earth science

Pre-Illinoian

Pre-Illinoian is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pre-Illinoian rather than just read about it. In short: The term Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America 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 Pre-Illinoian precedes the Illinoian Stage.

Key takeaways

Pre-Illinoian belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pre-Illinoian to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pre-Illinoian from memory before moving on to harder problems.

Reference excerpt

North America As the oldest stage in the North American regional subdivision of the Quaternary, the Pre-Illinoian precedes the Illinoian Stage. 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 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.

Great Britain 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. The end of the Pre-Illinoian stage has been correlated to the end of Marine Isotope Stage 9 at 300,000 BP. 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.

See also Ice age Glacial period Last glacial period Timeline of glaciation

References

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.

External links Aber, J.S., 2006, Regional Glaciation of Kansas and Nebraska Archived 2008-07-04 at the Wayback Machine, Emporia State University, Emporia, Kansas. anonymous, 1997, 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, 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, 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.

Worked examples

Example 1 — a first encounter with Pre-Illinoian

Start with the simplest possible case. Write down what Pre-Illinoian claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pre-Illinoian before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pre-Illinoian ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pre-Illinoian

In research: Pre-Illinoian appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pre-Illinoian in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pre-Illinoian is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology of Illinois, Glaciology of the United States, Ice ages, so understanding it makes those chapters shorter.
In everyday life: Look for Pre-Illinoian outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Pre-Illinoian in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pre-Illinoian means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pre-Illinoian out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pre-Illinoian in simple terms?

The term Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma (million years ago). North America As the oldest stage in the North American regional subdivision of the Quaternary…

Why does Pre-Illinoian matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pre-Illinoian?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pre-Illinoian.