Links: Auriferous Gravels in CA

Here are a few links about the Au-bearing gravels of the California foothills and Sierra Nevada. (It's time to get this out of my drafts folder.)

Early Tertiary Geology References - at Sierra Geology: where rocks meet the human environment (or vice versa) -- several good articles linked

Garside, Larry J., Henry, Christopher D., Faulds, James E., and Hinz, Nicholas H., 2005, The Upper Reaches of the Sierra Nevada Auriferous Gold Channels, California and Nevada, in Rhoden, H.N., Steininger, R.C., and Vikre, P. G., eds., Geological Society of Nevada Symposium 2005: Window to the World, Reno, Nevada, May 2005, p. 209-236.

Yeend, W.E., 1974, Gold-bearing gravel of the ancestral Yuba River, Sierra Nevada, California: U.S. Geological Survey Prof. Paper 772, 44 p., Plate 1 and Plate 2.

From the Road: Mountains Partly Covered with Sand

I stopped along the way to check out some run-down and decrepit old buildings in the valley near Twentynine Palms (the valley of Dale Lake, a dry lake or playa, sometimes called "Wonder Valley"), and came upon an area where not only were the mountains being choked and overrun by their own alluvium, they were also being buried by pinkish orange sand blowing in from the western Mojave. This is the southern Sheep Hole Mountains near the western approach to Clarks Pass. The pinkish orange color is from the abundance of K-feldspar often pink to pale orange in color) in the sand.

Death Valley Trip, Part 3: Northward, and over Daylight Pass

We're still on the road in Death Valley and have stopped between the turnoff to Natural Bridge and the southern entrance to the one-way Artist's Drive to look northeastward toward the Black Mountains.

Geology is everywhere in Death Valley, whether you look up or down, north or south, east or west. Consequently, although MOH and I were there mostly to see this year's "superbloom," the lion's share of the photos we took show a lot of geology, which I could only arm-wave or guess at when driving through. I've done a bit of research in these several days after getting back, read a few things, and looked at a map or two (see references below), thereby reacquainting myself with the general geology of the area. For this post, I'll mostly be using the geology, including formation abbreviations, from this USGS map and accompanying report.

So, what do we see in the first photo, besides a nice carpet of desert gold on the alluvial fan in the foreground? Well, I see a seemingly messy pile of white, buff, gray, and brown slope-forming rocks in front of reddish and brownish cliff-forming rocks, with the highest parts of the mountain topped by white, gray, pink, and brown layers. I suspected that the lower, rounded hills would correlated with the ashy layers occurring along Artist's Drive (the Miocene Artist Drive Formation), but I was wrong. Workman et al. (2002) mapped the lowers hills as Tvg: These are part of the 5.4 to 6.0 Ma Greenwater Volcanics, which consist of rhyodacite flows and ash-fall tuffs. The dark rocks in the cliffs behind the low hills are 8 to 12 Ma rhyolitic to andesitic flows and tuffs, mapped as Tar, with a couple thin, lighter-colored layers of what they map as Ts4: undifferentiated Pliocene to Miocene sedimentary rocks. Ts4 seemingly includes the Miocene Artist Drive Formation, although they don't specifically mention it in their report. The mountains are capped by the same ashy volcanic rocks that are in the low hills, possibly offset by faulting: The map shows two presumably normal (though not labeled) faults between the Tvg of the low hills and the Tvg capping the cliffy part of the Black Mountains.

Now, at the same location as in the first photo, we're looking north toward Artist's Drive, which is in the low area just left of center.

The low, dark hills in this second photo are composed of the Greenwater Volcanics (Tvg). Everything else is a jumble (or dog's breakfast) of lighter-colored  rocks mapped as Ts4 and brownish gray rocks mapped as Tb—i.e., a pile of faulted and interbedded (?) Artist Drive Formation (mapped as Ts4) and basalt (Tb).

Once again, MOH and I drove quickly through the Furnace Creek area without stopping, to continue northward. We finally came to the turnoff to the Daylight Pass cutoff at Beatty Junction. The next photo is from just after the turn onto the cutoff road.

Looking NE, with a  low part of the Grapevine Mountains in the background.

The low, dark brown hill beyond the desert-gold-carpeted alluvial fan is underlain by Ts4 (Artist Drive Formation?). The intricately dissected, crinkly hills just beyond, with numerous alluvial fans covered with desert gold, are underlain by what is mapped as QTa, or "oldest alluvium," thought to be middle Pleistocene to late Tertiary (Workman, et al., 2002a). The jagged-looking hills beyond, a low part of the Grapevine Mountains, are underlain by various Cambrian sedimentary formations.

As we drove a little farther up the road, the light was getting low.

Here we're looking southward toward the the 11,048-foot high (3367 m) Telescope Peak, barely visible behind closer ridges. Wildrose Peak is the rounded peak on the right; the peaks to the left include several unnamed ones along and above Colville Ridge.

Now we're standing on what looks like average desert pavement, with a little desert gold growing in a small rill.

It turns out that this graveled hill is underlain by what has been mapped as Qlc, "old lacustrine deposits" (Workman, et al., 2002), which are late to middle Pleistocene in age. In fact, this is one of two linear ridges, as seen below in a Google Earth image. These might be old spits or bars, and they are marked by lines that might be shorelines.

Google Earth image showing two linear ridges (Google Maps link). The pin marks the approximate location of 3DV006-009 (the previous two photos and the next two).  

Bright desert gold (Geraea canescens) on brown, wrinkled hills of QTa (oldest alluvium). The dark hill on the right is part of the Death Valley Buttes, which is underlain by CZw, the Cambrian-Precambrian Wood Canyon Formation.

Desert gold along one of the rills running southward off the linear ridge.

The dark brownish, low hills beyond the lacustrine ridges and alluvial slopes are composed of more Ts4 (I'm not qualified to say it's Artist Drive Formation), and the high country beyond is part of the Funeral Mountains, largely underlain by late Precambrian and Cambrian rocks. The tilted rocks in a hill or mountain just right of center is shown as Cnbc on our map: the Cambrian Nopah, Bonanza King, and Carrarra Formations. In general, it's the lower far hills and the mountains to the left that are underlain by Precambrian rocks.

While we were stopped at the roadcut through the liner ridge, a photographer told us we should look out for a particular desert five-spot that he had put a rock ring around, which would be up ahead near Milepost 8. Apparently the five-spot is considered one of the more beautiful of the myriad desert flowers, and it is sometimes described as rare.

We drove north up the cutoff road, diligently looking for Milepost 8. Just when we had given up on seeing any mileposts (where were they? hidden? were we distracted by wildflowers and geology??), we found MP 6. From there we counted our way slowly, and pulled over right next to MP 8. Where was the rock ring?

It wasn't far uphill from MP 8, right alongside the road.

Desert five-spot (Eremalche rotundifolium) inside a circle of rocks.

A closeup of the same plant.

The location of this plant (and all the photos) can be seen in the embedded MyMaps map, below.

The sun was low, we were hungry, so onward and upward we rolled, turning back to take one last photo or two looking south toward the mostly shadowed Death Valley.

Looking south toward the Death Valley playa.

Once again, the low, dark brown hills are underlain by Ts4; the wrinkly hill of oldest alluvium that we saw earlier can be seen to the right of the dark hills. Telescope Peak is the faintest, snow-covered peak in the distant Panamint Range, on the right; the Badwater and Mormon Point Turtlebacks can be seen in silhouette on the left, far down the basin toward and beyond Badwater.

=========

This post ends the first day of our Death Valley wildflower trip, although I haven't yet posted about the Titus Canyon leg of this journey. Part 1 was here, Part 2 here. This is Part 3. There has been a geologic component to all of these posts, so far. How could there not be?

I will probably now move all the way back to the beginning of our trip, which began two days earlier and miles to the north under cloudy skies. I'll work my way south to Titus Canyon, which may take more than one post. (Titus Canyon is huge, for geology!)

Selected References:
Greene, R.C., and Fleck, R.J., 1997, Geology of the northern Black Mountains, Death Valley, California: U.S. Geological Survey Open-File Report 97-79, 110p.

Hunt, C.B., and Mabey, D.R., 1966, Stratigraphy and structure, Death Valley, California [pdf]: U.S. Geological Survey Professional Paper 494-A, , 162 p.

Lengner, K.E., 2009, A trip through Death Valley's geologic past: Deep Enough Press, 66 p.

Lengner, K., and Troxel, B.W., 2008, Death Valley's Titus Canyon & Leadfield ghost town: Deep Enough Press, 175 p.

Miller, M.G., and Pavlis, T.L, 2005, The Black Mountains turtlebacks: Rosetta stones of Death Valley Tectonics [pdf]: Earth Science Reviews, v.73, p. 115-138.

Troxel, B.W., and Wright, L.A., eds., 1976, Geologic features, Death Valley, California [pdf]: California Division of Mines and Geology Special Report 106 [several articles].

Troxel, B.W., and Wright, L.A., 1987, Tertiary extensional features, Death Valley region, eastern California [pdf]: in Hill, M.L., ed., DNAG Centennial Field Guide v. 1, Cordilleran Section: Geological Society of America, Boulder, p. 121-132.

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.

Wright, L.A., Otton, J.K., Troxel, B.W., 1974. Turtleback surfaces of Death Valley viewed as phenomena of extensional tectonics [abs.]: Geology v. 2, p. 53-54.

Bonus Photos:

The crinkly, wrinkled hills in a wider view.

A zoomed view of desert gold and the Panamint Range, with Telescope Peak a little more apparent than in the earlier, wide-angle view.

A wide-angle view from the linear ridge.

All photos in this post were taken on Leap Day, 29Feb2016.

Death Valley Trip, Part 2: More of the Badwater Turtleback Fault

If you remember from a couple days ago, toward the end of the first of, hopefully, a few more posts about our trip to Death Valley and vicinity, we had walked up an alluvial fan down near Badwater and were looking at the Badwater Turtleback fault, which is essentially the entire range front above. Specifically, we were at the smooth, olive-brown surface on the far right edge of this first photo.

Not incidentally, these photos were all taken during the early days of this year's Death Valley "superbloom." We'll see some wildflowers in this post, but I'll be concentrating on the turtleback or detachment fault surface and not the flowers.

The Badwater Turtleback fault surface, looking north. Part, but not all, of the apparent curvature in this photo is from the 18mm wide-angle view (27mm in 35mm equivalent).

I was surprised to find what looked a lot like Quaternary or late Tertiary alluvium—alluvial fan, talus, or basin fill deposits—sitting in the upper plate of this fault, so I took quite a number of photos.

The apparent dip on the alluvial deposits is shallow, dipping slightly back to the east. This is only apparent dip, however.

I wondered if the older alluvium (older than the material on the active fans we had just hiked up) had been deposited right against the fault plane (the turtleback faults are often exposed, with hangingwall rocks having been stripped of by post-fault erosion), or if the deposits were, indeed, cut by the fault. If I could just get closer—close enough to touch the fault plane or the deposits—maybe it would be clear that this was a bunch of post-fault debris covering the fault. I couldn't, and it wasn't. The light brown, fairly poorly sorted material is definitely in the hangingwall of the fault: while there I could see visual evidence of shearing.

In this photo, you can see a more steeply dipping fault cutting the fan deposits in the hangingwall of the main shear zone. The slightly steeper hangingwall fault may flatten toward the main shears, but that's really unclear.

When checking out the literature after the trip, I found that, indeed, the hangingwall of the Badwater Turtleback fault or detachment does contain Pleistocene fanglomerate deposits (Miller and Pavlis, 2005).

Here we're looking up the plane of the fault surface, a kind of disorienting view.

The shadowy blob in the upper right (above) is part of the same shadowy surface seen in the next photo (below), and the light colored mass that looks like it's about to slide down on the photographer (me!) is another, larger mass of hangingwall fanglomerate.

This photo shows more older alluvium in the hangingwall of the turtleback fault surface, with the younger alluvium of a talus cone to the right. Notice the nice greenery with smallish flowers on the talus.

I scrambled upward near the base of the turtleback, but the terrain was a lot steeper than it looks in these photos, and the heat was getting to me some: although it was only 87° F (cool by Death Valley standards), it was a lot warmer than the 30s to 60s that I was accustomed to. Also, I had taken a scary tumble in Titus Canyon earlier that day, and wasn't comfortable with the steep slopes. I probably would have benefited from sturdier boots.

MOH looks up at the fault plane on the south side of the little drainage area or canyon near the base of the turtleback surface.

The same surface, perhaps a little closer.

Fault surface with wildflowers.

Because I couldn't get right up on the fault, I took these photos of a slickensided surface in float. Also, these tiny flowers—white with yellow centers like little daisies, tiny purple blooms, and others—were everywhere along the talus-ridden slopes.

The faint slickenlines are running across the photo here (same piece of float).

We walked back down the fan. It was easier going down, as it usually is, and I took a line more in tune with the recent rills and rocky, sandy washes, which no doubt ran last October when storms washed out numerous roads in the Death Valley area.

The turtleback fault plane is exposed in the shadows of a "slot" canyon just south from where we hiked up. Note the greenery with tiny wildflowers all across the fan.

And here's one of the tiny flowers. Does anyone know what this is?

(It's hard to Google "yellow wildflower death valley" right without coming up with just the desert gold.)

The Badwater Turtleback fault and a bit of desert gold.

We take one last look at the alluvial fan, the flowers, and the Badwater Turtleback. The flower show is dominated by yellow desert gold and purple notch-leaf phacelia.

Say goodbye to Badwater, before we head north.

    Location map:

Selected Reference:
Miller, M.G., and Pavlis, T.L, 2005, The Black Mountains turtlebacks: Rosetta stones of Death Valley Tectonics: Earth Science Reviews, v.73, p. 115-138.

All photos in this post taken on Leap Day, 29Feb2016.

Across the West and Back Day 2: Pequop Summit to West Wendover

On our journey eastward across Nevada, MOH and I were last seen approaching the Pequop exit in the Pequop Mountains. Just beyond that exit — which provides access to such places as Milk House Spring, Adele Spring, and Nanny Creek to the south and East Squaw Creek to the north — I-80 crosses Goshute Valley, heading for a passage over a low spot in the Toano Range.

Large alluvial fan in Goshute Valley.

Around the bend in the photo above, I-80 crosses a large alluvial fan coming southward off one area of the Toano Range. Both sets of mountains in the photo are parts of the Toano Range, with the low point in the center just beyond the fan being Silver Zone Pass.

A little farther on, in the center of Goshute Valley, you can look back toward the Pequops and see the drill roads of Newmont's Long Canyon project, which was acquired by buying Fronteer Gold (link to Fronteer's website now goes directly to a 2011 Newmont announcement about the buyout), who had done a good portion of the work on the property (along with others before them). An inferred resource of 2.6 million ounces of gold has been announced by Newmont.

Long Canyon drill roads on the east side of the Pequop Mountains.

About midway across Goshute Valley, shadows to the south made Shafter Knoll, about 13 miles distant, stand out against the faded blue of the Dolly Varden Mountains, which are about 42 miles south of the highway.

Looking south. Shafter Knoll is on the left, the Dolly Varden Mountains are in the center, and the Pequop Mountains are on the right.

Road construction on I-80 in the Toano Mountains.

As I've mentioned in earlier posts, we saw a lot of construction on the roads we travelled. This is the first time I've seen a mini-tunnel installed over a road to prevent rocks from falling, sliding, or flying through the air into the roadway. Two of these were being used, with the second spanning the westbound lanes of the freeway.

After crossing the Toano Range at Silver Zone Pass, I-80 goes into a straight section in the south end of Pilot Creek Valley. Here, the alluvial fan in the distance, coming off of the Leppy Hills north of the highway, looked as though it was crossing the valley to run up against the mountain range on the south, which is actually an eastern bulge in the Toano Range.

Looking southeast down I-80 at an alluvial fan coming out of the Leppy Hills on the left, with hills of the Toano Range on the right.

The topo maps of the area make it clear that alluvial fans from the Leppy Hills and meet fans from the Toano Range in the middle of the valley at a low, broad juncture between the ranges.

Topography is from the USGS TNM 2.0 Viewer (link).

The associated air-photo view shows a lot of shorelines from ancient Lake Bonneville. I'm wondering if the gravel pit seen in both views isn't in a gravel bar formed during Lake Bonneville times, but haven't found any literature to support that idea (and we zoomed by, not stopping for the fan or hypothetical gravel bar).

Air-photo view of the same area (link).

As we moved farther across the south end of Pilot Creek Valley, this unexpected view of rustic-looking buildings, reminding me of old western movie sets, popped into view.

Looking southwest toward the Toano Range.

Just beyond the buildings on the range front, I could see what looked like a small limestone mine. This turns out to be the Pilot Peak lime plant, operated by Graymont, which processes material quarried on site (you can see the highwall of the small mine behind the plant).

Pilot Peak lime plant and quarry.

A few minutes later, we were across Pilot Creek Valley, and our first glimpse of the Great Salt Lake Desert came into view beyond a low divide.

Looking southeast across  a bit of the Great Salt Lake Desert (white, beyond the closer hills), with Dutch Mountain about 35 to 40 miles away in the distance.

All through this leg of the trip, I'd been keeping my eye on the small portions of old U.S. 40 that hadn't been wiped out during construction of the interstate. Coming into Wendover, you end up looking straight down a still paved portion of the old highway, which is the main street in West Wendover, known as West Wendover Boulevard.

Looking nearly east down the main street of West Wendover to the Bonneville Salt Flats out beyond the NV-UT state line.

We had to get off in Wendover for some travel supplies, so we ended up driving on old highway 40 for a very short distance.

Be sure to check out the map insert below (and a larger view in Google Maps as desired), where I show the day's photos (to this point in the day). I've added a few of the locations mentioned in the post, including the alluvial fans shown above, Shafter Knoll, the lime plant, and an old part of U.S. 40 in West Wendover (which I'm often in the habit of calling Wendover, even though Wendover is in Utah and West Wendover is in Nevada).

View Day 2: Elko, NV to Vernal, UT in a larger map

Related Posts:
Across the West and Back Day 2: Looking for an Old Roadcut
Across the West and Back: The First Day
Intro to Recent Western Loop Trip

Meadow Valley Wash: Up the Canyon to Caliente

It’s now about mid-afternoon on the first day of my most recent Caliente field excursion, and after a quick lunch under a cottonwood tree on the side of the road, I decide that it’s time to continue my journey north on Highway 317 in Meadow Valley Wash. I’ve left Cottonwood Canyon, Elgin, and “the Narrows” behind. I have one more planned stop - despite the smoke and afternoon heat - before I head to the motel in Caliente: I want to find the road into our old mapping project near Boyd, so I can drive in and take a look around. In the meantime, one of the many trains that passes through the canyon has caught up with me.
The train keeps pace with me as I approach our 1978 camp area, which is just to the right of the highway in this photo. The train pulls through the bridge near camp and approaches the Boyd siding. Hard to say which vehicle is going faster, the locomotive or my truck – railway speed limits from Elgin to Caliente are mostly in the 30 to 40 mph range, and the highway speed limit is 35 mph or less, often marked 20, 25, or 30 mph because of curves and washouts.

What am I looking for exactly? Well, having not examined the old topo maps in detail, I’m looking for a place from memory, a place where we crossed over or under the train tracks. I think that place is just north of the Boyd siding, near the steep reddish cliffs we mapped, but I can’t really remember whether we drove over or under the tracks.
Whoosh! Past the north end of the Boyd siding I go, and past one possible way under the tracks. I continue driving north with the train, rather than stopping. By now, it seems like I'm racing the train - but I'd better not do that, because of all the washouts and places where the pavement was undercut by the 2005 flood.
I finally come to this little cement underpass, and although I'm north of the unnamed canyon central to the old project area, I decide to check it out - because it's there.
With the train still moving north, I walk under the cement underpass to the east side. No, this is not the place – not the place we crossed the tracks to get to the mapping project back in 1978. Although scrape marks about truck high on the wall suggest that people have driven through, the road heads off to the north, away from the area I’m trying to reach.
While driving north to the cement underpass, I’ve looked along this entire length of track for any approaches that might be possible places to cross over the tracks, and I really haven’t seen any. I take one last chance that there might be a place to drive over the tracks at this north Boyd marker - but as you can see, there isn't. Part of our former project area can be seen in the background: all those reddish, rhyolitic rocks, capped by what may be the Ox Valley Tuff.

At this point, I drive south, back towards the only other underpass I've seen, the only place that might provide access into the old project area.
Yes! This is the place! It even looks familiar! This underpass is here, just a little south of the northern Boyd marker (previous photo) and just a little north of the north end of the Boyd siding. This is the place we used to drive under the tracks to get to our map area. As you can see, it's chock full of green, rooted tumbleweeds (Russian thistle).
The road went under the bridge, and then straight into those bushes on the far side before turning to the left to head up the unnamed dry wash north of the reddish cliffs.
You can vaguely see where the old road would have gone into the bushes, although I really couldn’t follow it from there. The underpass is much higher and wider than the puny cement thing I walked under earlier. It doesn't, however, show any signs of recent use as a roadway!
As I walked around on the east side of the bridge, I found this railroad-parallel, two-track road - also inaccessible. I was disappointed not to be able to spend the rest of the afternoon driving up the old canyon road - possibly with vehicular agression I could have gotten part way in before getting stuck - and with the thick smoke hanging over the canyon and the afternoon heat increasing, I decided against climbing the steep talus slopes of the old project area.
So, I walked back to my truck...
...and drove north, bypassing the entrance to Kershaw-Ryan State Park on my way to Caliente.

But was I done for the day? No. I had it mind that I still had time to drive to the Ella Mountain Lookout, and from there into Pennsylvania Canyon from the east side, since I hadn't made it in from the west side at Elgin. That way, I would only have to stay in Caliente one more night. (Yay!) So I drove through Caliente and turned right onto the Clover Creek Road, took the dirt road past Tepee Rocks, and made it one hour into what turned out to be a four-hour-long, one-way journey to the lookout and into the canyon, before I realized that more than an afternoon's worth of driving was ahead of me if I continued on. I turned around.
Back in Caliente, I found a bar - but not the old Northern Lights that I remember from 1978. It closed about three or four years ago, according to some old-timers patronizing the Shamrock Pub, which is next door to what used to be the now-defunct bar.
As I sat there, Classic Vinyl played "Do It Again" by Steely Dan. It seemed like my entire trip was an attempt to recreate the past or to somehow do it all over again.

You go back Jack do it again
Wheel turnin' 'round and 'round
You go back Jack do it again