Pine Valley and Carlin Canyon Squiggles

What is this?!!1?1!?

It all started when I was trying to find out what rock formations and rock types I was seeing while making the long trip to work and back out near Elko. Looking around, I found this geologic map (Smith and Ketner, 1972), which even had a kmz file so I could load it directly into Google Earth—and so I did.

There I was, fiddling around looking at rock types and contacts. The map wasn't easy to look at in Google Earth (GE) because it was in black and white, so I started drawing the contacts on to GE, and lo and behold, the contacts were all screwy. It took me a while to figure out that the kmz file didn't register properly on GE; perhaps it didn't have a NAD27 to WGS84 correction or some such thing. I plotted a few static, known localities that I could identify on both the map and GE and determined that everything was off in a northwesterly direction (map to GE) by about 1500 to 1900 feet.

The map and GE locations of a small dam and the ghost town of Palisade.

I thought Palisade looked occupied the last time MOH and I visited, which was in the summer of 2013 (it was the only time either one of us has ever been there), so I was surprised to find it listed by search engines as a ghost town, rather than as a "census-designated area."

I was frustrated by this mis-registration of the map on Google Earth—what is the point of a kmz file of a map, after all, other than to be able to use it easily and forthwith—so I continued drawing on a few contacts in the area I was initially interested in: the area near the small (or old) dam shown above.

Oh look, there's a huge landslide or slump block mapped! I always find these fascinating, so I zoomed in on that, after figuring out that, indeed, I had stopped along the road once—in a pullout near the dam—and had found ash-flow tuff in the roadcut, just like I had remembered! (Although in this case, it was probably slumped or slid ash-flow tuff rather than 100%-in-place ash-flow tuff.)

And then I remembered that I'd always thought there was a pediment in Pine Valley, and recent drives through the area seemed to confirm that, though I wasn't sure if it would be considered a pediment because it seemed to be formed on Quaternary-Tertiary sediments. A couple of old reports (Regnier, 1960 and Eakin, 1961) confirmed that a pediment (or two, even!) had been identified in the valley—and that's when I went nuts with my GE squiggles, and started drawing in all the Quaternary gravels so I could better visualize the valley's geomorphology. That resulted in the squiggles seen in the first image: an incompletely labeled map with missing contacts but with pediment gravels outlined in great detail.

Then, I moved up to Carlin Canyon and—unsuccessfully in my opinion—tried to plot the unconformity contact. (See Ron Schott's Gigapan of the Carlin Canyon unconformity here.) And then I moved to the Carlin Formation east of the Carlin Tunnels. The Carlin Formation forms golden-brown outcrops and cliffs right alongside the highway, great examples of tafoni weathering, so close but inaccessible. I wanted to see if any roads led into the area, and there are none, but I drew some squiggles for the geology in that area anyway, and then moved south of the highway to draw in a few more areas of the Carlin Formation, because once I've started on something, it's hard to get me to stop.

An expanded version of my GE squiggles.

And that's what it all looks like at this point. Hopefully I'll be able to grab a few great photos of the pediment surfaces later this summer, when I move back into the area for another round of work way out there.

By the way, the completed geologic map (Smith and Ketner, 1978), published in color, can be viewed here (but without a kmz file).

From the Road: Talus Stripes and Shorelines along the Truckee River

Talus, shorelines, and fall colors.

It was a late fall day, and I stopped along Route 447 to see if I could get close to some of the brilliantly colored trees along the Truckee River a few miles north of Wadsworth. I didn't end up finding a good spot for pics of fall colors—other than maybe this one taken down near the Numana Hatchery—but I did find lots of wonderful talus stripes and some Lake Lahontan shorelines.

At two stops a little farther to the north, at and near the junction of 447 with Chicken Road and at the Historic Marker 448 pullout, I grabbed a hodgepodge of photos.

Looking SSE from the historic marker pullout.

These two photos look south-southeastward along the Truckee River toward distant Fernley. A good portion of the river in this area runs parallel or sub-parallel to Walker Lane strike-slip faults. Wadsworth Amphitheater, which shows up in the Google Earth images we'll see in a minute, is not visible from any of our photo sites; it's an amphitheater-shaped topographic feature cut into Lake Lahontan sediments right along the east bank of the Truckee, beyond the dark basaltic hills on the right side of these two photos (east side of the Truckee).

I love the lone Cottonwood in this photo.

I went ahead and drew a few lines on Google Earth, then I rotated the resulting images to two different orientations so we could see a little more of the terrain. Be sure to check the north arrow in the upper right! The linears I drew are parallel or sub-parallel to the trend of the Walker Lane. You might be able to pick out a few more in the images (or go to Google Earth and looking around a bit).

The Walker Lane—on Google Earth (G.E.)and on other aerial representations such as air photos—shows up best at very small scales; that is, if we zoom way out and observe the area from way above, we can see the trend of the Walker Lane better than if we zoom way in, like we've done here. Nevertheless, individual strike-slip faults have been identified throughout the Walker Lane, and a few of these occur right in this area.

The A is centered on Wadsworth Amphitheater. The purple camera icon shows the location of the first photo.

The next G.E. image zooms in to the area we can see in the photos. I've got all three photo locations turned on, the A for Wadsworth Amphitheater, and my drawn-in linears. These linears aren't necessarily faults, although I'm pretty sure the one on the far left is. Unfortunately, because I currently have a very lousy internet setup (thanks Frontier!), I can't load very many research web pages. Google works well—and Blogger is a Google product—so I can blog even with 25 to 100% packet loss (it's 50% this very moment). And because Google Earth is a Google product, it's working for me also! (But I can't routinely access my non-Google email.)

Back to the faults and linears. I do know from personal experience that Walker Lane structures pass through the Lake Lahontan sediments in the area where the Truckee is running in a particularly linear fashion. I know this from some work I did a long time ago with J.O. Davis, who was studying Lake Lahontan and using tephra beds to date various aspects of the stratigraphy. The two linears or faults in the lower right of the image cross through the area where I've seen older Lake Lahontan sediments faulted and highly contorted by the major structures that pass through the area. I can't say that my particular linears are right on the major structures, and I can see other possible lineaments.

UPDATE 3Feb2017: I now have good internet back, and I've been able to compare my "map" to a geologic map of the area (Bell, Garside, and House, 2005). My linear passing through the hatchery location (below) is spot on for their most prominent fault, which was mapped as a dominantly extensional fault.

A zoomed in G.E. view of the area.

Not sure why, but I prefer to spell amphitheater with an "re" at the end: amphitheatre. I also have a hard time sticking the first "h" into the word!

I sure wish Frontier was a better internet service provider! (I never had this kind of semi-routine trouble with AT&T in eastern and northern Nevada; their every-day speeds were faster, and service was (generally) provided more quickly.

Back to the photos! 😊

Horizontal Lahontan shorelines and vertical basaltic talus stripes.

Some of the same talus stripes in Google Earth.

This photo shows a juxtaposition of talus stripes, faint shorelines, and layered Lahontan sediments.

On this trip, I focused mostly on trying to get good photos of the talus, because that's really what caught my eye. I later noticed that a few shots showed the Lake Lahontan sediments fairly well.

White, gray, greenish gray, and pinkish layers of the Eetza Alloformation.

While driving through the area, I'd been assuming that the prominently exposed white units were part of the Sehoo Alloformation. I was wrong! The Sehoo is barely identifiable in this zoomed in photo, and it's the older Eetza that is most conspicuous. In fact, the Sehoo here is mapped as gravelly beach deposits, so it mostly comprises the dark gray or brownish gray layered deposits above the whitish units.

Note: I usually use "formation" when talking about the subdivisions within the Lake Lahontan section, but "alloformation" is technically correct. In explanation, Bell et al (2005) say this, "Lake Lahontan and related subaerial deposits were considered lithostratigraphic units in the early studies of Morrison and were designated as formations. With the revision of the North American Stratigraphic Code in 1983, new allostratigraphic and pedostratigraphic unit definitions were added which allowed the definition of time-transgressive, lithology-independent rock units and soils."

Qsm = middle member of the Sehoo Alloformation; Qe = Eetza Alloformation.

After taking all these photos, it was time to move on, so I looked to the north, in the direction I'd be heading.

What I saw was more talus, more shorelines, and more Lahontan sediments. (And some fall colors.)

Selected Reference:
Bell, J.W., Garside, L.J., and House, P.K., 2005, Geologic map of the Wadsworth Quadrangle, Washoe County, Nevada: Nevada Bur Mines and Geology Map 153.

Links: Headwaters of the Susan River and Lassen Volcanic National Park

Geologic Map of Lassen Volcanic National Park and Vicinity, California:
main page at USGS

Geologic Map of Lassen Volcanic National Park and Vicinity, California:
Sheet 1, geologic map

Geologic Map of Lassen Volcanic National Park and Vicinity, California:
Sheet 2, correlation chart

Geologic Map of Lassen Volcanic National Park and Vicinity, California:
Sheet 3, figures

Geologic Map of Lassen Volcanic National Park and Vicinity, California:
pamphlet (write up of the geology)

Susan River (Wikipedia)

Susan River Area Rapid Watershed Assessment (USDA NRCS)

Bizz Johnson Trail and Susan River (BLM)

Bizz Johnson Trail and Susan River (Friends of the River)

Great Basin (NPS)

Great Basin (Wikipedia)

Ishi, Thousand Lakes & Caribou Wilderness (order the wilderness map)

Repost: Blackhawk landslide, California - from Pathological Geomorphology

This article was originally posted at the soon-to-be-defunct Posterous.com site, Pathological Geomorphology, and was transferred here (thanks Kyle!) to the active Pathological Geomorphology (Tumblr). My original post was a response and addition to Callan's Blackhawk landslide post on Posterous, which is now here on the Tumblr site. I've transferred the original photos, added captions, and added a Google Maps location link at the bottom. I've added the original comments (with soon-to-be-dead links to Posterous) at the bottom. Also see this related post here on LFD.

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I'm posting a few additional views of the Blackhawk Landslide in California, to emphasize the truly pathological geomorphology of the area. In the views showing slide toe and slide source, I've moved the source area farther into the mountain from the original given by San Diego State [dead (kmz) link originally sourced here]. I've done this based on prior knowledge and published maps. Basically, the entire steep northern face of Blackhawk Mountain is the slide source area.

Google Earth view showing the slide source and slide toe.

Google Earth view looking from above the toe toward the source.

Google Earth view looking from above the source toward the toe.

Additionally, there are other older landslides in the area, most notably the one sometimes called the Silver Reef landslide, which is just east of the Blackhawk. Also, many additional breccias and possible landslide deposits have been mapped in the area. The geologic maps (Big Bear City quad and Cougar Buttes quad) are really awesome, especially if you know how complex the geology really is. There are numerous thrusts from the south, placing brecciated rocks of multiple ages on usually older rocks. In at least one place, bedrock has been pushed over one of the older breccias. Or is it really bedrock?

Back in the 1980's, I mapped a large area of Blackhawk Mountain and surrounding areas at 1inch = 500 feet. I found, and so have others working in the nearby northern slopes of the San Bernardino Mountains, that if you start at the top, clearly in bedrock, sometimes brecciated, and map down, then you will be tempted to map bedrock until you are clearly in landslide debris. If you start from the top and map up, the opposite is likely to happen.

Google Earth aerial view.

Aerial view with annotated geology.

The reason for northward thrusting is the bend in the San Andreas fault, causing the westward, southward side to be pushed northward, breaking over the steepened San Bernardino Mountains in low-angle faults. The thrusts cause brecciation, and the steepening, brecciation, and low-angle faulting predisposes the area to massive sliding. Stratigraphy is somewhat retained in the slides, and gold has been mined from nicely pre-broken landslid rock of the Blackhawk Slide. Silver occurs in somewhat disturbed veins in the Silver Reef Slide.

In the annotated view, the Younger LS deposits (yellow) are Holocene or late Pleistocene; the Older LS deposists (turquoise and pink) are middle or early Pleistocene; the Moderately Old LS deposits (purple and orange) are middle or early Pleistocene; the very old debris flow fan deposit (purple) is middle or early Pleistocene; and the QT Breccias (blue and red) are Pleistocene or Pliocene.

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Lockwood DeWitt responded:

Nice! The annotated map/image at the end really help clarify the messyness of interpretation here.

over 2 years agoSilver Fox responded:

And it doesn't even show the really screwed up bedrock!

over 2 years agoKatharine North responded:

Great images, Silver Fox! I'm going back and forth between the annotated image and the non-annotated ones, looking at the landscape differently each time, picking out the details. I like your note about the effect of where you start mapping - good to remember!

over 1 year agoJosiah Gardiner liked this post.

over 1 year agoAndrew Hammonds liked this post.

over 1 year agoEmil Dibble liked this post.

Sand Mountain for Sand Dune Week

Two dune posts in a row in a row creates a geoblogosphere meme, and Sand Dune Week has been proclaimed!
Sand Mountain — located on Highway 50 about 25 miles east of Fallon, NV — is a perfect candidate for Dune Week, being one of those booming or singing dunes described here on Cocktail Party Physics.

View angle, time of year and day (sun angle), and weather all affect the seemingly shifting appearance of Sand Mountain, sometimes dramatically. The first photo (above)was taken from the west-southwest during the middle of an early March day last spring, 2011.
This second photo was taken from the south in the late afternoon in late May, also 2011. Enlargement of the second photo will reveal a barely visible white line on the east side of the dune: the RV city usually sitting in the lee of the dune, where ATVers gather to run up and and down the face.
Here's the mountain in a wind storm, a late afternoon in mid-May of 2009. Any RVs present are getting sand blasted!
Lighting for pictures can be quite variable, and I often get flat pictures just driving by at random times of the day. But even mid-summer can be good for shadows and details, as shown by this photo taken early one morning in early July, 2010. Enlargement of this photo shows two tiny-looking ATVs on the west side (far left) of the dune, behind and a little to the right of a foreground dark spot that is possibly a rock or large bush. Look carefully!

Although I've driven up to the RV city and to the half buried Sand Springs Pony Express station, I've never gone on the dune to try to make it boom.

One thing that can be done fairly easily, as part of this mini virtual field trip, is to follow the sand from Sand Mountain back to its original source, back to the southwest across a mountain or two, then across Highway 95 south of Fallon, southwest toward the delta of the Walker River, where the river emptied into ancient Lake Lahontan. Start with this map and this air photo, then go here (scale change), then here, and then here (direction change). The last air photo is mostly below the high stand of Lake Lahontan, but shows the final current destination of the Walker River: Walker Lake.

Meme participants so far:
Galileo's Pendulum
Clastic Detritus
Cocktail Party Physics
In the Company of Plants and Rocks
Agile* - Journal
Ron Schott's Geology Home Companion Blog
Research at a snail's pace
Earth Science Picture of the Day
Sandatlas
Georneys
Pools and Riffles
Earth-like Planet
En Tequila Es Verdad
Through The Sandglass
EarthSky // Blogs // Space (Deborah Byrd)

Some References:
La Pointe, D.D., 2000, Earth Science Week 2000: Geology along America's Loneliest Highway. A field trip for families and rockhounds: Nevada Bureau of Mines and Geology Educational Series E-37.

Trexler, D.T., and Melhorn, W.N., 1986, Singing and Booming Sand Dunes of California and Nevada: California Geology, v. 39, no. 7, p. 147-152. Also reprinted here on Tom Sweich's webpages.

NOTE: The California Geology search page is quite finicky or counterintuitive. I finally searched using only the year, 1986. What also worked was %California% %Nevada% with the percent symbols, entered as keywords under "Title of Article."

A Tale of Two Trips

Looking east across the Great Salt Lake Desert toward Granite Peak from the vicinity of Dead Cedar Wash. March 3, 2010.

The first trip began early in the morning on ALT Highway 93 as I headed north toward Wendover, Nevada. The sun had barely risen, and reflections from the desert were a bright red orange.
The second trip ended with MOH and I driving past the same spot early in the evening of April 3, 2011, almost exactly 13 months later.

Silver Island Mountains and Bonneville Salt Flats. March 3, 2010.

On the first trip, I stopped at the southernmost rest stop near the Salduro siding, where an elevated viewing area provided me this view of the Silver Island Mountains north of the east and westbound lanes of I-80. The Bonneville Salt Flats were full of water when I passed by the first time; they were salty and mostly dry earlier this month, as seen in the first photo of my last post, and in the zoomed in version below.

Silver Island Mountains and Bonneville Salt Flats. April 3, 2011.

The Silver Island Mountains show some of the lower shorelines of Pleistocene Lake Bonneville: several old beaches near Silver Island Pass are highlighted by early morning shadows on the right; two wave-cut notches are almost hidden in shadow on the left. The snow-capped peaks are probably the Pilot Mountains. March 3, 2010.

The angle's a little different, but that's salt out in front of Tetzlaff Peak, the highest peak in the foreground, and maybe a bit of water or a thin mirage near the far edge of the flats. Those are the same low hills near Silver Island Pass on the right side of the photo, the same Bonneville shorelines and notches cutting the angular hillslopes as in the previous, somewhat zoomed in photo. April 3, 2011.
In March of last year, after leaving the Salduro rest stop and heading toward the SLC airport, I drove by the place where water of the Great Salt Lake was over the road in the spring following or during the El Niño of 1982-1983 (May, 1983). I thought the water looked kind of high, although I'm not well versed in its normal yearly fluctuations. I was about two and a half miles west of Burmeister and the Tooele-Grantsville exit on I-80 (MSRMaps location), looking toward the Oquirrh Mountains when I took the first picture (above) on March 3, 2010.
Strangely enough, the water once again looked high to me when we passed through early this month, and indeed it was higher: a year and one month after the first trip, spring runoff from the Wasatch Mountains (and other ranges) may have been in full swing. The second photo (above), from April 2, 2011, shows the exact same fence posts as the first, due to extreme luck and clever cropping.

For the first trip I arrived at the SLC airport and went off to Alaska. On the second trip, MOH and I arrived in Ogden and, before re-crossing the desert on our return trip, we visited a brewpub, dinosaur park, and very cool canyon.

Update From the Lake: Part of The Return Trip

Okay, so the update isn't supposed to be from Pyramid Lake, and it's a little late (about three weeks), but we did drive by that turquoise gem on our return trip after going to Middlegate the long way (up Ophir Canyon, through Ophir, to Ophir Summit, and over and beyond) and then going to our place at the lake. [I was going to add something about "I. C. Russell's white line" here, but can't find it being called that anywhere, so maybe later.]

I took zero pictures at the lake, if you can believe it. The leaves on our backyard aspens had only partly turned yellow, we had visitors, it rained all of one day. The rain was great: the sound of it hitting our nearly flat metal roof, the smell of it out in the evergreen trees, the almost Alaskan mistiness of it all. We ate out for dinner every night. One night we ate at two restaurants, and due to faulty order taking at the first one, we ate there for free the second night.
After visitors left, I raked some pine needles, disconnnected the drip system, moved one surviving blue spruce and one itsy-teeny black spruce — grown from a seed taken in Alaska — to a space underneath one of the pines.

All and all, it was a good trip. And on the way back, we went the long back way through Pyramid Lake. The back way turns out to be about one hour longer, and by the time we got to Sutcliffe I was hating it and was quite hungry. Hunger can make me cranky; we stopped in Fernley at Taco Bell.
Prior to arriving at Pyramid Lake, while on the long dirt part of the back way, we stopped at a little oasis in the desert, somewhere generally east of Honey Lake, probably located here, which I wrote about earlier.
As we got out of the truck, a huge predator-type bird flew out of the tall cottonwood tree and dropped the remains of a chukkar at our feet. It all happened too fast for me to get any kind of bird description other than dark with a very long wingspan — likely a turkey vulture, golden eagle, or bald eagle, although I suppose osprey isn't out of the running.

We then saw two amazingly shot-up signs. One was here, near Double Check Well, a major road junction if you happen to be going to Burning Man from California. I'm not saying that Burning Man attendees did it — many signs in Nevada are shot up — but I've never seen one quite like these two, and I do know that desert antics have increased manyfold since Burning Man moved to the Black Rock.

Sand Pass Road

Sutcliffe (unreadable miles) <--

Smoke Creek Road Jct 24 <--

County Rte 447 Jct 51 <--

Gerlach (unreadable miles) <--

Susan(?)ville 25 <--

Fish Springs Rd Jct .3 -->

Sutcliffe (unreadable miles) -->

Reno (unreadable miles) -->

Below, underneath red spray paint:

Reno (unreadable miles) -->

Below, with gray duct tape:

Gurlac [sic] 56 mi ... <--

Blackhawk Landslide Links & Danger in the Mojave

I recently uploaded my first post for Pathological Geomorphology, called Blackhawk: Truly Pathological. This post was inspired first by Kyle House's announcement that the subject of the month would be mass wasting, and second by Callan Bentley's post, Blackhawk Landslide, California. While writing the post, I collected a few related links.

• Caltech, 1999 , Ge 111ab: Applied Geophysics Seminar and Field Course: with reference list for the Blackhawk Landslide area.
• Miller, F.K., with Cosette, P.M., 2004, Preliminary Geologic Map of the Big Bear City 7.5' Quadrangle, San Bernardino County, California (version 1.0): U.S. Geological Survey Open-file Report 2004-1193, 1:24,000.
• Powell, R.E., and Matti, J.C., with Cosette, P.M., 2000, Geologic Map and Digital Database of the Cougar Buttes, 7.5' Quadrangle, San Bernardino County, California (version 1.0): U.S. Geological Survey Open-file Report 00-175, 1:24,000, with description.
• Shreve, R.L., 1959, Geology and Mechanics of the Blackhawk Landslide, Lucerne Valley, California Ph.D. Thesis, California Institute of Technology, Plate 1, 1:24,000.
• U.S. Geological Survey, 2006, Geology of the San Bernardino Mountains: Western Earth Surface Processes Team of the USGS.

As I mentioned at Pathological Geomorphology, I mapped in the Blackhawk Mountain area in the mid to late 1980's while doing some gold recon and exploration for Former Mining Company. It's a very neat place to work, with complicated and fascinating geology. The area is part of one of my mapping stories, about mapping from the top down or the bottom up and how the results might differ. As far as exploration went, we bulk sampled (as have so many other outfits), we mapped and sampled on the surface and underground, and we drilled using buckets to collect all the fines. All our work resulted in a geologic but not an economic success; we eventually, rather unwillingly on my part, moved on. Another exploration geo, also formerly of Former Mining Company, went back later while at another company; he may have put a couple small deposits together for smaller-scale mining than we had been interested in.

Blackhawk, which we maybe called something else so other companies wouldn't know which area we were talking about, was probably the first area in which I decided to go ahead and carry a gun in the field. This wasn't so much because that particular area was anymore dangerous than any other part of the Mojave (or, maybe it was*), but I thought I should act like a grown person in charge of my own protection, and start doing something about it. I haven't really gotten into the dangers of the Mojave that much before on this blog. Rest assured, the dangers are almost entirely related to people: people coming out of the vast basins or valleys south of the San Andreas fault, other people known as "L.A. escapees" who have escaped the mass city scene to live somewhere out in the desert, and people walking around carrying and shooting their own guns, many of them fully auto.

I found I really didn't like carrying a gun in a holster, either on my hip, or with a shoulder strap. It's extra weight (my version at the time was a .357 Magnum revolver), and carrying it made me feel just about as awkward as leaving the thing in my truck. Either way — whether I had the gun with me, whether it was in the truck behind the seat, or whether I didn't have one at all — I'd always watch my truck from some higher vantage point for several minutes prior to heading for it, to make sure no one was hanging around waiting for me. I'd also always leave the truck already turned around and ready to head out. I still do that; turning to face out, to face your exit direction, has nothing to do with the Mojave in particular, but the Mojave is probably where I started making that one of my own personal requirements.
Here's one of my favorite, out-of-the-way parking spots in the Blackhawk Mountain area, now apparently blocked by... a landslide!

*The unsafe nature of the northern San Bernardino Mountains relates to 1) the proximity of the Blackhawk area to the millions of people living in the L.A. and San Bernardino basins to the south, and 2) the proximity of the area to the tiny, then butt-ugly berg of Lucerne Valley (Google Maps), which at the time was a haven for drug thugs**. The worst of it for me was to call home or call the office from one of the two, count 'em, phone booths in town — the one in front of the Ace Motel — only to have someone drive up almost immediately in some fancy schmancy or beat up caddy and get out and start staring at me while I was talking: pointedly and impatiently staring after zero minutes. We had car phones, but they didn't work unless you got lucky or drove way down the road toward Apple Valley.

**Our claim staker, while using the other phone booth closer to the center of this supposed town, once had some slick dudes pull up on several motorcycles while he was conducting company business on said phone. While our guy was talking on the phone, Head Biker Dude jumped off one of the bikes, glared belligerently at our guy who was trying to say, "Hey, just a minute and I'll be done." Biker Dude then pulled a heavy chain outta somewhere, and then he started swinging it around and around in circles in an obvious threat: get offa my phone or I'll bust your face!

Friendly place. Can't say as I miss the town, but the geology was, and still is, great. And if you happen to be in the area, drive the road to the top of Blackhawk Mountain, to the peak called Silver Peak (MSRMaps): views from the road and from the top are impressive. Use 4WD.

Ancient Shorelines and a Basalt Dike southeast of Paisley, Oregon

In our last episode of the long saga of going to Oregon, hanging around, and then coming back, we had just left Paisley, where we had breezed through without stopping for the Annual Mosquito Festival. Past Paisley, we continued southeast on Oregon Route 31 toward our primary goal, the Winnemucca-to-the-Sea Highway. Prior to that turnoff, however, and only some ten miles down the road, we entered a freshly graveled stretch of pavement that points straight at The Narrows of the Chewaucan River (MSR Maps).

This is a good stretch of road for viewing a little geology. Near Milepost 107, you can catch a view of the ancient shorelines that wrap around the north side of Tucker Hill, a smallish, talus-covered and rocky butte on the south side of the highway.
These shorelines are from pluvial Lake Chewaucan, the remains of which now consist primarily of Summer Lake and Lake Abert. Lake Chewaucan reached an elevation of about 4500 feet at its high stand, the elevation of the highest terrace seen here.

For a much better view of the shorelines on Tucker Hill, see Andrew Alden's Outback Oregon Gallery (or take a road trip).

This little map, a modified version of this map, shows the extent of pluvial lakes in southern Oregon and will enlarge when clicked. I've highlighted Lake Chewaucan in bright periwinkle blue. The full extent of late Pleistocene pluvial lakes in the Great Basin can be seen here as Figure 13. Also see this pdf map of Pleistocene lakes in the western Great Basin; the map doesn't name Lake Chewaucan but shows its area.
Continuing along to the southeast, somewhere near Milepost 113 you will see one or two basalt dikes to the northeast. I managed to get a picture of the dike closest to the highway. It cuts vertically through basalt flows and intra-flow sediments, here showing a less than 90 degree apparent dip because we aren't looking straight down the strike of the dike. To look straight down strike, you should stop somewhere between MP 113 and MP 114.

This dike may be a feeder for the basalt flow capping the lower ridge: on Google Earth and Google Maps, it looks like the dike fails to cut through to the overlying flows.
Right at Milepost 114, you'll look almost perpendicular to the trace of the highway to see this view the dike. The second dike should be visible at this point, almost due north of the first and a little farther back in the hills. To get a closer look, try taking a dirt road that heads north and passes near the lower part of both dike outcrops. I won't, however, guarantee the condition of the dirt road — it's been many years since I passed that way, and who knows? For this trip, we just zoomed past in the Prius.

Also worth noting: more ancient shorelines are visible in the low rise to the right of the dike. In fact, shorelines abound throughout the area.

Some References:
Reheis, Marith, and Bright, John, 2010, Late Quaternary Paleohydrology of the Mojave Desert: U.S. Geological Survey, Geology and Environmental Change Science Center, page last modified on 15-Apr-2010 13:38:29 MDT.

U.S. Geological Survey, and Reheis, Marith, 1999, Extent of Pleistocene Lakes in the Western Great Basin: U.S. Geological Survey Miscellaneous Field Studies Map MF-2323, U.S. Geological Survey, Denver, CO.

View Bend OR to Winnemucca NV in a larger map

To be continued... onward to the Winnemucca-to-the-Sea Highway!

Tufa Tuesday: Tufa Domes and Thinolite at Pyramid Lake, Nevada

Pyramid Lake, located in northwest Nevada (MSRMaps), is named for a pyramidal-shaped tufa-mound island officially known as The Pyramid, also called Pyramid Rock. Hot water emanates from springs all around the base of The Pyramid near water level, a fact that can be tested by swimming out to the rock. Please note that the largest island in the lake, which is sometimes thought incorrectly by passers-by to be The Pyramid, is actually Anaho Island, a pelican nesting site. Although Pyramid Lake is entirely within the Paiute Indian Reservation, Anaho Island is a National Wildlife Refuge.

Anaho Island and The Pyramid as seen from an overlook near the junction of Nevada routes 445 and 446.

Anaho Island is the large island in the right and center part of the photo; The Pyramid is the small island closer to the far shore and immediately to the left of Anaho.

The Needles Rocks as seen near Thunderbolt Bay.

As you drive north of Sutcliffe, the paved road turns to dirt — variable dirt, from good conditions right after a blading, to execrable conditions of extreme and rocky washboard that will set your teeth on edge if you really want to get through to destinations to the north (Smoke Creek Desert), northeast (Gerlach and Black Rock Desert), and northwest (Honey Lake).

Eventually, The Needles Rocks comes into view (MSRMaps of The Needles Rocks).

The Needles Rocks tufa mounds seen in the distance from the pullout at George Washington Rock.

The tufa mounds or masses known officially as "The Needles Rocks" and locally as "The Needles" and even "the Needles Rocks," form two rough lineaments near some once popular hot springs at and near the lake margin. If you back out from the MSRMaps view in aerial photo mode, you'll see that the lineaments are parallel to faults or structures cutting bedrock to the north. It seems likely that the hot springs are related to the linear structural conduits, and that both are related to the formation of the mounds, although it turns out that most or all of the large-scale tufa mounds and features formed 26,000 to 13,000 years ago when calcium-rich springs, possibly cold, emanated from the lake bottom (Benson, 2004). Some tufa may still be depositing today, especially at places like The Needles Rocks, where springs may still contain high amounts of calcium (read more here and here).

I don't personally know much about the spring-water composition, but do know that the hot springs at The Needles Rocks are great, especially the hidden ones along water's edge, where you can swim beneath tufa into warm mini-caves.
This is the same view of The Needles Rocks, with a spherical tufa dome on the right.
Another view from the same point at George Washington Rock (Google Street View). I was really surprised to find that Google had driven this road — it used to be considered a road going from nearly nowhere to almost nowhere else: I mean, it goes places, but it's mostly traveled by locals.

I'm not sure which of the two or three large tufa mounds or masses at this pullout is George Washington Rock; a sign may explain things — or maybe the sign just reminds you that you should have a day-use permit to pull off the main road.
A nicely formed tufa dome. Go to The Pyramid to see some tufa "forts" — my word — where large, spherical domes have been eroded in half so you can see the many layers and types of tufa inside. The Stone Mother and the eroded forts uphill from her are great examples (MSRMaps location). Be prepared for a rough, though passable, drive in.
Inside most of the spherical tufa domes — which are called barrels or spheroids, see Figures 18 and 19, among others — you will find masses of elongate to radiating crystals of thinolite.
This partially eroded tufa spheroid shows multiple layers of thinolite crystals

"Thinolitic tufas, or thinolites are thought to be chemical precipitates that originally had the composition CaCO3.6H2O; that is, they precipitated as the mineral ikaite, which suggests the presence of very cold water (Shearman and others, 1989). The thinolites have since recrystallized to a more stable form of calcium carbonate (calcite)."

—Benson, 2004.
The Needles area is closed, and has been for quite some time.

The last time I was there, in June 1991, it was open to the public. I was leaning back in my camp chair, watching the sun dogs to the west, when I glanced straight overhead and saw a Kern arc. The sun was low on the western horizon, and the arc looked like a rainbow making a complete circle around the zenith. It was distinct, not faint like the one at Atmospheric Optics. At the time, I didn't even know such a thing was possible.

Some References:
Benson, Larry, 2004, The tufas of Pyramid Lake, Nevada: USGS Circular 1267.

Benson, Larry, 2004, The tufas of Pyramid Lake, Nevada: USGS Fact Sheet 2004-3044 (a shorter version of the above Circular).

Coolbaugh, M.F, and others, 2006, Geothermal Potential of the Pyramid Lake Paiute Reservation, Nevada, USA: Evidence of Previously Unrecognized Moderate-Temperature (150-70°C) Geothermal Systems: Geothermal Resource Council, Transactions, v. 30.

Ikaite (Wikipedia).