|Name||Santana Tuff from Sierra Rica caldera in Mexico|
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic-ash flow)rhyolitic ash-flow tuff erupted from a caldera in Sierra Rica area in Chihuahua, MX
|Comments||nonwelded to thoroughly welded vitric-crystal tuff, one to at least four flows, high percentage of glassy luster sanidine crystals; where nonwelded, friable, dull, porous, gray, brownish-yellow, and white; forms distinct orange cliffs; maximum thickness 550 ft in Santana Mesa area; K-Ar age 26.3 +_ 0.5 m.y. reported (Emory Peak-Presidio Sheet 1979), 27.8 Ma reported in Henry and others (1998).|
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.