THE TICONA CHANNEL, A POSSIBLE SUB-ICE TUNNEL VALLEY

The Ticona Channel in north central Illinois is a relatively narrow deep bedrock valley with few recognizable tributaries. In 1940 Bo Willman and again in 1950, Leland Horberg interpreted the channel to be a tributary to the Ancient (preglacial) Mississippi River, joining the Ancient Mississippi River where it changes from flowing southeasterly to southwesterly as it encountered the west flank of the LaSalle Anticlinorium. The age of the channel has remained a question. Was it a preglacial stream or did it originate during one of several glacial advances into Illinois. An interesting observation is that as a preglacial channel it would drain to the west, opposite the regional dip of the anticlinorium and the generally easterly slope of the top of bedrock. Recent high-resolution, shear wave seismic profiles across the channel revealed steep valley walls. The channel is filled with glacial diamicts overlying coarse grainular sediments. A core from a scientific borehole located along one of the seismic lines revealed Wedron (Wisconsin Episode) and Glasford (Illinois Episode) formation tills (total of about one hundred and twenty-five feet) above about seventy-five feet of sand and gravel. It is hypothized that the Ticona Channel originated as a consequent stream draining eastward, down the regional dip. During the Illinois Episode, as ice advanced from the northeast, up the regional gradient and dip, the Ticona Channel was deepened as a sub-ice tunnel valley, and its flow reversed as subglacial water flowed westward into the Ancient Mississippi River Valley.