Submitted to: Geological Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2000
Publication Date: N/A
Technical Abstract: Geochemical investigations are needed to establish background levels of trace metals in soils & soil-parent materials. This information is useful for various agronomic & environmental goals, including the production of abundant, nutritious food. Trace metal concentrations in soils can markedly affect yield & quality of food crops. Some soils require inputs of micronutrient metals to achieve good crop growth while others may contain such large amounts of trace metals that undesirable concentrations are accumulated in edible crops. As an example of the latter, some cultivars of flax, confectionary sunflower, & durum wheat may accumulate undesirable concentrations of cadmium. A major source of trace metals in northern North Dakota soils is Cretaceous shale, which was variably incorporated into the till. Earlier studies of Pleistocene stratigraphy defined two major lithostratigraphic units, the Dahlen & Hansboro, that differed in proportions of shale in the coarse sand fraction. We conducted a reconnaissance survey of trace element concentrations in soils developed on, and crossing the boundary between, borehole locations where these till units were characterized. First, 15 sites were sampled from within 1.5 km of 4 boreholes, to test if the soils formed on the 2 units represented significantly different sampling populations with respect to trace element content. Second, we collected soils along 2 transects, 30 & 57 km long, running between the known sites. About 16 sites were sampled on each transect with 3 subsites per site. Soil was sampled from A, B & C horizons at each subsite. Trace metal content is being evaluated with a chelating extractant (DTPA) to determine if a gradient in mobile & readily-available trace metals exists between the 2 lithostratigraphic units.