Since we last posted, the students have been continuing their work on the Mound House excavations. Sq 620 and Sq 621 have both reached the base of the plow zone, which is the upper layer of soil that has been disturbed by historic agricultural development. Artifacts within the plow zone are considered out of context, since they have been subjected to (in our case) decades of agricultural activity. Once we have reached the base of the plow zone, striations called plow scars usually become apparent in the floors of our test units. The plow scars are where the tines of the plow compacted and smeared the soil beneath the surface, creating differences in soil color and texture when compared with the surrounding matrix.
Roll over the picture of Sq 620-Level 02 to see the delimitations of a plow scar. Soil color changes are very subtle here in the Midwestern United States, so excavators need to keep a close eye on their work.
Once the plow scars were encountered and recorded in the field notes, Sq 621 noticed another soil contrast that should be familiar to those of you who read our blog: the post mold (PM 1059). In relation to previously defined post molds found in the adjacent excavation units, this new post mold seems to form a neat arc possibly indicative of a prehistoric structure. While this is an exciting discovery, we will have to wait until the post mold and surrounding soil is completely excavated in order to determine its authenticity and relation to nearby post molds.
Roll over the picture of Sq 621-Level 02 to see the delimitations of PM 1059. The limestone rocks seen within PM 1059 were most likely used as chinking to stabilize the post. Again, it took a keen eye to catch this feature early on in the excavation process.