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>