The Bearwallow Mountain Andesite or Bearwallow Mountain Formation is a geologic formation exposed in and around the Mogollon Mountains of southwest New Mexico. It has a radiometric age of 27 to 23 million years, corresponding to the late Oligocene to early Miocene epochs.
| Bearwallow Mountain Andesite | |
|---|---|
| Stratigraphic range: Oligocene to Miocene, | |
| Type | Geologic formation |
| Unit of | Mogollon Group |
| Underlies | Gila Conglomerate |
| Overlies | Bloodgood Canyon Tuff |
| Thickness | 300 m (980 ft) |
| Lithology | |
| Primary | Andesite |
| Other | Basaltic andesite, dacite |
| Location | |
| Coordinates | 33°26′56″N 108°40′08″W / 33.449°N 108.669°W |
| Region |  New Mexico |
| Country |  United States |
| Type section | |
| Named for | Bearwallow Mountain (33°26′56″N 108°40′08″W / 33.449°N 108.669°W) |
| Named by | W.E. Elston |
| Year defined | 1968 |
  Bearwallow Mountain Andesite (the United States)  Bearwallow Mountain Andesite (New Mexico) | |
Description
editThe Bearwallow Mountain Andesite is composed of calc-alkaline volcanic rock ranging from basaltic andesite to dacite, but predominantly andesite. These form a group of low cones or shield volcanoes and range in age from 27 to 23 million years old. Younger basalt flows and silica-rich dacites and rhyolites are excluded from the current definition of the unit.[1]
The formation overlies the Bloodgood Canyon Tuff[2] or eolian sandstones[3] and is in turn overlain by the Gila Conglomerate.[2] It is found throughout the Mogollon-Datil volcanic field as far southeast as the Black Range,[4] and is included in the upper Mogollon Group.[5]
The unit is interpreted as postcaldera volcanism of the Mogollon-Datil volcanic field along faults associated with Basin and Range Province extensional tectonics.[6]
Members
editThe unit is locally separated into lower and upper informal members by interbedded tuffs, such as the rhyolite of Angel Roost.[7]
History of investigation
editThe unit was first defined as the Bearwallow Mountain Formation by W.E. Elston in 1968 as a thick sequence of volcanic flows found in the vicinity of Bearwallow Mountain in the Mogollon Mountains.[8] In 1987, R.F. Marvin and coinvestigators restricted the definition to calc-alkaline andesites and basaltic andesites erupted as low cones or shield volcanoes.[9]
References
edit- ^ Marvin, R.F.; Naeser, C.W.; Bikerman, Michael; Mehnert, H.H.; Ratte, J.C. (1987). "Isotopic ages of post-Paleocene igneous rocks within and bordering the Clifton 1 degree x 2 degrees quadrangle, Arizona-New Mexico". New Mexico Bureau of Mines and Mineral Resources Bulletin. 118: 21–22. Retrieved 18 August 2021.
- ^ a b Reece, C.; Ruiz, J.; Duffield, W.A.; Patchett, P.J. (1990). "Origin of Taylor Creek rhyolite magma, Black range, New Mexico, based on Nd–Sr isotope studies". Geological Society of America Special Paper. 246: 265. ISBN 9780813722467. Retrieved 18 August 2021.
- ^ Cather, S. M.; Connell, S. D.; Chamberlin, R. M.; McIntosh, W. C.; Jones, G. E.; Potochnik, A. R.; Lucas, S. G.; Johnson, P. S. (1 January 2008). "The Chuska erg: Paleogeomorphic and paleoclimatic implications of an Oligocene sand sea on the Colorado Plateau". Geological Society of America Bulletin. 120 (1–2): 13–33. doi:10.1130/B26081.1.
- ^ Fodor, R. V. (1 March 1975). "Petrology of Basalt and Andesite of the Black Range, New Mexico". GSA Bulletin. 86 (3): 298. doi:10.1130/0016-7606(1975)86<295:POBAAO>2.0.CO;2.
- ^ Cather, Steven M.; Chamberlin, R.M.; Ratte, J.C. (1994). "Tertiary stratigraphy and nomenclature for western New Mexico and eastern Arizona" (PDF). New Mexico Geological Society Field Conference Series. 45: 259–266. Retrieved 27 August 2020.
- ^ Bove, Dana J.; Ratté, James C.; McIntosh, William C.; Snee, Lawrence W.; Futa, Kiyoto (December 1995). "The evolution of the Eagle Peak volcano — a distinctive phase of middle miocene volcanism in the western Mogollon-Datil volcanic field, New Mexico". Journal of Volcanology and Geothermal Research. 69 (3–4): 159–186. doi:10.1016/0377-0273(95)00031-3.
- ^ Ratté, James C. (2004). "A guide to the Mule Creek volcanic vent, the rhyolite of Potholes Country, and obsidian ledges, Gila National Forest, southwestern New Mexico" (PDF). New Mexico Geology. 26 (4): 111-122. Retrieved 18 August 2021.
- ^ Elston, W.E. (1968). "Terminology and distribution of ash-flows of the Mogollon-Silver City-Lordsburg region, New Mexico". In Titley, S.R. (ed.). Southern Arizona Guidebook. Vol. III. Arizona Geological Society. pp. 231–240.
- ^ Marvin et al. 1987, pp. 21–22.