Digital database of a 3D Geological Model of western South Dakota

This digital GIS dataset and accompanying nonspatial files synthesize the model outputs from a regional-scale volumetric 3-D geologic model that portrays the generalized subsurface geology of western South Dakota from a wide variety of input data sources.The study area includes all of western South Dakota from west of the Missouri River to the Black Hills uplift and Wyoming border. The model data released here consist of the stratigraphic contact elevation of major Phanerozoic sedimentary units that broadly define the geometry of the subsurface, the elevation of Tertiary intrusive and Precambrian basement rocks, and point data representing the three-dimensional geometry of fault surfaces. the presence of folds and unconformities are implied by the 3D geometry of the stratigraphic units, but these are not included as discrete features in this data release.  The 3D geologic model was constructed from a wide variety of publicly available surface and subsurface geologic data; none of these input data are part of this Data Release, but data sources are thoroughly documented such that a user could obtain these data from other sources if desired. This model was created as part of the U.S. Geological Survey’s (USGS) National Geologic Synthesis (NGS) project—a part of the National Cooperative Geologic Mapping Program (NCGMP).

The WSouthDakota3D geodatabase contains twenty-five (25) subsurface horizons in raster format that represent the tops of modeled subsurface units, and a feature dataset “GeologicModel”. The GeologicModel feature dataset contains a feature class of thirty-five (35) faults served in elevation grid format (FaultPoints). The feature class “ModelBoundary” describes the footprint of the geologic model, and was included to meet the NCGMP’s GeMS data schema. Nonspatial tables define the data sources used (DataSources), define terms used in the dataset (Glossary), and provide a description of the modeled surfaces (DescriptionOfModelUnits). Separate file folders contain the vector data in shapefile format, the raster data in ASCII format, and the nonspatial tables as comma-separated values. In addition, a tabular data dictionary describes the entity and attribute information for all attributes of the geospatial data and the accompanying nonspatial tables (EntityAndAttributes).

An included READ_ME file documents the process of manipulating and interpreting publicly available surface and subsurface geologic data to create the model. It additionally contains critical information about model units, and uncertainty regarding their ability to predict true ground conditions. Accompanying this data release is the “WSouthDakotaInputSummaryTable.csv”, which tabulates the global settings for each fault block, the stratigraphic horizons modeled in each fault block, the types and quantity of data inputs for each stratigraphic horizon, and then the settings associated with each data input.

本数字地理信息系统（GIS，Geographic Information System）数据集及配套非空间文件，整合了区域尺度三维体积地质模型的全部模型输出结果。该模型基于多类输入数据源，刻画了南达科他州西部的广义地下地质特征。

本研究区涵盖南达科他州西部全域，即密苏里河以西至黑山隆起与怀俄明州边界的区域。

本次发布的模型数据包括：明确界定地下几何形态的显生宙（Phanerozoic）主要沉积地层的层序接触面高程数据、第三纪侵入岩与前寒武纪基底岩石的高程数据，以及表征断层表面三维几何形态的点数据。地层单元的三维几何形态可间接反映褶皱与不整合面的存在，但本次数据发布未将其作为独立要素纳入数据集。

该三维地质模型基于多类公开获取的地表与地下地质数据构建，此类输入数据未包含在本次数据发布中，但已对所有数据源进行了详尽文档说明，用户可根据需求从其他渠道获取这些数据。本模型为美国地质调查局（USGS，U.S. Geological Survey）国家地质综合（NGS，National Geologic Synthesis）项目的成果，该项目隶属于全国合作地质填图计划（NCGMP，National Cooperative Geologic Mapping Program）。

WSouthDakota3D地理数据库包含25个栅格格式的地下层位数据，对应各建模地下单元的顶面，同时设有一个名为"GeologicModel"的要素数据集。"GeologicModel"要素数据集包含35个以高程栅格格式存储的断层要素类（FaultPoints）。"ModelBoundary"要素类用于描述地质模型的覆盖范围，其纳入是为了符合NCGMP的GeMS数据模式。

非空间数据表涵盖：所用数据源定义表（DataSources）、数据集术语释义表（Glossary），以及建模地层表面说明表（DescriptionOfModelUnits）。独立文件夹分别存储Shapefile格式的矢量数据、ASCII格式的栅格数据，以及以逗号分隔值格式存储的非空间数据表。此外，附带一份表格数据字典（EntityAndAttributes），用于说明地理空间数据及配套非空间数据表的所有实体与属性信息。

附带的READ_ME文件记录了处理和解译公开地表与地下地质数据以构建本模型的完整流程，同时包含建模地层的关键信息，以及模型预测实际地下工况的不确定性说明。随本次数据发布附带的"WSouthDakotaInputSummaryTable.csv"文件，汇总了各断层块的全局设置、各断层块中建模的层序地层、每个层序地层的输入数据类型与数量，以及各数据输入对应的相关设置。