Middle Miocene to Oligocene volcanic rocks (AZTv;0)

Middle Miocene to Oligocene volcanic rocks

Lava, tuff, fine-grained intrusive rock, and diverse pyroclastic rocks. These compositionally variable volcanic rocks include basalt, andesite, dacite, and rhyolite. Thick felsic volcanic sequences form prominent cliffs and range fronts in the Black (Mohave County), Superstition, Kofa, Eagletail, Galiuro, and Chiricahua Mountains. This unit includes regionally extensive ash-flow tuffs, such as the Peach Springs tuff of northwestern Arizona and the Apache Leap tuff east of Phoenix. Most volcanic rocks are 20-30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona, but this unit includes some late Eocene rocks near the New Mexico border in east-central Arizona. (11-38 Ma)

State	Arizona
Name	Middle Miocene to Oligocene volcanic rocks
Geologic age	Oligocene to Middle Miocene
Lithologic constituents	Major Igneous > Volcanic > Mafic-volcanic > Basalt (Pyroclastic-tuff) Igneous > Volcanic > Felsic-volcanic > Dacite (Pyroclastic-tuff) Igneous > Volcanic > Mafic-volcanic > Andesite (Pyroclastic-tuff) Minor Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic-tuff)
Stratigraphic units	Peach Springs Tuff, Apache Leap Tuff
References	Richard, S.M., Reynolds, S.J., Spencer, J.E., and Pearthree, P.A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000. Nealey, L.D., and Sheridan, M.F., 1989, Post-Laramide volcanic rocks of Arizona and northern Sonora, Mexico, and their inclusions, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Diges Spencer, J.E., and Reynolds, S.J., 1989, Middle Tertiary tectonics of Arizona and adjacent areas, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Digest 17, p. 539-574.
NGMDB product	NGMDB product page for 34746
Counties	Apache - Cochise - Gila - Graham - Greenlee - La Paz - Maricopa - Mohave - Navajo - Pima - Pinal - Santa Cruz - Yavapai - Yuma

Middle Miocene to Oligocene volcanic rocks

Richard, S.M., Reynolds, S.J., Spencer, J.E., and Pearthree, P.A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.

Nealey, L.D., and Sheridan, M.F., 1989, Post-Laramide volcanic rocks of Arizona and northern Sonora, Mexico, and their inclusions, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Diges

Spencer, J.E., and Reynolds, S.J., 1989, Middle Tertiary tectonics of Arizona and adjacent areas, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Digest 17, p. 539-574.