Preliminary Integrated Geologic Map Databases of the United States: Kentury, Ohio, Tennessee, West Virginia (OFR 2004-1324)

Open-File Report (2005-1324)

The growth in the use of Geographic Information Systems (GIS) has highlighted the need for regional and national digital geologic maps attributed with age and lithology information. Such maps can be conveniently used to generate derivative maps for purposes including mineral-resource assessment, metallogenic studies, tectonic studies, and environmental research. This Open-File Report is a preliminary version of part of a series of integrated state geologic map databases that cover the entire United States.

The only national-scale digital geologic maps that portray most or all of the United States for the conterminous U.S. are the digital version of the King and Beikman (1974a, b) map at a scale of 1:2,500,000, as digitized by Schruben and others (1994) and the generalized digital version (Reed and Bush, 2004) of the Geologic Map of North America (Reed and others, 2005a, b) compiled at a scale of 1:5,000,000. The present series of maps is intended to provide the next step in increased detail. State geologic maps that range in scale from 1:100,000 to 1:1,000,000 are available for most of the country, and digital versions of these state maps are the basis for this product. In a few cases, new digital compilations were prepared (e.g. Ohio, South Carloina, South Dakota) or existing paper maps were digitized (e.g. Kentucky, Texas). Also as part of this series, new regional maps for Alaska and Hawaii are being compiled and ultimately new state maps will be produced.

The digital geologic maps are presented in standardized formats as ARC/INFO export (.e00) files and as ArcView shape (.shp) files. Accompanying these spatial databases are a set of five supplemental attribute tables that relate the map units to detailed lithologic and age information. The maps for the CONUS have been fitted to a common set of state boundaries based on the 1:100,000 topographic map series of the United States Geological Survey (USGS). When the individual state maps are merged, the combined attribute tables can be used directly with the merged maps to make derivative maps. No attempt has been made to reconcile differences in mapped geology across state lines.

The various digital geologic maps that form the basis for this product were originally produced in a wide variety of formats. Although most of them are available as ARC/INFO export (.e00) files and/or ArcView shape (.shp)files, the items and formats in the polygon (PATs) and arc (AATs) attribute tables vary dramatically. To unify these disparate maps, it was necessary to create a set of standard formats, and then to convert the state digital geologic maps to conform to these standards. The details of these standards are presented in the documentation of this report. The creation of a unique map unit name, called unit_link, allows the different State maps to be merged. (Database field names are in italics). Unit_link consists of a two-letter State (ST) code, concatenated with the original geologic map unit name, which may be slightly modified to remove special characters for age designations, followed by a semicolon, and an integer that designates geographic regions (or provinces) within the map. For those states where provincial structure is absent, this integer is simply “0”. This variable, unit_link, can then be used as a key field to relate the tables that contain age and lithologic information to the spatial database (.dbf).

Compilation of a regional geologic map always requires compromises between the complexity of geologic information for a large region, and the need to keep the compiled map, and its explanation, relatively simple. Similarly, compromises are necessarily made in order to convert the large variety of formats in our source maps into the standard set of formats developed for this series.

Typically, spatial databases were modified from the source in the following general manner: The most recent data was obtained and the arcs and polygons were reattributed in the PAT according to the nomenclature adopted for this series (see documentation in this report and the metadata for individual spatial databases). When this reattribution was complete, the other attributes from the original spatial databases were deleted. Generally, if faults were not an integral part of the spatial database, arcs were retagged to make them so. Additionally, for those states where faults were mapped, fault arcs were extracted and provided as a separate .e00 or shape file (faults_dd, faults_lcc).

A second more detailed set of standardized attribute tables was generated by extracting information from the legends of the source maps and entering it into a set of five tables that record map unit information (STunits), lithologic information (STlith), age information (STage), and references (STref and STref-link). Some existing map legends provided an inadequate level of age or lithologic information. In these cases, we consulted the scientific literature, maps at smaller scales, and, in some cases, the original authors of the compilations or other regional experts. When we used updated information, it was recorded in the STage and STlith tables. Thus, the age and lithology information in these attribute tables may, in some cases, conflict with the information on the legends of the original source maps that may have been compiled decades ago.

In particular, the lithology table (STlith) may be much more extensive than the information in the map legends. Large regional compilations like these State maps often utilize map units that encompass a variety of lithologies. Volcanic rocks are commonly “lumped” extensively, combining tuffs, ash-flow tuffs, flows, and subvolcanic intrusions of a number of compositions, so that individual map units may contain dozens of unique lithologies. Although a dominant (most abundant) lithology has been designated for all map units, users seeking to use this information are advised to be cautious, as many map units simply have no dominant lithology.

Error correction is an ongoing process with most spatial databases. A typical state spatial database consists of tens of thousands of polygons and arcs, and errors introduced during the creation of these spatial databases are inescapable. One common type of error is data coding that does not conform to the original paper map. For example, polygons may be given the wrong map unit, or faults may be called normal faults instead of thrust faults. Some of these errors are unavoidable because, in a few cases, the original paper map cannot be read accurately.

In other cases, newer information is available that can be used to better describe the existing polygons and arcs that are based on decades-old compilations. This type of updating was done where necessary for some of the spatial databases. Any changes to the spatial data are documented (STchanges.txt where ST stands for the two-letter abbreviation for a given state.)

Spatial databases are provided in both Lambert Conformal Conic projection and geographic coordinates (decimal degrees).

Projection:

Lambert Conformal Conic

Horizontal datum: NAD 27 Spheroid: Clarke, 1866 Standard parallels: 33 degrees North 45 degrees North Central meridian: -100 degrees Reference Latitude: 0 degrees Horizontal units: meters False easting: 0 False northing: 0

Supplemental attribute tables are provided in Filemaker Pro format (.fp5), in dBase format (.dbf), and comma-separated value (.csv) text.

ArcView files can be viewed with the free viewer, ArcExplorer, which can be downloaded from http://www.esri.com/software/arcexplorer/.

King, P.B., and Beikman, H.M., 1974a, Geologic map of the United States: U.S. Geological Survey, scale 1: 2,500,000.

King, P.B., and Beikman, H.M., 1974b, Explanatory text to accompany the geologic map of the United States: U.S. Geological Survey Professional Paper 901, 40 p.

Reed, J.C. and Bush, C.A., 2004, Generalized Geologic Map of the Conterminous United States, U.S. Geological Survey, scale 1:7,500,000. (URL http://pubs.usgs.gov/atlas/geologic/)

Reed, J.C., Jr., Wheeler, J.O., and Tucholke, B.E., 2005a, Geologic map of North America: Geological Survey of America, Decade of North American Geology, 3 sheets, scale 1:5,000,000.

Reed, J.C., Jr., Wheeler, J.O., and Tucholke, B.E., 2005b, Geologic map of North America – Perspectives and explanation: Geological Survey of America, Decade of North American Geology, 28 p.

Schruben, P.G., Arndt, R.E., and Bawiec, W.J., 1994, Geology of the Conterminous United States at 1:2,500,000 Scale — A Digital Representation of the 1974 P.B. King and H.M. Beikman Map, U.S. Geological Survey Digital Data Series 11, release 2. (URL http://pubs.usgs.gov/dds/dds11/)

To download files, right click on the file that you want and either Save target as…(Internet Explorer) or Save link as…(Netscape).

A paper geologic map of Kentucky at a scale of 1:250,000 was published jointly by the Kentucky Geological Survey and the U.S. Geological Survey in 1981 (McDowell, and others, 1981). At the end of that decade, in conjunction with the Sesquicentennial of the Kentucky Geological Survey in 1988, a 1:500,000 scale paper map was produced by generalizing the earlier 1:250,000 scale state map (Noger, 1988).

In 2002, the 1:500,000 scale geologic map (including a separate fault file) was digitized by the Kentucky Geological Survey and made available to the public through the website http://www.uky.edu/KGS/gis/kygeol.htm. In 2004 the USGS re-digitized the existing paper 1:500,000-scale state geologic map of Kentucky (Noger, 1988), embedding faults in the polygon coverage. This updated version is provided here.

Additional spatial data can be downloaded from http://www.uky.edu/KGS/gis/geology.htm. Information about other products from the Kentucky Geological Survey can be found at http://www.uky.edu/KGS/home.htm.

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In 2002, the digital state geologic map of Ohio was produced by the Ohio Geological Survey at a scale of 1:500,000 as the product of a contract with the USGS. This map represents a significant revision of the most recent paper map (Bownocker, J.A., 1920).

An updated digital state geologic map will be released by the Ohio Geological Survey in the near future. The Ohio Geological Survey website at http://www.ohiodnr.com/geosurvey/ lists currently available publications, including digital data available both as downloads and on CD.

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The paper geologic map of Tennessee was produced in four sheets by the Tennessee Division of Geology in 1966 (Hardeman, 1966) at a scale of 1:250,000. In 2000 the U.S. Geological Survey Water Resources Office in Tennessee digitized the 1:250,000 scale map and the spatial data are available from http://water.usgs.gov/GIS/dsdl/geo250k.e00.gz with the metadata available from http://water.usgs.gov/GIS/metadata/usgswrd/XML/geo250k.xml.

Other spatial data for Tennessee can be downloaded from http://www.tngis.org/index.html. Information about other products from the Tennessee Division of Geology can be found at http://www.state.tn.us/environment/tdg/index.html.

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The paper state geologic map of West Virginia was published at a scale of 1:250,000 by the West Virginia Geological and Economic Survey in 1968 (Cardwell and others, 1968).

The digital bedrock map of West Virginia was digitized by the West Virginia Division of Environmental Protection in 1998 under a contract with USGS Water Resources Division Office in West Virginia. Several attributes were subsequently updated by the U.S. Geological Survey.

Spatial data can be downloaded from the West Virginia GIS Technical Center Data Clearinghouse website at http://wvgis.wvu.edu/data/data.php. Information about other products from the West Virginia Geological and Economic Survey can be found at http://www.wvgs.wvnet.edu/.

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Bownocker, J.A., 1920, Geologic Map of Ohio: Ohio Geological Survey, Map M-1, scale 1:500,000. (Reprinted in 1981.)

Cardwell, D.H., Erwin, R.B., and Woodward, H.P., 1968, Geologic map of West Virginia: West Virginia Geological and Economic Survey, 2 sheets, scale 1:250,000 (Reprinted and slightly revised in 1986).

Hardeman, W.D., 1966, Geologic map of Tennessee: State of Tennessee Department of Conservation, Division of Geology, four sheets, scale 1:250,000.

McDowell, R.C., Grabowski, G.J., Jr., and Moore, S.L., 1981, Geologic map of Kentucky: U.S. Geological Survey, 4 sheets, scale 1:250,000.

Noger, M.C., 1988 [1992], Geologic Map of Kentucky: Sesquicentennial edition of the Kentucky Geological Survey: U.S. Geological Survey Special Map prepared in cooperation with the Kentucky Geological Survey, scale 1:500,000.

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