Surficial geology of the Saybrook 7.5-minute Quadrangle, Mclean County, Illinois, USA

Abstract

This project involved the construction of a surficial (Quaternary) geologic map of part of McLean County, Illinois. The Saybrook 7.5-minute Quadrangle (scale 1:24,000) was the focus area. The quadrangle largely covers rural agricultural land, but also contains the small town of Saybrook. Multiple, major episodes of glaciation over the past 1,200,000 years have controlled the regional geologic history. The most recent (Wisconsin Episode) glaciation almost exclusively shaped the observed surficial geologic and geomorphic features in the quadrangle. Field observations, USDA soil survey data, private water well data, sparse stratigraphic borehole information, and LIDAR elevation data were used to construct the map. Computational methodologies included ACD Systems Canvas™ and Adobe Acrobat™ software. The surficial geologic map includes four lithostratigraphic units. In stratigraphic order (from oldest to youngest) are the Delavan Member, Tiskilwa Formation, Batestown Member, Lemont Formation, Henry Formation, and Cahokia Formation.

Keywords

• Surficial geologic map
• Illinois
• Quaternary
• Saybrook
• Wedron Group
• Henry Formation