Santana Tuff from Sierra Rica caldera in Mexico

Santana Tuff from Sierra Rica caldera in Mexico
State Texas
Name Santana Tuff from Sierra Rica caldera in Mexico
Geologic age Oligocene
Lithologic constituents
Major
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).
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.

NGMDB product
Counties Presidio