Wednesday, 23 April 2014

Geoarchaeological surveying in Powell Butte, OR

Deschutes National Forest
April is not usually this busy but I've been away for almost 2 weeks visiting family in Oregon, hence the lack of updates. Prior to that I had a mad week of coursework marking, and now upon returning there's a stack of exam marking in my near future. Do not despair however, exciting micrographs are ready to be posted for May, and to make up for the lack of posting in April, here are some lovely images from hiking in central Oregon.

Sorted sediments on meander beach
Although it was technically a holiday, I can never resist having a bit of a dig, and spent a lovely afternoon test pitting around the in-laws property in Powell Butte (Crook County). It's hard to break the habit of staring at the ground looking for finds whilst taking a stroll, and last year we found a single fragment of worked obsidian, so this year we decided to start a survey. Nothing archaeological in the test pits alas, but we hope to extend the survey gradually every time that we go back! Being the geo geek that I am, I got a little obsessed with the soil profile, and found this amazing soil resource for the US: http://websoilsurvey.nrcs.usda.gov/app/ 

It's an interactive GIS that lets you view soil (and other data) for anywhere in the US! So I managed to find our survey area and check my field descriptions against the official records. We are located on what is called the Ayresbutte-Ayres complex, which is an alluvial fan with a parent material of ash and alluvium from volcanic rock with a duripan. A duripan is a term used in US soil classification to describe a soil horizon cemented by illuvial silica. The silica has been displaced through the profile by rainwater, forming a very hard B horizon not too far below the surface.

The typical profile consists of a sandy loam that becomes increasingly gravelly and cobbly before turning into cemented material. Which brings us on to the point of this post - I am developing some new practical classes on soil and sediment analysis, and I need samples of different types and textures for lab testing. I have a few different examples but it would be great to have a wider variety, especially different types of clays. So, do you live near any exciting sediment types? Would you be willing to send me a sample bag of it? If so, send me an email! lisa@palaeo.eu

Map showing soils in the Powell Butte area http://websoilsurvey.nrcs.usda.gov/app/ 



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