Illinoian Stage

The Illinoian Stage is the name used by Quaternary geologists in North America to designate middle Pleistocene glacial and interglacial deposits. It precedes the Wisconsin Stage and follows the Pre-Illinoian Stage in North America. The Illinoian Stage includes two period of glaciation, the early Illinonian and late Illinoian glaciations. The Illinoian Stage, as currently defined, is temporally equivalent to Marine Isotope stages 6, 7, and 8.Johnson, W.H., 1986, Stratigraphy and correlation of the glacial deposits of the Lake Michigan lobe prior to 14 ka BP. Quaternary Science Reviews. vol. 5, pp. 17-22.] Richmond, G.M. and D.S. Fullerton, 1986, "Summation of Quaternary glaciations in the United States of America". Quaternary Science Reviews. vol. 5, pp. 183-196.] Thus, this stage started about 300,000 years ago and ended about 132,000 years ago.Lisiecki, L.E., 2005, [http://www.lorraine-lisiecki.com/LR04_MISboundaries.txt "Ages of MIS boundaries."] [http://www.lorraine-lisiecki.com/stack.html LR04 Benthic Stack] Boston University, Boston, MA] Lisiecki, L.E., and M.E. Raymo, 2005, "A Pliocene-Pleistocene stack of 57 globally distributed benthic d18O records. Paleoceanography." vol. 20, PA1003, doi:10.1029/2004PA001071]

The Illinoian Stage in North America is not an exact equivalent of the Wolstonian Stage of the British Isles. The Wolstonian Stage is equivalent to Marine Isotope stages 6, 7, 8, 9, and 10.McMillan, A.A., 2005, "A provisional Quaternary and Neogene lithostratigraphic framework Great Britain", Netherland Journal of Geosciences. vol. 84, no. 2, pp, 87-107.] Gibbard, P.L., S. Boreham, K.M. Cohen and A. Moscariello, 2007, [http://www.quaternary.stratigraphy.org.uk/correlation/POSTERSTRAT_v2007b_small.jpg"Global chronostratigraphical correlation table for the last 2.7 million years v. 2007b"] , jpg version 844 KB. Subcommission on Quaternary Stratigraphy, Department of Geography, University of Cambridge, Cambridge, England] and, thus, started about 352,000 years ago and ended 132,000 years ago.Lisiecki, L.E., 2005, [http://www.lorraine-lisiecki.com/LR04_MISboundaries.txt "Ages of MIS boundaries."] [http://www.lorraine-lisiecki.com/stack.html LR04 Benthic Stack] Boston University, Boston, MA] Lisiecki, L.E., and M.E. Raymo, 2005, "A Pliocene-Pleistocene stack of 57 globally distributed benthic d18O records. Paleoceanography." vol. 20, PA1003, doi:10.1029/2004PA001071] As a result, the Illinoian Stage is only temporally equivalent to the middle and late Wolstonian Stage in the British Isles. In North America, the term "Wolstonian Stage" is simply not used by geomorphologists and Quaternary geologistsWillman, H.B., and J.C. Frye, 1970, "Pleistocene Stratigraphy of Illinois." Bulletin 94, Illinois State Geological Survey, Champaign, Illinois.] Stiff, B. J., and A.K. Hansel, 2004, "Quaternary glaciations in Illinois." in Ehlers, J., and P.L. Gibbard, eds., pp. 71-82, "Quaternary Glaciations: Extent and Chronology 2: Part II North America", Elsevier, Amsterdam. ISBN 0-444-51462-7] to designate the glacial and interglacial deposits lying between the interglacial Sangamon and Yarmouth Soils (paleosols).

The Illinoian Stage is named for glacial deposits of the Illinoian Glacial Lobe lying between the Sangamon and Yarmouth paleosols. At its type exposure in Peoria County, Illinois, the Illinoian deposits consist of three till members of the Glasford Formation overlying the Pre-Illinoain tills, in which the interglacial Yarmouth Soil (paleosol) is developed, of the Banner Formation. In this exposure, the Illinoian Glasford Formation, in which the interglacial Sangamon Soil (palesosol) is developed, is overlain by early Wisconsin Stage loess, called the Roxana Silt. An interglacial paleosol, the Pike Soil, separates two of the till members within the Glasford Formation.

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.

References

External Links

*anonymous, 2007, [http://www.quaternary.stratigraphy.org.uk/correlation/chart.html "Global correlation tables for the Quaternary"] , Subcommission on Quaternary Stratigraphy, Department of Geography, University of Cambridge, Cambridge, England
*Hallberg, G.R., ed., 1980a, [http://gsbdata.igsb.uiowa.edu/gsbpubs/pdf/TIS-10.pdf "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, [http://gsbdata.igsb.uiowa.edu/gsbpubs/pdf/TIS-11.pdf "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, [http://www.igsb.uiowa.edu/gsbpubs/pdf/GB-03.pdf "Yarmouth Revisited: Midwest Friends of the Pleistocene 27th Field Conference"] , PDF version 4.6 MB. Guidebook no. 3. Iowa Geological Survey Bureau, Ames, IA.

Further reading

*Ehlers, J., and P.L. Gibbard, 2004a, "Quaternary Glaciations: Extent and Chronology 2: Part II North America", Elsevier, Amsterdam. ISBN 0-444-51462-7
*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. ISBN 978-0-444-51471-4
*Mangerud, J., J. Ehlers, and P. Gibbard, 2004, "Quaternary Glaciations: Extent and Chronology 1: Part I Europe", Elsevier, Amsterdam. ISBN 0-444-51462-7
*Sibrava, V., Bowen, D.Q, and Richmond, G.M., eds., 1986, "Quaternary Glaciations in the Northern Hemisphere, Quaternary Science Reviews", vol. 5, pp. 1-514.

ee also

*Ice age
*Glacial period
*Last glacial period
*Timeline of glaciation