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Elemental Geochemistry of Tidal Marsh Sediment and Its Potential as an Indicator of Sea‐Level Change in Cascadia

Anthony, Giang; Pilarczyk, Jessica; Hong, Isabel; Riou, Louise; Huntley, David; MacLeod, Roger; Ward, Owen; Clague, John; Bobrowsky, Peter; Hawkes, Andrea; Engelhart, Simon; Horton, Benjamin

Elemental Geochemistry of Tidal Marsh Sediment and Its Potential as an Indicator of Sea‐Level Change in Cascadia Thumbnail


Authors

Giang Anthony

Jessica Pilarczyk

Isabel Hong

Louise Riou

David Huntley

Roger MacLeod

Owen Ward

John Clague

Peter Bobrowsky

Andrea Hawkes

Benjamin Horton



Abstract

Holocene sea‐level reconstructions from tidal marshes are commonly derived from proxy indicators that have a consistent and quantifiable relationship with tidal elevation. While microfossils are most commonly employed, using multiple indicators leads to more robust reconstructions. We explore the utility of elemental geochemistry obtained through x‐ray fluorescence as a proxy indicator in tidal marshes at Port Alberni, British Columbia, Canada and Willapa Bay, Washington, United States. The elemental composition of bulk surface sediment collected from 141 stations along 10 transects was determined using an ITRAX Core Scanner. Partitioning Around Medoids cluster analysis on the elemental data distinguished between tidal flat, low marsh, and high marsh zones at both locations, similar to zones established from previously published microfossil (foraminifera, diatoms) data sets on the same samples. The elemental composition of low elevation samples from the tidal flat is dominated by lithogenic (Si, K, Ti, Fe) and biogenic (Sr) elements, whereas higher elevation samples have high proportions of organic content (Br, incoherent and coherent scattering ratio). Principal Component Analysis points to differences in organic versus inorganic content, a function of tidal elevation, as the main driver of geochemistry‐derived zones. Approximately 70% of the elemental variability within both marshes is controlled by the inorganic content, as indicated by lithogenic and biogenic elements versus organic content. The elemental composition of bulk surface sediment from two regions spaced ∼300 km apart shows a promising relationship with tidal elevation over a wider spatial scale and highlights the potential of this proxy for use in sea‐level reconstructions.

Citation

Anthony, G., Pilarczyk, J., Hong, I., Riou, L., Huntley, D., MacLeod, R., Ward, O., Clague, J., Bobrowsky, P., Hawkes, A., Engelhart, S., & Horton, B. (2025). Elemental Geochemistry of Tidal Marsh Sediment and Its Potential as an Indicator of Sea‐Level Change in Cascadia. Geochemistry, Geophysics, Geosystems, 26(5), Article e2024GC012129. https://doi.org/10.1029/2024GC012129

Journal Article Type Article
Acceptance Date Apr 18, 2025
Online Publication Date May 8, 2025
Publication Date May 1, 2025
Deposit Date May 9, 2025
Publicly Available Date May 14, 2025
Journal Geochemistry, Geophysics, Geosystems
Electronic ISSN 1525-2027
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 26
Issue 5
Article Number e2024GC012129
DOI https://doi.org/10.1029/2024GC012129
Keywords Cascadia, X‐ray fluorescence, tidal marsh, sea‐level change, surface transect, micropaleontology
Public URL https://durham-repository.worktribe.com/output/3936286

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