Duff Formation (with Decie Member from Paisano caldera shown separately), Cottonwood Springs Basalt, Potato Hill Andesite, Sheep Canyon Basalt, Crossen Trachyte, and Pruett Formation, undivided (TXOGEOd;0)

State	Texas
Name	Duff Formation (with Decie Member from Paisano caldera shown separately), Cottonwood Springs Basalt, Potato Hill Andesite, Sheep Canyon Basalt, Crossen Trachyte, and Pruett Formation, undivided
Geologic age	Phanerozoic \| Cenozoic \| Tertiary \| Eocene-Late Oligocene-Early
Original map label	OEd
Comments	in west Brewster Co., rhyolitic tuff, minor sandstone, conglomerate and mafic flows, felsic flows, and flow breccia. mafic flows, anygdaloidal, vesicular, andesitic flow breccia, porphyritic mafic flows, thin tuff and nonmarine limestone, prophyritic quartz trachyte, tuff, tuffaceous sandstone, conglomerate breccia, tuffaceous nonmarine limestone. Pruett Fm., about 330 ft thick in Fort Stockton Sheet (1982), mostly volcanic tuff, some tuffaceous sandstone, conglo., breccia, and tuffaceous fresh-water limestone which interfingers with other units named in this map unit. Thickness more than 4,500 ft.
Primary rock type	rhyolite
Secondary rock type	basalt
Other rock types	tuff; sandstone; conglomerate; limestone
Lithologic constituents	Major Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic, ash-flow) Minor Sedimentary > Clastic > Mixed-clastic > Siltstone-Mudstone Igneous > Volcanic > Felsic-volcanic > Trachyte Igneous > Volcanic > Mafic-volcanic > Basalt Incidental Sedimentary > Clastic > Conglomerate (Tuffaceous) Sedimentary > Clastic > Sandstone (Tuffaceous) Sedimentary > Carbonate > Limestone (Tuffaceous)
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, 1982, Fort Stockton Sheet, Geologic Atlas of Texas, University of Texas at Austin, scale 1:250,000. Bureau of Economic Geology, 1979, Emory Peak--Presidio Sheet, Geologic Atlas of Texas, University of Texas at Austin.
Geographic coverage	Brewster - Jeff Davis - Presidio