earth science

Mahantango Formation

Mahantango Formation 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 Mahantango Formation rather than just read about it. In short: The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania.

Key takeaways

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

Reference excerpt

The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Group, along with the underlying the Marcellus Formation Shale. South of Tuscarora Mountain in south central Pennsylvania, the lower members of this unit were also mapped as the Montebello Formation. Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.

Description The Mahantango Formation is a gray, brown, and olive siltstone and shale, characterized by coarsening-upward cycles.

Stratigraphic setting

The Mahantango Formation is typically found conformably overlying the Marcellus Formation, and underlying the Tully Limestone (where present). The Mahantango has been divided into four members:

Tully Limestone: a fossiliferous calcareous shale. The Tully is a conspicuous formation, which separates the Mahantango from the Hamilton Group. Sherman Ridge: Olive gray, fossiliferous, claystone and siltstone with interbedded fine sandstone coarsening upward. Montebello Sandstone: Olive gray, fossiliferous, coarse to fine-grained sandstone, interbedded with siltstone and claystone, in coarsening upward cycles. Fisher Ridge (also described as the Dalmatia and Turkey Ridge): silty claystone, siltstone, and very fine-grained sandstone. The Sherman Ridge and Fisher Ridge are ridge-formers. In south-central Pennsylvania, the Mahantango includes the Clearville, Frame, Chaneysville, and Gander Run Members.

Fossils

There are numerous marine fossils found in the Mahantango including brachiopods, crinoids, trilobites, bivalves, and bryozoans.

Brachiopods Athyris Chonetes Mucrospirifer Protoleptostrophia Tropidoleptus

Crinoids Ancyrocrinus

Trilobites Basidechenella Dipleura Eldredgeops (formerly Phacops) Greenops

Bivalves Actinodesma Grammysioidea Grammysia Leiopteria Modiomorpha Nuculites Orthonota

Bryozoa Atactotoechus furcatus

Coral Pleurodictyum Thamnoptychia (Trachypora)

Gastropods Bembexia Crenistriella Dictyotomaria? Glyptotomaria Loxonema Paleozygopleura Platyceras

Cephalopods Tornoceras Agoniatites Spyroceras Michelinoceras Bactrites Striacoceras Koenenites?

Age Relative age dating of the Mahantango places it in the Middle Devonian period, being deposited between 392 and 385 (±3) million years ago. It rests conformably atop the Marcellus Formation shale. Its upper contact is also conformable to the Trimmers Rock Formation and Harrell Shale. In 2012, Read and Erikson reported the formation as Givetian in Virginia.

Interpretation of depositional environments The Mahantango represents a terrestrial to marine transition zone that went through many transgressive-regression sequences. The fine-grained rocks represent a shallow sea environment and accounts for many of the fossils. Coarser grained sediments represent near-shore environments, beaches, or possibly delta lobes. These environments were tide-dominated and often had violent storms. The Montebello Sandstone member is an example of a storm dominated rock unit. Brachiopod fossils are scattered in massive sandstone beds throughout the rock unit, while the Sherman Ridge member is more laminated with fossilized ripple marks often indicating tidal current directions.

Illustrations

Worked examples

Example 1 — a first encounter with Mahantango Formation

Start with the simplest possible case. Write down what Mahantango Formation 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 Mahantango Formation 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 Mahantango Formation 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 Mahantango Formation

In research: Mahantango Formation 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 Mahantango Formation 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: Mahantango Formation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Beach deposits, Cliff-formers, Deltaic deposits, so understanding it makes those chapters shorter.
In everyday life: Look for Mahantango Formation 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 Mahantango Formation in 20 minutes

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

Frequently asked questions

What is Mahantango Formation in simple terms?

Why does Mahantango Formation 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 Mahantango Formation?

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 Mahantango Formation.