Wednesday, July 6, 2016

Approach to Titus Canyon: Just Below Red Pass

We're now about two thirds of the way up the hill toward Red Pass on the Titus Canyon road, a one-way road that runs approximately east to west from Nevada into California, starting not far south of the ghost town of Rhyolite. On this short section of our safari, we'll see some Titus Canyon Formation, although no more outcrop shots, sorry; we'll see some What-Used-To-Be Titus Canyon Formation, now Panuga Formation; and we'll see a bit of what lies above the Titus Canyon and Panuga Formations. Although there were a few places on the hill to pull over, I ended up taking most of these photos from the middle of the road: There was no one behind us for at least a half a mile or so.
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.
The map symbols I'm using are from Niemi (2012):
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.)
The main items to note in the labeled photo are 1) the hill of reddish Titus Canyon Formation (EOgtc) in the foreground, 2) the low, greenish cliffs of Titus Canyon Formations down the small wash, 3) the fault separating the Titus Canyon from the greenish slopes and cliff of the Panuga Formation (Tg). We can't actually see the fault from where we're standing because it runs behind the low rise of greenish Titus Canyon Formation rocks; I've drawn it in anyway. The Panuga includes a reddish crystal tuff at about midpoint (labeled in this photo, not in the next). I've labeled the background formations without marking the contacts: I'll leave those to your imagination. The Timber Mountain Group rocks (Tm) are probably just the uppermost, dark-brownish hill-capping units; the lighter brown Paintbrush Group tuffs (Tp) above the thicker, tan to red Crater Flat Group (Tc) tuffs are actually quite thin.

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!

Well, what happened was some regional correlation of key stratigraphic horizons and a bit of renaming. Firstly, the entire Green Conglomerate facies, formerly of the Titus Canyon Formation, was reassigned to the Panuga Formation (Snow and Lux, 1999), the main reasons being, as I understand them, that 1) it lies on an unconformity formed on the Variegated facies of the Titus Canyon Fm, and 2) clast composition changes across the unconformity, such that the Panuga contains some clasts of Tertiary volcanic rocks, whereas the layers below don't. Also, the reddish layer in the middle of the cliff is (I think) the crystal tuff that was correlated to the 15.7 Ma Tuff of Unconformity Hill by Snow and Lux (1999), giving that portion of the section a Miocene age.

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."
And by now, we all know what that pile of rocks is, right? Yes, it's Tw on Tg on EOgtc (with a crystal tuff in the middle of the Tg).
There's a major fault between us and Tw Hill, one that, perhaps, first appeared in maps by M.W. Reynolds (1969, 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:
This colorful map is modified from a small portion of Fig. 2-26 in Ridgway, et al (2011). The Titus Canyon and Panuga Formations (labeled Ts) are in yellow; Tertiary volcanic rocks are in orange; Cambrian rocks (and some Ordovician?) are in pink. Most of the labels are irrelevant to us. The actual Fall Canyon Fault is the one I've marked in blue that is farthest to the west. It joins southward with a low-angle fault or fault system: the Titus Canyon Fault, which squiggles around quite a bit. All of these faults, as I understand them, are related to extensive Tertiary extension that also formed the Boundary Canyon detachment fault, which outcrops mostly south of the Daylight Pass Road (Reynolds, 1974Saylor, 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).
Now, for a moment, I'd like to focus in on the arc I've emphasized below in sprayed cyan. This is a portion of the fault or fault zone labeled Fall Canyon Fault Zone by Niemi. I show more than one possible trace, partly because of the inexactitude of my method of transfer to Google Earth. Zoom in above to see that there is more than one possible trace; the two to the north are from Reynolds and Niemi, the two main ones to the south are from Reynolds (and maybe Niemi's trace is the same as his), and a linear I picked out from Google Earth. If I do a three-point problem on this fault near Red Pass, I get dips to the northeast of less than 30 degrees! Well, it may bend and curve a bit, as many faults do, so maybe that's not an accurate representation of the overall dip angle, but it appears to be a low-angle fault, at least in part. This might be a low-angle normal fault, or it might be one of the oblique-slip faults of the area (Saylor, 1991). Lengner and Troxel (2008) allude to a low-angle fault running about where I've drawn the sprayed line east of my arc, below, possibly running toward (and beyond??) White Pass. These all may hook up at depth with a regional low-angle fault (or faults), which may or may not be the Fall Canyon Fault itself, which is said to flatten rapidly at depth (Fridrich and Thompson, 2011), or the Boundary Canyon detachment, which has been hypothesized to hook up with the Bullfrog detachment (Saylor, 1991).
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.
Now, back to the rocks!
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.
I'd like to note that in the last post I stated that the dark rocks, which are in the center of the above photo, look more like Bonanza King Formation than the Carrara shown on Niemi's map. What we actually have—I finally realized—is dark, reddish brown Zabriskie Quartzite (the thick, cliffy ledge to the right of center, dipping to the north, or left) overlain by the slope-forming, lighter reddish brown Carrara Formation. Above that, just left of center, there is a small jumble of dark gray rocks. This is megabreccia composed of Bonanza King Formation fragments; the megabreccia, a mappable unit, is generally considered to be part of the Titus Canyon Formation.

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].

Location map

Related Posts:
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

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