GEOLOGIC MAP OF THE 7.5 MINUTE ROANOKE QUADRANGLE IN WOODFORD COUNTY, ILLINOIS

This study involved the construction of a geologic map of the Roanoke 7.5 minute quadrangle in Woodford County at a scale of 1:24,000. This area contained sections of the Eureka Moraine which is included in the Wisconsin glacier event. Methods used to construct this mapping area included using soil data from soil survey, well data, as well as LiDAR data. There were four major sediment formations that were found at the subsurface in the Roanoke quadrangle. The formations include the Cahokia Alluvium, the Wedron Group (Lemont Formation), The Henry Formation, and finally the Peoria formation. The Cahokia Alluvium consisted of interbedded sand, silt, clay, and gravel that were deposited by glacial loess. Alluvium is found along the river systems including West Branch Panther Creek. The Wedron Group consist of the Tiskilwa and Lemont formations but only the Lemont formation is found in the subsurface of the Roanoke quadrangle. The Lemont formation is a diamicton that ranges from blue to brown clay and is interpreted as a of silt loam. The Henry formation consists of an interbedded sand, gravel, and silt. This is interpreted as a glaciofluvial, and was formed when the melting of glaciers carried the deposits downstream. Finally the Peoria formation has been described as a light tan or brown silt to sandy silt eolian deposits.