MARINE GEARCHAEOLOGICAL INVESTIGATION IN DAMARISCOTTA RIVER, MAINE, USA

Investigation of marine settings for evidence of submerged prehistoric sites is complicated by the deep shoreface erosion of open-coast settings, specifically the transgressive ravinement surface capable of removing most if not all Holocene terrestrial sediments throughout submergence. We have focused on middle to upper estuarine locations as areas of high preservation potential for submerged sedimentological and anthropogenic deposits due to reduced energy and increased sedimentation in such settings. The eastern oyster, Crassostrea virginica, is a common occupant of estuaries and populations often congregate in reefs or bioherms that can be preserved in marine sediments. We are currently investigating relict oyster bioherms in Damariscotta River, Maine, at 4800 yBP and -10 mbsl, and the potential for submerged site association. We employ shallow marine geophysics, including seismic reflection profiling and side-scan sonar, and underwater vibracoring, coupled with computer processing and digital manipulation of data, to determine oyster reef configuration, reconstruct paleogeography, and identify areas of highest submerged archaeological site potential. Approximately 85 km of seismic reflection profiles and side-scan sonograph records as well as 14 vibracores have been collected thus far. Vibracores penetrated through Holocene sediment and refused on glaciomarine mud, while seismic profiles penetrated to bedrock and through correlation with vibracores were shown to be vertically accurate to within 10 to 20 cm. Data sets were imported into ArcGIS, a desktop Geographic Information Systems package, where we reconstructed the paleogeography of the study area and determined the spatial dimensions of the relict oyster bioherm. This method provided a base map for applying an archaeological site potential model to aid in locating submerged sites. We identified an area of high potential that appeared to be a submerged shell midden (pile of shell and refuse), which we vibracored. Analysis of cores from this location suggested that the deposit was a natural oyster bioherm. Future work should focus on those areas behind oyster bioherms that are too shallow for our current research vessel.