Floating in the Floodplain

Hello blog readers, this is Tommy from the 2016 field season. I’m back with a post on flotation samples!

            Botanical (plant) remains can be charred or uncharred and include remains such as seeds, charcoal, wood, corn cobs, kernels, and other plant parts. These remains are usually recovered from sediment samples by water flotation or directly from their cultural contexts during excavation. Botanical remains can provide evidence for the utilization, processing, or domestication of plant resources by the occupants of an archaeological site, which can help answer questions regarding diet, subsistence, season of occupation, trade, and site function.

The botanical remains at Fort St. Joseph are most often are recovered from cultural features such as hearths, fire pits, and middens (trash deposits). We are mostly looking for charred seeds that can tell us if the occupants of Fort St. Joseph were eating domesticated plants like wheat. During the 2016 field season we took several flotation samples. The process of gathering a flotation sample starts with identifying an area to gather float sample. We were looking for areas of Oxidized (burned) soil and middens. Once we found an area that we decided was suitable for a flotation sample we would trace a box around it and collect 10 liters of soil. Once the soil was collected we transferred it into a bag so we could bring it back to the lab for processing.

A sample that has been run through the screens

Back at our lab at Western Michigan University (WMU) we have begun processing our float samples. The first step when processing float samples is to run them through a Flote-Tech float machine. The float machine has two chambers, one to catch the heavy fraction (artifacts that don’t float) and one for the light fraction (botanical remains that float). Once the sample has been run through the float machine, we take the heavy and light fractions and let them dry. After the samples have dried we run them through a series of screens that are stacked on top of each other in order to separate the materials by size. We use 2 different screens when processing our float samples, one is 2 mm and the other is .85 mm. After the samples are run through the screen we sort the samples to pick out the botanical remains we are looking for from the other materials (root hairs).

So far, I have sorted 2 light fractions and one heavy fraction. I haven’t recovered any charred seeds, but I have recovered some unburned grape seeds. The heavy fraction had a lead bale seal inside of it. Bale seals were used to provide proof that cloth or other goods had met the standard set by the guild which controlled the materials in the bale. I hope to find a lot of other helpful materials during the rest of the semester!

A close-up view of the "heavy fraction"

Thanks for reading!

-Tommy