The Illinoian Stage is the name used by Quaternary geologists in North America to designate the period c.191,000 to c.130,000 years ago, 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 A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...

tills and outwash, which comprise the bulk of the

Glasford Glasford is a village in Peoria County, Illinois, United States. The population was 1,022 at the 2010 census. Glasford is part of the Peoria, Illinois Metropolitan Statistical Area. History Glasford or Glasco as it was called in 1868, was named fo ...

Formation, accumulated to create the Illinoian Glacial Lobe.Willman, H.B., and J.C. Frye, 1970, ''Pleistocene Stratigraphy of Illinois.'' Bulletin no. 94, Illinois State Geological Survey, Champaign, Illinois. It occurs at about the same time as the penultimate glacial period.

Definition

At its type exposure in Peoria County, Illinois, the Illinoian deposits consist of three till members of the Glasford Formation. They overlay Pre-Illinoian tills of the Banner Formation, in which the Yarmouth Soil (

paleosol In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science. In geolo ...

) has developed. In this exposure, the Illinoian Glasford Formation, in which the

interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene i ...

Sangamon Soil (palesosol) has developed, is overlain by early Wisconsinan stage loess, called the Roxana Silt. A paleosol, called the Pike Soil, separates two of the till members within the Glasford Formation.

Substages

The Illinoian Stage is further subdivided into: * the Liman Substage, * the Monican Substage, and * the Jubileean Substage.Ehlers, Jürgen and Gibbard, Philip Leonard (2004) ''Quaternary glaciations: extent and chronology, Part 2: North America'' Elsevier, Amsterdam
page 77

Correlation

Since 1986, the Illinoian Stage has been interpreted as consisting of two glaciations, the early Illinoian (

Marine Isotope Stage Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data f ...

8) and late Illinoian glaciations (Marine Isotope Stage 6) and the intervening interglacial period (Marine Isotope stage 7). In this interpretation, the Pike Soil is proposed to an interglacial (Marine Isotope Stage 7) paleosol. According to this interpretation, the Illinoian Stage started about 300,000 years ago and ended about 130,000 years ago. Lisiecki, L.E., 2005
''Ages of MIS boundaries.''
Boston University, Boston, MA

data: . However, later studies of the fluvial deposits of the Pearl Formation and Illinoian glacial tills of the Glasford Formation, which fill an ancient and buried Mississippi River valley in north-central Illinois, demonstrated that the Illinoian Stage in its type area consists of glaciations that occurred only during Marine Isotope Stage 6. The age of proglacial fluvial sediments underlying the oldest known glacial till ( Kellerville Member) of the Glasford Formation yield optically stimulated luminescence (OSL) dates that averaged 160,000 BP. The oldest fluvial sediments, which overlay bedrock in the deepest part of the valley, were dated by OSL dating to around 190,000 BP.McKay, E.D., 2007
''Six Rivers, Five Glaciers, and an Outburst Flood: the Considerable Legacy of the Illinois River.''
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, 11 p.McKay, E.D., and R.C. Berg, 2008

Geological Society of America Abstracts with Programs, Vol. 40, No. 5, p. 78 wit
Powerpoint presentation
/ref> These OSL dates demonstrate that the Illinoian Stage is temporarily equivalent only to Marine Isotope Stage 6, which ended at 130,000 BP and started at 191,000 BP. If the Illinoian Stage is 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 The Wolstonian Stage is a middle Pleistocene stage of the geological history of Earth from approximately 374,000 until 130,000 years ago. It precedes the Eemian Stage in Europe and follows the Hoxnian Stage in the British Isles. It is also appr ...

of the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

. The Wolstonian stage is equivalent to Marine Isotope stages 6, 7, 8, 9, and 10.Gibbard, P.L., S. Boreham, K.M. Cohen and A. Moscariello, 2007
''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 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 geologistsStiff, 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. to designate glacial deposits and paleosols lying between the Sangamon and Yarmouth soils (

s).

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 Carbondale is a city in Jackson and Williamson Counties, Illinois, United States, within the Southern Illinois region informally known as "Little Egypt". The city developed from 1853 because of the stimulation of railroad construction into the ...

. 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
''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. {{DEFAULTSORT:Illinoian (Stage) Glaciology of the United States Ice ages Middle Pleistocene Pleistocene geochronology Pleistocene North America Pleistocene United States Geology of Illinois