The Lanark Group is a late Silurian to early Devonian

lithostratigraphic Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneou ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

(a sequence of rock strata) in southern

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

. The name is derived from the town of

Lanark Lanark (; gd, Lannraig ; sco, Lanrik) is a town in South Lanarkshire, Scotland, located 20 kilometres to the south-east of Hamilton. The town lies on the River Clyde, at its confluence with Mouse Water. In 2016, the town had a population of 9 ...

. It consists of

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s 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 The Old Red Sandstone 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 northeastern seaboard of North America. It also exte ...

Supergroup.

Pentland Hills Volcanic Formation

The northern and eastern parts of the

Pentland Hills The Pentland Hills are a range of hills southwest of Edinburgh, Scotland. The range is around in length, and runs southwest from Edinburgh towards Biggar and the upper Clydesdale. Etymology The name is first recorded for the farm of Pentla ...

, south of

Edinburgh Edinburgh ( ; gd, Dùn Èideann ) is the capital city of Scotland and one of its 32 council areas. Historically part of the county of Midlothian (interchangeably Edinburghshire before 1921), it is located in Lothian on the southern shore of t ...

, 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.

References

{{Reflist Devonian System of Europe Silurian System of Europe Geology of Scotland Geological groups of the United Kingdom Geologic formations of the United Kingdom