|Name||Van Horn Mountains caldera volcanic rocks|
Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Stock or pipe, Dike or sill)
Igneous > Volcanic > Felsic-volcanic > Trachyte (Pyroclastic-tuff)
Sedimentary > Clastic > Sedimentary-breccia (Bed)
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Igneous > Volcanic > Felsic-volcanic > Quartz-latite (Flow)
Sedimentary > Clastic > Mudstone > Claystone (Bed)
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)
|Comments||from 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).|
|Stratigraphic units||Pantera Trachyte, Hogeye Tuff|
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., Igneous geology of Trans-Pecos Texas, field trip guide and research articles: The University of Texas at Austin, Bureau of Economic Geology, Guidebook 23, p. 164-177.
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 of Economic Geology, Guidebook 23, p. 31-43.
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.
|Counties||Culberson - Jeff Davis|