Tuesday, September 13, 2016

Leadfield: Geology...and a Cactus...on the Way Back to the Parking Area

We've left the far northwest mine building at Leadfield, have sauntered past a large chunk of Tertiary megabreccia (Mbx), and we're making our way back to the parking area by the Leadfield sign.
Looking to the SW, we see part of the broad fold in the Bonanza King Formation juxtaposed against the foreground mass of Mbx.
Wonderful barrel cacti grow right along the trail.
The barrel cactus here is of the genera Ferocactus, possibly the type known as California barrel cactus, or Ferocactus cylindraceus (there is more than one subspecies of F. cylindraceus).

From this same location, we also have the opportunity to see one of the area's several low-angle faults known collectively as the Titus Canyon fault zone (TCFZ). Here's one online version of the TCFZ in map view and cross section. On the map it's shown as a thick, hatched line wrapping around the upland south of Titus Canyon. It crosses the canyon at Klare Spring, and northward becomes the main strand of the Fall Canyon fault zone (FCFZ). I modified the figures by moving the scales, credits, and index map for cropping and added the location of Leadfield to the map. Note the askew north-south line indicated by the 117°00' mark; the long dashed line on the right is the skewed CA-NV border.
Source: Part of Fig. 1 of Reynolds, 1974 reprinted in Troxel and Wright, 1976 at NPS History eLibrary.
Source: Part of Fig. 3 of Reynolds, 1974 reprinted in Troxel and Wright, 1976 at NPS History eLibrary.
Back on the trail, we're looking south toward the low hills.
My labeled version of this photo shows both thrust (thick line with sawteeth) and low-angle normal (thick line with hatch marks) symbols. Reynolds' map (the one in Lengner and Troxel, 2008), shows this fault with a thrust symbol, but it hooks up with one that appears on Google Earth to wrap around the terrain to become part of the larger Titus Canyon Fault system, even though that part of the low-angle fault system doesn't appear on Reynolds' summary map (above) or this composite map (Workman et al, 2002). You can also see this low-angle fault on my marked-up Google Earth image (below); I've got it there with two colors, deep blue and a kind of dark magenta. I should probably just change it all to one color, but when I made the image, I was trying to correlate different strands of the fault system, which I've since determined is a rather futile project without some field mapping and perhaps a bit of surveying, neither of which I'm likely to do!

The low-angle fault south of Leadfield places younger rocks on older rocks, a hallmark of low-angle normal faults; thrust faults (low-angle reverse faults) can also do that, but they more commonly produce an older-over-younger scenario.
Photo with geology from Reynolds (1969, in Lengner and Troxel, 2008).
Although seen here mostly in fault contact, the usual section from bottom up is Cambrian Zabriskie Formation (Cz), Cambrian Carrara Formation (Cc), and Cambrian Bonanza King Formation (Cb). The Eocene-Oligocene Titus Canyon Formation (EOgtc) and batches of megabreccia within the lower part of the EOgtc (Mbx) sit entirely in fault contact with the Cambrian rocks along a normal, down-to-the northeast fault. Landsliding or slumping along this fault or the TCFZ might be what produced the breccia bodies now known as Mbx.
My (current) Google Earth version of the geology at Leadfield.
The geology I've drawn onto Google Earth (GE) is mostly from two maps: North and northeast of the Titus Canyon road, the geology is largely from Niemi (2012); south and southwest of the road, the geology is largely from a map in Lengner and Troxel (2008), which they took from Reynolds (1969). The contacts as transferred to GE should be considered approximate; I've modified them where I've seen fit and added possible faults and a few other things like marker beds.

Let's keep meandering back toward the parking area.
Dried wildflowers, probably from the spring or summer of 2015, grow out of a concrete foundation.
Lengner and Troxel list this former building as "Frame and Iron Compressor and Engine Room," located on Western Lead Mines Company's March Storm claim No. 2. I'd usually just call something like this an old mill foundation.

I paused below the main mine dump, next to the larger metal building that we saw last time, to take two zoomed shots looking eastward across the valley of lower Lost Canyon.
Interesting fracture pattern in greenish brown rocks above the red slope formers of the Titus Canyon Formation. Is that tilted columnar jointing? Tilted bedding? Stay tuned.
Reddish bluff (earlier called "Tc Hill") above orange, brown, red, and greenish layers. All the formations are dipping to the north.
When I took the photos, I wasn't thinking of making a panorama, but look! They splice together fairly well with just a tiny bit missing in the middle. All the better to see the geology with.
We look eastward, over the parking area near the Leadfield sign.
With some geology added!
Here we're seeing most of the Tertiary section (Paleogene to Neogene).

The Tertiary section (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)
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)

Part of the pre-Tertiary section:
Єb = Bonanza King Formation (mostly dolostone with lesser limestone)
Єc = Carrara Formation (mostly siltstone, also quartzite and limestone)
Єz = Zabriskie Quartzite (thick-bedded to massive quartzite)
ZЄw = Wood Canyon Formation (a miscellaneous formation bounded by two quartzites, consisting of siltstone, quartzite, dolostone, conglomerate, and limestone)

The section is sliced by two major, roughly north-south trending normal faults, part of the Fall Canyon Fault Zone (FCFZ). I've labelled these FCFZ/W (westerly strand) and FCFZ/E (easterly strand), not to imply that these are the only strands of this fault zone. The faults are moderate- to high-angle at the surface, flattening at depth. There is a bit of white rock along the westerly strand of the FCFZ; I'm not sure if this is a fault breccia or shatter zone along the fault or some light-colored bed (tuff?) smeared along the fault, and I'm not sure if it belongs in the hanging wall or footwall. I decided to show it as a possible shatter zone, marked in dashed blue lines.

The fault shown with an up arrow to its right, is a somewhat minor high-angle normal fault with its down side toward us (down-to-the-west); it is not a reverse fault. (I'm afraid the arrow makes it look that way, but I don't feel like redoing the labeling!)
Same photo with a little more labeling.
In the second geological panorama, I've added a few broad orange, pink, and lavender lines or strokes to indicate three marker beds in the Panuga Formation (Tg). These are possibly tuffs. In the geologic image below, the pink and lavender color of the upper two marker beds is reversed (my fault!).
Google Earth image of the same panorama.
The geologic map on Google Earth (same as earlier).
Next time, we'll finally get into the main branch of Titus Canyon!

A Few References:
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 summaryin 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.

Workman, J.B., Menges, C.M., Page, W.R., Taylor, E.M., Ekren, E. B., Rowley, P.D., Dixon, G.L., Thompson, RRA., and Wright, L.A., 2002, Geologic map of the Death Valley ground-water model area, Nevada and California: U.S. Geological Survey Miscellaneous Field Studies Map MF-2381-A, Pamphlet text, Sheet 1, Sheet 2.

Location map

Related Posts:
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
The Approach to Titus Canyon: Just Below Red Pass
A Hike at Red Pass, Titus Canyon Road, Death Valley, CA
Titus Canyon Road: A Little History and a Few Maps
Down into Titus Canyon: We Leave Red Pass Behind (Finally!)
Scribbles
Titus Canyon: The Upper Part of Lost Canyon
Leadfield: Scams with a Side of Geology
Leadfield: Views from Old Mine Buildings

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