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...


Lockwood said...

The basalt in the area has been mostly identified as Steens Mt. Basalt on field trips I've been on. I've always assumed the basalt in this cliff is the same. Steens is roughly contemporaneous w/ CRB (relationship hasn't been clarified as far as I know), so that puts it in Miocene, which is in the middle to later part of Western Cascades volcanism. WC volcs were very voluminous and ashy, so that has been my conjecture about this outcrop: Steens basalt overlain/interbedded with WC ash. As I remember, this stuff looks like it's been reworked by running water- not just simple ashfall.

This is a really nice wayside break; the shade of the cottonwoods is a relief from the scrubby sagelands. Coming from western OR with kids, they get kind of freaked by their first immersion in desert. This spot provides some welcome relief for them, while I'm chomping at the bit to get deeper into the desert...

tempus fugit à pressa said...

If anyone has any info about the geology of this cliff, please comment!
Ok i have some pictures of a similar cliff beside Ana River,in Oregon don't know if is the same
top sediments are white volcanic ash, nearly crystal-free, about 30 to 45 feet high

i have an article somewhere

tempus fugit à pressa said...

sorry not found but....
Allison, I.S. (1966a) Pumice at Summer Lake,
Oregon A correction....ergo a preliminar report exists
Geological Society
of America Bulletin 77, 329-330.

they are similar articles

Silver Fox said...

Lockwood, neat that you've been up to the outcrop, it's usually been pretty hot when I've been through, or at least that's my excuse for not walking up.

Yes, I always stop at the Summer Lake rest stop. Just a great place.

Thanks for the info!

Silver Fox said...

The Mazama Ash is exposed in places along the Ana River, an ash much, much younger than the ash in the cliff.

Gaelyn said...

That is a very interesting geologic pattern with the white and black. Don't know the area and not sure I want to visit the Mosquito Festival. ;)

Silver Fox said...

Yeah, Gaelyn, I'm always surprised when I see the sign. This year there was also some espresso at the Paisley Perk, a little drive up.

Lockwood said...

I haven't been up to the outcrop, merely looked at it through binocs. But you can't miss it, it's so contrasty. Is the Ana River outcrop under discussion the one north of K. Falls on 97?

Silver Fox said...

شكرًا على حسن انتباهكم & Lockwood, here is a link to the abstract for Ira Allison's original article about Quaternary ash beds along the Ana River. I think these are exposures near Summer Lake the town, below the cliff above, somewhere north of where the Ana River flows into Summer Lake the lake.

tempus fugit à pressa said...

ok...i dont know the area

only by articles und pictures
you are a field geologist
und by the silver in the fox
a 50's young one at least
with 30 years chasing outcrops i s'pose
a free link?
let's see

tempus fugit à pressa said...

a pay per view article
it figures
dië amerikanders have lots of data
but with $ signs attached

Silver Fox said...

شكرًا على حسن انتباهكم - yeah, the link just goes to the abstract.