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The '''El Paso Formation''' is a [[Formation (geology)|geologic formation]] that is exposed from the [[Permian Basin (North America)|Permian Basin]] of [[New Mexico]] and [[Texas]] to southeastern [[Arizona]]. It preserves [[fossils]] dating back to the [[Ordovician]] [[Period (geology)|period]].<ref name="richardson-1904">Richardson 1904</ref><ref name="richardson-1906">Richardson 1908</ref><ref name="gillerman-1958">Gillerman 1958</ref>
The '''El Paso Formation''' is a [[Formation (geology)|geologic formation]] that is exposed from the [[Permian Basin (North America)|Permian Basin]] of [[New Mexico]] and [[Texas]] to southeastern [[Arizona]]. It preserves [[fossils]] dating back to the [[Ordovician]] [[Period (geology)|period]].{{sfn|Richardson|1904}}{{sfn|Richardson|1908}}{{sfn|Gillerman|1958}}


==Description==
==Description==
[[File:Timber mountain.jpg|thumb|left|El Paso Formation forms the lowest part of the massive limestone beds atop Timber Mountain, New Mexico, USA.]]
[[File:Timber mountain.jpg|thumb|left|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 (rock)|dolomite]], [[limestone]], and smaller amounts of siltstone.<ref name="drewes-etal-1995">Drewes ''et al.'' 1995</ref> Total thickness is {{convert|137-300|meters|feet}}.<ref name="richardson-1904"/><ref name="drewes-1991"/><ref name="drewes-etal-1995"/> It lies unconformably on the [[Bliss Formation]]<ref name="richardson-1904"/><ref name="drewes-1991">Drewes 1991</ref> or the [[Coronado Sandstone]]<ref name="drewes-etal-1995"/> and is overlain by the [[Montoya Group]]<ref name="richardson-1906"/> or [[Portal Formation]].<ref name="drewes-etal-1995"/>
The formation is composed of gray cherty [[dolomite (rock)|dolomite]], [[limestone]], and smaller amounts of siltstone.{{sfn|Drewes|Du Bray|Pallister|1995}} Total thickness is {{convert|137-300|meters|feet}}.{{sfn|Richardson|1904}}{{sfn|Drewes|1991}}{{sfn|Drewes|Du Bray|Pallister|1995}} It lies unconformably on the [[Bliss Formation]]{{sfn|Richardson|1904}}{{sfn|Drewes|1991}} or the [[Coronado Sandstone]]{{sfn|Drewes|Du Bray|Pallister|1995}} and is overlain by the [[Montoya Group]]{{sfn|Richardson|1908}} or [[Portal Formation]].{{sfn|Drewes|Du Bray|Pallister|1995}}


==Fossils==
==Fossils==
The formation is only sparsely fossiliferous, but contains fossils of [[echinoderm]]s, [[gastropod]]s, [[trilobite]]s, sponge spicules, and ''Nuia''. Rare [[ostracod]]s, [[cephalopod]]s, and [[brachiopod]]s are also found, as is the trace fossil ''[[Planolites]]''. [[Bioherm]]s up to {{convert|6|meters|feet}} high are found in the McKelligon Member, built up of [[siliceous sponge]]s and [[Receptaculites|receptaculitid]] ''Calathium''.<ref name="mack-2004">Mack 2004</ref>
The formation is only sparsely fossiliferous, but contains fossils of [[echinoderm]]s, [[gastropod]]s, [[trilobite]]s, sponge spicules, and ''Nuia''. Rare [[ostracod]]s, [[cephalopod]]s, and [[brachiopod]]s are also found, as is the trace fossil ''[[Planolites]]''. [[Bioherm]]s up to {{convert|6|meters|feet}} high are found in the McKelligon Member, built up of [[siliceous sponge]]s and [[Receptaculites|receptaculitid]] ''Calathium''.{{sfn|Mack|2004}}


==History of investigation==
==History of investigation==
The formation was first named by G.B. Richardson in 1904 for exposures in the Franklin and Hueco Mountains. All Ordovician beds of the Franklin Mountains were originally included in the formation.<ref name="richardson-1904"/> Richardson later (1908) mapped the formation into the [[Permian Basin (North America)|Permian Basin]] and assigned the upper Ordovician beds to the Montoya Limestone.<ref name="richardson-1906">Richardson 1908</ref> In 1965, Zeller divided the formation in southwestern New Mexico into the Sierrita and Bat Cave Members.<ref name="zeller-1965">Zeller 1965</ref> Clemons (1991) divided the formation differently, into the Hitt Canyon, Jose, McKelligon, and Padre Members.<ref name="clemons-1991">Clemons 1991</ref>
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.{{sfn|Richardson|1904}} Richardson later (1908) mapped the formation into the [[Permian Basin (North America)|Permian Basin]] and assigned the upper Ordovician beds to the Montoya Limestone.{{sfn|Richardson|1908}} In 1965, Zeller divided the formation in southwestern New Mexico into the Sierrita and Bat Cave Members.{{sfn|Zeller|1965}} Clemons (1991) divided the formation differently, into the Hitt Canyon, Jose, McKelligon, and Padre Members.{{sfn|Clemons|1991}}


In 1964, R.H. Flowers proposed promoting the El Paso Formation to [[Group (stratigraphy)|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.<ref name="flowers-1965">Flowers 1964</ref> However, this has not been widely accepted,<ref name="hayes-1972">Hayes 1972</ref><ref name="drewes-etal-1995"/> and Greg H. Mack rejected both the promotion of the El Paso Formation to [[Group (stratigraphy)|group]] rank and the designation of [[Biostratigraphy|biostratigraphic zones]] within the El Paso as formations.<ref name="mack-2004"/>
In 1964, R.H. Flowers proposed promoting the El Paso Formation to [[Group (stratigraphy)|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.{{sfn|Flower|1964}} However, this has not been widely accepted,{{sfn|Hayes|1972}}{{sfn|Drewes|Du Bray|Pallister|1995}} and Greg H. Mack rejected both the promotion of the El Paso Formation to [[Group (stratigraphy)|group]] rank and the designation of [[Biostratigraphy|biostratigraphic zones]] within the El Paso as formations.{{sfn|Mack|2004}}


==See also==
==See also==

Revision as of 21:38, 4 March 2021

El Paso Formation
Stratigraphic range: Ordovician
El Paso Formation in road cut near Lake Valley, New Mexico, USA
TypeFormation
Sub-unitsSee text
UnderliesPortal Formation, Montoya Group
OverliesBliss Formation, Coronado Sandstone
Thickness137–300 meters (449–984 ft)
Lithology
PrimaryLimestone, dolomite
OtherSiltstone
Location
Coordinates31°54′N 106°29′W / 31.90°N 106.49°W / 31.90; -106.49
RegionTexas, New Mexico, Arizona
CountryUnited States
Type section
Named forEl Paso, Texas
Named byG.B. Richardson
Year defined1904
El Paso Formation is located in the United States
El Paso Formation
El Paso Formation (the United States)
El Paso Formation is located in New Mexico
El Paso Formation
El Paso Formation (New Mexico)

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.[1][2][3]

Description

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.[4] Total thickness is 137–300 meters (449–984 ft).[1][5][4] It lies unconformably on the Bliss Formation[1][5] or the Coronado Sandstone[4] and is overlain by the Montoya Group[2] or Portal Formation.[4]

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 6 meters (20 ft) high are found in the McKelligon Member, built up of siliceous sponges and receptaculitid Calathium.[6]

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.[1] Richardson later (1908) mapped the formation into the Permian Basin and assigned the upper Ordovician beds to the Montoya Limestone.[2] In 1965, Zeller divided the formation in southwestern New Mexico into the Sierrita and Bat Cave Members.[7] Clemons (1991) divided the formation differently, into the Hitt Canyon, Jose, McKelligon, and Padre Members.[8]

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.[9] However, this has not been widely accepted,[10][4] 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.[6]

See also

Footnotes

  1. ^ a b c d Richardson 1904.
  2. ^ a b c Richardson 1908.
  3. ^ Gillerman 1958.
  4. ^ a b c d e Drewes, Du Bray & Pallister 1995.
  5. ^ a b Drewes 1991.
  6. ^ a b Mack 2004.
  7. ^ Zeller 1965.
  8. ^ Clemons 1991.
  9. ^ Flower 1964.
  10. ^ Hayes 1972.

References

  • Clemons, R.E. (1991). "Petrography and depositional environments of the Lower Ordovician El Paso Formation". New Mexico Bureau of Mines and Mineral Resources Bulletin. 125.
  • Drewes, Harald (1991). "Geologic map of the Big Hatchet Mountains, Hidalgo County, New Mexico". U.S. Geological Survey Miscellaneous Investigations Series. Map I-2144. Retrieved 3 August 2020.
  • Drewes, Harald; Du Bray, E.A.; Pallister, J.S. (1995). "Geologic map of the Portal quadrangle and vicinity, Cochise County, Arizona". U.S. Geological Survey Miscellaneous Investigations Series. Map I-2450. Retrieved 3 August 2020.
  • Flower, R.H. (1964). "The nautiloid order Ellesmeroceratida (Cephalopoda)". New Mexico Bur. Mines and Mineral Resources Mem. 12.
  • Gillerman, Elliot (1958). "Geology of the central Peloncillo Mountains, Hidalgo County, New Mexico, and Cochise County, Arizona". New Mexico Bureau of Mines and Mineral Resources Bulletin. 57.
  • Hayes, P.T. (1972). "Stratigraphic nomenclature of Cambrian and Lower Ordovician rocks of easternmost southern Arizona and adjacent westernmost New Mexico". U.S. Geological Survey Bulletin. 1372-B: B1–B21.
  • Mack, Greg H. (2004). "The late Cambro-Ordovician Bliss and lower Ordovician El Paso Formations, southwestern New Mexico and west Texas". In Mack, G.H.; Giles, K.A. (eds.). The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11. pp. 95–136. ISBN 9781585460106.
  • Richardson, G.B. (1904). "Report of a reconnaissance in Trans-Pecos Texas north of the Texas and Pacific Railway". University of Texas, Mineral Survey Bulletin. 9.
  • Richardson, G.B. (1908). "Paleozoic formations in Trans-Pecos Texas". American Journal of Science, 4th series. 25 (49): 474–484.
  • Zeller, R.A., Jr. (1965). "Stratigraphy of the Big Hatchet Mountains Area, New Mexico". New Mexico Bureau of Mines and Mineral Resources Memoir. 16.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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