A DYNAMIC DATABASE FOR GEOCHEMICAL AND MINERALOGICAL DATA FOR SOILS OF THE CONTERMINOUS UNITED STATES COLLECTED FOR THE USGS GEOCHEMICAL LANDSCAPES PROJECT

New geochemical and mineralogical data will soon be released to the public as part of the U.S. Geological Survey Data Series, “Geochemical and Mineralogical Data for Soils of the Conterminous United States”. This low-density national-scale soil survey visited 4,857 sites (approximately one site per 1,600 sq. km.). Each site included: (1) a composite sample from the top 5 cm, (2) a composite of the soil A horizon, and (3) a sample from the soil C horizon or a sample from about 80-100 cm if the C horizon was deeper than 1 meter. The <2 millimeter fraction of each sample was analyzed for 45 major and trace elements using ICP-MS, ICP-AES, and selected analytical techniques for As, C, Hg, and Se. Additional splits from the samples of the A and C horizons were also analyzed for the mineralogical content using the quantitative X-ray diffraction method with Rietveld refinements.

The results of the chemical and mineralogical analyses will be available to the public as a set of three tables (0-5 cm depth, soil A horizon, and soil C horizon) downloadable from the USGS Mineral Resources On-Line Spatial Data website (mrdata.usgs.gov). All tables have an identical structure to allow the users to readily combine them into larger files.

A .kml file that opens with Google Earth®, ArcGlobe®, or other mapping software packages will also be available. This file greatly facilitates the visualization of the data, which then can be combined with other digital layers such as geologic maps or mineral occurrences. A digital geochemical and mineralogical soil atlas will be published on-line for the conterminous United States, with interpolated maps of the distribution of the analyzed chemical elements and the major minerals found in the soil samples as well as descriptive statistics and plots.