Perdiz Conglomerate, Tascotal Formation, and tuffaceous sediments of Fresno Formation (TXOGpf;0)

State	Texas
Name	Perdiz Conglomerate, Tascotal Formation, and tuffaceous sediments of Fresno Formation
Geologic age	Oligocene
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Tuffaceous) Sedimentary > Clastic > Conglomerate (Tuffaceous) Incidental Igneous > Volcanic > Felsic-volcanic (Pyroclastic-tuff)ash-flow tuff and tuffaceous sediments
Comments	Perdiz --weakly cemented fanglomerate of variable composition (dominantly of rocks of the Chinati Mountains caldera) shed mostly eastward from Chinati Mountains; occupies high plains north and east of Infiernito caldera; Clasts as much as 1 m in diameter and includes clasts from the Infiernito caldera in the north; unit is about 500 ft thick; Tascotal -- tuffaceous sediments that overlie the Mitchell Mesa Rhyolite and form a widespread blanket around the Chinati Mtns, including fan apron and eolian facies. Upper part sandstone, tuffaceous sandstone, and conglomerate; thickness about 800 ft, Fresno--interbedded sedimentary materials and flows; includes ash-flow tuff, eolian tuff, eolian tuffaceous sandstone.
References	Bureau of Economic Geology, 1979, Emory Peak--Presidio Sheet, Geologic Atlas of Texas, University of Texas at Austin. Walton, A.W., 1986, Volcaniclastic-sedimentary record of the Chinati volcanic center--the Buck Hill and Vieja Groups 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: Bureau of Economic Geology, Texas Mining and Mineral Resources Research Institute Guidebook 23, p. 251-265. 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	Brewster - Jeff Davis - Presidio

State

Texas

Name

Perdiz Conglomerate, Tascotal Formation, and tuffaceous sediments of Fresno Formation

Geologic age

Oligocene

Lithologic constituents

Major

Sedimentary > Clastic > Sandstone (Tuffaceous)

Sedimentary > Clastic > Conglomerate (Tuffaceous)

Incidental

Igneous > Volcanic > Felsic-volcanic (Pyroclastic-tuff)ash-flow tuff and tuffaceous sediments

Comments

Perdiz --weakly cemented fanglomerate of variable composition (dominantly of rocks of the Chinati Mountains caldera) shed mostly eastward from Chinati Mountains; occupies high plains north and east of Infiernito caldera; Clasts as much as 1 m in diameter and includes clasts from the Infiernito caldera in the north; unit is about 500 ft thick; Tascotal -- tuffaceous sediments that overlie the Mitchell Mesa Rhyolite and form a widespread blanket around the Chinati Mtns, including fan apron and eolian facies. Upper part sandstone, tuffaceous sandstone, and conglomerate; thickness about 800 ft, Fresno--interbedded sedimentary materials and flows; includes ash-flow tuff, eolian tuff, eolian tuffaceous sandstone.

References

Bureau of Economic Geology, 1979, Emory Peak--Presidio Sheet, Geologic Atlas of Texas, University of Texas at Austin.

Walton, A.W., 1986, Volcaniclastic-sedimentary record of the Chinati volcanic center--the Buck Hill and Vieja Groups 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: Bureau of Economic Geology, Texas Mining and Mineral Resources Research Institute Guidebook 23, p. 251-265.

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

Brewster - Jeff Davis - Presidio