South-West England GCR Block. See IGN-SW-E.

Tectonic setting and evolution

Following the end of the Caledonian Orogeny, in Late Devonian time (c. 370 Ma), the area of continental crust that now makes up the British Isles was part of the supercontinent of Laurussia (informally known as the ‘Old Red Sandstone Continent’). This had formed during the orogeny by the amalgamation of several pre-existing continents. The crust of Scotland and the far north-east of England had lain on the margin of the continent of Laurentia, which included Greenland and most of North America, whereas England and Wales were part of the microcontinent of Avalonia. The junction between these two plates, now concealed beneath younger rocks, is called the ‘Iapetus Suture’ and trends approximately north-east from the Solway Firth to the coast of Northumberland, around Seahouses .

From Late Devonian times onwards, the southern continent of Gondwana was in collision with the southern margin of Laurussia, leading to the Variscan Orogeny, and creating the supercontinent of Pangaea. The main orogenic belt associated with this collision was located far to the south of Great Britain in the Iberia–Armorica–Massif Central region. However, the northern limit of strong Variscan deformation, commonly known as the ‘Variscan Front’, migrated northwards during the orogeny and the final limit extends across southern Britain, between the Thames and Severn estuaries. To the north of this orogenic front, back-arc extension controlled structure, sedimentation and igneous activity in the British Isles throughout Late Devonian and Carboniferous times.

Five main sedimentary depositional ‘provinces’, separated from each other by important palaeogeographical highs, have been recognized:

• The Scottish Province, consisting essentially of the Midland Valley of Scotland, bounded by the Caledonian Highlands to the north and the Southern Upland High to the south.

• The Pennine Province of central and northern England, bounded by the Southern Upland High to the north and the Wales–London–Brabant High to the south.

• The Irish Province in the west.

• The Southern Province, south of the Wales–London–Brabant High.

• The Culm Basin of Devon and Cornwall.

The Scottish, Pennine and Southern provinces comprise the tectonic settings for the igneous rocks encompassed by this GCR block.The Culm Basin, south of the Variscan Front, is the setting for those covered by the Igneous Rocks of South-west England GCR Block.

The earliest magmatism occurred during the Tournaisian Epoch (c. 354–342 Ma) and is represented mainly by volcanic rocks around the Solway Firth and the England–Scotland border, although the volcanic rocks in the Mendips span from late Tournaisian to early Visean times.The most voluminous and widespread igneous activity occurred during the Visean Epoch (342–327 Ma), resulting in vast lava fields in the Midland Valley of Scotland, lavas and sills in Derbyshire, and minor volcanic sequences around the England–Scotland border.During the Namurian and Westphalian ages, volcanism became more localized in the Midland Valley of Scotland and in the East and West Midlands of England, with an increasing tendency for the magma to be emplaced as sills, and all activity died out in late Westphalian times.Following a major change in tectonic conditions, a short-lived episode of regional dyke and sill intrusion occurred in north-east England and across central Scotland in early to mid-Stephanian times, and late Stephanian and Early Permian times saw the emplacement of widespread but localized lavas, sills and dykes that now extend from the eastern Irish Sea to the north-west Highlands.Evidence of Late Permian igneous activity in Britain is restricted to dykes in the Orkney Islands.

The Carboniferous and Permian magmatism in Great Britain was of typical intraplate type, largely controlled throughout the Carboniferous Period by back-arc extension to the north of the Variscan orogenic front and, during Permian times, by major intracontinental rifting that heralded the eventual break-up of the supercontinent of Pangaea.In Scotland, the magmas were dominantly of transitional to mildly alkaline character, becoming generally more highly alkaline and silica-undersaturated with time. Some very primitive and compositionally extreme, alkali-rich lamprophyric and foiditic (feldspathoid-bearing) rocks characterized Early Permian lavas and intrusions of the Midland Valley as well as many of the dykes of the Scottish Highlands and Islands.However, many of the Tournaisian lavas around the Solway Firth and along the Scotland–England border are tholeiitic and the Visean lavas of Derbyshire are entirely tholeiitic.Some tholeiitic lavas also occur in the Westphalian rocks of the East Midlands, but other igneous rocks of central and southern England are alkaline.The principal exception to this overall pattern is the short-lived Stephanian event, which resulted in widespread intrusion of tholeiitic magmas as dykes and sills across much of central Scotland and north-eastern England.

GCR site selection

The sites illustrate the variety and distribution of the rocks and highlight critical localities of historical and continuing national and international importance, and can be ascribed to various suites in their full geological context, and the magmatism related to the overall tectonic history of north-west Europe.

The six GCR Networks for this GCR Block are based upon petrological affinity, age and geographical distribution. Some sites have features that fall within more than one network, but can be assigned to a network on the basis of their dominant features.

1. Dinantian volcanic rocks of the Midland Valley of Scotland and adjacent areas.

2. Dinantian rocks of Northumberland, Solway and Tweed basins

3. Silurian and Early Permian volcanic rocks of Scotland

4. Alkaline basic sills and dykes of Scotland

5. Tholeitic sills and dykes of Scotland and northern England

6. Carboniferous and Permian igneous rocks of central England and the Welsh borderland.

Volume Introduction

Carboniferous - Permian Igneous

Site List

Your selection found 50 GCR sites. Sites are sorted alphabetically by country, local authority and then by site name -
CodeNameCountryLocal AuthorityGrid RefGCR Site Account
1392Greenfoot QuarryEnglandDurham CCNY982392Not available
1444Whin Sill Exposures in Upper TeesdaleEnglandDurham CCNY880285Not available
2761Little Mell Fell QuarryEnglandEast CumbriaNY429239Not available
1830Middle HopeEnglandNorth and North East Somerset, South GloucestershireST322659Not available
2770Spring CoveEnglandNorth and North East Somerset, South GloucestershireST310625Not available
1449Budle Point - Harkness RockEnglandNorthumberlandNU163361Not available
2768Cottonshope Head QuarryEnglandNorthumberlandNT803058Not available
1447Cullernose Point to Castle PointEnglandNorthumberlandNU260187Not available
1448Holy IslandEnglandNorthumberlandNU124416Not available
1446Longhoughton QuarryEnglandNorthumberlandNU231153Not available
2767Steel Rigg - Sewingshields CragsEnglandNorthumberlandNY751677Not available
1445WydonEnglandNorthumberlandNY695629Not available
2769Clee Hill QuarriesEnglandShropshire CCSO595760Not available
2765Litton Mill Railway CuttingEnglandSouth and West DerbyshireSK158729Not available
2764Tideswell DaleEnglandSouth and West DerbyshireSK154740Not available
2762Water Swallows QuarryEnglandSouth and West DerbyshireSK084750Not available
2763Bothel Crags QuarryEnglandWest CumbriaNY186371Not available
2766Gill BeckEnglandWest CumbriaNY149342Not available
188Arthur`s Seat VolcanoScotlandCity of EdinburghNT285729Not available
1382South Queensferry to Hound PointScotlandCity of EdinburghNT138785Not available
1154Burntisland to Kinghorn CoastScotlandClackmannanshire and FifeNT252864Not available
1391East Fife CoastScotlandClackmannanshire and FifeNO408028Not available
1383Gloom Hill, DollarScotlandClackmannanshire and FifeNS964990Not available
1381North Queensferry (A90) Road CuttingsScotlandClackmannanshire and FifeNT126807Not available
1389Carron WaterScotlandDumfries and GallowayNS887024Not available
1149Langholm - Newcastleton HillsScotlandDumfries and GallowayNY423902Not available
1151River Esk, GlencartholmScotlandDumfries and GallowayNY376799Not available
2075Dumbarton RockScotlandEast and West Dumbartonshire, Helensburgh and LomondNS400745Not available
1384Mollinsburn Cuttings (A80)ScotlandEast and West Dumbartonshire, Helensburgh and LomondNS715718Not available
2076Ardrossan to Saltcoats CoastScotlandEast Ayrshire and North Ayrshire MainlandNS236416Not available
1379Benbeoch, DalmellingtonScotlandEast Ayrshire and North Ayrshire MainlandNS492085Not available
1377Howford BridgeScotlandEast Ayrshire and North Ayrshire MainlandNS515254Not available
1378LugarScotlandEast Ayrshire and North Ayrshire MainlandNS600215Not available
1152Kershope BridgeScotlandEast CumbriaNY495832Not available
1155Garleton HillsScotlandEast Lothian and MidlothianNT510765Not available
1375North Berwick CoastScotlandEast Lothian and MidlothianNT496858Not available
1376Traprain LawScotlandEast Lothian and MidlothianNT581746Not available
1153Dunrod HillScotlandInverclyde, East Renfrewshire and RenfrewshireNS240730Not available
2937Dubh Loch, ColonsayScotlandLochaber, Skye and Lochalsh and Argyll and the IslandsNR371947Not available
1148Machrihanish Coast and South KintyreScotlandLochaber, Skye and Lochalsh and Argyll and the IslandsNR625200Not available
1147Campsie FellsScotlandPerth and Kinross and StirlingNS535825Not available
1388Corsiehill Quarry, PerthScotlandPerth and Kinross and StirlingNO135235Not available
1390Lomond HillsScotlandPerth and Kinross and StirlingNO178043Not available
1387WallstaleScotlandPerth and Kinross and StirlingNS773912Not available
1386Heads of AyrScotlandSouth AyrshireNS279183Not available
1385Craighead Hill Quarry, AbingtonScotlandSouth LanarkshireNS919237Not available
1146Touch, Fintry and Gargunnock HillsScotlandSouth LanarkshireNS650367Not available
1380Hareheugh CraigsScotlandThe Scottish BordersNT689399Not available
1150Lintmill Railway CuttingScotlandThe Scottish BordersNT727463Not available
2183Golden Hill QuarryWalesMONMOUTHSHIRE AND NEWPORTST431971Not available
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