Interpretation of Sand Layers within a Soil Profile in an Urban Nature Center

This research project examines characteristics and lateral extent of sand layers within a soil profile in a Midwestern, urban nature center. This study investigates the origin of the sand, with a hypothesis that it represents material deposited on glacial till.  Methods used included mapping the lateral and vertical extent of sand within the soil, USDA field textural classification, and microscopy to examine surface texture of the sand grains. An auto-level and stadia rod were used to survey the site and create a map to illustrate the location of the targeted sand layer.  Soil probes were used to retrieve samples to examine soil profiles.  Each profile was analyzed for depth and thickness of soil horizons, color variations, soil texture, and depth to parent material. Glacial till was identified by acid reaction of its calcium carbonate component. Sand within the soil was found in two layers, distinguished by color and depth. Microscopic evaluation showed that the sand particles in both layers were similar in terms of grain size distribution and angularity, however they differed in color. The shallower sand is brown, with organic coatings, while the deeper sand is yellowish-brown due to oxidized iron coatings. Possible origins for the sand include aeolian, fluvial, beach, or human processes. The grain size distribution of the sand in soils at this site indicates transportation and deposition through aeolian processes.