MINNESOTA GEOLOGICAL SURVEY GEOCHEMICAL MAPPING

The Minnesota Geological Survey (MGS) conducts mapping and research while also working with partners to ensure the availability of the regional geological, geophysical, and geochemical information that the people of the State require to ensure wise stewardship of their water, land, and mineral resources. Systematic, statewide geochemical mapping is seen an as essential component of this activity. While awaiting the new, much-anticipated, USGS-led, all-soil national geochemical survey, MGS has compiled available statewide data, while also carrying out an indicator mineral survey for the whole state. Three geochemical datasets, for soil, soil parent materials, and groundwater were assembled as a basis for an atlas that is now providing an objective overview of patterns, and serving as a reference that will place local and site-scale environmental geochemical surveys into a context. Available USGS soil data also included analyses of previously collected stream sediments in the western part of the state. Soil parent material data are from sites underlain by till, sampled by MGS for indicator mineral purposes. Groundwater sampling by Minnesota Pollution Control Agency was from multiple aquifers utilized for drinking water, at greatly varying depth and geology. Atlas pages were prepared for each variable, with maps for each sampling medium on a single page, along with a generalized explanation. Maps, a poster, an explanation, and the data are available from the Minnesota Geological Survey web site. The chemistry of calcareous soils in northwestern and central regions, for example, differs starkly from the noncalcareous soils in the northeast, while elements such as arsenic and cadmium are elevated in the west, apparently due to shale and other factors.