Tuesday, September 27, 2016

Almost Titus Canyon: Is This a Fold? And... Apparent Dip with Post-it® Notes

(This is not a fold.)
As we leave the lower Lost Canyon section of the Titus Canyon road, we're also leaving the Leadfield area. (Say goodbye!) Less than a half mile from the Leadfield parking area, the road curves rather abruptly to the left, enters a canyon with steep walls, and presents us with the view seen above. Is this a fold? It looks like one at first, and in fact that's what I thought when first rounding this same bend many years ago: "Oh, look, a neat little syncline." Beds on the south (left) are dipping to the north, and beds on the north are nearly horizontal or dipping to the south—or are they?

Actually, we're looking at a nearly uniformly dipping section of the Cambrian Bonanza King Formation; the beds are dipping about 35° to the north and look bent or folded only because of our viewpoint and a nearly right-angle bend in the canyon wall.

Let's look at this a little more closely:
Here's the non-fold with a few colored lines.
In this second photo, I've drawn a magenta horizontal line from which I've measured dip angles of the beds in the north-south section of the canyon wall. These two dip measurements of 48° and 40° to the north might be what is called the apparent dip of the beds; they definitely are not true dip measurements, which are usually taken in the field with a type of compass called a pocket transit (mine is a Brunton compass; see my first, older-model Brunton here).

NOTE: There's a technicality about apparent dip that makes me unsure what to call the inclination of beds one can see at random angles in the field or when looking at photos like the one above. True dip is measured perpendicular to strike and is always greater than apparent dip, which is measured on a vertical plane that cuts through the rock or a map at any angle other than perpendicular to strike. As we'll see below, perspective can cause the slant of beds to look shallower or steeper than the angle of true dip. I've generally called this observed or ostensible angle "apparent dip" when I know I'm not looking straight down strike (which is most of the time if I haven't lined up with the level of a compass), but it's really something else; maybe it should be called "perspective dip" "positional dip" or "POV dip".

Getting back to the photo above, I've drawn an approximate apparent dip line of 0° on the portion of the canyon wall that is running nearly east-west (on the right). Are these beds really horizontal (or even dipping back to the south, which they appear to do above the cyan line)?

In the first Google Earth (GE) image below, we're standing about at the yellow pin marked "4370 - not fold", looking southwest at the canyon wall (4370 was my original photo number). I've drawn three strike and dip symbols and one strike line on the image in magenta. I took the strike by using points of equal elevation on four individual beds that I picked out. The two symbols on the hill south of the road, herein known as DS Hill, are on individual dip-slope beds that are quite obvious in GE; these strike lines are probably the most accurate of the four. (All four lines of strike should be considered approximate.)

So, we have a strike of about N70E, or 070° azimuth. From the photo and from the dip slope on DS Hill, we know that the dip direction for three of our points is to the northwest. For the beds north of the wash, I know from driving through the canyon that these beds also dip roughly to the north or northwest; also, if they were dipping to the south, the slope would look more like the dip-slope hill south of the wash.
Our location (yellow pin) with strike-dip symbols in magenta, a set of identifiable beds in cyan, and a small fault in dark blue.
The same area, now with two dip measurements.
To measure the dip, I selected a location to the east of of the dip-slope hill that was along strike and also at the same elevation of the larger of the two strike-dip symbols on the dip slope. In the GE image below, we are standing at that point, along strike and at equal elevation, measuring the dip angle where we see the longer of the four magenta lines. Note: Only that one line really shows up in its proper orientation due to various perspective problems with Google Earth. Also note that the northwest-dipping bedding in the "fold" area—the outcrop area just above the yellow pin that corresponds to the obviously dipping strata in our photo—doesn't really look that way in GE from this angle, also due to various perspective and topographical complications.
The prominent dip slope in Bonanza King Formation beds is marked by the longer of the four magenta lines.
From the orientation and elevation I'm sitting at above, I measured a 35° dip. Doing the same thing from the west, I was able to measure a 35° dip on the dipping beds looming in front of us as we start to drive into this canyon. If we walked up to these two locations to take a strike and dip with our Brunton, we'd probably get readings within 5 degrees or so of my GE measurements, in both strike and dip. We'd get similar readings if we measured the beds on the north side of the canyon wall.

To look at this in another way, I created an analogy to our beds with a stack of Post-it® notes. The first example approximates what we see directly ahead of us, on the north-south canyon wall, as we enter the canyon (first photo).
Our multi-colored, light and dark beds are dipping about 35° to the north.
As we move around to the south and look to the north—approximating our view of the east-west part of the canyon wall—these same beds appear to be horizontal.
The apparent dip of beds is 0° as we look to the north.
If we look to the south, we see a kind of dip slope, although here I'm looking down on them from above, so they don't look as steep as they would from the canyon floor.
We look south and see a dip slope, similar to the dip slope on the south wall of the canyon (GE image #3).
It's probably worth noting that the dips I measured directly from the "fold" photo are higher than the dip I got using Google Earth. As I mentioned earlier, our perspective can cause dip of beds to vary greatly; in fact, the angle we see from changing perspectives can vary from 0 to 90 degrees, depending on our viewing angle and orientation. When looking straight into dipping beds, that is when looking perpendicular to strike, the beds will look horizontal (as we saw in Post-it® photo #2). When viewing these same beds from a point along strike, they will appear to dip at exactly true dip (Post-it® photo #1).
Another set of Post-it® beds are dipping 35° to the north (right).
As we move around in the terrain to the ESE, these same beds look like they are dipping 40° to the NNE.
Now, having moved to the SSE, the beds appear to dip 70° to the ENE.
If we look at the same stack of beds from the south, they look almost vertical. In fact they can be measured with "apparent" dips of 85 to 88° to the east.
Without having a good handle on the strike of beds while wandering around from canyon to bluff and up, over, and across the terrain, we can't really tell the dip of beds!

I did try to simulate our canyon beds with a crudely modified block of Post-it® notes. Imagine our stack of beds as above, although this stack seemingly has some thinner, almost shale-like beds in it. Now we erode a canyon or amphitheater into the beds.
Block of dipping beds with a crude canyon eroded into it.
We can easily see the dip slope on the south side of the canyon (green slope on the left). I think that because our perspective is not from within our little amphitheater or canyon, we can't really get the feel of the beds on the north wall (right) that seemingly appear nearly horizontal (photo #1). I'd have to move a tiny camera into the beds, and maybe stand it on the purple horizon lying on the thick green unit, to get the same perspective that we have in our "fold – not-fold" photo. I tried this crude Post-it® method because most 3-D block diagrams (and physical blocks) don't show a cutout that would simulate standing in a canyon with dipping beds looming all around.

Well, let's get back to our travels down the canyon!
But first... some lupine from the spring of 2009, right below the faux fold.
After we round the bend to go past the dipping beds that we saw in our first photo, it's a mere 0.2 miles to the junction with the main branch of Titus Canyon, which comes in from the north. And then, about 0.3 miles past that junction, we come to this spot, where we can see that Titus Canyon, up ahead, widens a little.

But what else can we see?
I see some wonderful rocks in a dry wash, and...
More next time!

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!)
Titus Canyon: The Upper Part of Lost Canyon
Leadfield: Scams with a Side of Geology
Leadfield: Views from Old Mine Buildings
Leadfield: Geology...and a Cactus...on the Way Back to the Parking Area

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 hangingwall 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!)
Titus Canyon: The Upper Part of Lost Canyon
Leadfield: Scams with a Side of Geology
Leadfield: Views from Old Mine Buildings

Thursday, September 8, 2016

Leadfield: Views from Old Mine Buildings

Now we'll leave the parking area near the Leadfield sign and, as I promised last time, we’ll walk out to what I’ve been referring to as the “far west cabin," although maybe that should really be "far northwest cabin." (I have this habit of thinking of Titus Canyon as an east-west canyon, when in fact, the Leadfield section is oriented closer to southeast-northwest than east-west.)
From the trailhead across from the Leadfield sign, I zoomed in to get this shot of the northwesternmost cabin at Leadfield proper. It sits at the end of an old road, past the main dump and past downtown Leadfield.
Once again, these photos will be an agglomeration from two trips taken by MOH and I; the first was back in early May of 2009, the second was earlier this year in late February.
A prominent old building sits just below the main dump.
Lengner and Troxel (2008) have this building located on Western Lead Mines Company's (WLMC) March Storm Claim No. 2. It looks like it's #3 on their map; #3 is labeled “Frame and Iron Warehouse.” (The bolding is theirs, presumably to indicate the function or name of the building.)
A dried plant, last year's wildflower, in front of the old warehouse.
When we went through Titus Canyon in February, 2016, we were on our way to see the superbloom that was going great guns down near Badwater. It looked like Titus Canyon's wildflowers would be putting on a good show later in the spring.
Here's the view from inside the warehouse. We're looking nearly due north, up the main branch of Titus Canyon. We'll join this branch just below Leadfield.
Here's a geologically labeled version of the same photo.
The geology, from Niemi (2012), is fairly simple (now that someone else has mapped it!), with the Titus Canyon Formation (EOgtc) being overlain by the Panuga Formation (Tg), and it being overlain by the Wahguyhe Formation (Tw). From this angle, we can see one branch or splay of the Fall Canyon Fault Zone (FCFZ) snaking away from us, more or less heading up Titus Canyon where it disappears beneath a large jumble of what has been mapped as QTls, Quaternary or Tertiary landslide deposits.

But let’s move on.

Hike, hike, hike, walk, walk, walk…and we’ve arrived at the metal building we first saw from Red Pass (!); it's sitting on leveled ground next to a mine dump.

The creosote was in bloom when this photo was taken in May, 2009. When doing field work down in the Mojave (which this qualifies as, roughly speaking) we used to say, “The field season is over when the creosote starts blooming.”
The "far west cabin" at Leadfield is on WLMC's March Storm No. 1 claim according to Lengner and Troxel (2008). It's listed as "Frame and Iron Compressor and Engine Room."
A number of outcrops on the rocky slopes behind the old building show some goethitic iron-oxide staining. As I've mentioned before, these are the sorts of exposures that would catch the eye of an oldtimer prospector, and I'd be remiss, when doing exploration, if I didn't at least walk over to take a look.

It’s about this time during a typical Leadfield excursion that I usually note a bird or a lizard, if I haven't seen any on the walk over to this site.
And sure enough, here's a lizard sitting on what looks like a bit of breccia!
And what can we see looking out the window of this metal shack?
Well, depending on which window we choose, either a brushy, rocky slope or...some geology! (I see geology everywhere, however.)
We look to the north-northeast out a roughly square window that has been elongated by my crude photo stitching.
To this same photo, I've added some geological labeling (from Niemi, 2012).
This is fairly typical geology for this area, this time with a few down-to-the-east faults drawn in, including the mostly dotted-in fault that partly separates the foreground bluff from the background scrabbly-looking hills (it's dotted because we can't really see it from this angle). The faults are all essentially strands or offshoots of the FCFZ. A westerly major strand of the large fault zone lies just off the photo to the left (west, and seen in the geology-labeled earlier photo above), and an easterly major strand cuts through just beyond the Tp-covered ridges. The minor faults, most of which are ones that I mapped on Google Earth (and which are not shown on Niemi's map because they are too small), probably flatten to join the westerly major strand at depth, and off the photo to the right (southeast), the easterly strand joins the westerly strand (see Niemi's map). To emphasize how useful a few marker horizons can be, I’ve outlined the base of a few whitish cliff- and ledge-forming units in orange, pink, and lavender. I think these whitish layers are probably tuffs, and the thicker, middle one might be the crystal tuff marker bed we saw on “Tw Hill” over near Red Pass. These marker beds are entirely within in the Panuga Formation (Tg). Anyway, we’ve once again got the Titus Canyon Formation (EOgtc) overlain by the Tg, overlain by the Wahguyhe Formation (Tw), overlain by the Crater Flat Group tuffs (Tc), overlain by the Paintbrush Group tuffs (Tp), which are all ultimately overlain by the Timber Mountain Group tuffs (Tm; not seen here).
A better view of the bluff, as seen from the same window.
Standing on the mine dump in front of the corrugated shack, we have a great view of the adit and a collapsed building that doesn't show up on Lengner and Troxel's map of the claims, workings, and town. According to their map, the adit accesses a little more than about three thousand feet of drifts. The hill the adit cuts into has been mapped by Reynolds (1969, seen in Lengner and Troxel, 2008) as Mbx: Tertiary megabreccia in the lower part of the Titus Canyon Formation.
Beyond the hill, we almost get a glimpse of a low-angle fault.
In this enlarged shot of the adit, we see that the rocks do look like a breccia.
Carbonate breccia is exposed on the left rib. Blocks of carbonate or breccia have been used to wall up the opening.
This type of metal gate is not currently in use. Newer types of gates keep people out while also letting other animals use the mine (e.g., bats, snakes, owls, various rodents). Possibly bats can get through the small opening, but some species won't fly through something that small (I'm not sure whether any of the species of bats in Death Valley need the larger openings or are the type of bat that won't fly through a grate). Read more about bat gates here (pdf) and here.

For next time: cactus, more old building remains, and more geology!

Selected 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.

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!)
Titus Canyon: The Upper Part of Lost Canyon
Leadfield: Scams with a Side of Geology