Superficial deposits (formerly known as 'drift' by BGS) are the youngest geological deposits formed during the most recent period of geological time, the Quaternary, which extends back about 2.6 million years from the present. They rest on older deposits or rocks referred to as bedrock.
For DiGMapGB, superficial deposits that are of natural origin and 'in place', are held in the Superficial deposits theme. Other superficial strata may be held in the mass movement theme where they have been moved, or in the artificial ground theme where they are of man-made origin. Further information on superficial deposits is found in the BGS Rock Classification Scheme Volume 4.
Superficial deposits were originally recorded only onshore and around the coast where they were laid down by various natural processes such as action by ice, water and wind. More recently offshore deposits have been mapped and may be held in a separate sea-bed Sediments theme.
Most of these superficial deposits are unconsolidated sediments such as gravel, sand, silt and clay, and onshore they form relatively thin, often discontinuous patches or larger spreads. Almost all of these deposits were formerly classified on the basis of mode of origin with names such as, 'glacial deposits', 'river terrace deposits' or 'blown sand'; or on their composition such as 'peat'. Recently some of them have been given formal lithostratigraphic names such as 'Lowestoft Formation'. More information on some units is available in the BGS Lexicon of Named Rock Units.