| Lanark Group | |
| Type: | Group |
| Age: | Silurian to early Devonian epoch |
| Prilithology: | sandstone |
| Otherlithology: | conglomerates, calc-alkaline volcanic extrusive rocks |
| Namedfor: | Lanark |
| Region: | Midland Valley |
| Country: | Scotland |
| Unitof: | Old Red Sandstone Supergroup |
| Subunits: | Greywacke Conglomerate Formation, Swanshaw Sandstone Formation, Pentland Hills Volcanic Formation |
| Underlies: | Strathclyde Group, Inverclyde Group |
| Overlies: | North Esk Group |
| Thickness: | up to around 2500m (8,200feet) |
| Extent: | southern part of the Scottish Midland Valley |
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]
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':
Each is named from a locality where it is to be found within the Pentland range or within the city of Edinburgh.[2]