The
Illinoian Stage is the name used by Quaternary geologists in
North America to designate the period of
geologic time of ~191,000—130,000 years ago, a period of ~ during the middle
Pleistocene when sediments comprising the Illinoian Glacial Lobe were deposited. It precedes the
Sangamonian stage and follows the
Pre-Illinoian Stage in North America. The Illinoian Stage is defined as the period of geologic time during which the
glacial tills and
outwash, which comprise the bulk of the
Glasford Formation, accumulated to create the Illinoian Glacial Lobe.