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Stable carbon isotopes as potential sea-level indicators in salt marshes, North Carolina, USA

By Andrew C. Kemp, Christopher H. Vane, Benjamin P. Horton and Stephen J. Culver

Abstract

We compared the use of δ13C values and C:N ratios from salt-marsh sediments to reconstruct relative sea level (RSL) with an established approach using foraminifera. Analysis of bulk-organic sediment and plant samples collected along transects at two sites in North Carolina, USA demonstrates that sediment δ13C values can be used to distinguish between Spartina alterniflora-dominated low marsh (C photosynthetic pathway, δ13C values from —17.6‰ to 16.1‰) and Juncus roemerianus-dominated high marsh (C 3 photosynthetic pathway, δ13C values from —28.2‰ to —21.8‰) environments. Juncus roemerianus plants undergo little decompositional change in δ13C (average 0.8‰), although there is a clear difference between Spartina alterniflora tissue and bulk-organic sediments (approximately 4‰). C:N ratios on bulk-organic sediment from freshwater upland and salt-marsh environments converge during early diagenesis, rendering them of little use in reconstructing RSL. The utility of δ13C values as a sea-level indicator is limited by the elevational range of C4 plants, making it difficult to recognize salt-marsh subenvironments and improve the precision of RSL reconstructions. Furthermore, Juncus roemerianus-dominated high marsh and freshwater upland sediments cannot be adequately distinguished with δ13C values

Topics: Earth Sciences
Publisher: Sage
Year: 2010
DOI identifier: 10.1177/0959683609354302
OAI identifier: oai:nora.nerc.ac.uk:10280

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