SURFICIAL GEOLOGIC MAP OF THE DANVERS 7.5 MINUTE QUADRANGLE, MCLEAN AND WOODFORD COUNTY, ILLINOIS

The Danvers Quadrangle is located in McLean and Woodford counties and spans from 40° 30’ to 40° 37’ 30” north latitude and 89° 15’ to 89° 07’ 30” west longitude. This map was prepared using soil maps from the McLean and Woodford County Soil Survey. Parent materials were identified and grouped together, creating formation boundaries. Units had to be at least 2 m in thickness to be mapped. Well data was secured through the Illinois State Geological Survey (125 wells). After boundaries were delineated, a field check was conducted to adjust positions of contact. Quaternary units in excess of 100 m overlie the local bedrock valleys. Major Quaternary units include Cahokia alluvium, the Wedron Group till, the Mason Group glacial outwash, and the Peoria loess. Today, many rivers and streams are still present in the Danvers Quadrangle, and thus Holocene Cahokia alluvium is abundant in less than 5 meters of thickness. The El Paso and Bloomington Moraines are represented by the Wedron Group, which is Tiskilwa till and Lemont formation respectively. These till units consist of pink and grey diamicton units that are interbedded with proglacial river and lake sediments. Henry outwash is a sand/gravel unit of the Mason Group and is found south of the Bloomington Moraine less than 10 meters in thickness. Peoria Silt is fine-grained yellow-orange silt and clay that covers much of the Quadrangle.