USGS Home
Contact USGS
Search USGS

Preliminary integrated geologic map databases for the United States

Alabama, Florida, Georgia, Mississippi, North Carolina, and South Carolina

By: Connie L. Dicken, Suzanne W. Nicholson, John D. Horton, Michael P. Foose, and Julia A.L. Mueller

Version 1.1

Updated December 2007

Choose state Alabama Florida Georgia Mississippi North Carolina South Carolina

Introduction

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 digital version of the Geologic Map of North America (Reed and others, 2005a, b) compiled at a scale of 1:5,000,000 which is currently being prepared by the U.S. Geological Survey. 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 of this product. In a few cases, new digital compilations were prepared (e.g. OH, SC, SD) or existing paper maps were digitized (e.g. KY, TX). For Alaska and Hawaii, new regional maps are being compiled and ultimately new state maps will be produced.

The digital geologic maps are presented in standardized formats as ARC/INFO (.e00) export files and as ArcView shape (.shp) files. Accompanying these spatial databases are a set of five supplemental data 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.

Procedures

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 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.

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 (STrefs 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 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/.

References

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/)

Alabama

The paper state geologic map of Alabama was produced in four sheets (Szabo and Copeland, 1988a,b; Szabo and others, 1988; Osbourne and others, 1988) by the Alabama Geological Survey at a scale of 1:250,000. Detailed legends accompany the maps.

In 1998 a digital version of the geologic map of Alabama was produced by the Geological Survey of Alabama in cooperation with the USGS.

[STATE LIST] [BACK TO TOP]

Florida

In 2001 the Florida Geological Survey produced a new digital geologic map of Florida (Scott and others, 2001) at a scale of 1:750,000 in cooperation with the USGS. The spatial data can be downloaded as an Arcview project from the Florida Department of Environmental Protection at: http://www.dep.state.fl.us/geology/gisdatamaps/state_geo_map.htm.

[STATE LIST] [BACK TO TOP]

Georgia

The paper state geologic map of Georgia was produced by the Georgia Geological Survey in 1976 (Lawton and others, 1976) at a scale of 1:500,000.

The 1976 Geologic Map of Georgia (Lawton and others, 1976) was digitized in 1999 by the Georgia Geological Survey, a branch of the Environmental Protection Division of the Georgia Department of Natural Resources and updated on 10/9/2000 (as version 2).

The spatial data can be downloaded from the web site for the Georgia GIS Clearinghouse at: https://gis1.state.ga.us/index.asp.
Note: One must register with the Georgia GIS Clearinghouse to download data.

Metadata (GGS Documentation Report 99-20) accompanying this data set is available at: http://pubs.usgs.gov/of/2005/1323/documents/geology.txt

[STATE LIST] [BACK TO TOP]

Mississippi

The paper state geologic map of Mississippi was published at a scale of 1:500,000 by the Mississippi Geological Survey in 1969 ( Moore, 1969) and reprinted in 1985.

The digital bedrock map of Mississippi was digitized by the Center for Spatial Data Research and Applications, Jackson State University, based on the 1985 version of the 1969 Geologic Map of Mississippi (Moore, 1969; reprinted in 1985).

Spatial data can be found at the web site for the Mississippi Automated Resource Information System (MARIS) Technical Center at: http://www.maris.state.ms.us/HTM/DataWarehouse/Statewide_alpha.htm

Metadata for the spatial data set can be found at the same web site at: http://www.maris.state.ms.us/pdf/metadata_pdf/surfgeol.PDF.

Information about products of the Mississippi Geological Survey can be found at: http://www.deq.state.ms.us/MDEQ.nsf/page/Geology_home.

[STATE LIST] [BACK TO TOP]

North Carolina

The paper state geologic map of North Carolina was published by the North Carolina Geological Survey in 1985(Rhodes and Conrad, 1985) at a scale of 1:500,000.

The 1985 bedrock map of North Carolina (Rhodes and Conrad, 1985) was digitized by the North Carolina Geological Survey in 1993. These digital data are presented as three data sets: geological formations, dikes and faults and all three data sets are distributed together.

The spatial data are available for purchase from the North Carolina Center for Geographic Information and Analysis (NCCGIA) at: http://www.cgia.state.nc.us/cgdb/catalog/geol250b.html.

Information about products of the North Carolina Geological Survey can be found at: http://www.geology.enr.state.nc.us/.

[STATE LIST] [BACK TO TOP]

South Carolina

There is no published state geologic map for South Carolina. A digital compilation of the crystalline basement rocks (Appalachian Piedmont and Blue Ridge) of western South Carolina was completed by J. Wright Horton, Jr., and Connie L. Dicken in 2001, based on references cited in the metadata for USGS Open-File Report 01-298. The eastern half of the state is generalized as the Coastal Plain. As more detailed digital geology becomes available for the Coastal Plain, those data will be incorporated.

The data in this compilation can be downloaded from the USGS at: http://pubs.usgs.gov/of/of01-298/.

Information about products from the South Carolina Geological Survey can be found at: http://www.dnr.state.sc.us/geology/.

[STATE LIST] [BACK TO TOP]

References for maps

Horton, Jr., J. Wright, and Dicken, Connie L. , 2001, Preliminary Digital Geologic Map of the Appalachian Piedmont and Blue Ridge, South Carolina Segment: U.S. Geological Survey Open-File Report 01-298, U.S. Geological Survey, Reston, Virginia. (available both on CD and at: http://pubs.usgs.gov/of/of01-298/)

Lawton , D.E., and others, 1976, Geologic map of Georgia: Georgia Department of Natural Resources and Georgia Geological Survey, scale 1:500,000.
Note: The 1976 Geologic Map of Georgia (Lawton and others, 1976) was digitized in 1999 by the Georgia Geological Survey, a branch of the Environmental Protection Division of the Georgia Department of Natural Resources and updated on 10/9/2000 (as version 2).

Moore, William Halsell, 1969, reprinted 1985, Geologic Map of Mississippi, Compiled by Bicker, A. R., Jr., a revision of the geologic map published by the MS Geological Survey in 1945 in cooperation with the USGS, revised from data submitted by Dr. E. E. Russell of MS State University from published reports of the MS Geological Survey and from field revisions, Mercury Maps Inc., Jackson, MS.

Osbourne, W.E., Szabo, M.W., Neatherly, T.L., and Copeland, Jr., C.W., 1988, Geologic map of Alabama: Northeast sheet: Geological Survey of Alabama, Special Map 220, scale 1:250,000.

Rhodes, Thomas S., and Conrad, Stephen G., 1985, Geologic Map of North Carolina: Department of Natural Resources and Community Development, Division of Land Resources, and the NC Geological Survey, 1:500,000-scale, compiled by Brown, Philip M., et al, and Parker, John M. III, and in association with the State Geologic Map Advisory Committee.

The North Carolina Dept. of Environment, Health, and Natural Resources, Division of Land Resources, NC Geological Survey, in cooperation with the NC Center for Geographic Information and Analysis, 1998, Geology - North Carolina (1:250,000), coverage data file geol250. The data represents the digital equivalent of the official State Geology map (1:500,000 scale), but was digitized from (1:250,000 scale) base maps.

Szabo, M.W., and Copeland, Jr., C.W., 1988a, Geologic map of Alabama: Southeast sheet: Geological Survey of Alabama, Special Map 220, scale 1:250,000.

Szabo, M.W., and Copeland, Jr., C.W., 1988b, Geologic map of Alabama: Southwest sheet: Geological Survey of Alabama, Special Map 220, scale 1:250,000.

Szabo, M.W., Osbourne, W.E., and Copeland, Jr., C.W., 1988, Geologic map of Alabama: Northwest sheet: Geological Survey of Alabama, Special Map 220, scale 1:250,000.

Scott, T. M., Campbell, K. M., Rupert, F. R., Arthur, J. D., Missimer, T. M., Lloyd, J. M., Yon, J. W., and Duncan, J. G., 2001, Geologic Map of the State of Florida, Florida Geological Survey and Florida Department of Environmental Protection, Map Series 146, scale 1:750,000.

[STATE LIST] [BACK TO TOP]