North-Central Section - 42nd Annual Meeting (24–25 April 2008)

Paper No. 1
Presentation Time: 1:00 PM-5:00 PM


FORD, Elizabeth, Geology, Augustana College, 639 39th St, Rock Island, IL 61201,

Duck Creek is a small tributary of the Mississippi River that lies along the southeastern border of Scott County, Iowa. Despite excellent exposures of Devonian and Pennsylvanian bedrock in the lower 2.5 km of the creek, there is a paucity of published work concerning the geology of the area. The purpose of this project is twofold: 1) to map the exposures of bedrock units, locating, as accurately as possible, the contacts between units; and 2) determine locations where shale outcrops create unstable hill slopes, susceptible to mass wasting.

The Iowa state geologic map requires a slight update to the contact between the Devonian Wapsipinicon Group and the Pennsylvanian Cherokee Group. The contact identified within the study area shifts the previously known contact about 1 km west. ArcGIS is being used to create a geologic map of the area which will be submitted to the Iowa Geological Survey for processing.

The slopes overlying the Pennsylvanian System in the far western portion of the study area show signs of hummocky topography and possible ponded water. The tops of these slopes have been manipulated to allow houses to be built. Samples of the shallow subsurface will be analyzed for blue clay, which typically weathers from Pennsylvanian shale. A high-resolution DEM is being made from recently acquired LIDAR data for Scott County in order to highlight areas at risk of possible slope movement.