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Estimating shallow subsidence in microtidal salt marshes of the southeastern United States: Kaye and Barghoorn revisited

Marine Geology

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, ,
DOI: 10.1016/0025-3227(95)00087-F

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Abstract

Simultaneous measurements of vertical accretion and change in surface elevation relative to a shallow (3-5 m) subsurface datum were made in selected coastal salt marshes of Louisiana, Florida, and North Carolina to quantitatively test Kaye and Barghoorn's contention that vertical accretion is not a good surrogate for surface elevation change because of autocompaction of the substrate. Rates of subsidence of the upper 3-5 m of marsh substrate were calculated for each marsh as the difference between vertical accretion and elevation change measured with feldspar marker horizons and a sedimentation-erosion table. Surface elevation change was significantly lower than vertical accretion at each site after 2 years, indicating a significant amount of shallow subsidence had occurred, ranging from 0.45 to 4.90 cm. The highest rate of shallow subsidence occurred in the Mississippi delta. Results confirm Kaye and Barghoorn's contention that vertical accretion is not generally a good surrogate for elevation change because of processes occurring in the upper few meters of the substrate, including not only compaction but also apparently shrink-swell from water storage and/or plant production--decomposition at some sites. Indeed, surface elevation change was completely decoupled from vertical accretion at the Florida site. The assumption of a 1:1 relationship between accretionary and substrate processes. Consequently, the potential for coastal marsh submergence should be expressed as an elevation deficit based on direct measures of surface elevation change rather than accretion deficits. These findings also indicate the need for greater understanding of the influence of subsurface and small-scale hydrologic processes on marsh surface elevation.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Estimating shallow subsidence in microtidal salt marshes of the southeastern United States: Kaye and Barghoorn revisited
Series title:
Marine Geology
DOI:
10.1016/0025-3227(95)00087-F
Volume
128
Issue:
1-2
Year Published:
1995
Language:
English
Contributing office(s):
National Wetlands Research Center
Description:
p. 1-9
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Marine Geology
First page:
1
Last page:
9
Number of Pages:
9