Publications National Geochemical Atlases America


United States of America


Contacts:  (1) David B. Smith,, and (2) Federico Solano,



A soil geochemical survey of the conterminous United States of America (U.S.A.) was initiated in 2007. Sampling at 4857 sites in the conterminous U.S.A. was completed in 2010 (1 site per 1,600 square kilometres). The following samples were collected at each site: (1) soil from a depth of 0-5 cm; (2) a composite of the soil A horizon; and (3) a sample from the soil C horizon, or if the top of the C horizon was deeper than 1 metre, a sample was collected from about 80-100 cm. Each sample was air-dried at ambient temperature and sieved to <2 mm.  The <2-mm fraction of each sample was analysed for a suite of 45 major and trace elements by methods that yield the total or near-total elemental content.  The uniqueness of this project is the determination of major mineralogical components in the samples from the soil A and C horizons by a quantitative X-ray diffraction method using Rietveld refinement.  Sampling in the conterminous United States was completed in 2010, with chemical and mineralogical analyses completed in May 2013. The resulting data set provides an estimate of the abundance and spatial distribution of chemical elements and minerals in soil samples of the conterminous United States and represents a baseline for soil geochemistry and mineralogy against which future changes may be recognised and quantified.  This final report by Smith et al. (2019):  (1) describes the sampling, sample preparation, and analytical methods used; (2) gives details of the quality control protocols used to monitor the quality of chemical and mineralogical analyses over approximately six years, and (3) makes available the soil geochemical and mineralogical data in downloadable tables. 


  • Smith, D.B., Smith S.M., Horton, J.D., 2013.  History and evaluation of national-scale geochemical data sets for the United States. Geoscience Frontiers, 4(2), 167-183;
  • Smith, D.B., Cannon, W.F., Woodruff, L.G., Solano, F., Kilburn, J.E., Fey, D.L., 2013.  Geochemical and mineralogical data for soils of the conterminous United States.  U.S. Geological Survey Data Series 801, 19 pp.;
  • Smith, D.B., Cannon W.F., Woodruff, L.G., Solano, F., Ellefsen, K.J., 2014.  Geochemical and mineralogical maps for soils of the conterminous United States.  U.S. Geological Survey Open-File Report 2014-1082, 386 pp.;
  • Smith, D.B., Solano, Federico, Woodruff, L.G., Cannon, W.F., Ellefsen, K.J., 2019.  Geochemical and mineralogical maps, with interpretation, for soils of the conterminous United States.  U.S. Geological Survey Scientific Investigations Report 2017-5118; [Available as HTML].

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