GEOARCHAEOLOGICAL SURVEY FOR SUBMERGED ANTHROPOGENIC DEPOSITS IN DAMARISCOTTA RIVER, MAINE, USA

Regional models of prehistoric occupation in the state of Maine are impeded by a paucity of coastal sites before 5000 BP. Pre-5000 BP coastal sites were submerged by rising Holocene sea-level and are inaccessible by standard archaeological methods. We are currently addressing this problem in Maine's Damariscotta River through a combination of geophysical, geologic, and archaeological methodology. We focus on relict reefs of the eastern oyster, Crassostrea virginica, to refine the search for submerged prehistory. Methods for locating submerged sites often rely on large-scale geographic features such as drowned river valleys. Relict oyster reefs are spatially-restricted, easily identifiable indicators of potential site locations. At least two reefs occur in Damariscotta River. A reef in Salt Bay dates to 1325 ± 40 RCYBP. In Dodge Basin, our main study area, Shipp (1989) cored through a reef overlying salt marsh peat at 15 mbsl and 6340 ± 55 BP. The Damariscotta is a fully-marine estuary, though prior to transgression it comprised stair-step ponds separated by sills of varying elevations. As each sill flooded oysters colonized farther upriver. Shipp's (1989) radiocarbon date below the Dodge Basin reef is a minimum date for oyster colonization and human exploitation of oysters in the area. Occupation sites on Damariscotta River indicate human exploitation of oysters in the region, and provide a useful analogy for the characteristics of potential submerged counterparts. We acquired 62km of seismic reflection and side scan sonar data and nine vibrocores of lengths between 2 and 6 meters to reconstruct the paleogeography of Dodge Basin. Side scan data generated surficial geologic information, while seismic profiles provided subsurface data regarding depositional environments, erosional features, and oyster reef configuration. The Dodge Basin reef is preserved under at least 2 meters of Holocene mud, and is roughly 2100m long, 350m wide, and between 2 and 4 meters thick. The highest potential location for submerged sites is the east side of Dodge Basin, an area of intact, thick reef deposits and relatively high preservation of sedimentary environments. C. virginica boasts a broad geographic range, from the Gulf of St. Lawrence in Canada to the Gulf of Mexico in the USA. Given this extensive species distribution our methodology is widely applicable outside Damariscotta River.