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Van Horn Mountains caldera volcanic rocks

Van Horn Mountains caldera volcanic rocks
StateTexas
NameVan Horn Mountains caldera volcanic rocks
Geologic agePhanerozoic | Cenozoic | Tertiary | Eocene
Original map labelEvh
Commentsfrom top down: "andesite" dk gray; ignimbrite, sl. porphyritic rhyolite, conchoidal fracture, dk yell-brn, thickness 30 ft; tuff including tuffaceous sandst. and conglomerate, dk yell-brn to v. pale orange; thickness about 200 ft; basalt, sl. porphyritic, hard, grayish blk, thickness 20 ft; tuff, fine grained, friable, white, thickness about 50 ft; basalt, aphanitic, blk, thickness 42 ft; tuff friable, pale greenish yellow, weathers v. pale orange, thickness 28 ft; trachyte, aphanitic at base, vesicular at top, lt brownish-gray, weathers to thin plates, mod. brn to brnish-black, thickness more than 300 ft; vitric crystal tuff, coarse grained, friable, unbedded, yell-gray to pinkish-gray, thickness up to 140 ft. Pantera Trachyte--light brownish gray to grayish red, thickness about 40 ft. Hogeye Tuff --upper sandstone, 7-80 ft thick, lower vitric tuff with lenses of conglomerate, 180-355 ft thick. Unit includes intermediate to silicic rocks ranging from trachytes to high-silica rhyolites (Nelson and Nelson, 1986).
Primary rock typecoarse-grained mixed clastic
Secondary rock typetrachyte
Other rock typestuff; volcanic breccia (agglomerate); rhyolite; basalt; ignimbrite; andesite; hawaiite; vitrophyre
Lithologic constituents
Major
Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed)
Minor
Sedimentary > Clastic > Sedimentary-breccia (Bed)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Stock or pipe)
Igneous > Volcanic > Felsic-volcanic > Trachyte (Pyroclastic, tuff)
Incidental
Sedimentary > Clastic > Mudstone > Claystone (Bed)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Dike or sill)
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Igneous > Volcanic > Felsic-volcanic > Quartz-latite (Flow)
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.
Nelson, K.L., and Nelson, D.O., 1986, Magmatic evolution of the Van Horn Mountains caldera and comparison with alkaline magmatism in the eastern Trans-Pecos magmatic belt, west Texas in Price, J.G., Henry, C.D., Parker, D.F., and Barker, D.S., eds., Igne
Henry, C.D., and Price, J.G., 1986, The Van Horn Mountains caldera in Price, J.G., Henry, C.D., Parker, D.F., and Barker, D.S., eds., Igneous geology of Trans-Pecos Texas, field trip guide and research articles: The University of Texas at Austin, Bureau
Geographic coverageCulberson - Jeff Davis

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