One of the main things we learned last week is that the upper sediment zone at the site is, indeed, a plowzone. Clear plow scars were present at the interface of zones 1 and 2 at the base of zone 1 in Unit 9 (the 1m x 3m unit being excavated to create a straight profile wall). In Unit 9, the plowzone was about 28 cm thick.
With information from Unit 9 in hand, I hoped we'd be able to easily identify the same light-to-dark interface marking the base of the plowzone in the block units. Level 2 in Units 4 an 6 was targted to end at 50 cm below datum (cmbd), still within the upper zone. For level 3 in both of those units, we were able to easily discern the darker sediments immediately beneath the plowzone and excavate level 3 as a natural level, using trowels and shovels to remove the lighter plowzone sediment. I had the students in Units 4 and 6 finish off level 3 within the transition so that we could see the plow scars. Then they used trowels to remove the remaining light pockets of plowzone as level 4.
While the presence of a plowzone is clear, the status of the zone beneath the plowzone is not. When I first began working on the machine-exposed profile, I thought the buried dark zone (zone 2) was a buried plowzone. As I worked on the profile more, however, I began to think it was actually, perhaps, a remnant of intact prehistoric deposit. That was still my guess as of last week. We've now gotten a new, closer look at the zone in the straight profile being produced by the excavation of Unit 9, however, and I'm back to thinking it's more likely it might be a buried plowzone. The main detail affecting my thinking is the very crisp interface between the base of zone 2 and the sediment beneath it.
Jim Legg's fantastic adventure continues in the "downstairs" portion of the site as the excavation of Unit 9 plumbs the profile wall. After excavating the plowzone as a natural level, Jim and his students have begun excavating the remainder of the unit in 20 cm levels. They're now below zone 2, so they're into sediments that unquestionably contain intact prehistoric deposits. I've got my fingers crossed that they'll hit a feature or two as Unit 9 is excavated, as a couple of absolute dates would be of great help in understanding the deposits. If there's a big feature in there, however, it could really slow down the production of the profile wall. We'll see.