Английская Википедия:El Paso Formation

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Шаблон:Short description Шаблон:Infobox rockunit

The El Paso Formation is a geologic formation that is exposed from the Permian Basin of New Mexico and Texas to southeastern Arizona. It preserves fossils dating back to the Ordovician period.Шаблон:SfnШаблон:SfnШаблон:Sfn

Description

Файл:Timber mountain.jpg
El Paso Formation forms the lowest part of the massive limestone beds atop Timber Mountain, New Mexico, USA.

The formation is composed of gray cherty dolomite, limestone, and smaller amounts of siltstone.Шаблон:Sfn The formation often has a mottled appearance.Шаблон:Sfn Total thickness is Шаблон:Convert.Шаблон:SfnШаблон:SfnШаблон:Sfn It lies unconformably on the Bliss Formation,Шаблон:SfnШаблон:Sfn the Coronado Sandstone,Шаблон:Sfn or (in the Florida Mountains) Precambrian basement,Шаблон:Sfn and is overlain by the Montoya GroupШаблон:Sfn or Portal Formation.Шаблон:Sfn

Fossils

The formation is only sparsely fossiliferous, but contains fossils of echinoderms, gastropods, trilobites, sponge spicules, and Nuia. Rare ostracods, cephalopods, and brachiopods are also found, as is the trace fossil Planolites. Bioherms up to Шаблон:Convert high are found in the McKelligon Member, built up of siliceous sponges and receptaculitid Calathium.Шаблон:Sfn

History of investigation

The formation was first named by George Burr Richardson in 1904 for exposures in the Franklin and Hueco Mountains. All Ordovician beds of the Franklin Mountains were originally included in the formation.Шаблон:Sfn Richardson later (1908) mapped the formation into the Permian Basin and assigned the upper Ordovician beds to the Montoya Limestone.Шаблон:Sfn In 1965, Zeller divided the formation in southwestern New Mexico into the Sierrita and Bat Cave Members.Шаблон:Sfn Clemons (1991) divided the formation differently, into the Hitt Canyon, Jose, McKelligon, and Padre Members.Шаблон:Sfn

In 1964, R.H. Flowers proposed promoting the El Paso Formation to group rank and recommended several divisions into formations, based largely on biostratigraphy, such as the Big Hatchet Formation, the Cooks Formation, the Florida Mountain Formation, the Scenic Drive Formation, or the Victorio Hills Formation.Шаблон:Sfn However, this has not been widely accepted,Шаблон:SfnШаблон:Sfn and Greg H. Mack rejected both the promotion of the El Paso Formation to group rank and the designation of biostratigraphic zones within the El Paso as formations.Шаблон:Sfn

See also

Шаблон:Portal

Footnotes

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References

Партнерские ресурсы
Криптовалюты
Магазины
Хостинг
Разное

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