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Infiernito caldera volcanic rocks including Capote Mountain Tuff, Tsh2 of Shely Group, Buckshot Ignimbrite, and Tm1 of Morita Ranch Formation

Infiernito caldera volcanic rocks including Capote Mountain Tuff, Tsh2 of Shely Group, Buckshot Ignimbrite, and Tm1 of Morita Ranch Formation
StateTexas
NameInfiernito caldera volcanic rocks including Capote Mountain Tuff, Tsh2 of Shely Group, Buckshot Ignimbrite, and Tm1 of Morita Ranch Formation
Geologic agePhanerozoic | Cenozoic | Tertiary | Eocene-Late
Original map labelEin
CommentsPresent in Presidio Co.,TX. From older to younger--precollapse rhyolitic to trachytic lavas, Infiernito Tuff--a rhyolitic, thick intracaldera and thin outflow ash-flow tuff and interbedded caldera-collapse breccia, post-collapse lavas--coarsely porphyritic quartz trachyte lava and caldera-fill sediments (interbedded tuffaceous sediments, conglomerate, and debris-flow deposits), rhyolite dome, and the major intrusion of the infiernito caldera, the Ojo Bonito quartz monzonite. The possible maximum thickness of Infiernito Ignimbrite is estimated to be 5,900 ft. (Henry and others, 1992). Capote Mountain Tuff is one of seven formations of Vieja Group. The Capote Mt Tuff (on Marfa Sheet, 1979) contains fine-grained, vitric, tuffaceous sandst. and siltst., a few interbeds of conglomerate. In the north it is v. lt. gray and few pale red beds; in south, lower 2/3 is pale red, upper 1/3 v. lt. gray. Thickness 600-1,200 ft. Contains vertebrate mammalian fossils believed by some in 1979 to be Oligocene in age. Tsh2 of Shely Group--trachyte, to 400 ft thick, exposed at north end of Chinati Mountains.
Primary rock typetrachyte
Secondary rock typerhyolite
Other rock typessandstone; trachyandesite; latite; trachybasalt; basalt; ash-flow tuff; mudstone; conglomerate
Lithologic constituents
Major
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic, ash-flow)
Igneous > Volcanic > Felsic-volcanic > Trachyte (Flow)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow)
Minor
Igneous > Volcanic > Mafic-volcanic > Basaltic-andesite (Flow)
Incidental
Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed)
Igneous > Hypabyssal > Felsic-hypabyssal (Dike or sill)
Sedimentary > Clastic > Conglomerate (Bed)
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-rhyolite (Laccolith)
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-quartz-trachyte (Dike or sill)
Map references
Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000
Unit references
Bureau of Economic Geology, 1979, Marfa Sheet, Geologic Atlas of Texas: Bureau of Economic Geology and The University of Texas at Austin, scale 1:250,000.
Amsbury, D.L., 1958, Geology of the Pinto Canyon area, Presidio County, Texas: University of Texas at Austin, Bureau of Economic Geology Geologic Quadangle Map 22, scale 1:63,360.
Henry, C.D., Price, J.C., Duex, T.W., and James, E.W., 1992, Geology of the Infiernito caldera and magmatic evolution of the Chinati Mountains, Trans-Pecos Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations no.
Geographic coveragePresidio

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