Old Red Sandstone

Old Red Sandstone
Stratigraphic range: Late Silurian – earliest Carboniferous 419–358 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Folded Old Red Sandstone rock formation at St Ann's Head in Pembrokeshire, Wales
Type	Supergroup
Sub-units	See text
Thickness	More than 4 km (2.5 mi) (Shetland)
Lithology
Primary	Sandstone
Other	Conglomerate, shale, mudstone, siltstone, limestone
Location
Region	North Atlantic
Country	Canada, Greenland, Ireland, Norway, United Kingdom
Extent	700 km (430 mi)[1]

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.^[3] These areas were a part of the paleocontinent of Euramerica (Laurussia). In Britain it is a lithostratigraphic unit (a sequence of rock strata) to which stratigraphers accord supergroup status^[4] 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.