DOI: 10.5066/p953mc5c
title: Digital subsurface database of elevation point data and structure contour maps of multiple subsurface units, Powder River Basin, Wyoming and Montana, USA

description: This digital data release presents subsurface data from multiple geologic units that were part of a previous study of the regional subsurface structural configuration of the Powder River Basin in Wyoming and Montana. The original data within this geodatabase is sourced from an unpublished doctoral dissertation by Jessie Melick at Montana State University (Melick, 2013). Data contained in this release were generated from elevation grids developed by Jessie Melick using 28,000 wells and geophysical well logs penetrating Paleozoic to Mesozoic strata over a 70,000 square-kilometer area designated by the Department of Energy as a realistic locality for geologic carbon sequestration (Melick, 2013). Information included in this release represents a small component of the larger geomodel, which includes rock-property details such as facies analysis, porosity calculations, and net to gross thickness, among others. Well locations, well identification numbers, geophysical logs, and any other non-public data or information used in the creation of this dataset has been explicitly omitted. Data in this release includes elevation point features on the stratigraphic tops of the Mesaverde Group, Frontier Formation, Lakota Formation, Tensleep Formation, Madison Group, and Precambrian basement that were exported from the original horizon grids as points on a 500x500 m grid spacing. This release additionally contains structure contour maps of the tops of these same units; the contours were digitally generated from the point arrays using automated contouring methods within a geographic information system. Characterizing these units in the subsurface is of value, as they have been identified as potential reservoirs for the geologic sequestration of carbon, units of interest for geothermal energy production, may serve as regional groundwater aquifers, and are currently considered productive hydrocarbon reservoirs (Melick, 2013). Formation top points and structure contours were formatted and attributed as GIS data sets for use in digital form as part of U.S. Geological Survey?s ongoing effort to inventory, catalog, and release subsurface geologic data in geospatial form. This effort is part of a broad directive to develop 2D and 3D geologic information at detailed, national, and continental scales. This data approximates, but does not strictly follow the USGS NCGMP GeMS data structure schema for geologic maps.Structure contour lines for each formation are stored within separate ?IsoValueLine? feature classes, while formation tops for each formation are stored as point data in separate ?MapUnitPoints? feature classes. These are distributed within a geographic information system geodatabase and are also saved as shapefiles. Contour and point data are provided in both feet and meters to maintain consistency with the original publication and for ease of use. Nonspatial tables define the data sources used, define terms used in the dataset, and describe the geologic units referenced herein. A tabular data dictionary describes the entity and attribute information for all attributes of the geospatial data and accompanying nonspatial tables. Reference:�Melick, J., 2013, SUBSURFACE DESCRIPTION AND MODELING OF GEOLOGIC HETEROGENEITY IN LARGE SUBSURFACE DATASETS: USING TEMPORAL AND SCALAR HIERARCHIES, POWDER RIVER BASIN, WY AND MT, U.S.A., Unpublished Doctoral Dissertation, Montana State University, Bozeman, Montana, 237 p.