Tralcán Formation

Last updated
Tralcán Formation
Stratigraphic range: Rhaetian
Type Geological formation
Underlies Quaternary glacial deposits
Overlies Trafún Metamorphic Complex
Thickness>800 m (2,600 ft)
Lithology
Primary Conglomerate, sandstone, mudstone
Other Shale
Location
Coordinates 39°48′S72°30′W / 39.8°S 72.5°W / -39.8; -72.5 Coordinates: 39°48′S72°30′W / 39.8°S 72.5°W / -39.8; -72.5
Region Los Ríos Region
CountryFlag of Chile.svg  Chile
Type section
Named for Tralcán
Named byAguirre & Levi
Year defined1964
Relief Map of Chile.jpg
Pink ff0080 pog.svg
Tralcán Formation (Chile)

Tralcán Formation (Spanish : Formación Tralcán) is a sedimentary formation of Triassic age located in Los Ríos Region in south–central Chile. It overlies unconformably the Trafún Metamorphic Complex. Tralcán Formation and nearby Panguipulli Formation form possibly the remnants of an ancient lake and river system. The formation is named after Mount Tralcán on the western edge of Riñihue Lake. [1]

Spanish language Romance language

Spanish or Castilian, is a Western Romance language that originated in the Castile region of Spain and today has hundreds of millions of native speakers in the Americas and Spain. It is a global language and the world's second-most spoken native language, after Mandarin Chinese.

Sediment Particulate solid matter that is deposited on the surface of land

Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation and if buried, may eventually become sandstone and siltstone.

The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.

Contents

Description

The Tralcán Formation was first defined by Aguirre and Levi in 1964, based on the outcrop at Tralcán. The more than 800 metres (2,600 ft) [1] thick formation comprises reddish-grey conglomerates with a sandy matrix and intercalated reddish shales. The shales of the formation contain abundant fossil flora. Fossils of Cladophlebistenia oeshi have helped to redefine the age of the formation, that was formerly considered Late Jurassic (Kimmeridgian to Tithonian), to the Rhaetian of the Triassic. [2]

Outcrop visible exposure of bedrock or ancient superficial deposits on the surface of the Earth

An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth.

Conglomerate (geology) A coarse-grained clastic sedimentary rock with mainly rounded to subangular clasts

Conglomerate is a coarse-grained clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts, e.g., granules, pebbles, cobbles, and boulders, larger than 2 mm (0.079 in) in diameter. Conglomerates form by the consolidation and lithification of gravel. Conglomerates typically contain finer grained sediment, e.g., either sand, silt, clay or combination of them, called matrix by geologists, filling their interstices and are often cemented by calcium carbonate, iron oxide, silica, or hardened clay.

Sand A granular material composed of finely divided rock and mineral particles, from 0.063 to 2 mm diameter

Sand is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass.

Fossil content

The following genera of fossil flora have been identified in the formation: [1]

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

<i>Asterotheca</i> genus of plants

Asterotheca is a genus of seedless, spore-bearing, vascularized ferns dating from the Carboniferous of the Paleozoic to the Triassic of the Mesozoic.

<i>Cladophlebis</i> genus of plants

Cladophlebis is an extinct genus of fern which grew during the late Paleozoic and Mesozoic eras. It was a common plant during that time in both the northern and southern hemispheres, and belonged to the order of plants called Filicales.

<i>Dicroidium</i>

Dicroidium is an extinct genus of fork-leaved seed ferns that were distributed over Gondwana during the Triassic. Their fossils are known from South Africa, Australia, New Zealand, South America and Antarctica. They were first discovered in Triassic sediments of Tasmania by Morris in 1845. Fossils from the Umm Irna Formation in Jordan indicate that these plants already existed in Late Permian.

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References

  1. 1 2 3 Herbst et al., 2005
  2. Di Biase & Lillo, 1973, p.12

Bibliography

Ameghiniana is a peer-reviewed scientific journal covering palaeontology published by the Asociación Paleontológica Argentina. It is named after the 19th century Italian Argentine palaeontologist Florentino Ameghino. The discovery of many dinosaurs found in Argentina and South America have first been published in Ameghiniana; examples of this are Argentinosaurus and Herrerasaurus.