National- and regional-scale earth science datasets that are easily available and of high quality are critical to address a wide range of land-planning, resource, and environmental issues. U.S. Geological Survey (USGS) regional Surveys and Analysis projects are compiling, upgrading, utilizing and interpreting digital databases within four themes for the United States: geology, geochemistry, geophysics, and mineral occurrences. The regional projects work together to define common goals, set priorities, and ensure that products conform to consistent standards and protocols.
Much of the available information is the result of cooperative activities with State agencies. Where existing data are incomplete, new data are collected to ensure national coverage. As datasets are completed or revised, the information is made publicly available through a variety of media, including the Internet.
The data can be useful to members of Congress, State and Federal government agencies, researchers in academia, and the general public. Maps and analyses produced from the databases provide information that can be used for mineral resource assessments; environmental studies; regional and national land-use studies; and ongoing research, such as the identification of metallogenic terranes, determination of regional geochemical backgrounds, and study of the relationships between toxic elements and human health.
Status of the major datasets
We are creating an integrated national geologic map database utilizing State geologic maps. This database is intended make available quick-turnaround geologic base maps for regional- and national-level resource and environmental studies, lithologic maps, definition of geological or metallogenic terranes, and so on.
The first stage of the work is to obtain digital geologic map databases for all States. Databases for internal use are now available for all States except Ohio, South Carolina, South Dakota, Texas, Alaska, and Hawaii. By the summer of 2002, we anticipate that databases for all States, except for Alaska, will have been acquired. Existing databases are utilized when possible; otherwise existing paper maps are digitized or, if necessary, maps compiled. USGS has worked cooperatively with 22 State surveys in this effort. For Alaska, scientists are compiling 1:250,000-scale geologic quadrangle maps. More than 50 quadrangles are either completed or in progress, and preliminary digital geologic maps have been published for 38 quadrangles. The ultimate goal of this work is to compile a new State map for Alaska. A new State map for South Dakota by the South Dakota Geological Survey is also being cooperatively supported.
The second stage of this work consists of recoding all of the unit information on these maps to a single database standard that includes stratigraphic, age, and lithologic information. About a quarter of the available State databases have been coded to date. The third stage is integrating the individual State map databases into a single database. This work has not yet begun. Public release of the database will require close coordination with States because of proprietary issues for some of the data. Publication of derivative national maps showing features such as lithology is also anticipated.
We are producing a new stream-sediment-based geochemical survey for the United States at a nominal spacing of 17 by 17 kilometers. USGS scientists Andrew Grosz and Jeffrey Grossman are leading the effort and are ensuring that analytical routines and standards are consistent throughout the survey. Much of the survey has entailed reanalysis of approximately 35,000 archival samples from the National Uranium Evaluation (NURE) program. Where NURE samples do not exist, USGS has been working with cooperators to obtain new samples. To date, a total of about 50,000 stream-sediment samples have been analyzed for 42 elements, including arsenic, selenium, and mercury. About 10,000 more samples need to be collected and analyzed to complete the national survey.
Figure 1 - National Geochemical Map for selenium. Map was compiled by Andrew Grosz and Jeffrey Grossman.
A new Web site is being developed for the National Geochemical Survey and will be announced in a future issue of this newsletter. The site will highlight the results in a national atlas and will also make the data available to the general public. Follow-up interpretive work is also being planned. This work is being done cooperatively with the USGS National Geochemical Database project. Figure 1 shows our national selenium map utilizing presently available data.
Geophysical database development is closely coordinated with the USGS North American Magnetics and National Geophysical Database Projects. We are now producing on-line potential-field maps (gravity and magnetics) and datasets for each State and publishing them as USGS open-file reports. The reports are available online at: http://crustal.usgs.gov/geophysics/. Geophysical compilations for about a quarter of the States are presently available. Data for the remaining States are being prepared. Figure 2 shows a magnetic map for Georgia. New potential-field data have been collected for parts of Alaska and Wisconsin. An updated database of gravity data for the 48 conterminous States is underway and will be distributed via the Internet in cooperation with the University of Texas - El Paso.
Figure 2 - Georgia merged aeromagnetic anomaly map of Georgia with link to larger version of map, USGS Open-File Report 01-0106, http://pubs.usgs.gov/openfile/of01-106/
The regional Surveys and Analyses projects in cooperation with the Mineral Resources Database Project are helping to upgrade the USGS National Mineral Deposits Database, largely through cooperative agreements with State agencies. A primary focus is on developing comprehensive records for the most significant deposits in the United States. We also are selectively developing other data, such as industrial minerals information for part of the eastern United States, and incorporating older datasets not presently available in the national database.
For more information, contact:
Eastern United States
954 National Center
Reston, VA 20192
Central United States
DFC, P.O. Box 25046, MS 905
Denver, CO 80225
Western United States
USGS, MS 901
345 Middlefield Road
Menlo Park, CA 94025
Alaska and Hawaii
4200 University Drive
Anchorage, AK 99508