Geologic Mapping

Geologic maps show the distribution of bedrock and unconsolidated sediments using colors, lines, and symbols. These maps contain an explanation that describes the composition, texture, orientation, and age of the rocks. Geologic maps may be accompanied by one or more geologic cross-sections, showing the bedrock relationships in the subsurface. The locations of important features such as folds and faults are also shown on geologic maps.

Geologic maps provide basic information for land development and conservation projects. Large projects (dams, roads, bridges, and buildings) require detailed geological analysis because of monetary, health, and safety concerns. Smaller projects, such as waste disposal systems and water wells also benefit from an understanding of the local geology. Geologic maps are also used for:

• Evaluation of geologic hazards (landslides, earthquakes, land subsidence)
• Planning transportation and utility routes
• Site selection for public facilities (landfills, waste-treatment facilities, waste-disposal sites, schools)
• Land-use planning and evaluation of land-use proposals
• Regulatory decisions
• Environmental assessment and protection planning (underground storage tanks, landfills, aquifer contamination)
• Development and protection of groundwater
• Natural-resource assessment, exploration, development, and management
• Basic earth-science research

More details involving the creation, uses, and importance of geologic maps are described at http://www.agiweb.org/environment/publication/mapping/mappingbook.pdf

To find out what geologic and geoscience maps are available for Virginia, visit the USGS's National Geologic Map Database.

What is STATEMAP?

The National Geologic Mapping Act of 1992 established the National Cooperative Geologic Mapping Program to implement and coordinate an expanded geologic mapping effort by the U.S. Geological Survey, the state geological surveys, and universities. The primary goal of the STATEMAP program is to collect, process, analyze, translate, and disseminate earth-science information through geologic maps. In Virginia, priorities for the program are cooperatively developed through a Geologic Mapping Advisory Committee.

Virginia STATEMAP proposal
Virginia STATEMAP fact sheet

Future STATEMAP goals or areas in progress of being mapped in Virginia

Interstate 81 Corridor Project
Richmond Metropolitan Statistical Area Project
Williamsburg 30 x 60 Minute Quadrangle Project

Interstate 81 Corridor Project

The Interstate 81 Corridor project is a concentrated multi-year effort to complete 1:24,000-scale geologic mapping and digital compilation of existing geologic maps along the entire Interstate Highway 81 (I-81) corridor in Virginia. This portion of the Appalachian Valley is where most of the population of western Virginia lives, works, and travels on a daily basis. It is also home to a variety of farms, industries, and commercial enterprises.

For the purpose of this study, the I-81 corridor is defined to extend for 10 miles (16.1 km) on either side of the I-81 corridor. DGMR plans to complete 1:24,000-scale geologic mapping of all quadrangles that are wholly or substantially within this corridor. DGMR also plans to selectively map quadrangles that are adjacent to the I-81 corridor in areas of current or future growth, near interstate intersections, and in areas where detailed geologic mapping is warranted because of structural or stratigraphic complexity.

Intermediate products for this study will be 1:24,000-scale geologic maps of single or multiple quadrangles, to be published in paper or digital form, and a series of open-file reports, available on CDs, that contain files for the current extent of the digital compilation. The final product will be a 1:24,000-scale digital compilation of the entire I-81 corridor.

Richmond Metropolitan Statistical Area Project

The Richmond Metropolitan Statistical Area project is a concentrated multi-year effort to complete 1:24,000-scale geologic mapping and digital compilation of existing geologic maps in a portion of a 16-county area that has been designated as the Richmond Metropolitan Statistical Area (MSA). This area lies within both the Piedmont and Coastal Plain physiographic provinces and is situated at the intersection of three major interstates, I-95, I-64, and I-85. It is home to approximately one in seven of Virginia’s citizens, and accomodates many types of businesses and industries. Agriculture is a stable to growing part of the area’s economy, with approximately 4,300 farms on nearly one million acres (U.S. Department of Agriculture, 1997 and 2002). This area encompasses all or a portion of six regional planning districts.

DGMR is assigning the 95 unpublished 7.5-minute quadrangles that are substantially within the Richmond MSA either a high or low priority ranking. This ranking is based upon societal needs identified by the planning districts or other government agencies and an assessment of the potential for mineral resources or geologic hazards by DGMR staff. Quadrangles that are assigned a high priority ranking meet one or more of the following criteria:

• Significant change in land use anticipated;
• High potential for mineral resources;
• Known geologic hazards exist;
• Population center or highly developed area;
• Along an Interstate.

The goal of this project is to complete 1:24,000-scale geologic mapping of all quadrangles in the MSA that are identified as high priority. Ultimately, DGMR would like to use this data in combination with data on the low priority quadrangles to create a 1:100,000-scale geologic map of the entire MSA. Intermediate products for this study will be 1:24,000-scale geologic maps of single or multiple quadrangles, to be published in paper or digital form, and a series of open-file reports on CDs that contain files for the current extent of the geologic compilation.

Selected References:

United States Department of Agriculture, 1997, Census of agriculture: http://www.nass.usda.gov/Census_of_Agriculture/index.asp

United States Department of Agriculture, 2002, Census of agriculture: http://www.nass.usda.gov/Census_of_Agriculture/index.asp

Williamsburg 30 x 60 Minute Quadrangle Project

The purpose of the Williamsburg 30- x 60-minute quadrangle project is to complete geologic mapping and digital compilation in the Williamsburg 30- x 60-minute quadrangle. There are seven 7.5-minute quadrangles (and parts of two quadrangles on the Eastern Shore) that have not been mapped in detail. Six 7.5-minute quadrangles in the Williamsburg sheet were mapped for the years 2000 and 2001 STATEMAP funding. Mapping the Ware Neck and Gloucester 7.5-minute quadrangles will complete Gloucester and Mathews counties. The outer rim fault of the Chesapeake Bay Impact Crater is projected through Ware Neck quadrangle. Interstate 64 lies within the Walkers 7.5-minute quadrangle. The remaining 4 quadrangles lie mostly south of the James River. The Surry quadrangle includes Jamestown Island and vicinity where major infrastructure improvement is planned for the 400th anniversary of English colonization in America.

DGMR relies heavily upon the use of its auger-drilling rig for geologic mapping in the coastal plain. Although exposed map units may appear simplistic in some coastal areas, a refined delineation of the subsurface framework is critical to understanding the shallow aquifers and identification of sand/aggregate resources. STATEMAP funding will support assistance with mapping, drilling, sample analysis, and GIS compilation.

The final product for this project will be a 1:100,000-scale digital compilation of the entire Williamsburg sheet. DGMR anticipates that it will take approximately three years to finish the project.

Other Mapping Projects

The Division of Geology and Mineral Resources has other geologic mapping projects that are nearing completion. These include:

• Rockbridge County (1:50,000 scale map and text)
• Gate City/Kingsport (1:24,000 scale map and text)
• Monterey (1:24,000 scale map and text)

DGMR's Customer Survey

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