Editing Old Red Sandstone

{{short description|Assemblage of rocks in the North Atlantic region}}
{{Globalize|1=article|2=United Kingdom|date=August 2024}}
{{Infobox rockunit
| name = Old Red Sandstone
| image = Folded_Old_Red_Sandstone_at_St_Annes_Head_-_geograph.org.uk_-_629204.jpg
| caption = Folded Old Red Sandstone rock formation at St Ann's Head in [[Pembrokeshire]], Wales
| type = [[Supergroup (geology)|Supergroup]]
| prilithology = [[Sandstone]]
| otherlithology = [[conglomerate (geology)|Conglomerate]], [[shale]], [[mudstone]], [[siltstone]], [[limestone]]
| namedfor = 
| namedby = 
| region = [[North Atlantic]]
| country = Canada, Greenland, Ireland, Norway, United Kingdom
| coordinates = 
| unitof = 
| subunits = ''See text''
| thickness = More than {{convert|4|km|mi|abbr=on}} (Shetland)
| extent = {{convert|700|km|mi|abbr=on}}<ref name="Barclay" />
| area = 
| age = [[Late Silurian]]{{snd}}earliest [[Carboniferous]] {{fossilrange|419|358}}
| period = Devonian
}}
[[File:Siccar point SE cliff.jpg|thumb|[[James Hutton|Hutton's]] [[Hutton's Unconformity|angular unconformity]] at [[Siccar Point]] where 370-million-year-old [[Devonian]] Old Red Sandstone overlies 435-million-year-old [[Silurian]] [[greywacke]].<ref name="FieldExcursion" />]]

'''Old Red Sandstone''', abbreviated '''ORS''', is an assemblage of rocks in the North Atlantic region largely of [[Devonian]] age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the eastern seaboard of [[North America]]. It also extends northwards into [[Greenland]] and [[Svalbard]].<ref>Friend, P.F. and Williams, B.P.J. (eds) 2000 ''New Perspectives on the Old Red Sandstone''. Geological Society, London, Special publications '''180''' p1,35</ref> These areas were a part of the [[paleocontinent]] of [[Euramerica]] (Laurussia). In Britain it is a [[lithostratigraphy|lithostratigraphic]] unit (a sequence of [[rock strata]]) to which [[Stratigraphy|stratigraphers]] accord [[Geological unit#Lithostratigraphic units|supergroup]] status<ref>http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=ORS entry in BGS on-line rock lexicon</ref> and which is of considerable importance to early [[paleontology]]. The presence of ''Old'' in the name is to distinguish the sequence from the younger [[New Red Sandstone]] which also occurs widely throughout Britain.

== Sedimentology ==
[[File:OldRedSandstoneBeddingPlane.jpg|thumb|[[Bed (geology)|Bedding]] plane of Old Red Sandstone with [[quartz]] and [[chert]] pebbles, central England; scale bar is 10 mm]]

The Old Red Sandstone describes a group of [[sedimentary rock]]s deposited in a variety of environments in the late [[Silurian]], through  the [[Devonian]] and into the earliest part of the [[Carboniferous]]. The body of [[Rock (geology)|rock]], or [[facies]], is dominated by [[Terrigenous deposit|terrigenous deposits]] and [[conglomerate (geology)|conglomerates]] at its base, and progresses to a combination of [[dune]]s, and sediments that may have been laid down in [[lake]]s, [[river]], estuaries, and possibly other coastal environments. The Old Red Sandstone was long thought to have been deposited mostly in freshwater, but more recent studies have discovered marine fossils (such as [[Brachiopod|brachiopods]])<ref name="Goujet & Emig 1985">{{cite journal |last1=Goujet |first1=D |last2=Emig |first2=C. C. |title=Des Lingula fossiles, indicateurs de modifications de l'environnement dans un gisement du Dévonien inférieur du Spitsberg |journal=Des Lingula fossiles, indicateurs de modifications de l'environnement dans un gisement du Dévonien inférieur du Spitsberg |date=1985 |volume=301 |issue=13 |pages=945–948 |url=http://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=8419776 |issn=0764-4450}}</ref> in some locations. Its vertebrate fauna also occurs in typically marine environments,<ref name="Janvier 2007">{{cite journal |last1=Janvier |first1=Philippe |title=Living Primitive Fishes and Fishes From Deep Time |journal=Fish Physiology |date=1 January 2007 |volume=26 |pages=1–51 |doi=10.1016/s1546-5098(07)26001-7 |url=https://doi.org/10.1016/S1546-5098(07)26001-7 |publisher=Academic Press|isbn=978-0-12-373671-0 |url-access=subscription }}</ref> and an [[Isotope geochemistry|isotopic]] study also found significant marine influence indicating a [[Brackish water|brackish]] environment in mineralised tissues of its vertebrates,<ref name="Goedert et al. 2018">{{cite journal |last1=Goedert |first1=Jean |last2=Lécuyer |first2=Christophe |last3=Amiot |first3=Romain |last4=Arnaud-Godet |first4=Florent |last5=Wang |first5=Xu |last6=Cui |first6=Linlin |last7=Cuny |first7=Gilles |last8=Douay |first8=Guillaume |last9=Fourel |first9=François |last10=Panczer |first10=Gérard |last11=Simon |first11=Laurent |last12=Steyer |first12=J.-Sébastien |last13=Zhu |first13=Min |title=Euryhaline ecology of early tetrapods revealed by stable isotopes |journal=Nature |date=June 2018 |volume=558 |issue=7708 |pages=68–72 |doi=10.1038/s41586-018-0159-2 |pmid=29849142 |bibcode=2018Natur.558...68G |url=https://doi.org/10.1038/s41586-018-0159-2 |language=en |issn=1476-4687|url-access=subscription }}</ref> even in taxa that had long been thought to have been freshwater inhabitants.<ref name="George & Blieck 2011">{{cite journal |last1=George |first1=David |last2=Blieck |first2=Alain |title=Rise of the Earliest Tetrapods: An Early Devonian Origin from Marine Environment |journal=PLOS ONE |date=14 July 2011 |volume=6 |issue=7 |pages=e22136 |doi=10.1371/journal.pone.0022136|doi-access=free |pmid=21779385 |bibcode=2011PLoSO...622136G }}</ref><ref name="Laurin 2024">{{cite journal |last1=Laurin |first1=Michel |title=Habitat of early stegocephalians (Chordata, Vertebrata, Sarcopterygii): a little saltier than most paleontologists like? |journal=Fossil Record |date=30 December 2024 |volume=27 |issue=3 |pages=299–332 |doi=10.3897/fr.27.123291 |doi-access=free |language=en |issn=2193-0074}}</ref> Thus, at least some strata appear to have been deposited on the coast, probably in marginal marine environments.

The familiar red colour of these rocks arises from the presence of [[iron oxide]], but not all the Old Red Sandstone is red or sandstone{{snd}}the sequence also includes conglomerates, [[mudstones]], [[siltstones]] and thin [[limestones]] and colours can range from grey and green through to red and purple.  These deposits are closely associated with the erosion of the Caledonian Mountain chain which was thrown up by the collision of the former continents of [[Avalonia]], [[Baltica]] and [[Laurentia]] to form the [[Old Red Sandstone Continent]]- an event known as the [[Caledonian Orogeny]].

Many fossils are found within the rocks, including early fishes, arthropods and plants. As is typical with terrestrial [[red beds]], the vast majority of the rock is not fossil-bearing; however there are isolated, localized beds within the rock that do contain fossils. Rocks of this age were also laid down in [[South West England]] (hence the name 'Devonian'; from [[Devon]]) though these are of true marine origin and are not included within the Old Red Sandstone.<ref name=Barclay>{{cite book | last = Barclay | first = W.J. | title = The Old Red Sandstone of Great Britain | publisher = Joint Nature Conservation Committee (JNCC) | location = City | year = 2005 | isbn = 978-1-86107-543-7 |url=http://www.jncc.gov.uk/page-2936}}</ref>

== Stratigraphy ==
Since the Old Red Sandstone consists predominantly of rocks of [[Ecoregion#Terrestrial|terrestrial]] origin, it does not generally contain marine [[fossil]]s which would otherwise prove useful in correlating one occurrence of the rock with another, both between and within individual [[sedimentary basin]]s. Accordingly, local [[stage (stratigraphy)|stage]] names were devised and these remain in use to some extent today though there is an increasing use of international stage names. Thus in the Anglo-Welsh Basin, there are frequent references to the '''[[Devonian#History|Downtonian]]''', '''[[Devonian#History|Dittonian]]''', '''[[Devonian#History|Breconian]]''' and '''[[Devonian#History|Farlovian]]''' stages in the literature. The existence of a number of distinct sedimentary basins throughout Britain has been established.<ref name="Barclay"/>

=== Orcadian Basin ===
The [[Orcadian Basin]] extends over a wide area of North East Scotland and the neighbouring seas. It encompasses the [[Moray Firth]] and adjoining land areas, Caithness, Orkney and parts of [[Shetland]]. South of the Moray Firth, two distinct sub-basins are recognized at [[Turriff]] and at [[Rhynie, Aberdeenshire|Rhynie]]. The sequence is more than {{convert|4|km|ft}} thick in parts of Shetland. The main basin is considered to be an intramontane basin resulting from crustal rifting associated with post-Caledonian [[Extensional tectonics|extension]], possibly accompanied by strike-slip faulting along the [[Great Glen Fault]] system.<ref name="Michel">{{cite journal|last=Seranne|first=M.|title=Devonian extensional tectonics versus Carboniferous inversion in the northern Orcadian basin|journal=Journal of the Geological Society|volume=149|issue=1|pages=27–37|url=http://jgs.geoscienceworld.org/cgi/content/abstract/149/1/27|access-date=2010-02-25|doi=10.1144/gsjgs.149.1.0027|year=1992|bibcode=1992JGSoc.149...27S |citeseerx=10.1.1.464.5569|s2cid=128640763 }}</ref>

=== Argyll ===
There are a scatter of exposures of the Old Red Sandstone around [[Oban]] and the [[Kerrera|Isle of Kerrera]] on the [[West Highland]] coast, this unit is sometimes referred to as the Kerrera Sandstone Formation. The unit is up to 128m thick in its type area and consists of green and red sandstones and conglomerates, typically containing large ({{convert|10|-|30|cm|in|0|abbr=on|disp=or}} across) elliptical well rounded clasts, accompanied by siltstones, mudstones and limestones.<ref>{{cite web|url=https://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=KESA|title=Kerrera Sandstone Formation|website=BGS Lexicon of Named Rock Units|publisher=British Geological Survey|access-date=31 October 2018}}</ref> On Kerrera a conglomerate of [[andesite]] boulders rests unconformably on [[Dalradian]] black, [[Pyrite|pyritic]] [[slate]]s ([[Easdale]] Slate) of the [[Argyll_Group#Easdale_Subgroup|Easdale Subgroup]]. At Oban there is merely an erosional contact incorporating debris of the slate in a basal conglomerate. The ORS deposits around Oban are considered latest Silurian ([[Pridoli Epoch|Pridoli]]) to earliest Devonian in age. They are interpreted as [[alluvial fan]]s which filled a depositional basin from the east and northeast.<ref>British Geological Survey 1:50,000 scale geological map sheet 45W (Scotland) ''Connel'' 1991</ref>  Small [[inliers and outliers (geology)|outliers]] occur near [[Taynuilt]] and either side of [[Loch Avich]].<ref>British Geological Survey 1:50,000 scale geological map sheet 37W (Scotland) ''Furnace'' 2008</ref> The deposits are especially obvious on Kerrera where they form the bedrock across half of the island.<ref>British Geological Survey 1:50,000 scale geological map sheet 44E (Scotland) ''Lismore'' 1992</ref> These are conformably overlain by [[peperite]] and the [[basalt]]ic and andesitic [[Lorne plateau lavas]]. The ORS on Kerrera and isolated localities around Oban are known for their fossils, particularly fish.<ref>{{Cite journal|last1=Trewin|first1=N. H.|last2=Gurr|first2=P. R.|last3=Jones|first3=R. B.|last4=Gavin|first4=P.|date=November 2012|title=The biota, depositional environment and age of the Old Red Sandstone of the island of Kerrera, Scotland|url=http://sjg.lyellcollection.org/lookup/doi/10.1144/sjg2012-452|journal=Scottish Journal of Geology|language=en|volume=48|issue=2|pages=77–90|doi=10.1144/sjg2012-452|bibcode=2012ScJG...48...77T |s2cid=140575299 |issn=0036-9276|url-access=subscription}}</ref>[[File:Gardenstown Old Red Sandstone - geograph.org.uk - 178600.jpg|thumb|Old Red Sandstone at [[Gardenstown]], Aberdeenshire]]

=== Midland Valley of Scotland ===
The [[Central Lowlands|Midland Valley]] [[graben]] defined by the [[Highland Boundary Fault]] in the north and the [[Southern Uplands Fault]] in the south harbours not only a considerable amount of Old Red Sandstone sedimentary rocks but also igneous rocks of this age associated with extensive [[volcanism]]. There is a continuous outcrop along the Highland Boundary Fault from [[Stonehaven]] on the [[North Sea]] coast to [[Helensburgh]] and beyond to [[Isle of Arran|Arran]].  A more disconnected series of outcrops occur along the line of the Southern Uplands Fault from [[Edinburgh]] to [[Girvan]]. Old Red Sandstone often occurs in conjunction with conglomerate formations, one such noteworthy [[cliff]]side exposure being the [[Fowlsheugh Nature Reserve]], [[Kincardineshire]].

=== Scottish borders ===
A series of outcrops occur from [[East Lothian]] southwards through [[Berwickshire]]. Hutton's famous unconformity at Siccar Point occurs within this basin - see [[#History of study|History of study]] below.

=== Anglo-Welsh Basin ===
This relatively large basin extends across much of South Wales from southern [[Pembrokeshire]] in the west through [[Carmarthenshire]] into [[Powys]] and [[Monmouthshire]] and through the southern [[Welsh Marches]], into [[Herefordshire]], [[Worcestershire]] and [[Gloucestershire]]. Outliers in [[Somerset]] and north [[Devon]] complete its extent.

With the exception of south Pembrokeshire, all parts of the basin are represented by a range of lithologies assigned to the Lower Devonian and to the Upper Devonian, the contact between the two being unconformable and representing the complete omission of any Middle Devonian sequence. 

==== South Powys/Brecon Beacons ====
The lowermost formations are of upper Silurian age, these being the Downton Castle Sandstone Formation and the overlying Moor Cliffs Formation (formerly the Raglan Mudstone Formation). The top of this formation is marked by a well-developed [[calcrete]], the [[Bishop's Frome Limestone|Chapel Point Limestone]].<ref>{{Cite web|url=https://webapps.bgs.ac.uk/lexicon/lexicon.cfm?pub=BFLS|title=BGS Lexicon of Named Rock Units - Result Details|website=webapps.bgs.ac.uk}}</ref> The lowermost Devonian formation is the Freshwater West Formation (formerly the St Maughans Formation), itself overlain by the Senni Formation (formerly the Senni Beds) which is in turn overlain by the Brownstones Formation. In the east, a further calcrete, the Ffynnon Limestone (sometimes pluralised) is developed at the interface between the Freshwater West and Senni formations. The Senni Formation is not recorded further east.

The Upper Devonian sequence is rather thinner and comprises a series of formations which are more laterally restricted. In the [[Brecon Beacons]], the Plateau Beds Formation is unconformably overlain by the Grey Grits Formation though further east these divisions are replaced by the Quartz Conglomerate Group which is itself subdivided into a variety of different formations.[[File:Yensaby castle 1.JPG|thumb|180px|Lower Old Red Sandstone at [[Yesnaby]], Orkney, cross-bedded [[Aeolian processes|aeolian]] sandstone]]

==== Pembrokeshire ====
The sequence in Pembrokeshire differs from that of the main part of the basin to the east, and falls into two parts.<ref>Barclay, W.&nbsp;J. (2005) in ''The Old Red Sandstone of Great Britain'' (W.&nbsp;J. Barclay, M.&nbsp;A.&nbsp;E. Browne, A.&nbsp;A. McMillan, E.&nbsp;A. Pickett, P. Stone and P.&nbsp;R. Wilby) Geological Conservation Review series, No 31 JNCC, Peterborough pp.&nbsp;212&ndash;213</ref>

In North Pembrokeshire to the north of the [[Ritec Fault]], both the middle and upper ORS are missing with only the lower ORS present; this is divided into an earlier [[Milford Haven Group]] comprising in ascending order, the Red Cliff, Sandy Haven and Gelliswick Bay formations and a later [[Cosheston Group]] with, again in ascending order, its constituent Llanstadwell, Burton Cliff, Mill Bay, Lawrenny Cliff and New Shipping formations. These respectively equate with the Temeside, Raglan Mudstone and St Maughans formations of the central and eastern part of the basin. 
*''[middle and upper ORS missing]''
* [[Cosheston Group]]
** [[New Shipping Formation]]
** [[Lawrenny Cliff Formation]]
** [[Mill Bay Formation]]
** [[Burton Cliff Formation]]
** [[Llanstadwell Formation]]
* [[Milford Haven Group]]
** [[Gelliswick Bay Formation]]
** [[Sandy Haven Formation]] (including Townsend Tuff Beds)
** [[Albion Sands Formation]] / [[Lindsway Bay Formation]]
** [[Red Cliff Formation]]

In south Pembrokeshire to the south of the Ritec Fault, the lower ORS is represented by, in ascending order, the Freshwater East, Moors Cliff and Freshwater West formations. These are [[unconformity|unconformably]] overlain by the Ridgeway Conglomerate Formation. The middle ORS is missing whilst the Upper ORS is represented by the Gupton and West Angle formations.  
* [[Skrinkle Sandstone Group]]
** [[West Angle Formation]]
** [[Gupton Formation]]
* ''[Part of middle ORS missing]''
* [[Ridgeway Conglomerate Formation]]
* ''[Part of middle ORS missing]''
* Milford Haven Group
** [[Freshwater West Formation]] (including Rat Island Mudstone Member and Conigar Pit Sandstone Member)
** [[Moor Cliffs Formation]] (including Chapel Point Limestone Member and Townsend Tuff Bed)
** [[Freshwater East Formation]]

The Freshwater East Formation, and corresponding Red Cliff Formation of north Pembrokeshire, are both late Silurian in age.<ref>Howells, M.&nbsp;F. 2007 ''British Regional Geology: Wales'' (Keyworth, Nottingham. British Geological Survey) pp.&nbsp;100&ndash;101</ref>

=== Anglesey ===
A small and separate basin exists here where both [[alluvial]] and [[lake|lacustrine]] deposits are recorded. Both the middle and upper ORS are missing but the lower ORS is represented, in ascending order, by the Bodafon, Traeth Bach, Porth y Mor and Traeth Lligwy formations. Calcretes are also recorded representing carbonate-rich soils developed between periods of sediment deposition. The present day outcrop occupies a narrow zone from [[Dulas Bay]] on Anglesey's northeast coast, southwards to the town of [[Llangefni]].<ref name="Barclay"/><ref>British Geological Survey 1:50K special map sheet ''Anglesey''</ref>

== History of study ==
In 1787 [[James Hutton]] noted what is now known as [[Hutton's Unconformity]] at Inchbonny, [[Jedburgh]], and in early 1788 he set off with [[John Playfair]] to the [[Berwickshire]] coast and found more examples of this sequence in the valleys of the Tower and Pease Burns near [[Cockburnspath]].<ref name=monty>{{cite web |url=http://nagt.org/files/nagt/jge/abstracts/Montgomery_v51n5.pdf |title=Siccar Point and Teaching the History of Geology |access-date=2008-03-26 |author=Keith Montgomery |year=2003 |publisher=University of Wisconsin }}</ref> They then took a boat trip from Dunglass Burn east along the coast with the geologist [[Sir James Hall, 4th Baronet|Sir James Hall]] of [[Dunglass]] and at [[Siccar Point]] found what Hutton called "a beautiful picture of this junction washed bare by the sea",<ref>{{Cite web |url=http://www.james-hutton.org/One/Geology/05.htm |title=Hutton's Journeys to Prove his Theory |access-date=2018-12-14 |archive-url=https://web.archive.org/web/20110726201217/http://www.james-hutton.org/One/Geology/05.htm |archive-date=2011-07-26 |url-status=dead }}</ref> where 345-million-year-old Old Red Sandstone overlies 425-million-year-old [[Silurian]] [[greywacke]].<ref name=FieldExcursion>{{cite web |url=http://www.geos.ed.ac.uk/undergraduate/field/siccarpoint/ |title=Siccar Point |author=Cliff Ford |date=2 September 2003 |work=Field Excursion Preview |publisher=[[University of Edinburgh]] School of GeoSciences |access-date=2008-10-20}}</ref><ref name=Rance>{{cite web |url=http://geowords.com/histbookpdf/a22.pdf |title=Hutton's unconformities |author=Rance, Hugh |year=1999 |work=Historical Geology: The Present is the Key to the Past |publisher=QCC Press |access-date=2008-10-20 |archive-url=https://web.archive.org/web/20081203173042/http://www.geowords.com/histbookpdf/a22.pdf |archive-date=2008-12-03 |url-status=dead }}</ref>

In the early 19th century, the paleontology of the formation was studied intensively by [[Hugh Miller]], [[Henry De la Beche|Henry Thomas De la Beche]], [[Roderick Murchison]], and [[Adam Sedgwick]]—Sedgwick's interpretation was the one that placed it in the [[Devonian]]: he coined the name of that period. The term 'Old Red Sandstone' was originally used in 1821 by Scottish [[naturalist]] and [[mineralogist]] [[Robert Jameson]] to refer to the red rocks which underlay the 'Mountain Limestone' i.e. the Carboniferous Limestone. They were thought at that time to be the British version of Germany's [[Rotliegendes]], which is in fact of [[Permian]] age.<ref name="Barclay"/>  Many of the [[science]] of [[stratigraphy]]'s early debates were about the Old Red Sandstone.

In older [[geological]] works{{by who|date=February 2025}} predating theories of [[plate tectonics]], the United States' [[Catskill Delta]] formation is sometimes{{when|date=February 2025}} referred to{{by who|date=February 2025}} as part of the Old Red Sandstone.{{citation needed|date=February 2025}} In the modern day it is recognized that the two are not stratigraphically continuous but are very similar due to being formed at approximately the same time by the same processes.

== Use as a building stone ==
[[File:Siccar Point, St. Helen's chapel.jpg|thumb|right|St. Helen's Chapel at [[Siccar Point]] has walls faced in Old Red Sandstone, with [[greywacke]] used on the inner face and surrounding [[Dry stone|drystane dykes]]]]
The Old Red Sandstone has been widely used as a building stone across those regions where it outcrops. Notable examples of its use can be found in the area surrounding [[Stirling, Scotland|Stirling]], [[Stonehaven]], [[Perth, Scotland|Perth]] and [[Tayside]]. The inhabitants of [[Caithness]] at the northeastern tip of Scotland also used the stone to a considerable extent.  Old Red Sandstone has also frequently been used in buildings in Herefordshire, Monmouthshire and the former [[Brecknockshire]] (now south Powys) of south Wales.

=== Notable buildings ===
[[File:St Magnus Cathedral Kirkwall.jpg|thumb|[[St Magnus Cathedral]] in [[Kirkwall]], Orkney, constructed of locally quarried sandstone]]

==== Canada ====
* [[New York Life Insurance Building, Montreal]]

==== England ====
* [[Goodrich Castle]], [[Herefordshire]]<ref name="museumwales.ac.uk"/>
* [[Ross-on-Wye]] market hall, Herefordshire
* [[Shrewsbury Castle]], [[Shropshire]]
* [[Hereford Cathedral]], Herefordshire
* [[Taunton Minster| St. Mary Magdalene]] church, Taunton, Somerset

==== Scotland ====
* [[Arbroath Abbey]], [[Angus, Scotland|Angus]]
* [[Muchalls Castle]], [[Aberdeenshire]] 
* [[St Magnus Cathedral]], [[Orkney]]<ref name="BBC">{{cite web|url=https://www.bbc.co.uk/history/british/architecture_cathedral_01.shtml|title=The Cathedrals of Britain|last=BBC|access-date=4 March 2010}}</ref>
* [[Stonehaven Tolbooth]], Aberdeenshire 

==== Wales ====
* [[Raglan Castle]], [[Monmouthshire]]<ref name="museumwales.ac.uk"/>
* [[Tintern Abbey]], Monmouthshire<ref name="museumwales.ac.uk">http://www.museumwales.ac.uk/media/4/9/5/2/Newsletter_5.pdf{{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
* [[Brecon Cathedral]], [[Powys]]

== See also ==
{{Portal|Geology|Ireland|Norway|United Kingdom}}
* [[New Red Sandstone]]
* [[Geology of Great Britain]]

{{clearboth}}

== References ==
{{reflist}}

== External links ==
{{commons category|Old Red Sandstone}}
* [http://www.gly.uga.edu/railsback/BS-CC.html Cawdor Castle{{snd}}built from Old Red Sandstone]

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