GEOLOGIC PRESERVATION POTENTIAL OF COASTAL AND SUBMERGED ARCHAEOLOGICAL SITES

Archaeological sites originally sited on coasts are subject to potentially severe reworking and low preservation potential during sea-level rise and coastal erosion. The record of post-Pleistocene coastal and maritime adaptations is potentially crucial for understanding cultural changes, migrations into the New World, and evolving tools and techniques for exploitation of marine resources. However, much of that material record may be either submerged on the continental shelves, or was destroyed or disrupted from its original context by coastal processes. Kraft, Belknap and Kayan (1983) proposed a conceptual model of preservation potential based on rates of sea-level rise, coastal geomorphology, and strength of site materials. This model predicts greatest preservation potential, but lowest discovery potential, for back-barrier or estuarine margin sites in areas of gradual slopes and/or accelerated sea-level rise. Cliff- or bluff-top sites on high-energy coasts have little or no preservation potential, except as scattered artifacts or building stones. In stable or uplifting coasts, or sites well up river, maritime sites may be preserved relatively intact (e.g., Quebrada Jaguay in southern Peru). Illustrative sites from Maine include middens at eroding bluffs, coupled with submerged oyster bioherms that provide a model for preservation during sea-level rise and tidal river lateral erosion, and lead to a model for potential occupation sites. Recent near-shore studies revealed individual artifacts near submerged barrier spits, providing another model for coastal occupation. Several other offshore sites have produced only scattered individual artifacts, collected by draggers or washed up on beaches. Increasing use of high-resolution seismic reflection profiling, sidescan sonar and multibeam bathymetry is improving prospects for predicting site locations, if not yet direct imaging of intact middens, for example. Vibracoring and SCUBA diving on geophysically imaged sites improves development of geoarchaeological models for site localization and the potential for discovery of sites.