Lanark Group
Stratigraphic range: Silurian to early Devonian epoch
Type	Group
Unit of	Old Red Sandstone Supergroup
Sub-units	Greywacke Conglomerate Formation, Swanshaw Sandstone Formation, Pentland Hills Volcanic Formation
Underlies	Strathclyde Group, Inverclyde Group
Overlies	North Esk Group
Thickness	up to around 2,500 m (8,200 ft)
Lithology
Primary	sandstone
Other	conglomerates, calc-alkaline volcanic extrusive rocks
Location
Region	Midland Valley
Country	Scotland
Extent	southern part of the Scottish Midland Valley
Type section
Named for	Lanark

The Lanark Group is a late Silurian to early Devonian lithostratigraphic group (a sequence of rock strata) in southern Scotland. The name is derived from the town of Lanark. It consists of sandstones and conglomerates within the Greywacke Conglomerate and Swanshaw Sandstone formations together with a wide range of igneous lithologies within the overlying Pentland Hills Volcanic Formation. The group is itself a division of the Old Red Sandstone Supergroup.^[1]

Pentland Hills Volcanic Formation

The northern and eastern parts of the Pentland Hills, south of Edinburgh, are formed by a variety of rocks brought together within this formation. In stratigraphic order, i.e. youngest at top, they comprise the following 'volcanic members':

• Blackford Hill Volc. Mem.
• Braid Hills Volc. Mem.
• Fairmilehead Volc. Mem.
• Carnethy Hill Volc. Mem.
• Woodhouselee Volc. Mem.
• Caerketton Volc. Mem.
• Allermuir Volc. Mem.
• Capelaw Volc. Mem.
• Bell's Hill Volc. Mem.
• Bonaly Volc. Mem.
• Warklaw Hill Volc. Mem.
• Torduff Hill Volc. Mem.

Each is named from a locality where it is to be found within the Pentland range or within the city of Edinburgh.^[2]

References