Английская Википедия:Bell Ranch Formation
Шаблон:Short description Шаблон:Infobox rockunit The Bell Ranch Formation is a Late Jurassic (Kimmeridgian) geologic formation in eastern and northeastern New Mexico and the western Oklahoma panhandle. Fossil theropod tracks have been reported from the formation.Шаблон:SfnШаблон:Sfn
Description
At the type section near Tucumcari, the formation consists of alternating beds of light gray sandstone and brownish red siltstone. Bed thicknesses vary from Шаблон:Convert, distinguishing the unit from the massive sandstone of the underlying Exeter Sandstone and poorly bedded sediments of the overlying Morrison Formation. Small gypsum nodules are present in the upper beds. Thickness is up to Шаблон:Convert.Шаблон:Sfn Further north, in the valley of the Dry Cimarron, the facies changes to dark mudstone with no cycles and more abundant gypsum. Here the thickness is no more than Шаблон:Convert.Шаблон:Sfn
Fossil content
The formation contains sandy track beds which are "mud-cracked" with finer brownish silty interbeds and an overlying conglomeratic sandstone which fills the mudcracks of the upper bed.Шаблон:Sfn Three trackways of large dinosaurs are present.Шаблон:Sfn
- Ichnofossils
History of investigation
The beds making up the unit were originally assigned to the Wanakah Formation, but were renamed by Griggs and Read in 1959 for exposures at Carpenter's Point, Шаблон:Convert northwest of Tucumcari.Шаблон:Sfn The correlation with the Wanakah is uncertain.Шаблон:Sfn In 1987, Conrad et al. correlated the "brown-silt member" assigned by Baldwin and Muehlberger to the Morrison Formation in the valley of the Dry CimarronШаблон:Sfn to the Bell Ranch Formation.Шаблон:Sfn
In 1992, Anderson and Lucas advocated abandoning the Bell Ranch Formation in favor of the Summerville Formation.Шаблон:Sfn However, this has not be universally accepted.Шаблон:Sfn
See also
References
Bibliography
- Шаблон:Cite web
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- Шаблон:Cite book
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- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
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Further reading
- Английская Википедия
- Jurassic formations of New Mexico
- Geologic formations of Oklahoma
- Jurassic System of North America
- Kimmeridgian Stage
- Sandstone formations
- Siltstone formations
- Ichnofossiliferous formations
- Paleontology in Oklahoma
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- Википедия
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- Статья из Английской Википедии