Owyhee Map for AGU...almost there

I have reached a point of no return on the map and have gotten close to a final draft for inclusion on AGU poster(s). In this version, a lot of the detail is left out:

no bedrock older than Bogus Rim flow
undivided landslides,
undivided mainstem fluvial deposits (active channel is divided),
undivided lacsutrine deposits.

Reasons: map is too complicated for showing everything and too many loose ends in some units (mainly generalized bedrock) to build polys.

The colors are chosen to highlight the various features and are obviously not conventional geologic map colors. Mainly, those conventions are a real annoyance when you map detailed surficial units anyway. The snippets in this post should give you a good idea of where things stand. I am leaving town tomorrow afternoon and cannot have this map hanging over my head...and I bet that spud is tired of waiting.

It will be pretty easy to create a basemap using these data as the 1:250,000 version indicates. I need some feedback on where to go from here.

Map-tacular Effort

Great job on the mapping Kyle! I am looking forward to seeing it on our poster.
-Spud

Incision of Hell's Canyon

Hi again,

If you are not up on the evolution of the Western Snake River Plain (WSRP) and the timing of the cutting of Hell's Canyon in relation to the Owyhee intra-canyon lava flows then consider reading a paper by BSU Emeritus geomorphology professor Spencer Wood and his colleague Drew Clemens, "Geologic and Tectonic history of the Western Snake River Plain, Idaho and Oregon" Find it at:
http://earth.boisestate.edu/home/swood/WOODCLEM-2002.PDF
Among other things, the paper discusses where and when Lake Idaho existed and how and when Hell's Canyon was cut. It refers to work done by Kurt Otherberg, who Jim had mentioned before in the context of Hell's Canyon.
-Spud

Paleoclimate of northern Great Basin and Owyhee area

Hi folks,Two years ago I asked Peter Wigand for some direction insearching for papers that might help us understand thepaleoclimate (and therefore perhaps river discharge andstream power) of the Owyhee River basin.  He replied tome but I never was able to track down all the papers hesuggested.  I am providing his suggestions here in thehopes that we can improve our understanding of what theOwyhee River might have looked like during the existenceof the lava dams.  He said to start with the first onewhich had an extensive bibliography that wouldlead to some of the others.-SpudWigand, P. E. and D. Rhode. 2002. Great BasinVegetation History and Aquatic Systems: The Last150,000 years. Pp. 309-367. In Hershler, R., D. B.Madsen and D. R. Currey (eds.), Great Basin AquaticSystems History. Smithsonian Contributions to EarthSciences 33. Smithsonian Institution Press,Washington, D.C.Mladen Zic, Robert M. Negrini, Peter E. Wigand. 2002.Evidence of synchronous climate change across thenorthern hemisphere between the north Atlantic and thenorthwestern Great Basin, USA. Geology 30(7):635-638.Cohen, A. S., M. Palacios, R. M. Negrini, P. E.Wigand, and D. B. Erbes. 2000. A paleoclimate recordfor the past 250,000 years from Summer Lake, Oregon,U.S.A.: II. Sedimentology, paleontology, andgeochemistry. Journal of Paleolimnology 24(2):151-182.Negrini, R. M., D.l B. Erbes, K. Faber, A. M. Herrera,A. P. Roberts, A. S. Cohen, P. E. Wigand, and FranklinF. Foit, Jr. 2000. A paleoclimate record for the past250,000 years from Summer Lake, Oregon, U.S.A.: I.Chronology and magnetic proxies for lake level.Journal of Paleolimnology 24 (2):125-149.Mehringer, P.J., Jr. and P.E. Wigand. 1990. Comparisonof Late Holocene environments from woodrat middens andpollen, Diamond Craters, Oregon. In Martin, P.S., J.Betancourt and T.R. Van Devender (eds.), FossilPackrat Middens: The Last 40,000 Years of BioticChange. University of Arizona Press.Wigand, P.E. 1987. Diamond Pond, Harney County,Oregon: Vegetation history and water table in theeastern Oregon desert. Great Basin Naturalist 47(3):427-458.

OWY-19, river left outcrop of WC between Bogus Falls and Dogleg

Here are two photos--long overdue--that show the contact relations of the WC lava where I collected sample OWY-19. One shows the modern swale that has eroded around the WC lava that filled the paleo-swale. The other photo shows the nature of the contact between WC and lava flows within the Tertiary section: the WC lava sits on top of the Tertiary section there.
-Spud

Reply to depocenter in middle of WC flow

Yes, the comment fcn on the blog seems to be out of order--this post is in regard to Dr. Jerque's post of WC in VR hindsight, etc. etc.

Dr. Jerque,

The area marked by a question mark on the image you posted could certainly contain sediment from the Owyhee River as the river flowed over the top of the WC lava. I have been there and was impressed by this expansive, low relief area made mostly of silts. I will review my notes at home tonight on the matter. I do recall also acknowledging that the area could easily be a depocenter for Bogus Creek. The road that you can see in the upper right corner of the image is built on a ~1.5-2 m high (man-made) berm (levee!!) that ensures all of Bogus Creek flows north rather than between some tumuli down to the low relief silty area as it clearly could do in the drop of a hat (or a March rain-on-frozen-ground event).

Yes, there are some large gravel/cobble bars along the lower reaches of Bogus Creek near the kipuka. If i recall correctly, these happen to be low enough in elevation and downstream enough to be within reach of overflows from the Owyhee River passing through the possible depocenter but also from other overflows further downstream. (Having said that, there are some sizable ephemeral channels that pour off the Bogus Rim directly to the east of the kipuka and these could contribute a lot of discharge in a large convective event or spring rain on snow.) It may be worth considering auguring this silty depocenter or digging some test pits there to understand the deposits or find some datable material.

And yes, there are several different lobes and inflationary flow fronts to the WC lava flow that wrap around Bogus Point and create some unique positive and negative relief. I looked at these in stereo many times and walked around on the ground there with an eye towards assessing the timing of these lava pulses and the potential interaction with the river. After a lot of back and forth, I continue to return to my original interpretation that there is only one lava flow in the area--the WC-- and that water flowed through a narrow gap between several tumuli far more upstream than the rounded boulders on the edge of the modern cliff of WC adjacent to Chalk Basin show. I am pretty sure that this nascent paleo channel is the upstream-most one shown on my maps of several years ago. Furthermore, there probably is a complex set of damming and overflow events because even though there is probably only one lava flow there, it probably made several surges or advances in its battle with the river and rising lake.

I sure wish I could have come to Bend!
-Spud

Ouch. I missed these... comment by Lisa

Lisa e-mailed a nice comment that I have placed on the blog for the record. I agree with her points. Something appears to be wrong with the commenting function in blogger...not with Lisa.

I recently re-read Howard et al.'s paper. The difference I see is that they stop short of going into detail about the impact of the lava dams on the geomorphic evolution of the canyon. Their paper provides a great basis of comparison for ours, but we can take ours much further with our more extensive dating, mapping and our possibly greater interest in the river canyon geomorphology. The Howard et al. paper was not that long, and mainly focused on the description of the lava flows and dams. We have more controls on incision rates through different lava flows at different times and places on the river, which I think will lead to interesting discussion.

I've sent away for a few more references to lava dams in the last couple of days. I'll circulate them when I get a chance to look them over. Quite a few on the Snake River, some in Canada, one in China.

Ouch. I missed these...

On my (not so) recent trip down the Grand Canyon, I had a lingering memory of Cassie suggesting that Keith Howard had been a little hard to convince as to the reality of lava dam failure and catastrophic flooding there, but that some of the field evidence finally convinced him. I had that lingering memory because I was weakly skeptical based on the lack of such evidence on the Owyhee, but was confused because I had read (and reviewed) a couple of her papers. Turned out that I really needed to see the stuff in person with a better backlog of personal observations. As I noted in a previous post, some of the flood evidence was (to me) hilariously clear and my skepticism was baseless for the most part.

Now that I have finally read Keith's Boise River lava dam paper, I can understand why he was skeptical given the striking parallels between the Boise River story and the Owyhee River story. (thanks to Lisa for sending the pdf). Moreover, the Howard and Fenton abstract (that, admittedly, I was not aware of) reads just like the thoughts I had in mind while thinking of the Owyhee while floating the Colorado. Some of the differences are profound.

Admission of guilt: I am truly embarrassed that I had not read the Howard et al. paper years ago, as it would have made it far easier and faster for me to understand the history of the Owyhee River. Oh well....As for the more recent abstract...no excuses there either.

We should really consider checking out the Boise River sites sometime.

LAVA DAMS COMPARED IN BOISE RIVER CANYON AND GRAND CANYON

HOWARD, Keith A., U.S. Geol Survey, Menlo Park, CA 94025, khoward@usgs.gov and FENTON, Cassandra R., U.S. Geol Survey, 1675 W. Anklam Rd, Tucson, AZ 85745 Pleistocene intracanyon basalt flows that dammed the Boise River, Idaho offer comparisons to those that dammed the more powerful Colorado River in Grand Canyon. In both canyons, olivine basalts erupted several times from vents near canyon rims, and flowed down steep canyon walls into the rivers and onto thick gravel beds. The multiple lava dams in Grand Canyon exhibit many stratigraphic complexities as compared to the simpler stratigraphic structure of the dams built on the Boise River, best exemplified by the Steamboat Rock Basalt and the Smith Prairie Basalt on the Boise River’s south fork. These two dams were each constructed to heights of 150 m from multiple flow units of basalt, which flowed tens of kilometers downstream while building lava deltas into the growing reservoirs on the dam’s upstream faces. Paleowater levels in the lava deltas, where lava flowed into rising reservoir waters behind the dams on the Boise River, are easily recognized as passage zones where topsets of subaerial pahoehoe pass abruptly downward into upstream-dipping foresets of pillows and hyaloclastite. Successive flow units entering a rising reservoir resulted in an asymmetric dam, much longer on the downstream face, and cored by massive subaerial basalt that interfingered upstream with a series of upstream-thickening wedges of pillow basalt. Grand Canyon lava dams also show evidence of upstream deltas where lava interacted with dammed water (described by Hamblin), but coarse hydroclastitc breccia dominates over pillows and foreset-bedded hyaloclastite; the deltaic structures are complex. Whereas several dams in the Grand Canyon failed catastrophically to produce outburst floods (described by Fenton and colleagues), the dams on the Boise River were incised gradually. Their long downstream lengths contributed stability. The long flows and abundant pillows relative to breccias suggest fluidity of the lavas, and suggest rates of eruption and lava flow that were high relative to the discharge of the river that they entered. The Colorado’s discharge is twenty times that of the Boise River South Fork.

Rocky Mountain (56th Annual) and Cordilleran (100th Annual) Joint Meeting (May 3–5, 2004)

Funny aside: at the meeting in Bend, I 'independently' developed a diagram for how we could graphically convey the last 1.8 my of the persistently interrupted incision history of the Owyhee. Much to my dismay, within minutes of touting the merits of my exmple figure, I was faced with a nearly exact example prepared by Howard et al. Lisa had the paper with her and I read it for the first time right then and there. In addition to the figure, many of the concepts presented in the paper were identical to discussions that we always have and were having that day. We then became concerned about how we could distinguish our study from theirs beyond just stating that it also happened somewhere else not very far away. I keep verging toward a discussion of the differences between landslide dams and lava dams with interesting counterpoints from the Colorado River and the Rio Grande.