BGS Geology - 50k (DiGMapGB-50) version 8

Data identifying landscape areas (shown as polygons) attributed with geological names. The scale of the data is 1:50 000 scale. Onshore coverage is provided for all of England, Wales, Scotland and the Isle of Man. Data are supplied as five themes: bedrock, superficial deposits, mass movement, artificial ground and linear features. 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. The lithostratigraphic scheme arranges rock bodies 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. Superficial deposits are younger geological deposits formed during the most recent geological time; the Quaternary. These deposits rest on older rocks or deposits referred to as bedrock. The superficial deposits theme defines landscape areas (shown as polygons) attributed with a geological name and their deposit-type or lithological composition. Mass movement describes areas where deposits have moved down slope under gravity to form landslips. These landslips can affect bedrock, superficial or artificial ground. Mass movement deposits are described in the BGS Rock Classification Scheme Volume 4. However this data also includes foundered strata, where ground has collapsed due to subsidence (this is not described in the Rock Classification Scheme). Caution should be exercised with this data; historically BGS has not always recorded mass movement events and due to the dynamic nature of occurrence significant changes may have occurred since the data was released. Artificial (man-made) theme (shown as polygons) indicates areas where the ground surface has been significantly modified by human activity. Whilst artificial ground may not be considered as part of the 'real geology' of bedrock and superficial deposits it does affect them. Artificial ground impacts on the near surface ground conditions which are important to human activities and economic development. Due to the constantly changing nature of land use and re-use/redevelopment, caution must be exercised when using this data as it represents a snapshot in time rather than an evolving picture hence the data may become dated very rapidly. Linear features (shown as polylines) represent 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). 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. Landform elements are associated with both bedrock and superficial deposits. All five data themes 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），数据比例尺为1:50000。数据覆盖英格兰、威尔士、苏格兰全境及马恩岛的陆上区域。数据集包含五大主题图层：基岩（bedrock）、表层沉积物（superficial deposits）、块体运动（mass movement）、人工地表（artificial ground）及线性地质要素（linear features）。基岩地质指构成地壳主体的固态岩体。基岩遍布全域，既可裸露于地表形成露头（outcrop），也可隐伏于表层沉积物或水体之下。地质名称基于岩石地层学（lithostratigraphic）或岩石体地层学（lithodemic）等级体系。岩石地层学方案依据岩石类型与形成地质时代，将岩体划分为不同地层单元。若岩体类型无法归入岩石地层学体系，则以其岩石类型或岩性（lithological）组成进行分类，例如经热压作用形成新或改性岩石的侵入型、变形岩体。该分类依据岩性的可见特征，如结构、构造、矿物组成（mineralogy）。表层沉积物（superficial deposits）为最新地质时代——第四纪（Quaternary）——形成的年轻地质堆积物，覆于被称为基岩的古老岩体或沉积物之上。表层沉积物主题用于识别标注有地质名称及其沉积类型或岩性组成的地貌区域（以多边形矢量要素表示）。块体运动（mass movement）指沉积物在重力作用下沿斜坡移动形成滑坡的区域。此类滑坡可影响基岩、表层沉积物或人工地表。块体运动堆积物的分类依据《英国地质调查局岩石分类方案》第4卷（BGS Rock Classification Scheme Volume 4）。但本数据集还包含沉陷地层，即因地面沉降（subsidence）发生塌陷的地层（该类地层未被纳入上述岩石分类方案）。使用本数据集时需谨慎：历史上英国地质调查局（British Geological Survey，BGS）并非始终记录所有块体运动事件，且由于块体运动发生的动态性，数据发布后可能已发生显著变化。人工地表（artificial ground）主题以多边形矢量要素表示，指代受人类活动显著改造的地表区域。尽管人工地表通常不被视为基岩与表层沉积物这类‘真实地质’的组成部分，但它会对上述地质体产生影响。人工地表会改变近地表地质条件，而这对人类活动与经济发展至关重要。由于土地利用、再利用及再开发的持续变化，本数据集仅为某一时间点的快照，而非动态演化的全貌，因此可能会快速过时，使用时需格外谨慎。线性地质要素（linear features）以多段线（polylines）矢量要素表示，代表地质构造特征（如断层、褶皱）或地貌特征（如埋藏河道、地表或基岩表面（覆于表层沉积物之下）的冰川排水河道）。线性地质要素与基岩主题关联最为紧密：既可作为基岩的固有组成部分（如海相层（marine bands）），也可因断层等作用对基岩产生影响。地貌要素则同时与基岩和表层沉积物相关联。五大主题图层均以矢量格式提供，即包含各要素几何信息与关联属性数据库记录的ESRI形状文件（ESRI shapefiles），并遵循英国地质调查局（BGS）数据许可协议进行分发。