| Pre-Illinoian | |
|---|---|
| Usage information | |
| Celestial body | Earth |
| Regional usage | Regional |
| Time scale(s) used | North American |
| Definition | |
| Chronological unit | Age |
| Stratigraphic unit | Stage |
The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5β0.2 Ma (million years ago).[1]