biology

North Horn Formation

North Horn Formation is a biology 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 North Horn Formation rather than just read about it. In short: The North Horn Formation is a widespread non-marine sedimentary unit with extensive outcrops exposed in central and eastern Utah. The formation locally exceeds 3,600 feet (1,100 m) in thickness and is characterized by fluvial, lacustrine, and floodplain dominated systems, representing a terrestrial, high energy, depositional environment.

Key takeaways

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

Reference excerpt

The North Horn Formation is a widespread non-marine sedimentary unit with extensive outcrops exposed in central and eastern Utah. The formation locally exceeds 3,600 feet (1,100 m) in thickness and is characterized by fluvial, lacustrine, and floodplain dominated systems, representing a terrestrial, high energy, depositional environment. The sediments date from Late Cretaceous (Maastrichtian) to early Paleocene in age and include the K-Pg extinction event boundary; however, this boundary is extremely difficult to locate and there is no strong stratigraphic evidence available that indicates a specific marker bed such as an iridium rich clay layer. Thus far, the only visible evidence is represented in the form of faunal turnover from dinosaur to mammal-dominated fossil assemblages. Taxa from the Cretaceous part of the formation include squamates, testudines, choristoderes, crocodyliforms, sharks, bony fishes, amphibians, mammals, dinosaurs, eggshell fragments, trace fossils, mollusks, plant macrofossils, such as wood fragments, and palynomorphs.

Stratigraphy

The North Horn Formation is a non-marine, stratigraphic unit located in east and central Utah which unconformably overlies the Late Cretaceous Price River Formation west of the San Rafael Swell, and the Tuscher Formation east of the swell. The formation is overlain by the late Paleocene-early Eocene Flagstaff Formation, also called the Flagstaff Limestone. The North Horn type section is located on North Horn Mountain in Emery County, Utah. Laterally, the North Horn Formation nearly spans an 87-mile (140 km) long east–west transect that extends from the Wasatch Plateau on the west and the Book Cliffs, near Green River, on the east, separated in the middle by the San Rafael Swell. The North Horn Formation varies greatly in thickness and lithology, representing a time transgressive stratigraphic sequence, which means that the age of the base and top of the formation changes as one moves laterally. West of the San Rafael Swell, near Price Canyon, Utah, the basal contact for the North Horn Formation is Maastrichtian (latest Cretaceous) in age, whereas its base is Paleocene in age on the eastern side of the swell. Some of the most complete sections of the North Horn Formation are exposed west of the San Rafael Swell at North Horn Mountain in which the local stratigraphy sometimes exceeds 3,600 ft (1,100 m) in thickness. Further to the east, towards Green River, Utah, stratigraphic sections are significantly thinner compared to sections in the west with thicknesses varying between as little as 50 to 130 ft (15 to 40 m).

Subdivisions The formation is divided into three informal units based on broad but distinct lithological characteristics. These units include the lower variegated unit at the base, a middle coal unit (in which the K-Pg boundary is located), and the upper variegated unit at the top. The units themselves are further divided into a total of eight sub-units, or lithofacies, based on facies scale lithological features. A detailed sedimentary study of the North Horn Formation was conducted by Lawton et al. These units, from oldest to youngest, include a 330 ft (100 m) thick basal conglomerate unit that consists of an upward fining conglomerates and sandstone and lacks any interbedded shale, followed by the lower redbed unit, a 790 ft (240 m) thick sequence dominated by red sandy siltstone, conglomerate, and pebbly sandstone. The third unit is the sheet sandstone unit and is composed of sheetlike sandstone beds that are interbedded with gray and carbonaceous siltstones. Some limestone beds are present but are uncommon. The fourth unit is characterized by 131 to 374 ft (40 to 114 m) thick coal beds and coal-streaked siltstone deposits and are referred to as the coal-bearing unit. This unit is overlain by a 833 ft (254 m) thick sequence of primarily calcareous siltstone beds, called the calcareous siltstone unit. The big mountain unit consists of nearly 750 feet (230 m) of interbedded conglomerates and trough cross bedded sandstones, followed by a 200 ft (60 m) thick set of strata composed of sandstone, pebbly sandstone, and conglomerates which make up the coal canyon unit. The uppermost unit is the upper redbed unit, which is nearly a 390 ft (120 m) thick and is composed of red brown mottled siltstone and sandy siltstone.

Paleontology Characteristic dinosaur taxa include the ceratopsian Torosaurus utahensis, the titanosaurian sauropod Utetitan zellaguymondeweyae, and the theropod Tyrannosaurus rex; however, the most frequently occurring taxon in the Cretaceous strata of the North Horn Formation is the lizard Polyglyphanodon. Dinosaur footprints have been found here. Fauna recorded from Paleocene strata within the formation appear to be far more diverse and over 70 different taxa have been identified, including frogs, numerous multituberculate, protoeutherian, periptychid, arctocyonid and phenacodontid mammals, crocodyliforms, choristoderes, trace fossils, and palynomorphs. Marsupial remains similar to Alphadon and Eodelphis have also been found here as well. Pterodactyloid tracks present at an unnamed site. The specimens are kept at the Dinosaur Tracks Museum, of the University of Colorado at Denver. Bird and dinosaur eggs have also been found at the site, along with unidentified hadrosaur fossils (possibly from Edmontosaurus or Kritosaurus).

Fossil content

Tetrapods

Fish

See also List of dinosaur-bearing rock formations Kaiparowits Formation

References

Illustrations

Worked examples

Example 1 — a first encounter with North Horn Formation

Start with the simplest possible case. Write down what North Horn Formation claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 North Horn 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 North Horn 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 North Horn Formation

In research: North Horn Formation appears in biology 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 North Horn 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: North Horn Formation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Coal in the United States, Conglomerate formations of the United States, Cretaceous–Paleogene boundary, so understanding it makes those chapters shorter.
In everyday life: Look for North Horn 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 North Horn Formation in 20 minutes

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

Frequently asked questions

What is North Horn Formation in simple terms?

Why does North Horn Formation matter?

Because it connects several biology 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 North Horn 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 North Horn Formation.