| New Red Sandstone Supergroup | |
|---|---|
| Stratigraphic range:Permian-Triassic ~300–200 Ma | |
 Cliff of New Red Sandstone inOddicombe, Devon | |
| Type | Supergroup |
| Sub-units | |
| Underlies | Penarth Group |
| Overlies | Unconformity with folded Devonian and Carboniferous rocks |
| Thickness | up to 2,000 m (6,600 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Arkose,conglomerate,breccio-conglomerate |
| Location | |
| Country | United Kingdom |
| Extent | Originally in Scotland, range extended to all red-bed sequences of Permian and Triassic age in southwest England, and parts of northwest and northeast England. |
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TheNew Red Sandstone, chiefly inBritishgeology, is composed of beds of redsandstone and associated rocks laid down throughout thePermian (300 million years ago) to the end of theTriassic (about 200 million years ago), that underlie theJurassic-Triassic agePenarth Group.[1] The name distinguishes it from theOld Red Sandstone which is largelyDevonian in age, and with which it was originally confused due to their similar composition.
Its upper layers consist ofmudstones, but most of the formation consists of reddish to yellowish sandstones, interbedded with rareevaporite minerals such ashalite andgypsum. These indicate deposition within a hot and arid palaeo-environment, such as a desert orsabkha.[2]
The New Red Sandstone was originally identified inScotland, at quarries inElgin. It covers large parts of theMoray Firth Basin. In this area it overlies theOld Red Sandstoneunconformably (missing the intervening rocks), and both sandstones were used extensively in architecture in the Highlands and Islands of Scotland. It also covers much of centralEngland, where it generally forms a low-lying plain except for theMid Severn Sandstone Plateau. Thick layers (up to 1,100 metres (3,600 ft) thick) are present in thefaultedCheshire Basin which also extends beneath northShropshire. There are numerousescarpments forming small prominent hills within this area. The sandstone also underlies parts ofLancashire andCumbria, and east of thePennines it extends throughNottinghamshire and centralYorkshire. Smaller outcrops occur in other parts of Britain such as the Red Cliffs ofDawlish and EastDevon.
In terms of itslithology, the New Red Sandstone comprises true sandstones,mudrocks and evaporitestrata.[1] The sandstone units are monomineralic, consisting only ofquartz grains (negligible amounts of other minerals may be present), and they are cemented together with the ferric iron oxidehaematite (Fe2O3). The presence of this particular iron oxide is evidence for aterrestrialenvironment of deposition such as adesert, and gives the rocks the red colour which they are named after. The common effect ofrusting produces exactly the same deposit, but as a result of a different process. The sandstone units generally lackfossils (as do most terrestrial rocks). The grains in the member have a high degree ofsphericity, are verywell sorted and typically have a small size range (0.5 to 2 millimetres (0.020 to 0.079 in)).
The NRS is a texturallymature rock. Certain units of the New Red Sandstone (e.g.Hopeman Sandstone Formation andHelsby Sandstone Formation) feature commonly as building stone due to their abundance and mechanical strength.
The New Red Sandstone has yielded many fossils, including the world-famousElgin Reptiles. These arelate Permian to Late Triassic in age, and include mammal-like reptiles and some of the earliest predecessors of dinosaurs.[2] An earliest Permian (Asselian) fauna is known from theKenilworth Sandstone Formation of the English Midlands, including primitivesynapsids andtemnospondyl amphibians.[3]
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Many ancient buildings of Devon Red Sandstone can be found inExeter the ancient capital ofDevon,[4] notably the castle, Roman / medieval city walls, several churches and many buildings of theCathedral Close. The local quarry was atHeavitree by which name the local sandstone – actually a type ofbreccia – is generally known.[5]
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