Open-File Report 01-021
This report contains files that provide a digital version of USGS map I-1853-A, "Precambrian Basement Map of the Northern Midcontinent, U.S.A.," compiled by P.K. Sims and published in 1990. The files are provided in two formats: (1) Arc export (e00) files, which can be imported directly into a number of applications, and (2) Arcview shapefiles and a related Arcview project, which allow direct viewing and manipulation of the map information.
The intent of this release is solely to make the original map data available digitally, not to make updates or modifications to the map based on new data acquired in the past decade since the original map was published. Thus, the information in the database files is distilled from the original map and preserves the terminology used therein. To further preserve the original map, ancillary information such as the Correlation of Map Units and Description of Map Units are included as images that were scanned from the printed map.
The data are presented in several data layers. A polygon coverage presents the distribution of map units in which each polygon is attributed with 15 geological parameters. An accompanying line coverage shows faults. Additional coverages show location of drill holes used in the original compilation and structure contours on the Precambrian basement surface.
The files and folders are as follows:
midcontinent.apr - The ArcView project file
midcontinent_dd.aep - ArcExplorer project in geographic coordinates
midcontinent_lam.aep - ArcExplorer project in Lambert projection
data - ArcView shapefiles
counties - Base data that contains the county and state name
drill_holes - Locations of wells
faults - Fault locations
geology - Geologic units
latlong - latitude and longitude grid of the coverage area
state_bdry - Base data that contains state lines in the area
struct_hash - Hash line that indicate structure depressions
structure - Structure contour lines
data/lam - ArcView shapefiles that are projected in lambert
docs - Metadata for data in this ArcView project
metadata.txt - metadata file for geographic files
metadata_lam.txt - metadata files for lambert projection files
e00 - Coverages that are in ARC export file format (.e00)
e00/lam - Lambert projected coverages that are in ARC export file format (.e00)
images - tif images
correlation.tif - legend for the correlation of map units
index_map.tif - map showing the geographic location of the coverage area
map_units.tif - legend of the geologic map units
tectonic_index.tif - simplified tectonic map of the coverage area
Posted online October 21, 2009
For additional information contact:
ESRI provides a free viewing software called ArcExplorer. It can be downloaded from their website at the following address: http://www.esri.com/software/arcexplorer/download.html
Dicken, C.L., Pimley, S.G., and Cannon, W.F., 2001, Precambrian basement map of the northern midcontinent, U.S.A. -- A digital representation of the 1990 P.K. Sims map: U.S. Geological Survey Open-File Report 01-021, available online only.