Dear Reader, do you come across a lot of ancient blubber concrete in the course of a normal day? I got some exciting news from Mattias Pettersson Tuesday morning regarding his and Roger Wikell’s Mesolithic sites in the Tyresta nature reserve. As Aard’s regulars know, Tyresta is a former archipelago that is now wooded highlands due to isostatic land uplift, all full of early post-glacial seal-hunting camps. It’s easy to share Mattias’s enthusiasm (and I translate):
Does anyone remember the burnt bubbly lumps we found under the hut floor at the 85 m a.s.l. site in Tyresta? Now Sven Isaksson of the Archaeological Research Lab has done a chemical analysis, and the results are awesome: there are remains of marine fat in the lumps! It’s di-hydroxi fatty acids and isoprenoid fatty acids among other things. The latter fats are made by plankton and then wander up the food chain. Alkyl-phenyl fatty acids are there as well, and they’re a decompositional product of marine fatty acids. Holy shit! Sven took the largest lump to be on the safe side, and it turned out to consist mainly of organics with only a small mineral-grain component. At first he thought it looked like tar. Sven repeated the test several times with different solvents, and the results are consistent. The material apparently formed through the burning of “tissue, fat and skin of marine origin”, to quote Sven. [Think seal blubber.]
The Tyresta material is chemically different from north-Norwegian finds of spekkebetong, “blubber concrete” (1600-1200 BP), but the differences may be due to the vast difference in age [thousands of years]. Now of course we must carbon date a lump.
You can really see on the lumps that the material has been fluid, bubbling away in the hearth pit. The lumps retain their original surface, their shapes bubbly and rounded. They also seem to carry imprints of stuff that has burned off, twigs or maybe bones. Now we wonder if we happened to hit the spot that is richest in lumps on the hut floor, or if there may be even better squares to dig just nearby? [...] One idea is to perform some kind of microscopic analysis to check for tiny seeds, carbonised parts of invertebrates, pollen, spores etc. that may be embedded in the lumps.
Roger Wikell will present the blubber concrete and other findings from the site at the Meso 2010 conference in Spain a few weeks from now. I’ve been blogging enough about the Mesolithic that it deserves its own tag around here.