earth science

Venado Formation

Venado 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 Venado Formation rather than just read about it. In short: The Venado Formation (Spanish: Formación Venado, Oir) is a geological formation of the Agua Blanca Group, in the Eastern Ranges of the Colombian Andes, cropping out along the Venado River in northern Huila. The sequence of pyrite containing dark grey micaceous shales interbedded with siltstones and sandstones dates to the Ordovician period; Middle to Late Floian epoch, and has a maximum thickness of 670 metres (2,20…

Key takeaways

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

Reference excerpt

The Venado Formation (Spanish: Formación Venado, Oir) is a geological formation of the Agua Blanca Group, in the Eastern Ranges of the Colombian Andes, cropping out along the Venado River in northern Huila. The sequence of pyrite containing dark grey micaceous shales interbedded with siltstones and sandstones dates to the Ordovician period; Middle to Late Floian epoch, and has a maximum thickness of 670 metres (2,200 ft) in the type section. The unit is one of the few Early Paleozoic fossiliferous formations of Colombia; many graptolites of the genus Phyllograptus have been found in the Venado Formation. The graptolites are mostly found in the silty beds and indicative of a fair weather environment on a siliciclastic shallow marine platform at the northern edge of Gondwana. The shallow sea where the Venado Formation was deposited ranged into the deeper cold Iapetus and Rheic Oceans, separating the South American continent of the time from Laurentia, Avalonia and Baltica.

Etymology The formation was first described by Villarroel et al. in 1997 and named after the Venado River, a left tributary of the Cabrera River.

Description

The Venado Formation is one of few Ordovician formations outcropping in Colombia. The formation, part of the Agua Blanca Group, crops out on both banks of the Venado River in El Totumo, a vereda of the municipality Baraya in the department of Huila. The thickness of the Venado Formation proper at its type section is 670 metres (2,200 ft), put in faulted contact with an overlying 30 metres (98 ft) thin unit and an underlying 50 metres (160 ft) sequence. The series is unconformably overlain by the Jurassic Saldaña Formation. The Venado Formation has been correlated to the contemporaneous El Hígado Formation of the Central Ranges in Tarqui.

Lithologies The Venado Formation comprises laminated dark grey micaceous shales, with intercalating siltstone levels and very fine sandstone beds. Calcareous concretions up to 1 metre (3.3 ft) in diameter are present. The shales frequently contain aggregates of pyrite. The formation is heavily folded and in a faulted contact with the Cretaceous Caballos Formation, at time of definition of the Venado Formation considered part of the Villeta Group.

Depositional environment The Venado Formation was deposited in a shallow marine environment, on a siliciclastic platform with persistent normal wave action with repetitive storm wave activity. Anoxic conditions of the shallow sea probably led to the deposition of pyrite. The siltstone layers contain fragmented fossils of graptolites and are probably indicative of a fair weather environment and the coarser sediments resulted from episodic and rhythmic storms.

Paleogeography During the Ordovician, the present-day area of northwestern South America was located in the southern temperate region. The cold Iapetus Ocean to the north of the South American terrane separated the landmass from Laurentia, most of present-day North America. The Rheic Ocean separated South America from the paleocontinents Baltica and Avalonia, that today is part of northeastern North America and northwestern Europe. North of the emerged continent of Gondwana, a shallow sea existed, bordering the Guyana and Brazilian Shields comprising the oldest crustal parts of the current South American continent. During this time in the Ordovician, Gondwana was experiencing an orogeny; the Famatinian orogeny, when the Iapetus Plate was subducting beneath Gondwana.

Fossil content Fossiliferous formations of the Early Paleozoic are rare in Colombia. Apart from the Venado Formation, El Hígado Formation of the Central Ranges also in Huila, has provided fossils dating to the Ordovician, the Cambrian Duda Formation of the Serranía de Macarena in Meta contains fossils of the trilobite Paradoxides, and the westernmost Ordovician unit in Colombia, La Cristalina Formation in the Central Ranges of eastern Antioquia that provided four species of Didymograptus. The formation has provided many fossils of graptolites; the most frequently occurring genus is Phyllograptus. Additionally, Villarroel et al. (1997) reported having found Lingulella sp. and Didymograptus cf. D. artus in the formation. The latter graptolite genus fossils have been assigned rather to Acrograptus filiformis by Gutiérrez Marco in 2006.

Regional correlations

Legend group important formation fossiliferous formation minor formation (age in Ma) proximal Llanos (Medina) distal Llanos (Saltarin 1A well)

See also List of fossiliferous stratigraphic units in Colombia Geology of the Eastern Hills Geology of the Altiplano Cundiboyacense Iscayachi Formation, contemporaneous fossiliferous formation of Bolivia Pircancha Formation, contemporaneous fossiliferous formation of Bolivia San Lorenzo Formation, contemporaneous fossiliferous formation of Bolivia San Juan Formation, contemporaneous fossiliferous formation of Argentina Great Ordovician biodiversification event

Notes

References

Bibliography Borrero, C.; Sarmiento, G.N.; Gómez González, C.; Gutiérrez Marco, J.C. (2007), "Los Conodontos de la Formación El Hígado y su contribución al conocimiento del metamorfismo y la paleogeografía del Ordovícico en la Cordillera Central Colombiana", Boletín de Geología, 29: 39–46, retrieved 2019-03-07 Chernicoff, Carlos J.; Zappettini, Eduardo O.; Santos, João O.S.; Allchurch, Shelley; McNaughton, Neal J. (2010), "The southern segment of the Famatinian magmatic arc, La Pampa Province, Argentina", Gondwana Research, 17 (4): 662–675, Bibcode:2010GondR..17..662C, doi:10.1016/j.gr.2009.10.008, retrieved 2019-03-07 González, Humberto (2001), Mapa Geológico del Departamento de Antioquia - 1:400,000 - Memoria explicativa, INGEOMINAS, pp. 1–120 Moreno Sánchez, Mario; Jesus Gómez Cruz, Arley de; Castillo González, Hardany (2008), "Graptolitos del Ordovícico y geología de los afloramientos del Río Venado (norte del Departamento del Huila)" (PDF), Boletín de Geología, 30: 9–19, retrieved 2019-03-07 Toro Toro, Luz Mary; Moreno Sánchez, Mario; Gómez Cruz, Arley (2014), "Metagabro del Ariarí, plutonismo MORB, Cordillera Oriental de Colombia" (PDF), Boletín de Geología, 36: _, retrieved 2019-03-07 Villarroel A., C.; Macia S., C.; Brieva B, J. (1997), "Formación Venado, nueva unidad litoestratigráfica del Ordovícico colombiano", Geología Colombiana, 22: 41–49, retrieved 2019-03-07

Maps Acosta, Jorge; Caro, Pablo; Fuquen, Jaime; Osorno, José (2002), Plancha 303 - Colombia - 1:100,000, INGEOMINAS, p. 1

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Venado Formation

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

In research: Venado 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 Venado 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: Venado Formation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Floian, Geography of Huila Department, Geologic formations of Colombia, so understanding it makes those chapters shorter.
In everyday life: Look for Venado 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 Venado Formation in 20 minutes

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

Frequently asked questions

What is Venado Formation in simple terms?

Why does Venado 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 Venado 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 Venado Formation.