CHEMICAL EVIDENCE OF ENVIRONMENTAL-CHANGES AND ANTHROPOGENIC INFLUENCES IN A BAY-OF-FUNDY SALT-MARSH

A 4.3 m vibracore, retrieved from a Bay of Fundy saltmarsh, was analys ed for total extracted S, Fe, Mn, Pb, Zn, Cu and Organic C. Macrofossi ls were also identified in several key samples from the core. Results showed stable concentrations of all elements except for surficial enri chment of Zn, Cu and Pb and foul down-core maxims in Fe, S and Mn conc entrations. There was an anomalous elevation of Zn, Pb and Cu concentr ations coinciding with the second down-core peak of Fe, S and Mn. Macr ofossil analysis revealed a transition from fresh- or brackish water s pecies to Spartina alterniflora and later to Spartina patens. The earl iest saltmarsh sediments, located at 334 cm, were radiocarbon dated at 2560 +/- 60 yr BP. Both paleoenvironmental and more recent historical interpretations were made from the data. The simultaneous presence of S. alterniflora rhizomes and a rise in Fe and S concentration suggest s a low marsh environment existed at a depth of 224-237 cm. The two up permost concentration maxims are most likely the result of the presenc e of a redox boundary within the sediment matrix and, therefore, an ac tive site of geochemical processes. Zinc, Cu and Pb concentrations sho wed an increase shove background levels from 30 cm upwards. The positi ve correlation between the macrofossil and chemical data, combined wit h the discovery of surficial contamination at a relatively pristine si te, clearly demonstrates the usefulness of chemical analysis as a meth od for paleoenvironmental reconstruction and determination of anthropo genic influences.