Pre-Illinoian

As the oldest stage in the North American regional subdivision of the Quaternary, the Pre-Illinoian precedes the Illinoian Stage.{{cite journal|author=Hallberg, G.R.|year=1986|title=Pre-Wisconsin glacial stratigraphy of the Central Plains region in Iowa, Nebraska, Kansas, and Missouri|journal=Quaternary Science Reviews|volume=5|pages=11–15|doi=10.1016/0277-3791(86)90169-1|bibcode=1986QSRv....5...11H}}{{cite journal|author=Richmond, G.M.|author2=D.S. Fullerton|name-list-style=amp|year=1986|title=Summation of Quaternary glaciations in the United States of America|journal=Quaternary Science Reviews|volume=5|pages=183–196|doi=10.1016/0277-3791(86)90184-8|bibcode=1986QSRv....5..183R}} Researchers have identified 11 distinct glacial stages during the Pre-Illinoian Stage.

The Pleistocene prior to the Illinoian stage had previously been subdivided into the Nebraskan, Aftonian, Kansan, and Yarmouthian stages (ages).{{cite book |author=Flint, Richard Foster |title=Glacial Geology And The Pleistocene Epoch |publisher=Lodge Press |year=2008 |isbn=978-1-4437-2173-8 }} However, detailed studies of these stages revealed that the assumptions and criteria on which they were defined proved to be wrong to such a point that these stages became meaningless in terms of the actual glacial–interglacial record.{{cite journal |author=Dort W |title=Nebraskan and kansan stades: complexit and importance |journal=Science |volume=154 |issue=3750 |pages=771–2 |date=November 1966 |pmid=17745986 |doi=10.1126/science.154.3750.771 |bibcode=1966Sci...154..771D |s2cid=2258822 }}{{cite journal|author=Boellstorff, J|year=1978|title=Chronology of some Late Cenozoic deposits from the central United States and the Ice Ages|journal=Transactions of the Nebraska Academy of Science|volume=6|pages=35–49|url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1330&context=tnas|format=pdf|access-date=2012-04-04}}{{cite journal |author=Boellstorff J |title=North American pleistocene stages reconsidered in light of probable pliocene-pleistocene continental glaciation |journal=Science |volume=202 |issue=4365 |pages=305–7 |date=October 1978 |pmid=17817644 |doi=10.1126/science.202.4365.305 |bibcode=1978Sci...202..305B |s2cid=12724466 }}

For example, instead of two glaciations having occurred prior to the Illinoian Stage, researchers found that 11 distinct glaciations had occurred. In addition, what was presumed to have been a single volcanic ash bed, which was used to correlate and differentiate between Kansan and Nebraskan glacial deposits, was found to be three volcanic ash beds of greatly differing ages. Similarly, paleosols used in the definition of the stages were found to have been greatly miscorrelated, as they consisted of paleosols of greatly differing ages. Because of these and other major problems, the concepts on which the Nebraskan, Aftonian, Kansan, and Yarmouthian (Yarmouth) stages are defined were discredited. North American geologists discarded these stages as unusable and merged them into the Pre-Illinoian Stage.{{cite journal|author=Roy, M.|author2=P.U. Clark|author3=R.W. Barendregt|author4=J.R. Glasmann|author5=R.J. Enkin|name-list-style=amp|year=2004|url=http://geo.oregonstate.edu/files/geo/Royetal-GSAB-2004.pdf|title=Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States|journal=Geological Society of America Bulletin|volume=116|issue=1|pages=30–41|doi=10.1130/B25325.1|bibcode=2004GSAB..116...30R|access-date=2012-04-04|archive-url=https://web.archive.org/web/20180928051015/http://geo.oregonstate.edu/files/geo/Royetal-GSAB-2004.pdf|archive-date=2018-09-28|url-status=dead}}

The Pre-Illinoian stage is contemporary with the Bramertonian, Pre-Pastonian, Pastonian, Beestonian, Cromerian, Anglian, Hoxnian, and lowermost Wolstonian stages of the British Isles combined.{{cite web|year=2011|vauthors=Cohen KM, Gibbard PL |url=http://www.quaternary.stratigraphy.org.uk/correlation/POSTERSTRAT_v2011.pdf.20110222-162627 |title=Global chronostratigraphical correlation table for the last 2.7 million years|publisher=University of Cambridge |access-date=2012-04-04}} The end of the Pre-Illinoian stage has been correlated to the end of Marine Isotope Stage 9 at 300,000 BP.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, MALisiecki, 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}} More recent geologic mapping, coring, and optically stimulated luminescence (OSL) dating of Illinoian glacial tills (Glasford Formation) and outwash (Pearl Formation) of the Illinoian Glacial Lobe in North-central Illinois demonstrates that the start of the Illinoian stage and end of the Pre-Illinoian stage correlates with the beginning of Marine Isotope Stage 6 at 191,000 BP.{{cite book|author=McKay, E.D.|year=2007|url=http://ilrdss.sws.uiuc.edu/pubs/govconf2007/session2a/DonMcKay.pdf|chapter=Six Rivers, Five Glaciers, and an Outburst Flood: the Considerable Legacy of the Illinois River|title=Proceedings of the 2007 Governor's Conference on the Management of the Illinois River System: Our continuing Commitment 11th Biennial Conference, Oct. 2-4, 2007|page=11|access-date=2012-04-04}}{{cite journal|url=http://gsa.confex.com/gsa/2008NC/finalprogram/abstract_137641.htm|author=McKay, E.D.|author2=Berg R.C. |year=2008|title=Optical ages spanning two glacial-interglacial cycles from deposits of the ancient Mississippi River, north-central Illinois|journal=Geological Society of America Abstracts with Programs|volume=40|pages=78|access-date=2012-04-04}}{{cite book |editor=Keith C. Hackley |editor2=Kolata, Dennis R. |editor3=Shilts, William W. |editor4=Leighton, Morris W. |editor5=McBride, John |editor6=Sargent, Michael G. |editor7=Thomas G. Hildenbrand |editor8=Donald G. Mikulic |editor9=Joanne Kluessendor |editor10=Rodney D. Norby |editor11=Cheryl K. Nimz |editor12=Joseph A. Devera |editor13=Russell J. Jacobson |editor14=Ardith K. Hansel |editor15=Wang, Hong |editor16=Samuel V. Panno |title=Geology of Illinois |publisher=Illinois State Geological Survey |year=2010 |isbn=978-0-615-41739-4 |author=Hansel, A.K. |author2=E.D. McKay |name-list-style=amp|chapter=Quaternary Period}}

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

{{reflist|30em}}

• 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.

• Aber, J.S., 2006, [http://academic.emporia.edu/aberjame/ice/lec17/lec17.htm Regional Glaciation of Kansas and Nebraska] {{Webarchive|url=https://web.archive.org/web/20080704171916/http://academic.emporia.edu/aberjame/ice/lec17/lec17.htm |date=2008-07-04 }}, Emporia State University, Emporia, Kansas.
• anonymous, 1997, [https://web.archive.org/web/20081230040252/http://www.emporia.edu/earthsci/gage/pre-wisc/gmap0.htm Glacial Map of North-Central United States], Work Group on Geospatial Analysis of Glaciated Environments (GAGE), INQUA Commission on Glaciation, Emporia State University, Emporia, Kansas.
• anonymous, 2000, [https://web.archive.org/web/20080513181655/http://www.emporia.edu/earthsci/gage/pre-wisc/pre-wisc.htm Pre-Wisconsin Glaciation of Central North America], Work Group on Geospatial Analysis of Glaciated Environments (GAGE), INQUA Commission on Glaciation, Emporia State University, Emporia, Kansas.
• 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, [https://web.archive.org/web/20100713231337/http://www.igsb.uiowa.edu/webapps/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, [https://web.archive.org/web/20100713105822/http://www.igsb.uiowa.edu/webapps/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, [https://web.archive.org/web/20100713172100/http://www.igsb.uiowa.edu/webapps/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.

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Category:Glaciology of the United States

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Category:Geology of Illinois

Category:Interglacials