Digital Geological Map Data of Great Britain - 25k (DiGMapGB-25) Linear version 2

Linear features (shown as polylines) represent six classes of geological structural features e.g. faults, folds or landforms e.g. buried channels, glacial drainage channels at the ground or bedrock surface (beneath superficial deposits). Limited coverage within Great Britain, data exists for 167 10x10km tiles. Most primary geological mapping was carried out at 1:10 000 scale but in some areas of Wales and Scotland mapping at 1:25 000 was adopted as the norm including areas with complex geology or in some areas of classic geology. Linear features are associated most closely with the bedrock theme either as an intrinsic part of it for example marine bands or affecting it in the case of faults. However landform elements are associated with both bedrock and superficial deposits. The linear features are organised into seven main categories: Alteration area, indicating a zone of change to the pre-existing rocks due to the application of heat and pressure that can occur round structural features such as faults and dykes. Fault, where a body of bedrock has been fractured and displaced by a large scale process affecting the earth's crust. Fold, where strata are bent or deformed resulting from changes or movement of the earth's surface creating heat and pressure to reshape and transform the original horizontal strata. Folds appear on all scales, in all rock types and from a variety of causes. Fossil horizons, where prolific fossil assemblages occur and can be used to help establish the order in which deposits were laid down (stratigraphy). These horizons allow correlation where sediments of the same age look completely different due to variations in depositional environment. Landforms, define the landscape by its surface form; these include glacial features such as drumlins, eskers and ice margins. Mineral vein, where concentrations of crystallised mineral occur within a rock, they are closely associated with faulting but may occur independently. Rock, identifies key (marker) beds, recognised as showing distinct physical characteristics or fossil content. Examples include coal seams, gypsum beds and marine bands. The data are available in vector format (containing the geometry of each feature linked to a database record describing their attributes) as ESRI shapefiles and are available under BGS data licence. Another batch of tiles was added to the data in 2012 to bring the total to 167 for this version 2 release.