SURFICIAL GEOLOGIC MAP OF THE PONTIAC NORTHEAST 7.5 MINUTE QUADRANGLE IN LIVINGSTON COUNTY, IL, SCALE 1:24,000

The Pontiac Northeast 7.5 Minute Quadrangle (Scale 1:24,000) is located in Livingston County, Illinois. This region contains an assemblage of Quaternary glacial deposits that are exposed along the Vermilion River and its tributaries. Methods used in the preparation of this surficial geologic map were the analysis and conversion of soil survey data, the analysis of LiDAR data and the interpretation of well water logs, and traditional field observations. The surficial geology of the quadrangle is comprised of Quaternary glacial sediment units that were deposited during the Wisconsin episode. Quaternary units include the Equality, Henry, and Lemont Formations as well as the Cahokia Alluvium. The Henry Formation and the Lemont Formation make up the majority of the surficial geology of the Quadrangle with the Henry Formation being in the SW region of the map. The Lemont Formation, is a gray, pebbly silty clay diamicton, which was deposited as a ground moraine. The Henry Formation is a yellow/gray-brown stratified sand to boulder deposit, which is either an outwash plain or valley train deposit. The Equality formation is a yellow-brown sandy silt that was deposited in slackwater or lacustrine environments. The Cahokia Alluvium contains poorly sorted sand, silt and clay sized grains and can be found in abundance along the Wolf Creek, a tributary to the Vermillion River.