Illinoian Stage
Encyclopedia
The Illinoian Stage is the name used by Quaternary geologists in North America
to designate the period of geologic time of ~300,000—130,000 years ago, a period of ~ 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 till
s and outwash, which comprise the bulk of the Glasford Formation, accumulated to create the Illinoian Glacial Lobe.
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
) has developed. In this exposure, the Illinoian Glasford Formation, in which the interglacial
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.
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.
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. 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 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 (paleosol
s).
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.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
to designate the period of geologic time of ~300,000—130,000 years ago, a period of ~ during the middle Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
when sediments comprising the Illinoian Glacial Lobe were deposited. It precedes the Sangamonian stage
Sangamonian Stage
The Sangamonian Stage, also known as the Sangamon interglacial, is the name used by Quaternary geologists to designate the last interglacial period in North America from 125,000—75,000 years ago, a period of...
and follows the Pre-Illinoian Stage in North America. The Illinoian Stage is defined as the period of geologic time during which the glacial till
Till
thumb|right|Closeup of glacial till. Note that the larger grains in the till are completely surrounded by the matrix of finer material , and this characteristic, known as matrix support, is diagnostic of till....
s and outwash, which comprise the bulk of the Glasford Formation, accumulated to create the Illinoian Glacial Lobe.
Definition
At its type exposureType locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
in Peoria County
Peoria County, Illinois
Peoria County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 186,494, which is an increase of 1.7% from 183,433 in 2000. Its county seat is Peoria....
, Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
, the Illinoian deposits consist of three till
Till
thumb|right|Closeup of glacial till. Note that the larger grains in the till are completely surrounded by the matrix of finer material , and this characteristic, known as matrix support, is diagnostic of till....
members of the Glasford Formation. They overlay Pre-Illinoian tills of the Banner Formation, in which the Yarmouth Soil (paleosol
Paleosol
In the geosciences, paleosol can have two meanings. The first meaning, common in geology and paleontology, refers to a former soil preserved by burial underneath either sediments or volcanic deposits , which in the case of older deposits have lithified into rock...
) has developed. In this exposure, the Illinoian Glasford Formation, in which the interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
Sangamon Soil (palesosol) has developed, is overlain by early Wisconsinan stage loess
Loess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...
, called the Roxana Silt. A paleosol, called the Pike Soil, separates two of the till members within the Glasford Formation.
Correlation
Since 1986, the Illinoian Stage has been interpreted as consisting of two glaciations, the early Illinonian (Marine Isotope StageMarine isotope stage
Marine isotope stages , marine oxygen-isotope stages, or oxygen isotope stages , are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples...
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.
However, later studies of the fluvial
Fluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
deposits of the Pearl Formation and Illinoian glacial tills of the Glasford Formation, which fill an ancient and buried Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
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
Optically stimulated luminescence
In physics, optically stimulated luminescence is a method for measuring doses from ionizing radiation.The method makes use of electrons trapped between the valence and conduction bands in the crystalline structure of certain types of matter . The trapping sites are imperfections of the lattice -...
(OSL) dates that averaged 160,000 BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...
. The oldest fluvial sediments, which overlay bedrock in the deepest part of the valley, were dated by OSL dating to around 190,000 BP. 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 of the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
. 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 (paleosol
Paleosol
In the geosciences, paleosol can have two meanings. The first meaning, common in geology and paleontology, refers to a former soil preserved by burial underneath either sediments or volcanic deposits , which in the case of older deposits have lithified into rock...
s).
Extent
During the Illinoian Stage, the Laurentide ice sheetLaurentide ice sheet
The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and...
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, Illinois
Carbondale is a city in Jackson County, in the state of Illinois, within the Southern Illinois region. It is located at the junction of Illinois Route 13 and U.S. Route 51, southeast of St. Louis, Missouri, on the northern edge of the Shawnee National Forest...
. At their maximum extent, the edge of Illinoian ice sheet(s) lay further south than the southernmost extent, i.e. Douglas County, Kansas
Douglas County, Kansas
Douglas County is a county located in northeast Kansas, in the Central United States. As of the 2010 census, the county population was 110,826...
, of any of the Pre-Illinoian ice sheets.
See also
- Bull Lake glaciationBull Lake glaciationThe Bull Lake glaciation is the name of a glacial period in North America that is part of the Quaternary Ice Age. The Bull Lake glaciation began about 200,000 years ago and ended about 130,000 years ago, and was concurrent with the Illinoian Stage of the Quaternary Ice Age...
- Ice ageIce ageAn ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
- Glacial periodGlacial periodA glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate within an ice age...
- Last glacial period
- Timeline of glaciationTimeline of glaciationThere have been five known ice ages in the Earth's history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively...
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
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.