In widely separated areas through southern Illinois are low, elliptical hills of glacial origin. They are in the area of Illinoian glaciation and are somewhat segregated in the western part of the State.
The common occurrence of these hills has instigated recent field studies in south-western Illinois. The elongate drift hills surmount the uplands and are surrounded by wide expanses of the prairie plains. In some instances they are associated with the knolls of eroded moraines. Their long axes parallel approximately the present drainage lines, and, in one or two instances, they are aligned with pre-glacial drainage trends.
Many of the hills show loess and till in the summit slopes and in road cuts. Others exhibit assorted and stratified drift in deeper road cuts, and certain hills apparently contain gravel cores. In many hills till is abundant, but well logs indicate appreciable thicknesses of gravel. The linear pattern of the hills, their subparallel margins, the position on the uplands, and the presence of gravel or a gravel core, together with other salient features, are considered in the paper as evidence supporting a hypothesis of glacial-fluvial origin for at least some of the hills.
- Received 5 July 1939.
- © 1940 Geological Society of America