Van Horn Mountains caldera volcanic rocks (TXEOvh;0)

State	Texas
Name	Van Horn Mountains caldera volcanic rocks
Geologic age	Eocene
Lithologic constituents	Major Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed) Minor Igneous > Volcanic > Felsic-volcanic > Rhyolite (Stock or pipe, Dike or sill) Igneous > Volcanic > Felsic-volcanic > Trachyte (Pyroclastic-tuff) Sedimentary > Clastic > Sedimentary-breccia (Bed) Incidental 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
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., 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.
NGMDB product	NGMDB product page for 68390
Counties	Culberson - Jeff Davis

State

Texas

Name

Van Horn Mountains caldera volcanic rocks

Geologic age

Eocene

Lithologic constituents

Major

Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed)

Minor

Igneous > Volcanic > Felsic-volcanic > Rhyolite (Stock or pipe, Dike or sill)

Igneous > Volcanic > Felsic-volcanic > Trachyte (Pyroclastic-tuff)

Sedimentary > Clastic > Sedimentary-breccia (Bed)

Incidental

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

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., 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.

NGMDB product

NGMDB product page for 68390

Counties

Culberson - Jeff Davis