SALTMARSH EVOLUTION AS A FUNCTION OF RELATIVE SEA-LEVEL RISE, SEDIMENT SUPPLY, AND MARSH PRODUCTIVITY: CASE STUDIES IN LOUISIANA, SOUTH CAROLINA, AND MASSACHUSETTS

WILSON, Carol A., Dept. of Earth and Environmental Science, Vanderbilt University, Stevenson Science Center, Bldg.5, Nashville, TN 37235, FITZGERALD, Duncan M., Department of Earth and Environment, Boston University, 685 Commonwealth Avenue, Boston, MA 02215, HUGHES, Zoe J., Department of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, PENNINGS, Steve, Department of Biology and Biochemistry, University of Houston, Houston, TX 77204 and ALLISON, Mead A., Institute for Geophysics, University of Texas at Austin, 10100 Burnet Road (R2200), Austin, TX 78758-4445, c.wilson2@vanderbilt.edu

The response of coastal marshes to sea-level fluctuations is strongly related to relative sea-level rise (RSLR) rates, sediment supply, and marsh productivity. The relative importance of these factors is being explored in Louisiana, South Carolina, and Massachusetts saltmarshes using historical imagery, topographic surveys, stratigraphic and geotechnical analysis of sediment cores, and long-term (decadal) sediment accumulation rates as determined from Pb-210 and Cs-137 radioisotopes. Results indicate that similar physical and ecophysical processes lead to shoreline retreat, expansion of tidal channel networks, and/or deflation of the marsh platform and ensuing submergence, depending on the RSLR rate, influx of inorganic sediment, marsh below ground biomass production, and tidal range. High rates of RSLR coupled with low sediment influx have caused retreat of Louisiana marsh shorelines and submergence from interior ponding. The mesotidal range coast of the Santee Delta, South Carolina is responding differently to microtidal Louisiana. Here, increased flooding and draining of marshes and reduced sediment supply are resulting in an expansion of the tidal network. A third type of response is observed in the backbarrier saltmarshes of Plum Island, Massachusetts which exhibits a comparatively large tidal range. These systems display interior ponding, however these water-filled depressions within the marsh platform are formed from enhanced decomposition of the organic substrata and are eventually drained by headward eroding creeks and ultimately recolonized by vegetation. Thus, the northern marshes are undergoing reworking, but have not yet begun to diminish in extent. Investigating saltmarsh processes along a continuum of tidal range and sediment supply broadens the applicability of individual studies, enhancing the understanding of complex marsh dynamics as they respond to sea level rise.

Session No. 221

T139. The Barrier Island System: Evolution in Response to Changing Sea Levels

Tuesday, 2 November 2010: 1:30 PM-5:30 PM

Room 405 (Colorado Convention Center)

Geological Society of America Abstracts with Programs. Vol. 42, No. 5, p.524

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