Surficial geology of the Woodstock, IL 7.5 minute Quadrangle, Mchenry County, Illinois, scale 1:24,000

Abstract

The surficial geology of the Woodstock 7.5-minute Quadrangle, which is located in the northwest part of the Chicago-Metropolitan Area, was mapped to better address natural resource issues and better understand local geologic history. In the study area, the population is dependent completely upon groundwater for water supplies, and groundwater withdrawals are expected to increase dramatically in coming decades. The landscape and surficial geologic materials in the Woodstock Quadrangle are a result of numerous glaciations during the Quaternary. Surficial sand and gravel deposits, along with buried outwash deposits from older glacial events, constitute important aquifer and aggregate resources for local residents and industry. The landscape within the Woodstock Quadrangle includes glacial moraines, ice-walled lake plains, kettles, incised valleys, and glacial lacustrine deposits. These landforms, coupled with the thick glacial sediments, record a complicated geologic history associated with glacial processes and paleoclimate change. The surficial geologic map of the Woodstock Quadrangle consists of seven lithostratigraphic units associated with the most recent Wisconsinan glaciations in North America. These geologic units include multiple till deposits, outwash sediments, lacustrine sediments, and modern alluvium and peat deposits. This map provides the base geologic knowledge for planners, decision-makers, and other scientists.