earth science

Los Adobes Formation

Los Adobes 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 Los Adobes Formation rather than just read about it. In short: Los Adobes Formation is an Early Cretaceous (Aptian) geologic formation in Chubut Province, in the Cañadón Asfalto Basin of central Patagonia, Argentina. The formation belongs to the Chubut Group and represents the Early Cretaceous K1 megasequence in the basin, unconformably overlying the Late Jurassic Cañadón Calcáreo Formation and is overlain by the Albian Cerro Barcino Formation.

Key takeaways

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

Reference excerpt

Los Adobes Formation is an Early Cretaceous (Aptian) geologic formation in Chubut Province, in the Cañadón Asfalto Basin of central Patagonia, Argentina. The formation belongs to the Chubut Group and represents the Early Cretaceous K1 megasequence in the basin, unconformably overlying the Late Jurassic Cañadón Calcáreo Formation and is overlain by the Albian Cerro Barcino Formation. Los Adobes Formation was deposited in an alluvial to fluvial environment and the mudstones of the overall sandy and conglomeratic unit have provided fossils of a chelid turtle whose indeterminate remains were described by Sterli et al. in 2020.

Description

Los Adobes Formation, the lower unit in the Chubut Group was first described in 1970 by Tasch and Volkheimer. The formation underlies the Cerro Barcino Formation and unconformably overlies the Late Jurassic Cañadón Calcáreo Formation. The formation crops out in the southern Cañadón Asfalto Basin, south of the North Patagonian Massif until the Meseta de Canquel. In the Sierra de Traquetrén, in the extreme northwest of the Cañadón Asfalto Basin, Los Adobes Formation has been thrusted onto the Maastrichtian Paso del Sapo Formation. The formation is absent in the Cañadón del Zaino around Cerro Baya and Gastre, where the Early Jurassic Las Leoneras and Lonco Trapial Formations as well as the Middle Jurassic Cañadón Asfalto Formation crop out. The oldest overlying formations in this area are the Neogene La Pava and Cráter Formations.

Geologic framework During the late Early Cretaceous, the Cañadón Asfalto Basin was a back-arc basin with thinned underlying crust. The subduction of the Chasca and Catequil Plates, forerunners of the Farallones Plate, caused volcanic activity in the present Andean terrain represented by the Divisadero Group in Chile. Los Adobes Formation represents the K1 megasequence in the basin history, following the Jurassic megasequences when the depocenter of the basin was deeper.

Lithology and depositional environment The formation comprises mudstones, sandstones and conglomerates, deposited in a terrestrial alluvial to fluvial environment. Paleocurrent analysis of the sediments suggest a transport direction towards the south and east. Los Adobes Formation is correlated with the Pozo D-129 Formation of the Golfo San Jorge Basin to the south. The basal part of Los Adobes Formation is irregular, covering the Jurassic sediments in small depocenters. The maximum noted thickness is 700 metres (2,300 ft). The formation shows progressive unconformities that show up in seismic sections as onlap structures.

Age U-Pb dating of the formation has provided ages ranging from 118 to 114 Ma. At this time, during the Aptian extinction events (~117-116 Ma) and the opening of the South Atlantic, the Neuquén Basin to the northwest was experiencing the Middle Mirano unconformity, dated at 117 Ma and separating the contemporaneous Huitrín Formation.

Fossil content The formation has provided fossils of an inderminate chelid turtle.

See also Aptian formations Paja Formation, contemporaneous fossiliferous formation of the Altiplano Cundiboyacense, Colombia Caiuá Formation, contemporaneous fossiliferous formation of the Paraná Basin, Brazil Crato Formation, contemporaneous fossiliferous formation of the Araripe Basin, Brazil Agrio and La Amarga and Lohan Cura Formations, contemporaneous fossiliferous formations of the Neuquén Basin Río Belgrano Formations, contemporaneous fossiliferous formation of the Magallanes or Austral Basin

References

Bibliography Geology Echaurren González, Andrés (2017), Evolución tectónica del sistema orogénico Andino en la Patagonia norte (42-44° S) (PhD thesis) (PDF), Universidad de Buenos Aires, pp. 1–170, retrieved 2019-02-27 Di Pietro, Pablo Federico (2016), Geología de la zona del Cerro Bayo, Bajo de Gastre, Provincia de Chubut (B.S. thesis) (PDF), Universidad de Buenos Aires, pp. 1–107, retrieved 2019-02-27 Figari, Eduardo G.; Scasso, Roberto A.; Cúneo, Rubén N.; Escapa, Ignacio (2015), "Estratigrafía y evolución geológica de la Cuenca de Cañadón Asfalto, Provincia del Chubut, Argentina" (PDF), Latin American Journal of Sedimentology and Basin Analysis, 22: 135–169, retrieved 2018-09-10 Leanza, Héctor A (2005), "Las principales discordancias del Jurásico Superior y el Cretácico de la Cuenca Neuquina", Anales de la Academia Nacional de Ciencias Exactas, Físicas y Naturales, 57: 147–155, retrieved 2019-02-14 Paleontology Sterli, Juliana; Vlachos, Evangelos; Krause, Marcelo; Puerta, Pablo; Oriozabala, Carolina (2021), "Contribución a la Diversidad del Registro Fósil de Tortugas (Testudinata) de la Provincia de Chubut (Argentina) y Su Significado en la Comprensión de la Evolución de las Tortugas en el Sur de Sudamérica", Publicación Electrónica de la Asociación Paleontológica Argentina, doi:10.5710/PEAPA.26.02.2021.338

Worked examples

Example 1 — a first encounter with Los Adobes Formation

Start with the simplest possible case. Write down what Los Adobes 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 Los Adobes 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 Los Adobes 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 Los Adobes Formation

In research: Los Adobes 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 Los Adobes 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: Los Adobes Formation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alluvial deposits, Aptian Stage, Cañadón Asfalto Basin, so understanding it makes those chapters shorter.
In everyday life: Look for Los Adobes 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 Los Adobes Formation in 20 minutes

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

Frequently asked questions

What is Los Adobes Formation in simple terms?

Why does Los Adobes 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 Los Adobes 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 Los Adobes Formation.