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Archaeological evidence for local environmental change is obscured by the tendency for humans to remove natural resources from places of procurement and deposit them elsewhere, sometimes at great distance. This is especially problematic for changes in relative sea level, which clearly affected the inhabitability of low-elevation coastal landforms but not necessarily the regional availability of resources of cultural or economic value. Needed are proxies for relative sea level from non-dietary taxa. One genus of terrestrial snails, Truncatella, offers good potential in this respect because of its specific niche at the interface between seawater and land. However, like food resources displaced by people, Truncatella shells are displaced by storms and redistributed landward of the coastline. Distinguishing between autochthonous and allochthonous deposits is essential to inferring relative sea level from the occurrence of this taxon alone. To this end, assemblages of Truncatella shell from stratified sites along the north Gulf Coast of Florida, USA are compared to associated archaeological snails of other taxa and to snail shells from the wrack of proximate foreshores to infer changes in relative sea level over the past four millennia. Variation in the morphology of shorelines and in the accumulation rates of archaeological midden mitigates any direct relationship between terrestrial snail frequencies and sea level, but the results of this study suggest that our approach can be applied to other non-dietary taxa occupying marginally terrestrial niches to refine estimates for sea level derived from the sedimentary records of geological cores. [ABSTRACT FROM AUTHOR]

Low-gradient coastlines are susceptible to inundation by rising water, but they also promote marsh aggradation that has the potential to keep pace with sea-level rise. Synergies among hydrodynamics, coastal geomorphology, and marsh ecology preclude a simple linear relationship between higher water and shoreline transgression. As an archive of human use of low-gradient coastlines, archaeological data introduce additional mitigating factors, such as landscape alteration, resource extraction, and the cultural value of place. The Lower Suwannee Archaeological Survey (LSAS) is an ongoing effort to document the history of coastal dwelling since the mid-Holocene, when the rate and magnitude of sea-level rise diminished and the northern Gulf coast of Florida transitioned into an aggradational regime. Results of the first 6 years of the LSAS suggest that multicentury periods of relative stability were punctuated by site abandonment and relocation. Subsistence economies involving the exploitation of oyster and fish, however, were largely unaffected as communities redistributed themselves with changes in shoreline position and estuarine ecology. After AD 200, civic-ceremonial centers were established at several locations along the northern Gulf coast, fixing in place not only the infrastructure of daily living (villages), but also that of religious practice, notably cemeteries and ceremonial mounds. Intensified use of coastal resources at this time can be traced to a ritual economy involving large gatherings of people, terraforming, feasting, and the circulation of socially valued goods. To the extent that religious practices buffered the risks of coastal living, large civic-ceremonial centers, like aggrading marshes, afforded opportunities to “outpace” sea-level rise. On the other hand, centers introduced a permanence to coastal land-use that proved unsustainable in the long term. [ABSTRACT FROM PUBLISHER]