Archaeology Update for the Week of November 7
Let’s roll up our sleeves and dig back to a quieter time here at the Headwaters thousands of years ago, shall we?
This past week, the rains stayed away for the most part and allowed our crews to get back to work in earnest. Even though we all had to crowd into one block (Block A) for most of the week due to the other blocks still being swimming pools, the crew excavated through 65 unit levels during the last week. A “unit level” is just that: it’s one 10-centimeter (3-inch) excavation level in a 1 x 1-meter (roughly 1 x 1 yard) test unit. If this were all dug in one test unit, that would be a hole going down about 21 feet!
Burned rocks visible about two feet down in a test unit in Block A.
The archaeologists appear to be finding the remains of Late Prehistoric-period (roughly 1,200 to 400 years ago) occupations in Block A with crews recovering three Leon Plain and/or Doss Redware ceramic pieces (we call them “sherds”) among the much more common stone flakes and tools. From studies elsewhere in the region, we know that ceramic technology didn’t reach this part of Texas until this Late Prehistoric period, so finding ceramics at a site gives us a good marker for how old those portions of the deposits probably are. We call these technological markers “temporal diagnostics,” meaning they are items that can tell us by themselves (without doing other studies) how old they are.
Small ceramic sherds from an earlier phase of the Headwaters at the Comal excavations. Similar sherds were recovered here this week.
It’s important to not put too much weight behind estimating site or site deposit ages using individual diagnostics, only because there’s no telling how an individual artifact may have gotten to where you found it. Sure, you might know pretty well that a dart point may have been made 5,000 years ago, but maybe someone 2,000 (or even 20!) years ago may have found it and dropped it somewhere new. To combat this problem, we look for many diagnostics of the same type in a similar location and also potentially compare them with other dating techniques like radiocarbon samples. Finding three sherds from the same area gives us better confidence that we’re looking at a Late Prehistoric deposit than if we’d only found one, but we’ll be more confident if we follow a few more data leads first. Diagnostics are kind of like the old Russian maxim re-used to great effect by President Reagan back in the ‘80s: Trust, but Verify.
We uncovered two single-use hearths in Block C before the really heavy rains hit a couple weeks ago. These are essentially small campfire sites or cooking stoves that a small group of people used thousands of years ago. We hoped that the tarps protected them so they could be carefully studied, but unfortunately learned this week after the block had dried that they were at least partially destroyed from all the water. Though that was a bummer, we were able to preserve one of the features digitally in this 3d model. We can make measurements and drawings from the virtual version even though the actual one isn’t in the best shape anymore.
Over in Block D, the test units have reached roughly two feet deep and are coming down on a dense, large lens of burned rock that has all the hallmarks of a burned rock midden. These features were discussed in the Prehistoric Background section, but as a quick refresher: burned rock middens are communal cooking ovens that are one of the main hallmarks of the Archaic period here in central Texas. They also are a sign of increased group sedentism. To make an oven in ancient times people would heat rocks in a fire, then place food next to the hot rocks. Those rocks retain the heat for a while and, when buried with raw plants and meats, allow people to bake food without actual flames. These cooking rocks would be used and re-used over and over by a group living nearby and as more rocks are piled on, it gets bigger and bigger, forming a burned rock midden. Some middens are several feet across and others may be 50 feet wide or more. All of this cooking means they’re often treasure-troves of organic data, like what foods people ate and when. We’re pretty sure this is one of those burned rock middens and look forward to what we hope to learn! We’ll keep you posted.
The upper-most layers of a possible burned rock midden visible in Block D.
Along with continued excavation in the coming week, we are planning to start working on the water-screening operation! Woohoo! This should be interesting!
You can watch the crews hard at work in our first live video update from last week, which is available on our YouTube Channel. As archaeologists, we don’t really deal with videography all that often and in the immortal words of Forrest Gump: “[Videoin’] is tough…” We’re tweaking the video setup and look forward to better sound in particular for tomorrow’s broadcast. Check in and let us know how we did!
Alrighty. I suppose that’s about all for this week. Come out and see us and check in this time next week.