August 15, 2018
WOW-WOW-WE-WOW everybody!
 |
| Unit N11 W4 southeast corner full of oxidized soil, ash, and charcoal. |
Andrea here, and today I am going to get down and
dirty on float sampling. But first, let me give you a little background on how
our sample came to be. It was the 3rd of August 2018, and the day before the
annual Fort St. Joseph Open House (and for the record our unit floor was
extremely level at this point). Our south east corner was looking rather
oxidized, ashy and full of charcoal. It was decided that our unit would be
sampled. To begin, we measured and marked out a 45cm x 75cm square. We needed to
fill a 10 liter bucket. We literally chunked up large pieces of sediment to prevent
compromising any of the organic material that may be in the soil sample. Our
purpose for taking the float sample was to hopefully gather remains of any
organic material consumed or utilized by the inhabitants of Fort St. Joseph.
So, we filled our bucket, but we may have forgotten to keep in mind we weren't
going to go past 45cm below our datum point. As we cleaned up our South East
corner it was clear we had gone too deep approximately 47cm below datum. And
that's how we came to have our undulating (uneven/really bumpy) floor...
 |
| Undulating floor. |
 |
| Austin teaches students how to use the flote-tech flotation machine. |
Flash forward 2 weeks
later, our hideous floor has been buried and we are out of the swamp and back
in the lab at WMU. Today, a past field school student came in to show us how to
use the flote-tech flotation system machine (there was no manual and the video
was on VHS). This machine looks like a hotdog vender cart turned into a fancy
wet screen operation. It consists
of a water reservoir, flotation tank and a water pump. The machine is split in
half and the pump is used to move the 100-gallon water supply in a closed loop
from the water reservoir into the floatation tank. One half of the machine
houses the coarse-fraction screen and the other the fine-fraction screen. The machine gyrates and separates the organic
material (fine-fraction) from the soil, it then floats to the surface while the
heavier particles (coarse-fraction) sinks to the bottom. The floating material
floats over the lip of the flotation tank and into the fine-fraction screen. As
we began to process our sample the water movement was non-existent. We drained
the tanks and began to disassemble the loop of PVC pipes for the pump system.
The system was clogged! We blasted the slimy clay like silt from the pipes and
every nook and cranny with the hose.
After reassembling the system, we started to process the sample again
and boy did it make a difference! We
were cooking with gas and organics were floating to the surface with a purpose.
After all of the fine-fraction organics have floated over and all of the soil
has completely filtered out of the coarse-fraction screen we removed both
screens. The fine-fraction screen is tied up to dry to await analysis (most
likely under a microscope) and the coarse-fraction screen is set aside for
further screening. When you pull out the course-fraction screen many artifacts
are immediately visible for example lead shot, seed beads, and bone;
these artifacts will be bagged and sorted like usual. After we finished
processing all the samples we tore the machine down and flushed it out for the
next guy! All in all, it was a great day and another archaeology skill in the playbook.
 |
| Austin and Gary cleaning the flotation machine. |
 |
| Fine-fraction and coarse-fraction samples after screening. |
 |
| Diagram of the Flote-tech flotation system machine. |
 |
| Fine-fraction organics floating into the fine-fraction screen. |
 |
| Andrea and Gary fluffing the coarse-fraction ( I like to imagine he is a proud papa!). |
 |
| Austin and Gary clean out the pipes. |
No comments:
Post a Comment