BGS Geology - 625k (DiGMapGB-625) 2008

Data identifying landscape areas (shown as polygons) attributed with geological names. The scale of the data is 1:625 000 providing a simplified interpretation of the geology and may be used as a guide at a regional or national level, but should not be relied on for local geology. Onshore coverage is provided for all of England, Wales, Scotland, the Isle of Man and Northern Ireland. Data are supplied as four themes: bedrock, superficial deposits, dykes and linear features (faults). 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 of the rocks. 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. The dykes theme defines small, narrow areas (shown as polygons) of a specific type of bedrock geology; that is igneous rocks which have been intruded into the landscape at a later date than the surrounding bedrock. They are presented as an optional, separate theme in order to provide additional clarity of the bedrock theme. The bedrock and dykes themes are designed to be used together. Linear features data (shown as polylines) represents 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). All four 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 delivered free of charge under the terms of the Open Government Licence.本数据集用于标识带有地质名称属性的景观区域（以多边形形式呈现）。数据集比例尺为1:625 000，仅对地质情况进行简化解译，仅可作为区域或国家级层面的地质参考依据，不可用于局部地质的精准研判。 数据集覆盖英格兰、威尔士、苏格兰、马恩岛以及北爱尔兰的全部陆上区域。 本数据集包含四大主题：基岩（bedrock）、浅表沉积物（superficial deposits）、岩脉（dykes）以及线性构造（linear features，即断层）。 基岩地质主题描述构成地壳主体的固态岩石集合。基岩广泛分布于各处，既可出露地表形成露头，也可被浅表沉积物或水体覆盖。地质名称基于岩石的岩石地层（lithostratigraphic）或岩石体（lithodemic）层级体系划分。岩石地层分类方案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该体系，例如经历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组成作为分类依据，该分类需考量岩石的结构、构造、矿物组成等可见特征。 浅表沉积物为最新地质时代——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石或沉积物之上。浅表沉积物主题用于标识带有地质名称及其沉积类型或岩性组成的景观区域（以多边形形式呈现）。 岩脉主题用于定义特定类型基岩地质的小型狭窄区域（以多边形形式呈现），即较周围基岩后期侵入形成的火成岩。为提升基岩主题的清晰度，岩脉主题作为可选独立主题提供，且基岩与岩脉主题建议配合使用。 线性构造数据（以多段线形式呈现）代表地表或基岩表面（浅表沉积物下方）的地质断层。地质断层指基岩体因受地壳大规模作用（构造应力）发生破裂与位移的构造。断层主题用于定义地表或基岩表面（浅表沉积物下方）的地质断层（以多段线形式呈现）。 四大主题数据均以矢量格式（包含各要素几何信息与关联属性的数据库记录）提供，格式为ESRI形状文件（ESRI shapefiles），并依据《开放政府许可》（Open Government Licence）条款免费发布。