Digital Geological Map Data of Great Britain - 250k (DiGMapGB-250) version 4

Data identifying landscape areas (shown as polygons) attributed with geological names. The scale of the data is 1:250 000 scale providing a generalised geology. Onshore coverage is provided for all of England, Wales, Scotland and the Isle of Man. Data are supplied as two themes: bedrock and linear features (faults), there is no superficial, mass movement or artificial theme available onshore at this scale. Bedrock geology describes the main mass of solid rocks forming the earth's crust. Bedrock is present everywhere, whether exposed at surface in outcrops or concealed beneath superficial deposits or water bodies. Geological names are based on the lithostratigraphic or lithodemic hierarchy. This means rock bodies are arranged into units based on rock-type and geological time of formation. Where rock-types do not fit into the lithostratigraphic scheme, for example intrusive, deformed rocks subjected to heat and pressure resulting in new or changed rock types; then their classification is based on their rock-type or lithological composition. This assesses visible features such as texture, structure, mineralogy. Data identifying linear features (shown as polylines) represent geological faults at the ground or bedrock surface (beneath superficial deposits). Geological faults occur where a body of bedrock has been fractured and displaced by large scale processes affecting the earth's crust (tectonic forces). The faults theme defines geological faults (shown as polylines) at the ground or bedrock surface (beneath superficial deposits). 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.本数据集用于识别标注有地质名称的地貌区域，以多边形矢量要素表示。数据集比例尺为1:250 000，呈现概化地质成果。其陆上覆盖范围涵盖英格兰、威尔士、苏格兰全境及马恩岛。数据集包含两大主题图层：基岩（bedrock）与线性要素（断层）；此比例尺下的陆上数据暂未提供表土、块体运动及人工地貌相关主题图层。基岩地质指构成地壳的固态岩石主体。基岩广泛分布，既可能以露头形式裸露于地表，也可能被表土沉积物或水体覆盖。地质名称基于岩石地层（lithostratigraphic）或岩石体（lithodemic）分级体系，即依据岩石类型与形成地质时代将岩体划分为不同单元。若岩石类型无法归入岩石地层体系，例如因受热压作用形成新类型或发生蚀变的侵入变形岩石，则以其岩石类型或岩性成分作为分类依据，该分类可通过观测岩石的结构、构造、矿物组成等特征实现。用于识别线性要素的数据以多段线矢量要素表示，代表地表或基岩表面（表土沉积物下方）的地质断层。地质断层指因影响地壳的大规模作用（构造应力）导致基岩岩体发生断裂与位移的地质现象。断层主题图层用于标注地表或基岩表面（表土沉积物下方）的地质断层，以多段线矢量要素表示。本数据集以矢量格式提供，包含各要素的几何信息与关联的属性数据库记录，格式为ESRI形状文件（ESRI shapefiles），可依据英国地质调查局（BGS）数据许可协议获取使用权限。