PRE-WISCONSIN SPILLWAYS ALONG THE LICKING RIVER-KENTUCKY RIVER DIVIDE, CENTRAL KENTUCKY

Field examination and GIS analysis of digital elevation data have been used to investigate pre-Wisconsin glacial spillways from the Licking River valley in central Kentucky. Pre-Wisconsin glacial ice in the Ohio River Valley impounded the Licking River in central Kentucky, leading to the development of a large lake in the obstructed valley. The lake level would have risen until it reached the lowest point (col) on the valley’s divide, and then spilled over into the Kentucky River valley to the southwest. Extensive lake deposits have been documented in the Licking River basin (e.g. the Claryville Clay). Three primary spillway cols in the Licking-Kentucky divide probably carried all but peak discharge flows. Extreme flows would have led to overtopping of the divide across broader areas, especially near the ice front. Blockage of the Ohio River valley with the ice at the mouth of the Licking River would mean that all flow in the upper Ohio River system upstream of the Licking River would also have to pass over the Licking River spillways.

Spillways near Walton on the Boone-Kenton county line, and north of Sherman in Grant County, are proximal to the ice front and drained water from the Licking River basin into the Eagle Creek valley, a tributary of the modern Kentucky River system. The Camargo-Levee spillway, in Montgomery County, is much wider and funneled water from the Licking River valley into the Kentucky River system. Deposits associated with the Camargo-Levee spillway are geomorphically lower and thus inferred to be younger than the extensive Irvine Formation deposits of the Kentucky River valley (ca. 1.5 Ma model age).

The age of the spillway deposits is constrained as older than Wisconsin glaciation, because Wisconsin ice did not enter the Ohio River valley, and younger than the Irvine Formation deposits in the Kentucky River valley. Previous workers have inferred as many as three pre-Wisconsin glaciations entering the Ohio River valley. This study has thus far been unable to confirm or deny the presence of more than one pre-Wisconsin glaciation in the region or to establish multiple episodes of flow through the spillways.