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Friday, July 24, 2015

Stratigraphy Ah Ha moment

Leslie finds the bottom of the site unexpectedly early

On Tuesday Leslie found the glacial till at the bottom of the site. This is the hard packed gravel layer laid down by glaciers more than 14,000 years ago.  It should have been a LOT deeper down there.  Last year we found the bottom of the site almost 2 meters down below the surface.  This year Leslie digging in the field behind the site found it less than 1/2 a meter below the surface.  What is going on?

What's interesting is that Leslie did find all the normal layers from about 4500 years ago to present.  It is just all the old layers that are missing.  Cue back to last year when we were excavating the lower layers of the site and finding multiple layers of re stacked, 'tossed' sods.  Guess where they came from? You guessed it - Leslie has found the sod quarry.  It seems the people living at the site prior to about 4500 years ago harvested sods from the field behind the site and brought them to the front of the site to build their structures.  

The fact that they stopped doing this around 4500 years ago indicates that people started to use the site differently.  Other than harvesting and importing sods, I am still not sure exactly what people were doing prior to 4500 years ago at the site, but I do know what they were doing later in time - smoke processing meat of some sort!

At the bottom of Leslie's pit there is a layer of weathered ash mixed with beach pebbles and flecks of charcoal.  We have been calling the layer L2A.  It is capped by a homogenous weathered and largely sterile ash we call L2 that seems to represent a volcanic ash fall from about 3800 years ago.  We find the same layer in all our excavations near the city of Kodiak.  We don't always find the L2A layer, but I think I know what it represents - repeated smoke processing.

In the main excavation in the same layer we have been finding pits filled with alternating layers of beach pebbles mixed with charcoal and sods.  I think the pits basically represent smudge fires for smoking sea mammal meat.  They heated up gravel to retain heat and then covered the fire with sod to lower the oxygen and maintain the fire.  Basically a low heat fire that lasted a long time without the addition of more valuable wood.

From this time period we are pretty much only finding sea mammal hunting and butchering gear so I suspect the site was a place people visited seasonally to hunt sea mammals.  In the other excavation at block B, in more recent deposits, they even found bits of calcined sea mammal bone, but they also found some fishing line weights.

In any case, Leslie's discovery of the bottom of the site with nothing older than L2A on it indicates that from L2A times forward Alutiiq people stopped intensively quarrying sods, and only used the site to catch and process meat - a hunting camp.  I am hopeful that the older sod quarrying is an indication that the site was used more intensively prior to the 'L2A' time period.  Maybe it was a small village where they were building houses with sod walls and roofs?  

We'll see when we get there!  Patrick

Rachel uncovers the top of a 'L2A' smoke processing pit

The beginnings of a much bigger smoke processing pit from block B

Soloman with some fishing gear - line weights?

Profile of a 'L2A'  smoke processing pit

1 comment:

Molly Odell said...

Cool stuff! Looking forward to digging next week.