Yucca Formation (TXKyu;0)

State	Texas
Name	Yucca Formation
Geologic age	Phanerozoic \| Mesozoic \| Cretaceous-Early
Original map label	Kyu
Comments	On Marfa Sheet (1979) in mountains west of I-90 and east of Rio Grande, is basal Cretaceous unit exposed north of Chinati Mtns, Presidio Co. Overlain by Cretaceous Bluff Mesa Fm. and disconformably overlies Permian Pinto Canyon Fm. Limest.-pebble conglomerate, limestone, shale, marl, and sandstone. Upper part 500-550 ft of cliff-forming units of red ls, red and purple shale, brown sandstone. Lower part is about 100 ft of cliff-forming conglomerate of well-rounded pebbles and cobbles of limestone, some chert, boulders of Pinto Canyon Fm, grades up to nodular, fine-grained limestone.
Primary rock type	conglomerate
Secondary rock type	sandstone
Other rock types	siltstone
Lithologic constituents	Major Sedimentary > Clastic > Conglomerate (Bed) Minor Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed) Sedimentary > Carbonate > Limestone (Bed) Sedimentary > Clastic > Sandstone (Bed)
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	Plummer, F.B., and Moore, R.C., 1921, Stratigraphy of the Pennsylvanian formations of north-central Texas: University of Texas Bulletin 2132.
Geographic coverage	Culberson - Hudspeth - Presidio