Tuesday, August 31, 2010

Travel Tuesday: Cliff near Summer Lake, Oregon

This cliff of black and white volcanic rocks is easily viewed from the Summer Lake, OR, rest stop, and from points north on Oregon Route 31, the Outback Scenic Byway. If anyone has any info about the geology of this cliff, please comment! What I see is a dark-colored mass of mafic or intermediate ash-fall material overlain by some layers of white, probably felsic, air-fall tuff, the deposition of which was interrupted by a basalt flow toward the left, so that some of the older whitish tuff layers are below the basalt flow, and some are above the basalt flow. Just a guess, however.

Google Maps: Summer Lake is the junction in the southeast, cliff is the white area in the northwest.
Detail of part of the cliff, showing some hoodoos.

This is the part of Oregon covered by Andrew Alden's recent post and photo gallery about the Oregon Outback. I've personally driven by here many times, usually in late July; this picture is from Day 8 of our recent Oregon trip (Day 7: volcano observatory, rock garden, Smith Rock).
I've never made it to the annual Paisley Mosquito Festival. Have always wondered ... have never stopped ... and have always keep my windows closed!

Trip report to be continued...

Saturday, August 28, 2010

A Friday Field Update

...on a Saturday evening.

As many of you may have guessed, and as some of you may know, I've recently started working a fairly intense schedule and have been unable to do much of anything online without detracting from my sleep time. The schedule includes the 10-hour days that are usually expected of field geologists (in mineral exploration, at least), and it currently includes an unspecified length of time. One likely scenario would be to work about 20 days and then to take about 10 days off. I described a few typical schedules a couple years ago, though I didn't describe several currently popular options, including the 4 and 3 or the 8 and 6. From the 8 and 6, one might extrapolate a schedule of 16 days on and 12 days off, but I haven't seen that in place anywhere. Anyway, the upshot is that I'm "in the field" — that is, I'm not working at home, and I'm not working in an office. One definition: the field is the everywhere that you do geology — whatever kind of geology you happen to do — and that geology is usually, although not always, done out there away from town and away from home.

This particular job is a little unusual in that I really don't know how long it will last: there is plenty of work to be done, but is there enough money to do it? In my experience, this has been a bit of a problem during the last couple years, at least for some exploration companies. I personally have been fortunate during my long career to work through some fairly flush times, and also to work through leaner times with companies that maintained a healthy exploration budget. No exploration = no mining down the line, so it's a good thing (IMO) for companies to maintain a healthy exploration budget.

Recently, many of the larger companies — the few existing majors in particular — have devoted a fair portion of their time and money toward buying already proven or nearly proven reserves, and they've dedicated the rest of their time and money toward exploring on site, an M.O. sometimes called "brownfields exploration." In the last several years, brownfields exploration has largely been conducted at the expense of stepping outside the mine area, outside the property, and — heaven forbid! — at the expense of actually doing some well conceived "greenfields" or even "grassroots" exploration. (That is not true, by any means, in all cases, and the trend may be changing.) So if you, as an exploration geologist, don't know exactly where you want to drill because you are thinking of stepping outside the box, you might not find anyone willing to fund the mapping and sampling necessary to go find or prove up the next big one. The next big one might well be what will keep the current operation going.

Disclaimer: I haven't yet devoted any of my own time or money to this type of exploration, either, though many of my career-long colleagues have.

Thursday, August 26, 2010

Highway 50 Links

I'm getting ready to post a Highway 50 Series list, but first I want to post general links for Highway 50. Many of these are road and travel links with some geology and history thrown in. The book recommendations at the bottom go directly to Amazon.com. This is my first non-retroactive use of Affiliate links (I've added links like these to a few old posts.) The way these work is that I might get paid, but only if someone clicking through actually buys something, and only if they buy something within some certain period of time. Hopefully, this doesn't seem outrageous - I often link to Amazon.com for books I talk about. These are all books I own, books I would recommend to anyone traveling Highway 50 in Nevada (the books at the bottom).

Some General Travel and Highway Links:
Experience the old west in Pony Express Territory, Nevada - Pony Express Territory

The Official Hwy 50 Survival Guide: Loneliest Road in America - TravelNevada.com

U.S. Highway 50 - Nevada - AARoads

U.S. Route 50 in Nevada - Wikipedia

U.S. Route 50 in Nevada - Answers.com (similar to Wikipedia, possibly more references)

US50 -- Nevada - US50 Coast to Coast

Nevada's Highway 50 - VIA Magazine, California State Automobile Association

History and Geology Links:
Captain James Hervey Simpson and Highway 50 - The Online Nevada Encyclopedia

Geology of Nevada; a discussion to accompany the Geologic map of Nevada (USGS): Stewart (1980), NBMG Special Publication 4 (link to NBMG sales info).

Books I Own and Recommend:
Geology of the Great Basin

Traveling America's Loneliest Road

Sagebrush Country

Touring California and Nevada Hot Springs

Hot Springs of Nevada

Sunday, August 22, 2010

Oregon Trip Day 7: A Volcano Observatory

Photo from Windy Point: I'm standing next to 50,000 year old basaltic andesite from Black Crater (foreground, age approximate), looking across a 2,900-year-old basaltic andesite flow from Little Belknap (dark flows beyond the foreground trees), at the snow-capped peak of the 300,000- to 35,000-year-old Mt. Jefferson stratovolcano (Windy Point location, MSRMaps).

(If you don't know what observatory I'm speaking of, then you need to read on — and then you need to go there: you go down there — I mean, up there.)
Our third stop on the seventh day (after the rock garden stop) was in the town of Sisters, Oregon, where we had lunch indoors, and ice cream outdoors. The clouds were threatening when we arrived. They had cleared some by the time we left, but had regrouped before our fourth stop...
...at the Dee-Wright Observatory on top of McKenzie Pass (Google Maps). That's a view of Black Crater behind the sign — it's a partly glaciated shield volcano that extruded basaltic andesite flows about 50,000 years ago (see Cashman et al, 2009*).
At Dee Wright, you either climb steep stairs made of basalt (or basaltic andesite) or you walk a paved, gentle incline.
More than half way up, you come to a circular room with windows looking off in several specific directions. Each window frames a particular volcano; this is Mt. Jefferson.
It's worth going all the way to the top of the observatory for the view, and also to see this bronze "peak finder." According to long-time residents, this compass — which points to many but not all of the volcanoes visible from the top — has had to be replaced more than once. If you read the arrow in front of the snow-covered mountain on the horizon, you'll see that it's pointing to the North Sister, 6.6 miles distant, 10,094 feet elevation (according to the bronze plaque; according to the Dee Wright Observatory page at the CVO , the elevation is 10,085 feet). The Middle Sister, youngest of the three, is just right of the North Sister; Little Brother (the oldest) is on the right edge of the photo.
The Dee Wright Observatory is built on basaltic andesite flows that erupted from the base of Yapoah Crater, a 2,000 year B.P. cinder cone on the north flank of the North Sister (Cashman et al, 2009). The cone is visible but hard to point out from this angle.
Off to the northeast, the light brown volcano on the left is Belknap Crater, a basaltic andesite to andesite shield volcano that erupted 2,635 to 1,500 years B.P. Little Belknap is the dark point right of Belknap near the right edge of the photo. It erupted basaltic andesite about 2,900 years B.P. (these dates are from Cashman et al, 2009). The dark flows in the distance, behind a narrow swath of trees, are from Little Belknap; they flowed around a patch of older volcanic material (green area roughly in the center), forming what is called a kipuka (as seen in Cashman et al, 2009; USGS definition).

UPDATE: Read more about kipukas at Geotripper, who is currently in Hawai'i!
On the way down, a flock of small brownish birds with yellow colorings — possibly pine siskins — were hanging out amongst the basaltic flow rock.
If you drive a little ways to the west, you can look up toward the North Sister along a treeless flow from Yapoah Crater, the relatively barren cinder cone that barely sticks up above the mostly tree-covered skyline on the left side of the photo. It appears to have a white patch of snow on it's north side. In this Google Street View, Yapoah Crater is just left of the centered tree.

And you already know what we did after the field trip: we went to the Terrebonne Depot, had a great meal and good ale.

Main References:
Cashman, K.V., Deligne, N.I., Gannett, M.W., Grant, G.G., and Jefferson, Anne*, 2009, Fire and Water: Volcanology, Geomorphology, and Hydrogeology of the Central Cascades and Adjacent Areas, Oregon: Geological Society of America, Field Guide 15 (field trip no. 409).

*Anne Jefferson, who blogs at Highly Allochthonous, sent me a copy of this field guide, which I used extensively during this portion of our road trip. Thanks, Anne!

USGS Cascades Volcano Observatory.

Trip report to be continued... not necessarily in a timely fashion.

Friday, August 20, 2010

Oregon Trip Day 7: The Petersen Rock Garden

For day seven's second stop, which naturally came after the first, we went to the Petersen Rock Garden, which is a couple miles west of Highway 97, about 6 miles southwest of Redmond, Oregon.

The rock garden is a little difficult to find if you're trying to get there the way we did, which was by looking for a sign on Highway 97 south of Redmond, then turning right, and then following more signs at turns on the back roads west of the highway. I don't know if the garden would have been any easier to find following signs from Highway 26 west out of Redmond and then south: the signs are old, several (all?) are right at the turns instead of conveniently before the turns, and many (all?) have faded. My mom, who had been there many years prior, managed to tell us which way we would turn prior to each turn using some suddenly manifested sense of direction. Usually it's my dad who doesn't need a map. Here's the location of the garden on Google Maps.
The Petersen Rock Garden is an interesting combination of cool green shade,
...lily-covered ponds,
...rocks, mostly from Oregon,
...and a museum with, you guessed it, more rocks (and minerals) from Oregon and elsewhere,
...including one of the largest thunderegg collection I've ever seen, ...and peacocks.

Trip report to be continued...

Wednesday, August 18, 2010

You Go Down There

In a somewhat unrelated aside, here's a plug for one of the best movies the west has ever known, Little Big Man, and one of my many favorite quotes from that movie, "You go down there," said unambiguously to Custer by our hero Jack Crabb upon the eve of Custer's last stand. The part in question starts about half way through, at 2:37.

"You want me to think that you don't want me to go down there, but the subtle truth is you really *don't* want me to go down there!"
A probably more accurate version of the events that day can be listened to here.

And here's a possibly related non-road song to go with the movie quote, by one of my earliest favorite singers, Johnny Horton.

"But Custer didn't listen, at Little Big Horn Custer died."
I don't suppose there's any moral to all this, it's just what came up while I was writing another post.

Tuesday, August 17, 2010

Oregon Trip Day 7: The Tuff of Smith Rock

As I mentioned earlier, I'm skipping a few Oregon trip days, primarily because not much happened in the geological realm during that time; we've now gone from Day 4 to Day 7. I'm also going to break Day 7 into two or three posts.

On the seventh day, four of us took a day-long field trip around the Bend-Prineville-Sisters area; our first stop was at Smith Rock State Park.

Throughout the day, we saw lots of volcanic rocks (can you imagine?), and I became fond of taking pictures showing more than one volcano or more than one age of volcanism. The picture above, looking southwest, shows the tuff of Smith Rock in the foreground, a rhyolitic ash-flow tuff about 29 to 30 million years old (McClaughry et al, 2009, page 39). The snow-capped mountain in the background is Broken Top, a complex stratovolcano of the Three SistersBroken Top area. Broken Top is much younger than the tuff of Smith Rock, and it's heydey as a composite volcano was probably between about 300,000 and 100,000 years ago. As part of the High Cascades, the Three Sisters–Broken Top area is potentially active.

The black specks in the first two photos are turkey vultures.
Looking along the Crooked River back to the northeast, we can see the tuff of Smith Rock dipping more or less to the south or southeast, with the dips being shown by the tops of the cliffs in the background hill. The dark rocks in the foreground are basalt: columnar-jointed flow rock from the Newberry volcano south of Bend. The basalt is about 500,000 to 300,000 years old.
I had to zoom in on these fine examples of the tops of columnar joints.
We've now moved around and are looking back to the southwest again, with a picture nearly identical to one shown on page 38 of McClaughry et al, 2009, not that I planned it that way. Once again, you can see the buff to brownish ash-flow tuff dipping in a southerly direction (left), marked by layering especially near the top of the buff to brown cliff. You can also still see the dark flows of the much younger Newberry Basalt around the bend of the river. That's 30 to 29 million year old rock (tuff) next to 0.5 to 0.3 million year old rock (basalt).
In a closer view, we can still see a little of the layering in the high cliff on the right side of the photo, with the layering being compaction foliation in this ash-flow tuff. The darker brown, fractured looking rock in the middle ground of the photo, jutting out in spires lower and closer to the river than the layered cliff (behind the bridge from this viewpoint), is a rhyolite dike intruding the tuff of Smith Rock (McClaughry et al, 2009). It looks to me as though some of the rock in the far distance, also darker and showing vertical fracturing, could be dike material, but it was reported as tuff in the 2009 field guide, and I didn't cross the river to examine it. I did, however, align two major fractures or contacts in the rock in the foreground with similar looking (from a distance) fractures in the background, but don't know if they are related. Another field trip and some geologic mapping are in order!

It's now thought that the tuff of Smith Rock at Smith Rock is the intracaldera tuff of the huge Crooked River caldera. For comparison, the aerial size of the Crooked River caldera is given here (page 27 has a nice graphic) as larger than the Long Valley caldera in California and smaller than the McDermitt caldera complex of northern Nevada. This is a caldera of true "supervolcano" size.

As a bonus, this tuff, and other widespread air-fall and ash-flow tuffs that erupted from the Crooked River caldera, correlate with tuff units in the John Day Formation. We saw at least one of the younger ash-flow tuffs at Sheep Rock: the so-called "Picture Gorge Ignimbrite ." From what I understand, McClaughry et al, 2009 correlate the Picture Gorge Ignimbrite with what they call the Member H tuff, which may also be correlative with the tuff of Barnes Butte. (I think one needs to be a little more familiar with the stratigraphy of the John Day Formation to follow these various regional names and correlations.)

A few online reports describe Smith Rock as part of a much smaller rhyolitic tuff ring; apparently that interpretation has been superseded by McClaughry et al, 2009, which provided much of my information about Smith Rock. Their field trip guide is well worth reading, and I wish I had read it prior to going out there!

Main References:
McClaughry, J.D., Ferns, M.L., Gordon, C.L., and Karyn A. Patridge, K.A., 2009, Field trip guide to the Oligocene Crooked River caldera: Central Oregon’s Supervolcano, Crook, Deschutes, and Jefferson Counties, Oregon: Oregon Geology, v. 69, no. 1, p. 25-44

USGS Cascades Volcano Observatory.

Trip report to be continued...

Thursday, August 12, 2010

Oregon Trip Day 4: Coffee, Fossils, Formations, Basalt, and Brew

Now that I've gotten back from driving through a low desert locality with huge mountains on the western side of the valley, and then driving across central Nevada on one of the dustiest roads in existence, we can return to the trip to Oregon that MOH and I took last month. Where were we? Oh yeah, we had traveled from Jarbidge, NV, to Baker City, OR, on various backroads and I-84.

The morning after attending Barley Brown's Brew Pub, we awoke in our strange motel room (Google Maps), and after checking out the okay but crowded coffee and continental breakfast, we opted for some real coffee and walked downtown to a small cafe that had espresso (Google Maps). We sat outside and enjoyed the view of the brightly colored town of Baker City.
Eventually we packed our stuff into the Prius, bought more ice for the Ruby Mountain beer in our ice chest, and headed down Oregon Route 7 toward U.S. Route 26, which we joined at Austin Junction. Between Austin Junction and Prairie City, we crossed over a small part of the famed Blue Mountains. The Blue Mountains are high, cool, and covered with a mixed conifer forest, species of which include one of my favorite tree, the larch.
Just west of Dixie Summit, we walked a short trail down to a small section of track that has been laid on the old Sumpter Valley Railroad grade (Google Maps Street View). It's a nice place to take a little break from driving.
The third main highlight of the day was coming to the Sheep Rock Unit of the John Day Fossil Beds National Monument, which is mostly north of Highway 26 (MSRMaps, in purple). This national monument comes in three main pieces scattered over eastern Oregon, and the fossils are in several fossil assemblages that range in age from 44 to 7 Ma. I'm not going to get into the palaeontology in any detail, but will to say that the Thomas Condon Paleontology Center has a huge display of ancient flora and fauna including lots of mammal, reptile, and amphibian bones and skulls, and lots plant fossils including nuts and leaves. This first overlook (Google Maps) is of the Mascall Formation, one of the youngest mammal-bearing formations in the park, about 12 to 16 million years old.

The Mascall Formation forms nice badlands of tilted strata overlying flows of the tilted Picture Gorge Basalt (about 16 Ma, in part correlative to basalts seen at Multnomah Falls, and part of the Columbia River Basalt Group). The Mascall is capped by the nearly flat-lying Rattlesnake Tuff, the thin orange-brown unit on the mesa. At first I thought — no, this is Oregon, that must be basalt. I later realized that the Rattlesnake Tuff is a widespread ash-flow tuff unit, often called an ignimbrite at John Day, which erupted 7 million years ago and covered a 30,000 to 40,000 km2 area (as much as 15,000 square miles) of eastern to central Oregon. It's present-day distribution can be seen here.
So now, everytime I see a thin, reddish to orangish brown unit amongst a bunch of basalt flows, I wonder...
From the Mascall overlook, we looked north along Highway 26 and the John Day River, into Picture Gorge. Just beyond Picture Gorge, you can see a bit of Sheep Rock sticking up, also capped by the 16 Ma Picture Gorge Basalt.
We're getting closer: this is the part of Picture Gorge where Rock Creek flows in from the west to join the John Day River flowing north toward Sheep Rock.
This is the view of Sheep Rock from the Thomas Condon Paleontology and Visitor Center (Google Maps location). The dark, capping layers are flows of the Picture Gorge Basalt (16 Ma); the central brownish layer is the Picture Gorge Ignimbrite (28.7 Ma). The upper buff to pinkish layers are ashy claystones of the Kimberly Formation (25 to 28 Ma). The lower greenish sediments are ashy claystones of the Turtle Cove Formation (28 to 33 Ma); the green Turtle Cove sediments lie mostly below the Picture Gorge Ignimbrite but also form a thin band above it. The entire section below the capping basalt is part of the John Day Group.
A matching photo with some explanations from the Visitor Center (click to enlarge).
Zooming in on the Picture Gorge Ignimbrite and the greenish layers below, we can see a fault offsetting the units. The thin white cliffy unit in the middle of the lower section is the Blue Basin Tuff (28.9 Ma). This tuff layer, along with a couple other tuffs and many other sub-units used for correlating different fossil beds, can be see below (click to enlarge). Read more about the stratigraphy and regional geology here. My blathering doesn't really do it justice!
The ranger giving an overview of the geology preferred not to use the word fault for the planar-looking structure seen offsetting the units in the previous four photos — and it's called a "minor fault" in displays inside — instead calling it a "crack." I think this was to emphasize that the structure is an old, inactive fault that people shouldn't be afraid of, rather than an "earthquake fault" about to go off at any moment, but possibly he meant it was a growth fault that didn't extend upward through the entire section.

Also, he apparently had to explain constantly that there aren't any dinosaurs at the museum because the fossils are from the Age of Mammals. I guess some people come expecting or hoping to see dinosaurs, but the sediments and tuffs post-date the KT boundary and dinosaurs by about 20 to 60 million years.

It was very hot when we were at John Day Fossil Beds in late July — go early in the morning if it's summer, or wait until fall!
So, we left without taking any planned hikes: the road had been long and we still had miles to go — and it was cooler in the Prius. We could follow some of the formations westward toward Redmond, but we finally lost track of whether we were seeing the Rattlesnake Tuff or the same basalts.
After settling in at a nice but inexpensive motel in Redmond, we met some Alaskans and joined them for dinner and ale at the Red Dog Depot.
I can't really say what kind of IPA was favored, because they changed the available beers almost daily. One was less hoppy than the other; both were less hoppy than the WFO IPA at Barley Brown's in Baker City. The 20" Brown was enjoyed by non-IPA drinkers.

View Baker City, OR to Redmond, OR in a larger map

Trip report to be continued... (although I will skip a couple non-travel days).

Tuesday, August 10, 2010

Travel Tuesday: A Dusty Road

While taking a shortcut from Tonopah toward Eureka yesterday — no, wait, it wasn't a *short* cut at all — I purposefully came upon this former stage station on what was seemingly one of the worst roads for narrowness, a paucity of pullouts and turnaround points, and dust.

This is Pritchard's Station, and the road is so bad that the Ghost Towns website doesn't have a picture, instead explaining, "It is said the site is a definite must, and is well worth the hair-raising drive to get there. But it is four-wheel drive territory at best." Indeed. In fact, I could find only one website with exactly three photos of the place. I've been to Pritchard's Station a few to a half dozen time over the decades; what struck me this time was that it's built of ash-flow tuff (more on that later).

View Larger Map

See this Google Maps route showing my "shortcut" — Pritchard's Station is Point E. Moore's Station is Point D. Project Faultless is the disturbed area a little southwest of Moore's Station (Google Maps location).
At first glance, the road leaving the station to the northeast doesn't look that bad, though I had already crossed about eight to ten miles of powdery road, and was now driving uphill. See all those dusty windrows on both sides of the road? The road had just been scraped; the dust was deep and fresh with few tracks.
This is the kind of thick powdery dust that makes you wonder if you should stop and clean your air-filter en route so the vehicle won't choke and stop running (which does happen, sometimes with dire consequences to engines).
This part of the road — from Pritchard's Station to Point G on my Google Maps route, a mere 10 miles — is uphill. The Nevada road atlas says, "Impassable When Wet," and I'd venture to add, barely or not passable with two-wheel drive. I used 4WD and was still fighting through the powder, being pushed around willy nilly, almost like I was driving through sand or mud.
Here, at Point F, just before making a whoop-di-do into and out of a side drainage of this magnificent wash known as Pritchard's Canyon, you can see what the road is built on: dark brownish gray sagebrush soil over thick ashy silt. The ash is from weathering of the surrounding ash-flow tuff formations. You are just beyond the inferred boundary of the Williams Ridge and Hot Creek Valley calderas (part of the central Nevada caldera complex), and there is weathered tuff and ashy material everywhere.
Just around the corner from Point F, I spotted this coyote running away from me; I barely got this photo because the camera was still set to wide angle.
And, after getting onto a currently better road just past Point G (judging by the old ruts, maybe not always better), near the ruins of Summit Station, I scared up this small band of horses.

Some References:
Dixon, G.L., Hedlund, D.C., and Ekren, E.B., 1972, Geologic map of the Pritchards Station quadrangle, Nye County, Nevada: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-728, scale 1:48,000.

Ekren, E.B., Hinrichs, E.N., Quinlivan, W.D., and Hoover, D.L., 1973, Geologic map of the Moores Station quadrangle, Nye County, Nevada: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-756, scale 1:48,000.

Steve Ludington, Dennis P. Cox, Kenneth W. Leonard, and Barry C. Moring, 1996, Cenozoic Volcanic Geology of Nevada, Chapter 5 in Donald A. Singer (ed.), An analysis of Nevada's metal-breaing mineral resources: Nevada Bur. Mines and Geology, Open-file Report 96-2, p. 5-1 to 5-10.

Stewart, J.H. and Carlson, J.E., 1976, Cenozoic rocks of Nevada: Nevada Bureau of Mines and Geology, Map 52, scale 1:1000000.