The 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 unit is locally separated into lower and upper informal members by interbedded tuffs, such as the rhyolite of Angel Roost.[7]
History of investigation
The 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]
^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.
^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.
^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.
