Category: radiocarbon

Got some new C14 dates in

We were able to run a pair of C14 dates on materials from Deering as part of the WALRUS project.  I just got the results back today.  I have to share the calibrated dates with the folks in Deering first.  They were kind enough to let me include the samples, which were found during the monitoring work we did there late last summer, in the WALRUS studies.

They were found together in a fairly thin organic layer (likely midden) in the wall of one of the trenches.  Very little walrus has been found there, so we were lucky.

W16_2095
Samples were from the upper dark layer visible in the trench wall.

Getting a bit cross-eyed…

I’ve been working on dating the various samples from the WALRUS project.  Since walruses are marine mammals, direct C14 dating is problematic.  In fact, that is one of the things we are looking at with the project.  We ran a number of sample pairs of walrus  and terrestrial material and compared the offsets.  The bad news, there is not just one offset.

That meant that we couldn’t just use that to correct walrus dates.  So, we are reliant on construction of chronologies using the caribou dates we have run, as well as other available dates, to figure out how old the walrus samples are.  This is simple when we have a terrestrial sample from the same context.  When we don’t we need to see if we have dates from earlier and/or later levels (both is better) which gives us boundaries for the context we are trying to date.  To do that, we need to understand how the layers were arranged.  I’ve been using

For some sites, we have very little information beyond the mound or midden square from which the samples came, or the depth of the arbitrary level they were excavated from.  For others, we have more detailed stratigraphic information.  I’ve been developing schematic descriptions of stratigraphy for the sites from which we have samples , using the Harris Matrix as a means of representation.  Some of these are relatively easy to do and others are more complex.  For simplicity’s sake I have only been including sampled contexts in the Harris matrices, although someday I can add other excavated units.  The  one on the left below is from a site where we have little information on most mounds (we have samples from six), and those we do have info on were apparently dug in arbitrary levels, as far as can be told from the field notes.  The one on the right shows the two sampled  mounds from a site where I have extremely detailed provenience information.

 

These help me check that the dates we have are consistent with the stratigraphy, and are helpful in construction of more complex dating models in OxCal.   The process helps me think about how the models should be built, and also serves as a bit of a check, since having a crude model with some dates makes it easier to spot cases where a complex model may have been specified incorrectly (and therefore is giving incorrect results).

Boxes and Boxes

Tony and I spent the day going through boxes containing animal bones from the 1990s excavations at Pingusugruk.  Tony made a list of boxes that contained the sample bags we wanted, which we then had to find in the warehouse.

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There were over 300 boxes from that site, so it was a long day.  We didn’t have to open all the boxes, thank goodness, but we had to move most of them.  I suspect I’ll be sore tomorrow.  Not really in full fieldwork shape yet, unfortunately.

Tomorrow, we’ll do a bit of modeling, before Tony leaves on the evening plane.

Lab work

So far it has been pretty busy with Tony here.  He’d picked out a number of possible samples in advance, and we’ve been finding them.  I’ve also been going through the column samples we took last year at Walakpa, and finding contexts that have 2-3 datable samples of both land and marine animal bone.  That way, there will be multiple terrestrial dates to give us both a date on the level and information to use to develop correction factors for marine mammal bones.  Marine mammal bones tend to give radiocarbon dates that are too old, but sometimes they are the only thing available to date.  People generally don’t run dates in those circumstances, but if there were decent correction factors available it would be possible.

We went over to the Inupiat Heritage Center this morning to look at the material they have from Utkiagvik.  It looks like there is enough for a whole project there, although the location of the 1981 field notes was unknown for the moment.  Some of the staff came out to the lab later and looked at a couple of sewn objects.  The mystery one is made out of gut which has been stitched to form a sort of pointed tube, although it is pretty crumpled up.  If we get a conservator to visit, it would be great if they were able to rehydrate it a bit and straighten it out.

Tomorrow we are going to be going through boxes of faunal material from Pingusugruk to find suitable samples.  There are hundreds of boxes, so Tony is trying to select some contexts to pull, and then I have to ID appropriate bones.  I am really hoping that the intern  shows up for work.

On the Walakpa front, I’ve been talking with the UIC Science logistics folks, working on how to handle temporary housing for those transiting in and out of the field, and starting to work on travel arrangements.