OSL Results....Thermodisappointmence?

Before my last field outing, I contacted the USU OSL lab about our samples. The good news: preliminary data are available. The bad news: wtf do they mean?

From: *Tammy Rittenour* <tammy.rittenour@usu.edu

<mailto:>tammy.rittenour@usu.<wbr>edu>>
Date: Tue, Sep 30, 2008 at 3:03 PM
Subject: RE: Owyhee OSL?
</mailto:>

To: Kyle House <pkhouse@gmail.com <mailto:>pkhouse@gmail.com>></mailto:>
<mailto:>
Kyle-

Ive attached the preliminary results from your Owyhee River samples.
They are about 75% complete at this moment. I am working on sending
them in for further processing because of some initial feldspar
contamination, but you should have the final results by the end of the
month.

The samples are all ~22-23ka, if they were taken from the same deposit,</mailto:>
<mailto:>then OSL seems to be working quite well.

Errors on the ages will go down when they are completed, but I dont
expect them to change much at all.

Good luck in the field,

Tammy

</mailto:>

What do we make of this information? Well. We suspected that these lacustrine seds were related to damming by the West Crater flow. Given their distribution with respect to the upstream face of that flow this seems like a valid assumption. However, these ages are far younger than the likely age of the West Crater flow. That is a problem. Also, the samples cover a large range of elevation. I expected that there would possibly be a correlation between the elevation of the sample below the likely dam and its age. This is not the case. Check the figure below for a visual cross-check:This figure is a profile from the 10 m DEM data. The profile hits the four sample spots in the area. The geology is schematic (obviously) and hastily drawn (more obviouslyer).

Note the large elevation range of the three sample areas*. Each sample is denoted by a yellow circle (excpet the highest circle, that is a gravel deposit that wasn't sampled). We are still awaiting an identification of an obvious tephra bed that was sampled below the lowest OSL sample. Sent that (and all others) to WSU in early August....USGS has been sitting on it for over a year. If that comes back with a confident ID, then we will have some additional perspective on the OSL data. Any thoughts? Break down and add to the blog....

*I have wondered aloud on numerous occassions about the lowest one...possibly related to landslide dam? Its elevation is pretty low relative to the sublava paleochannel of Ryegrass Creek. The paleotopography implied by this (if related to West Crater) is pretty deep.
<tammy.rittenour@usu.edu><mailto:tammy.rittenour@usu.edu><pkhouse@gmail.com><mailto:pkhouse@gmail.com></mailto:pkhouse@gmail.com></pkhouse@gmail.com></mailto:tammy.rittenour@usu.edu></tammy.rittenour@usu.edu>

Topo Profiles in Study Area

I whipped up these images while revisiting the mapping in earnest today. These can be made in seconds using GlobalMapper. All offer some insights and are interesting to consider. We need to choose some key ones to illustrate with stratigraphy etc. If you lose your bearings, just click to go to the online album and check the map.

Geologic Froth: The Ultimate Digital Tool for Dummies and Luddites?

Geologic Froth: The Ultimate Digital Tool for Dummies and Luddites?

Geologic Froth: My new digital love, the cheap and rugged Laser Range Finder.

Gadget alert:

Geologic Froth: My new digital love, the cheap and rugged Laser Range Finder.

Dave's landslide blog: The Yigong Rock Avalanche, Tibet

Dave's landslide blog: The Yigong Rock Avalanche, Tibet

Yet another interesting post from Dave. Great photos of landslide and ensuing effects of river blockage.

Compelling evidence for lava-dam failure in Grand Canyon

As I noted earlier, there are some pretty clear indications for linkages between lava dams and large floods on the Colorado River in Grand Canyon that stand in contrast to what we see on the Owyhee. One particularly interesting morpho-stratgraphic association includes the following assemblage:

1. Lava flow on river gravel; no evidence for water interaction other than flowing down the channel.
2. Flagrant flow morphology characterized by relatively thin colonnade (with very fat columns in the example below) overlain by considerably thicker entablature.
3. Coarse-grained, complex fluvial deposit containing abundant reworked lava and hyaloclastite material.

Here is a 'Grand' example from mile 192:

What might be going on here? Well, following some discussion with Ryan Crow and some reading about entablature formation that he recommended, I think that this assemblage permits the following interpretation:

1. Lava flow enters canyon and blocks river, allowing flow to continue unimpeded downstream (lava on gravel with no evidence for lava-water interaction)
2. Clear water begins to pass over or through the dam (or both) and greatly accelerates cooling of the lava (induces the elaborate and thick entablature structure)
3. Dam eventually (soon) fails catastrophically and coarse gravel is deposited on the lava flow that now forms the bed of the river.
   

The overlying gravel deposit in this case is notable for the large blocks of poorly rounded colluvial gravel that it contains. That appears to be a common characteristic of these flood deposits. Some likely reasons include: elevation of the channel bed and conveyance of deep high velocity flow at stages not typical of the pre-lava dam river. It is also reasonable to expect that the demise of the dam may have occurred at the buttress of lava on colluvium. I am certain that Cassie suggested this in one or more papers.

With respect to the distinct morphology of the cooling structure of the lava flow, it seems almost inevitable that the very thick and elaborate colonnade reflects the influence of rapid cooling of the lava flow by a very large volume of water. In this case, I am inferring that this huge amount of water is the continuous, initially clear flow of the Colorado around, over, or through the dam. It is also notable that the overlying deposit is multi-phased. There are several beds and only some are extremely coarse. The sequence may contain evidence for the progressive failure of the dam and other vagaries of the hydrograph.

It would be interesting to know if there was any evidence that the gravels were deposited on a cooling lava flow...maybe there are some key erosional forms to look for. Didn't think of that at the time.

This seems like a strong case for failure of a lava dam. There are no assemblages like this on the Owyhee River.

Check this abstract for a discussion of the role of water in forming the colonnade:

Here are some other articles of interest (from a longer list compiled in 5 minutes using Zotero)

Grossenbacher, K. A., and S. M. McDuffie. “Conductive cooling of lava: columnar joint diameter and stria width as functions of cooling rate and thermal gradient.” Journal of Volcanology and Geothermal Research 69, no. 1-2 (1995): 95-103.<o:p></o:p>

Long, P. E., and B. J. Wood. “Structures, textures, and cooling histories of Columbia River Basalt flows.” Bulletin of the Geological Society of America 97, no. 9 (1986): 1144-1155.<o:p></o:p>

Lyle, P. The eruption environment of multi-tiered columnar basalt lava flows. Vol. 157. Geological Soc London, 2000.<o:p></o:p>

Walker, G. P. L. “Basaltic-volcano systems.” Geological Society London Special Publications 76, no. 1 (1993): 3.

GC vs Owyhee

Dr. Jerque,

In a rare moment of 9-5 nonbillable geology work I submit:

The four observations you list (added below in italics) as some of the differences between the Owyhee and GC intra-canyon lava dams are some of the exact same ones I note in the manuscript that is collecting dust on my desk at home.
1. Volume of lava vs. volume of water
2. Mode of entry: canyon rim cascade vs. tributary valley route
3. Severity of topography (vertical and lateral trajectory of lava incursion)
4. Proximity of volcanic vent to the canyon; abundance of pyroclastic material.
This is fabulous! I look forward to hearing more about these items and your other GC observations.
-Spud

Best Owyhee example of lava dam features

The Sand Springs Wash area on the Owyhee retains the best example of a lava dam in the field area. At this site, there are two lava flows from the Saddle Butte vent to the west. The overlying flow is separated from the underlying flow by a spectacularly well-developed lava delta with pillow-laden foresets that dip upvalley. The dam forebay is a turtle-back like feature with a 'carapace' of chilled lava. The surface of the older Saddle Butte lava upstream of the dam is covered with lacustrine mud which is capped with fluvial gravel.

Upstream of this site, the older Saddle Butte lava flow overlies Owyhee River gravel at the site of the Weeping Wall where a spring issues from the contact between the gravel and the lava. Upstream of Weeping Wall, the older Saddle Butte lava contains a sequence of lava deltas and subaerial lavas that suggest a complex interaction with the river.

Downstream, the eastern margin of the younger Saddle Butte flow is wasting away on a grand scale.

SHRIMP in the Owyhee?? Fire up the barbee mate!

Dear Dr. Froude et al.:

I concur with Dr. Jerque. He refers to a plethora of field evidence that adds detail to the story presented in Ninad's work. I'd like to add that you may want to check out a paper from the Idaho State crowd of Beranek, Link, and Fanning (see below). This paper came out some time back and offers a few possible numbers for ages of big picture events in the region. If I recall correctly, the most Owyhee-relevant discussion items are based on only a few data points compared to other drainages studied and could be strengthened by additional analyses. Nontheless, it is pretty darn interesting to this spud farmer trapped in the concrete jungle.

Miocene to Holocene landscape evolution of the western Snake River Plain region, Idaho: Using the SHRIMP detrital zircon provenance record to track eastward migration of the Yellowstone hotspot

Luke P. Beranek, Paul Karl Link, and C. Mark Fanning

Geological Society of America Bulletin Volume 118, Issue 9 (September 2006) pp. 1027–1050 DOI: 10.1130/B25896.1

-Spud

P.S. Dr. Jerque: I think we are on the same page about the Rytuba and Vander Meulen work. I did overstate its relevance in reference to the Now Voluminous (Once Dreaded) Rim Gravels but refer to it merely in the context that it provides evidence of a long-occurring interaction between volcanism, the fluvial system, and expansive sedimentation in the region. I wonder if it is even relevant to the latest question because "The inital influx of major fluvial systems into the volcanic field after about 14.5 Ma is reflected...."(see abstract)?

How old is the Owyhee?

Today, Dr. Froude presented the most basic question: How old is the Owyhee River. I pulled some stuff out of the air in a quick response, and ultimately claimed the river developed between about 5-8 Ma and 1.8 Ma. I decided my response was too quick, and too poorly founded, so I started looking for some of Ninad's data. Turns out that Miami Univ puts all of their dissertations online. Very handy. Thus, I present some of Ninad's dissertation below to serve as a reference point for all of us. By combining his data with our collective field observations, I think we can answer the question. For the sake of completeness, here is my response to Froude's query:

Bogus Rim flow and underlying flows fill a surprisingly deep paleovalley that runs along the alignment of the modern canyon below iron point. Gravels are present at the base of the sequence in a few places (including possibly in the Owyhee Breaks area) and there are erosional intervals preserved between some of the flows. Not sure how well constrained the ages of the lowest flow (the 'lower Bogus lavas') are, but somewhere between 5 and 8 comes to mind (without looking anything up). There was a river flowing north before the Bogus lavas were emplaced. This river created the paleotopography in the Grassy Mountain Rhyolite and sediments before the first big barf of basalt flowed north. Based on the thickness of the Bogus Lavas in the Rinehart Canyon area, there were some deeply incised tributaries flowing into the river.

In terms of field evidence, the biggest influx of gravel occurs in conjunction with the end of the damming event caused by the Bogus Rim flow. I believe that evidence is mounting that a very large lake occupied the area upstream of where the Bogus Rim flow would have created a dam somewhere near Iron Point. Thus, the pre Bogus Rim river was probably a nearly full blown Owyhee. Possibly the full blown river developed in conjunction with surmounting the Bogus Rim dam? That should have been sometime after about 1.8 Ma. I recently collected a tephra from the lake sediments that I postulate were deposited into a Bogus Rim dammed lake. Dating that may be of some value.

Here is the geochronology from our area as reported by Ninad Bondre:

Here is a nifty map that places these data in a better context:

Also, Ninad's thesis includes a handy little geologic map:

Some thoughts:

Despite the geochronology, I am thinking that the Owyhee Butte lava must predate the Bogus Bench lava. Field relations suggest that the gravel that pervasively overlies the Owyhee Butte lava is related to damming of the Owyhee River by the Bogus Bench (Rim) lava. I have not seen any gravel below the Owyhee Butte lava (forms the Artillery Rim), but Liz and I noted in July that there are hyaloclastite units in the upper parts of this package. Note also that the Bogus Bench (Rim...Brim?) lava has no gravel on top until you get a few km downstream from Iron Point. There, you find a 5-8 m thick deposit of locally derived, but rounded gravels. (I have shown pictures of this before in a previous post, but may add them again soon for emphasis). We know from multiple locations that the Bogus Rim lava flowed down a channel of the Owyhee River and overlies rounded gravel in various places. The local gravel pile likely relates to decommissioning of the dam.

Thus, the river is at least 1.92 Ma old. Note that the 4569 vent has a date of approximately 5.64 Ma. The one-sided plateau morphology of that vent and flow complex supports the idea that it formed a lake on its south side, much like Bogus Bench. However, I have not seen (nor looked hard for) gravel. My hunch is that this may be related to a precursor drainage. Speculative.

My preliminary conclusion is that the river formed between 5.6 and 1.92 Ma, probably closer to 1.92. Any thoughts?

All figures and the table in this post taken from:

Bondre, N.R., 2006, Field and geochemical investigation of basaltic magmatism in the western United States and India. PhD. Dissertation, Miami University, Miami, OH., 252 p.

http://www.ohiolink.edu/etd/send-pdf.cgi/Bondre%20Ninad%20R.pdf?miami1164916380

What's up with upper-tier landslides?

After looking at landslide after landslide along the Owyhee, it is pretty clear that there are several modes of failure typical of the river corridor. Of course we have the basic earthflow type (the Hole in the Ground has great examples); the basic rotational slump type (Artillery landslide complex; Heaven's Gate landslide complex); and the basic cantilever slab type failures along the margins of the Quaternary intracanyon lava flows. Yes, there are complex combinations of all of these things as well. Recently, Liz and I were noting that there are areas where only the upper part of an exposued section is peeling away...this is particularly true in areas where there are stacks of massive lavas with occassional interbeds of lacustrine sediments or, more importantly, piles of lava-water interaction deposits. The Bullseye landslide in 'Sweetwater Canyon' (name from river guidebook) is a good example. There, the upper lava flow is peeling back across a cruddy looking bed of lava-water interaction deposits (LWID). The LWIDs overlie a relatively massive stack of lavas. It appears that the Bullseye landslide's head scarp is below the peeling section. Its ultimate failure would not have been possible without the peeling in the upper tiers of the section. This makes Bullseye a lower-tier slide candidate.

There are lots of examples of upper-tier sliding along the river. Possibly the most impressive is right across from Iron Point. In that case, the failing area is pinned on rhyolite. There are several landslides in this general reach that sole-out on rhyolite. Not sure whether they occurred when the river was at the level or if they freaking cascading over the rhyolite into the river. Probably the former since the latter sounds so cool.

There are many examples where the upper-tier sliding seems to be associated with an underlying LWID (like a lava delta) or otherwise incompetent unit (like a lens of mud). In some places, the lava deltas are obviously linked to massive landlsiding; in others, they support massive cliffs. Maybe when you peel away the top, they lead to massive landslides. Probably not that simple. Any thoughts? Anyone?

Shockingly Voluminous (Once Dreaded) Rim Gravel, redux

Alas, brother spud, unless we are on different conceptual planes here, the paper in question does not directly address the SV(OD)RG. Instead, it is focused on the fluvial sediments in the middle Miocene part of the section, specifically the arkosic sandstone and mudstones that we see interbedded with rhyolite just downstream from AM-PM camp:

In the context of our studies, this part of the record is only a glimpse into an ancient precursor drainage system. In fact, I think that a fair amount of the SV(OD)RG in our study area is related to lava damming events in the latest(?) Miocene and into the Pliocene (i.e. the Bogus Rim).Thus, is is possible that the SV(OD)RG represent blockage of an integrated / partially integrated Owyhee. Recall that the base of the Bogus lava sits on river gravel in various places between Iron Point and Birch Creek. I suspect it was the blockage of this system in the early Pliocene to late Miocene(?) that deposited the gravels that form a flat surface at 3900'. Subsequent and possibly sporadic incision through the gravel cover after the breach formed several discernible levels of gravel. This is directly analogous to the distribution of the much less widespread and voluminous gravels above the Quaternary blockages. It is that latter point that really pulls me in. Any counter arguments? Anyone?

In the figure below, I have pointed out some features of the gravel. I have approximated its MINIMUM extent using the snow-like pattern. Have also noted the problem with the Ice Axe as Bogus Rim (stay tuned for explanatory post on that one). This is a crude mock-up. A more formal figure will be forthcoming with lots of elevation data...(just got me a Trimble XH...arrived today!).

(click on image for full size)