Chon Aike Formation

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Chon Aike Formation
Stratigraphic range: Mid Jurassic-Berriasian
~170–140 Ma
File:El Chalten ignimbrite El Quemado Complex.jpg
Ignimbrite of the El Quemado Complex, uppermost part of the Chon Aike Formation
TypeGeological formation
Unit ofBahía Laura Group
UnderliesLa Matilde & Pampa Rincón Formations
OverliesTobífera Formation
Area~100,000 km2 (39,000 sq mi)
Lithology
PrimaryRhyolites, ignimbrites, lavas
OtherAgglomerates, tuffs
Location
LocationPatagonia
CoordinatesLua error: callParserFunction: function "#coordinates" was not found.
Approximate paleocoordinatesLua error: callParserFunction: function "#coordinates" was not found.
RegionSanta Cruz Province
CountryArgentina
ExtentDeseado Massif & Austral Basin
Type section
Named forCerro Chon Aike

The Chon Aike Formation is an extensive geological formation, present in the Deseado Massif in north-central Santa Cruz Province, Patagonia, Argentina. It covers an area of approximately 100,000 square kilometres (39,000 sq mi) and consists of rhyolitic volcanic rocks, particularly ignimbrites and lavas, with smaller amounts of agglomerates and tuffs.[1] Within dacitic rocks, plant fossils have been found.[2]

Description

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The Chon Aike Formation forms part of the Chon Aike Province, also known as the Tobífera Series, a large igneous province that covers 1,700,000 square kilometres (660,000 sq mi).[3]

The northern part of the formation, Río Pinturas, has been dated to the Late Jurassic (140–160 Ma), while the western and eastern sections have been dated to 162 ± 11 Ma and 168 ± 2 Ma respectively, indicating Middle Jurassic eruptions. Fossil flora, however, suggests a Middle to Late Jurassic age. (See La Matilde Formation.)[4]

During the break-up of Gondwana around 180–165 Ma, the opening of the Weddell Sea lead to extension along the western margin of the South American Plate, resulting in intra-plate volcanism in the Chon Aike area and rifting in the Magallanes Basin.[5] The Chon Aike volcanism was probably related to the subduction of the Pacific Phoenix and Farallon plates.[6]

According to Riley, "Early Jurassic silicic volcanic rocks of the Chon Aike Province (V1: 187-182 Ma) are recognized from many localities in the southern Antarctic Peninsula and northeast Patagonia and are essentially coeval with the extensive Karoo (182 Ma) and Ferrar (183 Ma) large igneous provinces of pre-breakup Gondwana.[7]

See also

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References

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  1. ^ Channing, Zamuner & Zúñiga 2007, Regional geological setting, pp. 401–402
  2. ^ Estancia Bajo Pellegrini at Fossilworks.org
  3. ^ Sruoga, Rubinstein & Hinterwimmer 2004, Geological setting, pp. 32–33
  4. ^ Pankhurst et al. 1998, Chon Aike Formation, pp. 118–119
  5. ^ Franzese et al. 2003, Abstract
  6. ^ Torsvik et al. 2009, 6.1 Jurassic reconstructions (180 and 150 Ma), p. 1325
  7. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).

Bibliography

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Further reading

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  • R. E. Barrio, O.G. Arrondo, A.E. Artabe and B. Petriella. 1982. Estudio geologico y paleontologico de los alrededores de la Estancia Bajo Pellegrini, Provincia de Santa Cruz. Revista del Asociacion Geologica Argentina 37(3):285-299
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