Friday Field Photos: Tepee Rocks

More than a month ago, on my Caliente trips, while driving up the washboarded dirt road toward the Ella Mountain Lookout, I came around a corner and spied these unusual rock formations in tuff, formations I had forgotten all about since last seeing them in 1978.
These are the Tepee Rocks, located about 6 miles east-southeast of Caliente. They are a type of rock formation called tent rocks, teepee rocks, or hoodoos, and they have formed here in the tuff of Tepee Rocks (sometimes spelled "tuff of Teepee Rocks"). The tuff of Tepee Rocks is "crystal-poor, poorly welded, low-silica rhyolite ash-flow tuff" with an Ar-Ar age of 17.8 Ma (Rowley et al, 1995). It's about 100 m thick in the Tepee Rocks area.

To get to the Tepee Rocks, you drive east out of Caliente on a mostly dirt and sand road that follows the railroad along Clover Creek (Clover Creek Road). You may not need 4WD, but be prepared for soft sandy areas that appear suddenly and wide creek crossing. Before the Eccles siding, you turn south on the dirt road that goes to Ella Mountain and Fife Flat, among other places.
It can be a bit difficult to get the timing right for best sun-angle on these hoodoos; I made two stabs at it. Morning and afternoon, not too early and not too late, are best.
In this close-up, you can see some holes weathering out in the tuff, forming a small version of what is known as cavernous weathering. Hoodoo formation in general is explained here.
At the Tepee Rocks, the teepees or hoodoos are forming in massive, cavernous-weathering, very light gray to whitish tan tuff below layered, tan to light orange tuff, which may be part of the tuff of Tepee Rocks or may belong to an overlying formation. The layered tuff can be seen in the previous two photos.
A slope just south of the Tepee Rocks shows the massive tuff capped by the upper layered tuff and by overlying talus. Little hoodoos are starting to form as the whitish tan to light gray tuff weathers out from beneath the talus and capping tuff layer.
A few small teepees stick out on the lower part of this slope across the road from the Teepee Rocks. The cliffy formation capping this butte is probably not part of the tuff of Tepee Rocks, based on the description given by Rowley et al (1995).

Some References:
Page, W.R., Dixon, G.L., Rowley, P.D., and Brickey, D.W., 2005, Geologic map of parts of the Colorado, White River, and Death Valley groundwater flow systems, Nevada, Utah, and Arizona: NBMG Map 150, map and text.

Rowley, P.D., Nealey, L.D., Unruh, D.M., Snee, L.W., Mehnert, H.H., Anderson, R.E., and Gromme, C.S., 1995, Stratigraphy of Miocene ash-flow tuffs in and near the Caliente caldera complex, southeastern Nevada and southwestern Utah: in Scott, R.B. and Swadley, WC, eds., Geologic Studies in the Basin and Range - Colorado Plateau transition in southeastern Nevada, southwestern Utah, and northwestern Arizona, 1992, U.S. Geological Survey Bulletin, 2056-B, p. 43-88.

More Photos of Hoodoos:
Hoodoo, New Mexico at About.com Geology

Time Almost Beyond Imagining: Who Do the Magic that Hoodoo? at Geotripper

Hoodoos Redux: What I'm Reading at Geotripper

Limestone Hoodoos, Bryce Canyon National Park at Rosetta Stones