Elemental composition of surface sediment as a sea/land-level indicator in Cascadia salt marshes

This thesis explores the utility of elemental geochemistry obtained through x-ray fluorescence as a sea-level indicator. Elemental data of modern salt marsh sediment from Port Alberni, British Columbia and Willapa Bay, Washington reveals consistent relationships between elemental composition and tidal elevation. Lithogenic (Si, K, Ti, Fe) and biogenic (Sr) elements are most abundant at low elevations where clastic deposition dominates, while organic proxies (Br, incoherent coherent scattering ratio) are most prevalent at high elevations where marsh vegetation is most established. Cluster analysis shows that the vertical zonation patterns of elements within the salt marshes agree with previously determined foraminifera and diatom distributions at Port Alberni and Willapa Bay. This project establishes the first modern elemental training set relating elemental composition to tidal elevation and highlights the applications of elemental geochemistry as a new sea-level indicator.