Introduction

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:

Files:

midcontinent.apr - The ArcView project file

midcontinent_dd.aep - ArcExplorer project in geographic coordinates

midcontinent_lam.aep - ArcExplorer project in Lambert projection

Folders:

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

counties_lam

d_holes_lam

faults_lam

geology_lam

latlong_lam

state_bdry_lam

struct_hash_lam

structure_lam

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)

drill_holes.e00

faults.e00

geology.e00

latlong.e00

struct_hash.e00

structure.e00

e00/lam - Lambert projected coverages that are in ARC export file format (.e00)

d_holes_lam.e00

faults_lam.e00

geology_lam.e00

latlong_lam.e00

struct_hash_lam.e00

structure_lam.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
CD originally published in 2001