Preliminary Sand Map Completed for Bureau County
A preliminary map showing the distribution of wind-blown eolian sand and waterlain outwash sand in Bureau County has recently been completed. Sand and gravel deposits are widespread in northwestern Bureau County, the southern edge of the Green River Lowland, and are also found scattered throughout the rest of the county. They are largely the direct or indirect result of glacial process. Sand dunes formed by wind are prominent landforms in this county. These eolian landforms generally lie above outwash plains, moraines, and terraces. This unique geological setting provides an excellent opportunity to study sand from two different origins: wind-blown eolian sand and waterlain fluvial/glacial outwash sand. Previous differentiation of eolian and outwash sand was at the statewide scale, and this map gives much more detailed information at the county level, helping geologists to better understand the distribution of sand and gravel resources and eolian and glacial/fluvial processes.
Classification of the sand origins was determined using combined data from topography, parent materials of soil reported in the county soil survey, water and related well records, grain size. and carbonate content. For example, the distinct shape of parabolic dunes, shown by the shaded relief map of digital elevation model can be used to classify the area as eolian. Lobe-like sand above the Bloomington Morainic System is clearly eolian, because only eolian sand can climb up on a topographically high moraine. Sediments that contain gravel and are calcareous likely are not eolian in origin.