Analyzing Legacy U.S. Geological Survey Geochemical Databases Using GIS? Applications for a National Mineral Resource Assessment

Legacy geochemical and locality data for 414,304 rock, 397,625 soil and stream sediment, and 335,547 water samples acquired over the 100-year history of the U.S. Geological Survey are digitally compiled in the National Geochemical Database. Upcoming mineral environmental and resource assessments of the Nation will utilize some or all of these data to define geochemically anomalous areas. In such assess- ments it is advantageous to define the watershed from which sediment, soil, and water samples were derived. The goal of this study was to determine the most expedient methods to delineate and display the source catchments and hydrologic contributing areas of geochemically anomalous sediment, soil, and associated rock samples.