Classification of 1:50 000 Series Geological Maps
The principal map versions used by geologists are the 'Solid and Drift' and the 'Solid with Drift' versions: for most purposes these will provide the best representation of the underfoot geology. BGS has now changed the terminology which describes the geology themes on its maps. 'Bedrock' replaces 'Solid' and 'Superficial Deposits' replaces 'Drift'. From 2003, new maps and new editions of older maps will use these descriptions. Until this replacement is complete, all the existing maps will be available in their current editions.
Bedrock (B); replacing Solid (S)
The geology shown on these maps is that of the bedrock only, in colour, together with boundary lines and geological symbols. Superficial drift deposits may be omitted or shown only as uncoloured areas indicated by pecked lines.
Superficial Deposits (Sup); replacing Drift (D)
The geology shown on these maps is that of the superficial deposits only, in colour. These usually unconsolidated deposits include glacial and postglacial deposits although artificial deposits, such as landscaped, worked and made ground are also shown. On these maps, any outcrops of bedrock are normally shown as a single unclassified colour.
Bedrock and Superficial Deposits (B&Sup); replacing Solid and Drift (S&D)
The geology shown on these maps is both the bedrock and the superficial deposits, merged to represent the geology at surface. Geological lines and symbols for the surface outcrops of both bedrock and superficial deposits are shown, but details of bedrock overlain by superficial deposits are normally abridged.
Solid with Drift (SwD)
These maps also show the solid and drift geology; but the drift deposits are uncoloured or only have coloured outlines. The (concealed) geological boundaries of the solid deposits occurring beneath the drift are shown in full.
Combined maps
In most circumstances, a single map will be just one version. However, for some areas where the land area is very small, a combined map is produced which shows two versions of the geology as separate map faces. These editions may be any of the map versions described above. Combined maps are indicated in the form '(B, Sup)', '(S,D)' or '(S,SwD)', or as appropriate.
Earlier classifications.
Prior to 1995 the classification of geological maps was somewhat different; thus for several areas where maps have been in print for many years the classification marked on the map face (or map case) may be different to the terms now used. For England & Wales the earlier maps marked as 'Solid' are now described as as 'Solid with Drift' and maps marked as 'Drift' are now described as 'Solid and Drift'. For Scotland and Northern Ireland the classifications remain more-or-less the same, with only subtle differences.
Other abbreviations
Provisional editions
Maps that may include substantial but not complete revision of the geology are indicated by the symbol [P]: they are recognised by the integral yellow cover which is part of the map.
Facsimilie editions
These are 1:50 000 scale reprints of earlier 1:63 360 scale maps, are indicated by the letter 'F'.
One inch to one mile scale maps (1:63 360)
These are still the current editions for several areas: the scale is indicated in the lists.