earth science

Sangamonian

Sangamonian 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 Sangamonian rather than just read about it. In short: The Sangamonian Stage (or Sangamon interglacial) is the term used in North America to designate the Last Interglacial (130,000-115,000 years ago) and depending on definition, part of the early Last Glacial Period, corresponding to Marine Isotope Stage 5 (~130-80,000 years ago). While often historically considered equivalent in scope to MIS 5, it is now often used in a more narrow sense to refer to the Last Interglac…

Key takeaways

Sangamonian 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 Sangamonian to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sangamonian from memory before moving on to harder problems.

Reference excerpt

The Sangamonian Stage (or Sangamon interglacial) is the term used in North America to designate the Last Interglacial (130,000-115,000 years ago) and depending on definition, part of the early Last Glacial Period, corresponding to Marine Isotope Stage 5 (~130-80,000 years ago). While often historically considered equivalent in scope to MIS 5, it is now often used in a more narrow sense to refer to the Last Interglacial only (corresponding to MIS 5e and the European Eemian). It preceded the Wisconsinan (Wisconsin) Stage and followed the Illinoian Stage in North America.

Definition The Sangamonian Stage, originally the Sangamon interglacial stage, is defined on the basis of the Sangamon Soil, a paleosol, which is developed in contemporaneous colluvium and older glacial tills and loesses and overlain by Wisconsinan loesses or tills. Although originally described from water wells in northwestern Sangamon County, Illinois, the current type sections for the Sangamon Stage are the Rochester section in eastern Sangamon County and the Chapman section in Morgan County, Illinois. In the Rochester Section, the Sangamon Soil is developed in Sangamonian colluvial sediments, called “accretion gley”, that accumulated contemporaneously with the development of the Sangamon Soil. In the Rochester section, the Sangamon Soil is developed directly in Illinoian glacial till and overlain by Roxana Silt, the oldest of the two regional Wisconsinan loesses.

Correlations In its typical and broadest usage, the Sangamonian Stage is equivalent to all of Marine isotope stage 5 between 75,000 and 125,000 BP. Although it includes the same time span, the Sangamonian Stage (sensu lato) is not temporally equivalent to the Eemian in Europe. In its much less common usage, the Sangamonian Stage (sensu stricto) is equivalent to Marine Isotope Substage 5e and the Eemian. In case of this usage, Marine Isotope Substages 5a, 5b, 5c, and 5d are collectively referred to as the Eowisconsinan Stage. In its broadest sense (sensu lato), the Sangamonian Stage precedes the Wisconsinan (Wisconsin) Stage and follows the Illinoian Stage in North America. Research concerning the age and degree of development of the Sangamon Soil demonstrates that it actively developed, at the least, over all of Marine Isotope Stage 5, which is a period of time from 125,000 to 75,000 BP. Unlike Europe, the development of ice sheets in Canada was limited during Marine Isotope Substages 5b, 5c, and 5b and either completely disappeared or were greatly reduced in size during Marine Isotope Substage 5a. Because of the continuous development of the Sangamonian Soil in the Midwest and the limited development of ice sheets in North America during this marine isotope stage, the Sangamonian Stage, unlike the Eemian in Europe, is regarded as encompassing all of Marine Isotope Stage 5.

Dates The start of the Sangamonian Stage is constrained by optically stimulated luminescence (OSL) dates obtained from 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. The age of fluvial sediments overlying the youngest glacial till (Radnor Member) of the Glasford Formation yield optically stimulated luminescence (OSL) dates that averaged 131,000 BP. These OSL dates demonstrate that the Illinoian Stage ended and the Sangamonian Stage started about 125,000 BP. These dates refute older dates, i.e. between 220,000 and 450,000 BP, given by older publications for the start of the Sangamonian Stage.

Events The steppe bison (Bison priscus) migrated into the heartlands of North America from Alaska at the beginning of the Sangamonian, giving rise to the giant long-horned bison Bison latifrons (which is first known from the Snowmass site in Colorado, dating to around 120,000 years ago) and ultimately all North American bison species, and marking the beginning of the Rancholabrean faunal age in North America. Also in the Sangamonian the American lion (Panthera atrox) appeared and become widespread across North America, having descended from populations of the Eurasian cave lion (Panthera spelaea) that had migrated into Alaska during the preceding Illinoian.

Worked examples

Example 1 — a first encounter with Sangamonian

Start with the simplest possible case. Write down what Sangamonian 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 Sangamonian 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 Sangamonian 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 Sangamonian

In research: Sangamonian 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 Sangamonian 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: Sangamonian is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology of Illinois, Glaciology of the United States, Interglacials, so understanding it makes those chapters shorter.
In everyday life: Look for Sangamonian 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 Sangamonian in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sangamonian 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 Sangamonian out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sangamonian in simple terms?

Why does Sangamonian 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 Sangamonian?

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 Sangamonian.