[While we finish up in the field today, Alicia Michalski has provided a great post on what has been keeping her busy for the last few weeks: bisecting postholes!]
While the ditch has been the main focus in the latter part of our excavations, I have been concentrating on the post holes that lay outside of the larger feature in Unit 8 (the 5×3).Th ese may look less impressive than a massive earthwork ditch, but the data we collect when we bisect postholes can reveal the answers to very important questions. Bisecting a post hole and recording the various measurements is one way to find a possible pattern among what at first looks to be a random scattering of features.
In order to bisect a post hole, I first need to clean scrape the surface area in which I am working. This reveals darker sediment, more brown in color than the yellow fill which surrounds it, indicating a possible post hole. Then I take a top elevation of the post hole, which indicates the depth at which the post hole was dug in relation to the surface. Next, I cut the post hole in half and create a mini-profile, digging down and keeping the back wall as clean and straight as possible. The difference in the color of the sediment is one of the most important factors in this process. It reveals the boundary of the post hole, if it veers off or is diffuse (indication of a rodent burrow) and where the post hole stops. This is why keeping the back wall clean and smudge-free is critical.
Once I’m sure I’m at the bottom of the post hole, I record bottom elevation and a description of how the bottom is shaped (pointed, rounded, or flat). Then I take out the remainder of the post hole from the wall I had bisected, leaving a round column from where the sediment that had filled the post hole had been. The sediment from the post hole is then screened to reveal any artifacts that may be associated with it.
Bisecting a post hole is certainly a process that takes a bit of skill and a lot of patience when the lighting isn’t cooperating. But the data that has been collected from all the posts will be invaluable when it comes to teasing out similarities and differences in post features that might relate to different architectural structures.