Thursday, December 1, 2016

More From the Road: The Colorado River Aqueduct

When I drove to the area on the south side of the Whipple Mountains where I ended up camping amidst downpours and nearby lightning, I thought I'd grab a few photos of the Colorado River Aqueduct, which passes through just north of CA Highway 62 on its way to the greater L.A. area, but an RVer was camped just beyond the aqueduct overpass, so I blew it off until I left. (I'm not terribly social while in the field, especially when traveling along.) On my way in, I took one shot showing the signage and the overpass (first photo). In the Whipples (and elsewhere), the aqueduct goes underground in several places, usually to allow passage of large dry washes. It's at these points that dirt roads can cross. The sign says, "Private Right of Way. Any Person Entering Thereon Does So at His Own Risk. Permission to Pass Revocable at Any Time. The Metropolitan Water District of Southern California." It is probably referring to the road paralleling the aqueduct, rather than the road crossing it, but who knows.

I stopped to take a few more photos on the way out during the early morning of the next day (after having coffee, of course!). These photos can be used to help illustrate a few stories I have about doing recon and exploration in the Whipple Mountains area—stories that date back to 1981, resume in 1983, and continue off and on after that through the late 1980s. (That's really why I went out of my way to drive into the area in the first place.)
The entire aqueduct, where above ground, is surrounded by a fairly hefty chain-link fence and more "No Trespassing" type signage in English and Spanish.
In this second view (above), Savahia Peak and its detachment-tilted Tertiary volcanic rocks, which we saw earlier, is sticking up a little.
View of the aqueduct looking through the chain-link fence.
While working in the area during a misconceived June recon program (June: ugh and yikes!), my field partner and I fantasized about cooling off in the water by tying ourselves off to the fence with ropes. We didn't think we'd want to be sucked downstream into the next underground section of the aqueduct, even though that section is a relatively short one: only 204 feet (61 m). But the rope idea, that might work!

Monday, November 28, 2016

The Left-Lateral Strike-Slip Garlock Fault Near Highway 395

While out on the last road trip, I started taking pictures from places where roads crossed the Great Basin Divide. Unfortunately, I soon gave that up because freeways, which I traveled not exclusively but considerably, are lousy places from which to take pictures. But thinking about divides also made me think about the Garlock fault, and how I'd be crossing it on 395 heading south into the Mojave. Here I've pulled over as I'm about to cross the fault.
I've drawn the Garlock fault with a thick blue line, and a secondary strand (air-photo linear) with a thinner blue line.
Besides the two fault strands, you can see the towns of Randsburg and Johannesburg, which were founded in 1896. The Yellow Aster open-pit gold mine was operated by Glamis Gold from about 1987 to 1997.

The haze was thick and the day overcast, and it looked like the photos I was taking would be fairly lousy, but MS Photos was surprisingly able to revive the dark, lackluster originals (I usually don't rely on the Photos app, but in this case it worked better than my other free programs).

After crossing the fault on 395, I took the road toward Goler Heights and Garlock. (Goler Gulch in the El Paso Mountains at Goler Heights is unrelated to Goler Wash in the Panamint Range at the edge of Death Valley National Park.)
Looking west along the southern range front of the El Paso Mountains toward Goler Heights.
The Garlock fault is mostly behind low hills in this shot, and it runs to the right of us about three quarters of a mile to the north.
I've drawn in two (or three) apparent strands (or air-photo linears―my interpretation may not be precise in all cases) in dashed blue lines; where thin, the fault is behind hills or out of view.
We're now back near the junction of the Goler Road with Highway 395, looking to the northeast.
I took this photo thinking that we might be seeing part of the Garlock fault, when in fact what we're seeing is a couple of fault strands parallel to the Garlock (air-photo linears).
The Garlock fault proper is out of view beyond the low hills.
A little more than a mile to the NNE from the place I took that last photo (above), there's a great example of a shutter ridge and offset drainages.
Google Earth image with a blue line I added using the "Path" function.
The same image with more scribbles.
This marked up Google Earth image shows a small portion of the left-lateral Garlock fault (long blue line). The fault line is basically the same as shown here (Roder, 2012). If you blur yours eyes a little (and even if you don't), you'll probably see several lines or linears that are running parallel to the main fault trace. I drew a few of these in with thinner dark blue lines. I can easily spot a few more.

The fault has offset two drainages in a left-lateral sense; that is, the south side of the fault, moving to the northeast (right) has brought in a ridge that has blocked the dry wash in the center of the image, forcing it to flow to the northeast to get around the ridge. That ridge is labeled "shutter ridge," which is the term for a ridge that blocks a drainage in this fashion along any strike-slip fault, whether it's right lateral, like the San Andreas, or left lateral like the Garlock. A second drainage way off in the upper right corner of the image has been blocked and offset in the same fashion. That drainage appears to have two shutter ridges, one that is north of the main trace of the fault, and another that looks like it's south of the main trace (at least the way the main trace has been drawn; we can see by drawing in just a few air-photo linears that there may be a few complications, and faults often meander around a bit).

I got back onto Highway 395 and continued south toward my destination, figuring that I could get a photo looking back toward the Garlock from somewhere up near the turn-off to Randsburg. I finally found a pullout on the east side of the highway; it offered me a four-wheeling opportunity to drive a very narrow, rocky road to the top of a small hill. The photos I took from there looked really lackluster, so I didn't spend a lot of time trying to get a really good panorama. Consequently, the two photos I've stitched together below do meet up on the horizon, but they are way off in the foreground, primarily because I ended up moving to keep the dirt road I was on out of the picture. We can, nevertheless see where the Garlock and a couple parallel strands or linears are located.
Stitched photo. The center of the photo is looking just west of north.
The same photo with a few labels.
And that's basically it for the Garlock fault, but there's a location near Goler Heights that might be a good spot to look around the fault, and there are probably some good locations near Garlock.
Looking northeast from Goler Heights along the Garlock fault.
UPDATE: Be sure to view Ron Schott's GigaPan of this portion of the Garlock fault.

Sunday, November 27, 2016

Links: Here Are a Few, But Great, Great Basin and Great Basin Divide Links

Great Basin—Mojave Desert Region - the hydrographic, physiographic, and floristic Great Basin (GB) regions and climate; v. good map of vegetation zones, lots on flora and fauna; pretty good map of the GB itself although it goes all the way to Colorado River (!!); Fremont coined "Great Basin".

Quaternary stratigraphic, hydrologic, and climatic history of the Great Basin, with emphasis on Lakes Lahontan, Bonneville, and Tecopa - Morrison, cited in the first ref, said the area of the GB "exceeds 500,000 square kilometers" ; this source is not available online, is part of DNAG - this volume.

The Great Basin: A Natural Prehistory - Grayson, at Amazon. (and here's a Google Book preview.) A better map of the GB. Grayson discounts having the Salton Sea in the Great Basin on page 11. His map, page 12, also ends the Great Basin in Pahranagat Lake, as justified below (Witt etal, 2008):

Jonathan D.S. Witt, Doug L. Threloff, and Paul D.N. Hebert -
Genetic zoogeography of the Hyalella azteca species complex in the Great Basin: Rapid rates of molecular diversification in desert springs:
Geological Society of America Special Papers, 2008, 439, p. 103-114, doi:10.1130/2008.2439(05). Page 104 (clip from Google Books):
(Witt et al, 2008 is in GSA Special Papers 439:
Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives -
edited by Marith C. Reheis, Robert Hershler and David M. Miller).

Fishes of the Great Basin - a Google Books preview - shows the White River above the lower end of Pahranagat Valley as in Great Basin.

Google Earth image of the West with a lot of lines. The Great Basin divide according to me is in magenta, wrapping around the Great Basin. Note the two possibilities at Pahranagat Lake, and no Salton Sea.
There is a mention of the Great Basin divide (GBD) in "Ore Deposits of the Jarbidge Mining District" 1912, (Google Books preview).

The Jarbidge Mining District, 1923 - mentions the GBD.

Thursday, November 24, 2016

From the Road: A Joshua Tree Lunch Stop with Volcanic Rocks

It wasn't long after I stopped to make coffee on the Turtle Mountains road, that it was time for lunch.

(Actually, before I found a place for lunch, I mistakenly pulled off on the paved road to McLaughlin, thinking that I could get a better picture of the Castle Mountains, a place I had worked long before, only to find that the road had no legitimate turnarounds until nearly reaching the Colorado River. This unforeseen escapade surely added an extra hour to my driving time!)

North of Searchlight, I found a suitable dirt road and drove away from the four-lane highway on blessed dirt. (Highway 95 wasn't four-laned in this part of the world the last time I drove on it; road widening began sometime after publication of the 2002-03 Nevada road map and was complete by the publication date of the 2005-06 road map.)

Before making lunch (and then more coffee), I wandered around and took a few pictures, including this one of an alive but bent over and half-burned Joshua tree. (I don't know if the tree was hit by lightning or lit on fire by an obnoxious passerby. The other Joshua trees nearby showed no signs of fire, so I don't suspect an old wildfire.)
What's that in the distance beyond the Joshua tree?
It's a hill of light-colored rocks covered by darker rocks (part of the Highland Range, Clark County, NV) .
My idea of the geology while out there was simple, and turned out to be fairly incorrect. I did get the type of rock right: Yes, it's (primarily) volcanic. I was thinking of a fairly thick ash-flow tuff sheet, with a thick poorly welded zone (in buff or pale orange), a very thin to intermittent vitrophyre (the thin black bed on the far hill), all overlain by a strongly welded zone (the sloping dark brownish hill-capping formation). Wrong. And wrong.

I found the detailed geology in this M.S. thesis (Colombini, 2009); the basics of her geology was largely from a map by Faulds et al (2002), but with more detail than I want to report. The larger picture consists of hill-capping basaltic andesite (this section might commonly be identified as basalt in the field) overlying a thin, dark, glassy rhyolite to rhyodacite flow (I guess I was partly correct on this!), overlying pale orange non-welded tuffs of mixed sedimentary and volcanic origin (and partly correct on this). Some flow-banded rhyolitic flows are mostly hidden at the base of the orange hills, barely sticking up high enough to be seen in the photo.

These rocks are all mid-Miocene in age, and they have all been tilted to the west (away from us) by widespread extreme extension related to detachment faulting within the Colorado River extensional corridor. The structure of the area is complicated by being within or near the Black Mountains accommodation zone (Faulds et al, 2002; abstract only, the rest is behind a paywall).

Tuesday, November 22, 2016

Titus Canyon: The Klare Spring Breccia

Klare Spring in Titus Canyon is well known as a petroglyph site (with a sign and everything); it is less well known as a breccia site and as a place to view the low-angle normal faults of the Titus Canyon fault zone (TCFZ). MOH and I were both immediately attracted to the breccia, and then—after examining it closely—we turned our attention to the various petroglyphs. (If you want petroglyphs, go here, here, or here, or to other Google-able websites.)
The breccia is the orange-brown mass of rock that MOH is inspecting intently. It's composed largely of fragments of Carrara Formation (Єc), with a few scattered chunks of gray limestone, which are presumably from either the Carrara Formation or the tectonically higher Bonanza King Formation (Єb). The upper strand of the Titus Canyon fault zone (TCFZ) cuts above the breccia, somewhere between my Єc and Єb labels, possibly at the base of the first cliff, or possibly behind and above that cliff. Rocks in this lower part look brecciated to me, but I didn't scramble up the slope to see them in person.

In fact, here are some of my ideas about the placement of the upper strand (or multiple upper strands?) of the TCFZ.
An image from Google Earth approximating the first photos.
I wasn't sure whether the two very large angular fragments of gray limestone, including the block festooned with petroglyphs, were an actual part of the tectonic breccia, or whether they had at some point slid down the cliffs and been cemented in place by the waters of Klare Spring.
Angular fragments of the Carrara Formation are healed by travertine.
The waters of Klare Spring emerge from the lower strand of the Titus Canyon fault zone, just down-canyon from the petroglyph site. The lower strand has placed this fractured, shattered, and brecciated Carrara Formation over the older Wood Canyon Formation (ZЄw, see next photo set).
Looking up canyon past Klare Spring.
I happened to shoot this pic looking eastward, back toward Klare Spring from a couple hundred yards down canyon. Once again, I had fortuitously grabbed a view of the TCFZ, this time including the lower strand that runs right through Klare Spring, and also including the upper strand (although the exact location is of that strand(s) is imprecise).
The same view with some geologic labels, including a few question marks.
The faults up the canyon (on the right) were seen in more detail in an earlier post; basically, we're looking at the upper strand of the TCFZ, which has placed the Bonanza King (Єb) over the Carrara (Єc) and some possible breccia (labeled "?"). Klare Spring is past the white car in the lower left of the photo. The lower strand of the TCFZ, which runs right through Klare Spring according to many, places the pale orange brecciated Carrara (Єc bx) over the reddish brown rocks of the Wood Canyon Formation (ZЄw). I've labeled the Bonanza King where I'm sure of it (Єb), and have left the first light gray cliff above the Єc breccia as "?". These lower cliffs, held up by rocks that appear brecciated in the first set of photos, might be composed of Carrara or Bonanza King, or even some tectonic jumble of both.

And so, we've left Klare Spring, and will continue our way down the canyon...

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
Almost Titus Canyon: Is This a Fold? And... Apparent Dip with Post-it® Notes
Titus Canyon: The TCFZ, the FCFZ, and a few Other Faults
Titus Canyon: Another Look at the Titus Canyon Fault and A Scramble
Titus Canyon: We Make Our Way Toward Klare Spring