The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

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 betw ...

and

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 in ...

periods of

geologic time The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

from ~2.5–0.2 Ma (million years ago).

North America

As the oldest stage in the North American regional subdivision of the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

, the Pre-Illinoian precedes the

Illinoian Stage 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 ...

. 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). 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. 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 Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...

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,

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 ...

s 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.

Great Britain

The Pre-Illinoian stage is contemporary with the Bramertonian,

Pre-Pastonian The Pre-Pastonian Stage or Baventian Stage (from Easton Bavents in Suffolk), is the name for an early Pleistocene stage used in the British Isles. It precedes the Pastonian Stage and follows the Bramertonian Stage. This stage ended 1.806 Ma (millio ...

, Pastonian, Beestonian,

Cromerian The Cromerian Stage or Cromerian Complex, also called the Cromerian (german: Cromerium), is a stage in the Pleistocene glacial history of north-western Europe, mostly occurring more than half a million years ago. It is named after the East Anglian t ...

, Anglian,

Hoxnian __NOTOC__ The Hoxnian Stage was a middle Pleistocene stage (Pleistocene from million to 11,700 years BP) of the geological history of the British Isles. It was an interglacial which preceded the Wolstonian Stage and followed the Anglian Stage. ...

, and lower most

Wolstonian 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 appro ...

stages 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, ...

combined. The end of the Pre-Illinoian stage has been correlated to the end of

Marine Isotope Stage 9 Marine Isotope Stage 9 (MIS 9) is a Marine Isotope Stage in the geological record. It is the final period of the Lower Paleolithic, and lasts from 337,000 to 300,000 years ago according to Lisiecki and Raymo's LR04 Benthic Stack, which has been ad ...

at 300,000 BP.

Lisiecki, L.E. Lorraine Lisiecki is an American paleoclimatologist. She is a professor in the Department of Earth Sciences at the University of California, Santa Barbara. She has proposed a new analysis of the 100,000-year problem in the Milankovitch theory of ...

, 2005
''Ages of MIS boundaries.''
Boston University, Boston, MA

, and M.E. Raymo, 2005, "A Pliocene-Pleistocene stack of 57 globally distributed benthic d18O records", ''Paleoceanography'', vol. 20, PA1003, More recent geologic mapping, coring, and

optically stimulated luminescence In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications: * Luminescence dating of ancient materials: mainly geological sediments and sometimes fired pott ...

(OSL) dating of Illinoian glacial

till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

s (

Glasford Formation 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 ...

) and

outwash An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and ca ...

(

Pearl Formation A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle) of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pearl is composed of calcium carb ...

) of the

Illinoian Glacial Lobe 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 ...

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.

References

External links

*Aber, J.S., 2006
''Regional Glaciation of Kansas and Nebraska''
Emporia State University, Emporia, Kansas. *anonymous, 1997

Work Group on Geospatial Analysis of Glaciated Environments (GAGE), INQUA Commission on Glaciation, Emporia State University, Emporia, Kansas. *anonymous, 2000

Work Group on Geospatial Analysis of Glaciated Environments (GAGE), INQUA Commission on Glaciation, Emporia State University, Emporia, Kansas. *anonymous, 2007

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. {{Continental Glaciations Glaciology of the United States Ice ages Middle Pleistocene Pleistocene geochronology Pleistocene North America Pleistocene United States Geology of Illinois Interglacials

North America

Great Britain

See also

References

Further reading

External links