If I was subtitling these posts, I'd call this one "A Tale of Two Plowzones?"
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.
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.
Cleaning up at the base of plowzone in Units 4 (right) and 6 (left front). Shovel excavation of Unit 5 (left rear) in progress.
In Unit 5, level 2 will proceed to the base of plowzone rather than stop at 50 cmbd. It was almost complete by the end of the day. We'll be able to get into the sub-plowzone deposits in all three units on our next day in the field.
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.
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.
So far, we have no evidence of any intact cultural features in zone 2. As of now, my plan is to excavate through this zone in the block units by shovel skimming. That will give us the opportunity to keep our eyes open for cultural features originating within or immediately beneath zone 2, and will also allow us to piece-plot artifacts that are encountered if it makes sense to do so. Shovel skimming and piece-plotting will be new methods for the students, so they'll learn something by doing it even if it turns out that zone 2 actually is a buried plowzone rather than an intact cultural zone.
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.
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.
Excavations in progress in Unit 9. Block excavation area visible in background.
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