GEOPHYSICAL INVESTIGATION OF THE TICONA BURIED BEDROCK VALLEY, MARSEILLES QUADRANGLE, LASALLE COUNTY, ILLINOIS

A geophysical investigation of the Marseilles 7.5’ Quadrangle, 88°45’00” to 88°37’30” west longitude, and 41°15’00” to 44°22’30” north latitude, was completed using shear wave seismology to determine hydrogeologic and geologic parameters of the Ticona Channel. This project is part of the long-term research investigation of the geology of LaSalle County, Illinois by Illinois State University faculty and students. Research is funded by the Illinois Board of Higher Education through the Illinois State Geological Survey, and by a United States Geological Survey EDMAP grant. The Ticona Channel is a buried bedrock valley located in north-central Illinois. Research herein focuses on the headwaters of the Ticona Channel, which diverges from the Illinois River east of Marseilles and trends southwest and west to rejoin the Illinois River near Spring Valley. Seismic profiles were conducted using SH-wave (horizontal shear) reflection techniques. Seven km of data were collected along three north-south trending roads in the southern region of the Quadrangle. Results obtained from the investigation demonstrated the orientation, occurrence of the valley, and geologic control of the valley along the three transects perpendicular to the bedrock valley. Valley infill is composed of sand and gravel deposits of the Pearl Formation, which is overlain by Illinoisan Stage Glasford Formation and Wisconsin Wedron Group tills. SH-wave profiles indicate sand and gravel deposits obtained 50 to 80 ft in thickness within the lowermost terrace of the buried valley. Hydraulic parameters of valley infill were determined in part through the use of well log data compiled by the Illinois State Geological Survey (ISGS).