1Relating to or denoting a Pleistocene glaciation in North America, preceding the Wisconsin and approximating to the Saale of northern Europe.
- ‘These well-drained, sloping soils developed on Illinoian glacial till overlain with loess and have a compact fragipan that restricts root growth.’
- ‘During glacial retreat in the second of three advances, the flat Illinoian till plain was lain down in the lower third of the state north of Shawnee Hills.’
- ‘This preserve is located on a käme (a hill or mound of stratified drift deposited by glacial meltwater) formed during the Illinoian glacial epoch.’
- ‘The Labradorean domain was more extensive in Minnesota and Illinois during the Illinoian glaciation than in the Wisconsinan glaciation.’
- ‘The forest studied in Pike County, Illinois was on Illinoian glacial till in the Glaciated Section of the Mississippi River Border Division.’
- 1.1The Illinoian glaciation or the system of deposits laid down during it.
Mid 19th century: from Illinois + -an.