by Jason D. Moser
It’s springtime, and you know what that means—fieldwork time! Yes, that’s right; an archaeological field school has arrived in Citrus County. This year, the University of South Florida (USF) has begun an archaeological field school at Crystal River Archaeological State Park. For those of you who aren’t familiar with the park it is a 61-acre site located just north of the town of Crystal River. The park encompasses a large part of an American Indian ceremonial mound complex located on the banks of the Crystal River. The complex includes two burial mounds, two shell temple/platform mounds, a plaza area, and substantial shell middens. Shell middens were dump areas created from the accumulated waste and debris of a community over the course of many generations.
The Crystal River site was used for 1,600 years making it one of the longest continuously occupied sites in Florida. Perhaps, due to this long occupation, extensive midden deposits are found throughout the park. They are composed mostly of shells, but they also contain broken pottery, discarded, broken shell and stone tools, and the bones from many of the birds, fish, mammals and reptiles that the inhabitants trapped and hunted. The presence of so many-well preserved artifacts make the midden deposits, some of the most interesting places that archaeologists can investigate.
The USF field school is part of a new investigation of the site called the Crystal River Early Village Archaeological Project (CREVAP) which is funded through a National Science Foundation (NSF) grant. The investigation is designed to address previously unresolved questions about the formation of early village societies and the dynamics of relationships between the prehistoric people in the Crystal River area. The project is being carried out under the direction of Dr. Thomas Pluckhahn (USF), Dr. Brent Weisman (USF), and Dr. Victor Thompson (Ohio State University). Additional information about the project can be found at http://www.crystalriverarchaeology.org/
To assist with these investigations USF has brought in several experts to conduct highly specialized investigations that are often beyond the expertise of typical archaeologists. This week I had the opportunity to speak with two of them while they were working at the park and to find out exactly what they were up to!
First, I spoke with Dr. Glen Doran–an archaeologist at Florida State University (http://www.anthro.fsu.edu/). Dr. Doran and his team brought a specialized piece of equipment that is designed to take soil cores from the ground. These cores are a way to sample the layers of shell and other material, or stratigraphy of the site without large scale excavations.
Site stratigraphy is a layering effect that occurs over time on archaeological sites. To visualize stratigraphy, imagine a multi-layer cake, with alternating layers of icing and cake. Just like making a layer cake—the first layer of the cake is located on the cake plate—and that layer is then covered with icing and subsequent layers of cake and icing are added. On an archaeological site, the process is very similar—the oldest layers of the site along with the oldest artifacts are located at the bottom of the site (Usually!). The layers that are on top of base layer are not as old, and contain more recent artifacts. Once you understand the stratigraphy and the processes that might ruin the stratigraphy—then you can understand exactly when the site formed, the periods in which it was used, and when the site was abandoned. Widespread excavations—which are both time consuming and expensive to undertake would also significantly impact the archaeological site and limit the types of information that might be recovered in the future.
Dr. Doran’s team used a powerful machine to collect soil cores that were approximately 2-inches in diameter. The machine is a custom made 540 RT/D direct push coring system manufactured by Geoprobe (http://geoprobe.com/). Geoprobe has also generously provided technical assistance and additional equipment for this project. The geoprobe machines use a high speed hammer to rapidly pound the steel core into the ground. The device will penetrate shell, clay, or the types of soft rock that are present in Florida. The soil cores are collected within a clear PVC tube which is fitted inside the exterior core sleeve. Once a core section has been pounded into the ground the operators withdraw the core from the ground using a hydraulic system. Getting the sample out of the ground is relatively easy, getting the clear PVC liner out of the sleeve, is actually much more difficult than it sounds!
After the core is out of the ground, the steel core is withdrawn from the machine and opened. A nearly perfect profile of the soil on the site is contained within the interior clear PVC tube. The plastic tube is removed from the machine and capped with color coded caps to mark which end is up and which end is down. Each tube is marked with relevant information about sample such as the location and depth of the test core. The process can be repeated as many times as necessary to create a cross section of a soil that is up to 10 meters in depth. However, most of the cores sampled at Crystal River are only three to four meters in depth. The cores were collected on a grid pattern at locations across the site and on some of the shell mounds.
The clear PVC tubes enable the team to immediately view the results. Because the cores are sealed they can later be submitted to labs for all types of additional processing and analyses. Soil grain size and composition can provide information about how the soil was formed such as whether the soil was formed from human activity, or whether it was blown in by the wind. Pollen and phytoliths samples can help reconstruct what the environmental and climate conditions near the site were during the past. Soil chemistry can indicate how specific parts of the site were used. For example certain activities leave specific types and combinations of chemicals in the soil. Radiocarbon dating of charcoal recovered during the coring can help establish a timeline for individual layers of the site, and provide specific information about the building sequence of the mounds.
As you can see–soil coring can often provide a huge amount of information about the people at Crystal River and how they lived. The cores that Dr. Doran and his team recovered from Mound A (The big mound) surprisingly indicate the presence of shell completely through the mound—with midden soil below the mound, and then clay, sand, limestone below the midden.
Once the remainder of the testing is completed—Dr. Doran’s team will hand over the soil cores to USF and move on to work at other sites in the area. USF will begin analyzing the soil cores after the field school is over. This will take quite a long time to complete. Hopefully, we will have some of the preliminary results by March 2012 when Dr. Pluckhahn will speak at an event during next year’s archaeology month. If you are interested in the Geoprobe work of Dr. Doran and his team, check out their website at http://www.anthro.fsu.edu/research/doran/geoprobe/geoprobe.html