|We're looking northeasterly toward some distant hills capped by Miocene ash-flow tuffs. But it's really the closer rock formations that we're interested in.|
Tm = Miocene Timber Mountain Group (ash-flow tuff)
Tp = Miocene Paintbrush Gp (ash-flow tuff)
Tc = Miocene Crater Flat Gp (ash-flow tuff)
Trp = Miocene Rhyolite of Picture Rock (rhyodacite to latite flow rock)
Tw = Miocene Wahguyhe Fm (sedimentary and volcanic rock)
Tg = Miocene Panuga Fm (conglomerate, sandstone, and minor tuff)
EOgtc = Eocene-Oligocene Titus Canyon Fm (various sedimentary facies)
|The same view, labeled. (We've already seen this cliff from another angle and from a distance, here, so this should be somewhat familiar.)|
I'll be calling the cliffy hill on the left "Tw Hill" because it's capped by Tw. All of the greenish rock on Tw Hill used to be part of the late Eocene to Oligocene Titus Canyon Formation. Now, only the very lowest greenish rock, exposed in the low cliff just down that little wash in the foreground, is Titus Canyon Formation. Beyond that—and past at least one fault or past a broad fault zone—the greenish rock on the slopes and in the cliff, above and below the thin reddish layer bisecting the hill, is part of the Miocene Panuga Formation. What changed? Surely the rocks didn't actually change in age from Oligocene to Miocene!
MOH and I drove a little farther up the hill. Not far below Red Pass, I took another opportunity to take a picture of Tw Hill: I wanted to get a good shot of the reddish layer, because we had hiked up to it in 2009.
Before going on, I'm going to break a general rule of mine and say something about the quality of the photos. The greenish rocks in the area, which are in both the EOgtc and the Tg, are a relatively unusual color of green for rocks, a color that I've found hard to capture accurately. You can see the difference in color balance between my first and second photos The first was taken in 2009, when a lot of green plants were growing; the second was taken in 2016 before many plants had popped their heads out of the ground—and the plants have something but not everything to do with the difference. For further color comparisons, check out photos of the same area at Geotripper (also 2016).
|Another view of "Tw Hill."|
1974). Reynolds' original 1969 map is not available online, but a small portion of the map is included in a book by Lengner and Troxel (2008), a book that explains the geology and natural history at Leadfield and along the Titus Canyon Road (I highly recommended it!). This fault (the one dashed in above) is marked on Niemi's map as "Fall Canyon Fault Zone" (FCFZ). The reason I've questioned this name in the photo is because to the west in Fall Canyon, Niemi labels a single fault "Fall Canyon Fault." I didn't really find a clarification of this in the report accompanying his map. He does say that the fault zone basically separates the Paleozoic section to the west from Cenozoic section to the east. In a broad sense, several large and small faults combine to accomplish this separation east of Fall Canyon; perhaps all or a few of these are considered part of a larger FCFZ. In other words, perhaps the FCFZ is the broader fault system I've emphasized roughly below in blue:
Reynolds, 1974; Saylor, 1991).
Either way, there are several faults, possible faults, and linears that can be identified in the area of Red Pass and Tw Hill. A few of these can be seen in the two labeled Google Earth images below:
|Some faults and possible faults in the general Red Pass area. The only contacts I've left in are ones between the Tertiary sedimentary formations and the overlying volcanic formations (i.e., between the Tg and Tw).|
|A sprayed arc along the low-angle fault cutting across Red Pass (FCFZ?) and a sprayed line along the trace of a possible low-angle fault between upper Titanothere Canyon and White Pass.|
|I've zoomed in to a portion of the crystal tuff in the middle of the Panuga Formation (Tg) on Tw Hill. We'll see this up close, next post.|
|The contact between the Tg and overlying Tw is marked by an abrupt change in color and increase in erosive resistance.|
|Looking back to the east toward White Pass.|
And with that, we'll zip up the rest of the way to Red Pass.
A Few References:
Fridrich, C.J., and Thompson, R.A., 2011, Cenozoic tectonic reorganizations of the Death Valley region, southeast California and southwest Nevada: U.S. Geological Survey Professional Paper 1783, 36 p. and 1 plate.
Lengner, K., and Troxel, B.W., 2008, Death Valley's Titus Canyon & Leadfield ghost town: Deep Enough Press, 175 p.
Niemi, N.A., 2012, Geologic Map of the Central Grapevine Mountains, Inyo County, California, and Esmeralda and Nye Counties, Nevada: Nevada, Geological Society of America Digital Maps and Charts Series, DMC12, 1:48,000, 28 p. text.
Reynolds, M.W., 1969, Stratigraphy and structural geology of the Titus andTitanothere canyons area, Death Valley, California [Ph.D. thesis; not available online]: Berkeley, University of California, 310 p.
Reynolds, M.W., 1974, Geology of the Grapevine Mountains, Death Valley,California; a summary, in Death Valley region, California and Nevada, Geological Society of America Cordilleran Section, Field Trip 1 Guidebook: Death Valley Publishing Company, Shoshone, California, p. 91–97.
Ridgway, Kenneth, Stamatakos, John, Gutenkunst, Michele, and Dubreuilh, Philippe, 2011, Stratigraphic analysis and regional correlation of Oligocene and early Miocene strata in the Yucca Mountain area, Prepared for U.S. Nuclear Regulaatory Commission contract NRC-02-07-006: Center for Nuclear Waste Regulatory Analyses San Antonio, Texas.
Saylor, B.Z., 1991, The Titus Canyon Formation: Evidence for early Oligocene extension in the Death Valley area, California [M.S. thesis]: Massachusetts Institute of Technology, Cambridge, 65 p.
Snow, J.K., and Lux, D.R., 1999, Tectono-sequence stratigraphy of Tertiaryrocks in the Cottonwood Mountain and northern Death Valley area, Californiaand Nevada, in Wright, L.A. and Troxel, B.W. eds., Cenozoic basinsof the Death Valley region: Geological Society of America Special Paper 333, p. 17–64 [Google Books].
Beatty: Old Buildings, A Fold, and Onward toward Titus Canyon
The Approach to Titus Canyon: Amargosa Narrows, Bullfrog Pit, and the Original Bullfrog Mine
Mineral Monday: Close-Ups of Bullfrog Ore from the Original Bullfrog Mine, Nevada
The Approach to Titus Canyon: Tan Mountain
The Approach to Titus Canyon: Up and over White Pass
The Approach to Titus Canyon: To Red Pass