North American Database of Archaeological Geophysics
North American Database of Archaeological Geophysics
Abstract/Summary:
Project Name: Jamestown Island (Brewhouse Area), VA;
Reference: Bevan, B. (1995). Geophysical Remote Sensing at the Colonial National Historical Park, Findings of the June 1995 Course. Submitted to Colonial National Historical Park, Yorktown, Virginia.
In June of 1995, geophysical investigations were conducted at two locations within the Colonial National Historical Park as part of a geophysical training course that was held during the week of June 12-16, 1995. The surveys used a variety of geophysical techniques with varying degrees of success.
The first survey took place in an open lot in historic Yorktown. The lot was located at the corner of Main and Read Streets. There were formerly one or more houses on this lot. Only the most basic and inexpensive instruments were used at this location as a learning exercise. The methods used were resistivity and magnetometry. The resistivity survey found distinctly low values at the north end of the survey area. This may have been caused by a thicker or more organic soil. There is an indication of a former driveway entrance from Main Street that might correlate with a high resistivity anomaly. The magnetic survey detected three significant anomalies of unknown origin.
The second survey was conducted in the settlement area on Jamestown Island, Virginia. Historical records suggest that there might have been a building in this area devoted to brewing beer. The geophysical methods that were used include ground penetrating radar, electrical resistivity, resistivity sounding, and magnetometry. An electromagnetic conductivity reconnaissance survey was also conducted to quickly locate areas of interest. An interesting alignment of magnetic anomalies were detected along a diagonal at the southern part of the grid. This pattern can be caused by an underground brick wall. This line is also parallel to a ditch feature that was encountered during earlier excavations. The resistivity data revealed a distinct high resistivity area at the southern end of the grid. This may have been caused by a layer of sandier or drier soil at a shallow depth. The GPR profiles indicate rather deep echoes (at 1 to 2 meters) near the south end; this is near where earlier excavations found structure S-116. However, these radar echoes extend outside the area where that structure was found, and they may also be deeper than the structure. It is possible that they have a completely natural, geological origin such as a lens or ridge of sandy soil from an ancient flooding of the James River. The geophysical surveys showed no clear evidence for a large brick structure, which could mark the former brewhouse.