Reinterpretation of past sea-level variation of the Bay of Fundy

Abstract

Reports of shifts in rates of aggradation in a salt marsh deposit at Amherst Point, Nova Scotia have been linked with fluctuations in eustatic sea level, crustal subsidence and, possibly, changes in tidal amplitude. However, evidence for the most recent fluctuation is an artifact of early Acadian land reclamation that occurred in the seventeenth century at Amherst Point. Acadian settlers had constructed dikes to prevent regular tidal flooding, but probably allowed occasional flooding of the surface by tidal waters, thus maintaining the salt marsh signature of the deposit. Statistical analysis of the pollen assemblage from the uppermost deposit interpreted as a regressive sequence aligns critical depths with pollen assemblages retrieved from modern soils of diked and drained marshes. Inspection of historical aerial photographs confirms that the dikes persisted on the site until at least 1939. Interpretations of earlier fluctuations recorded in deposits below this regressive sequence remain valid. It is possible that the Bay of Fundy experienced a regressive period just prior to Acadian diking, but future research on unexamined salt marsh deposits here or elsewhere must include an exhaustive search of historical documents to avoid misinterpretation of anthropogenic modifications.