Marine Geoarchaeological Investigation of Damariscotta River, Maine, USA

Peter A. Leach

As of 2002, Degree of Master of Science (MS) Quaternary and Climate Studies published under the auspices of the Climate Change Institute.


A pronounced gap in the record of prehistoric coastal adaptation on the Maine coast before 5000 14C y.B.P. is the direct result of submergence of archaeological sites by rising Holocene sea-levels. I have conducted research focused on the search for the submerged sites of this time period in Damariscotta River, Maine, USA. Relict oyster reefs in Damariscotta River provided the opportunity to refine the search for submerged prehistory by investigating the submerged archaeological site potential of these easily located and spatially and temporally restricted prehistoric biological resources. I utilized shallow marine geophysics, including seismic reflection profiling and side-scan sonar, coupled with marine vibracores, in this endeavor. Through near-complete seismic reflection profile coverage it was possible to reconstruct the paleogeography of Dodge Basin, and to understand the effects of marine processes on the Holocene evolution of the basin. Vibracores containing organic samples for radiocarbon dating aided paleogeographic reconstruction efforts, and ground-truthed significant seismic strata. Submerged oyster middens were not found preserved in association with the Dodge Basin oyster beds. Tidal current scour and channel aggradation and migration have removed and reworked sediments between the oyster beds and the current shoreline. However, the basin has not been completely scoured and reworked, as the presence of a 6200 14C y.B.P. submerged and buried paleosol attests. This paleosol was preserved during a 'preservation window' in the Maine Relative Sea-Level Curve between 7000 and 5500 14C y.B.P.. Natural oyster beds and cultural oyster middens have numerous similarities and differences that were investigated in this study. I separated the signatures into three stages or scales of inquiry: macroscopic, mesoscopic, and microscopic. The macroscopic scale encompasses the initial survey for submerged middens and/or paleosols through shallow marine geophysics, with close attention paid to the location, internal stratigraphy, and basal stratum of marine shell deposits. The mesoscopic scale comprises investigation of vibracore or grab-sample features with the unaided eye, including preservation state of oyster shells, consideration of the articulation or disarticulated nature of oyster shells in natural and cultural shell deposits, and general vibracore stratigraphy. The microscopic scale involves those signatures that cannot be readily identified by the unaided eye. The most important of these signatures are miniscule terrestrial gastropods and mycorrhizal fungi, both of which strongly argue for terrestrial origins of submerged contexts.