April 6, 2013
by Meagan Ratini
If you’ve been following the blog lately, you may have seen several posts relating to our recent work at Sylvester Manor. Located on Shelter Island, New York, this site has deep connections with the Fiske Center. In mid-March, a team from UMass Boston spent several days conducting a small geophysical survey on the grounds of the manor.
Steve Mrozowski (right, foreground) and John Steinberg take the GPR unit on a test run before beginning a full survey. John Schoenfelder (background) maps the area.
The original multi-year research project at Sylvester Manor was concerned with understanding the interrelationships of the various groups of people who interacted at the site in the 1600s and 1700s, including Anglo-Dutch colonists, enslaved Africans, and Native American laborers. These peoples’ presence was known from historic documents, although not all of them left their own writings. What is clear from this and the archaeological findings are that the interactions among all of these people changed them and their cultures in profound ways. However, it is often difficult to tease out these specific influences from the artifacts alone (Mrozowski et al. 2007:2-8).
One particular location on the manor’s grounds where these kinds of changes may be more visible is the area said to be the manor’s slave cemetery. Since the late 19th century, a memorial has stood commemorating the “Burial Ground for the Colored People of Sylvester Manor.” This memorial and local lore attest to the idea that this place was where the plantation’s slaves were being buried, as early as the 1600s. Although a fence marks off its location from the surrounding low hills, and some small rocks dot the area like grave markers, it is not possible to confirm or deny the story just by looking at the ground’s surface. Out of respect for the dead and respect for any living descendants, as well as in accordance with various laws and good archaeological practice, Fiske Center researchers planned no excavations of the cemetery grounds to try to answer this question.
GPR Slice image of the study areas, about 60 centimeters below the ground surface. The red box marks the location of the fence. The smaller area to the right is the control area.
In order to see if the area holds any burials, the team (including Drs. Steve Mrozowski, John Steinberg, and John Schoenfelder, as well as three UMass Boston graduate students) opted to use a shallow geophysical technique called ground-penetrating radar (GPR). GPR works by sending out regular pulses of electromagnetic energy into the ground at a similar frequency to cell phone transmissions. These waves bounce off of different kinds of surfaces underground, such as geological layers, rocks, or buried human-made features like foundations and graves. The GPR unit receives the reflected waves and produces a radargram, which is read for particular kinds of anomalies. Since these readings are taken in closely-spaced straight lines across the study area, the radargrams produced are then “sliced” so that it’s possible to see what the ground looks like at various depths across the whole area at once. These slices effectively “excavate” the ground at different depths and allow researchers to see the kinds of things that may be found at those depths. (See John Steinberg’s illustration of this, including what archaeologists look for in the radargrams.)
Since other kinds of anomalies, such as tree roots, can sometimes appear like graves, we also collected data in a control area–a second area outside of the fenced cemetery but nearby and still within the same type of natural setting. Even in the field, it was clear that the areas looked very different in terms of the GPR. The types of anomalies seen in the fenced area were not being found outside of it, potentially proving that the cemetery, is, in fact, where it’s said to be.
UMass Boston graduate students Nadia Kline (left) and Allison Conner process GPR data on a day when fieldwork was rained out.
More analysis needs to be conducted in order to draw any definitive conclusions about the data, but the preliminary results suggest the presence of graves within the area known as a burial ground. It is highly unlikely that the GPR alone would be able to show whether the burials are of enslaved persons, but positive geophysical results lend credence to the stories told about this place.
This study marked the first archaeological field research conducted at Sylvester Manor in about five years, and certainly proves that there is always more that places like this can teach us. In this case, finding probable graves within the cemetery reminds us not to dismiss oral histories, but to explore how they bear out under further scrutiny.
Mrozowski, Stephen A., Katherine Howlett Hayes, and Anne P. Hancock
2007 The Archaeology of Sylvester Manor. Northeast Historical Archaeology 36: 1-15.