limited in duration to Marine Isotope Stage 6, the Yarmouth Soil (paleosol) spans a period of geologic time equivalent to Marine Isotope stages 7, 8, 9, 10, and 11. The Illinoian Stage in North America is not exactly equivalent to the Wolstonian Stage of the British Isles. The Wolstonian stage is equivalent to Marine Isotope stages 6, 7, 8, 9, and 10. and, thus, started about 352,000 years ago and ended 130,000 years ago. As a result, the Illinoian Stage is only temporally equivalent to either middle and late Wolstonian stage or late Wolstonian stage in the British Isles. In North America, the term "Wolstonian stage" is not used by geomorphologists and Quaternary geologists to designate glacial deposits and paleosols lying between the Sangamon and Yarmouth soils (paleosols). Extent During the Illinoian Stage, the Laurentide Ice Sheet covered about 85 percent of Illinois. At its maximum extent during this stage, this ice sheet reached its southernmost extent in North America near Carbondale, Illinois. At their maximum extent, the edge of Illinoian ice sheet(s) lay further south than the southernmost extent, i.e. Douglas County, Kansas, of any of the Pre-Illinoian ice sheets. See also Wolstonian Stage Bull Lake glaciation Ice age Glacial period Last glacial period Timeline of glaciation References Further reading Ehlers, J., and P.L. Gibbard, 2004a, Quaternary Glaciations: Extent and Chronology 2: Part II North America, Elsevier, Amsterdam. Gillespie, A.R., S.C. Porter, and B.F. Atwater, 2004, The Quaternary Period in the United States. Developments in Quaternary Science no. 1. Elsevier, Amsterdam. Mangerud, J., J. Ehlers, and P. Gibbard, 2004, Quaternary Glaciations: Extent and Chronology 1: Part I Europe, Elsevier, Amsterdam. External links anonymous, 2007, Global correlation tables for the Quaternary, Subcommission on Quaternary Stratigraphy, Department of Geography, University of Cambridge, Cambridge, England Hallberg, G.R., ed., 1980a, Pleistocene stratigraphy in east-central Iowa, PDF version 15.6 MB. Technical information Series. no. 10. Iowa Geological Survey Bureau, Ames, IA. Hallberg, G. R., ed., 1980b, Illinoian and Pre-Illinoian stratigraphy of southeast Iowa and adjacent Illinois, PDF version 19.3 MB. Technical information Series. no. 11. Iowa Geological Survey Bureau, Ames, IA. Hallberg, G. R., T. E. Fenton, T. J. Kemmis, and G. A. Miller, 1980, Yarmouth Revisited: Midwest Friends of the Pleistocene 27th Field Conference, PDF version 4.6 MB. Guidebook no. 3. Iowa Geological Survey Bureau, Ames, IA. Glaciology of the United States Ice ages Middle Pleistocene Pleistocene geochronology Pleistocene North America Pleistocene United