Accretion of a New England (U.S.A.) Salt Marsh in Response to Inlet Migration, Storms, and Sea-level Rise

• Published in: Estuarine, coastal and shelf science Vol. 45; no. 6; pp. 717 - 727
• Main Authors: Roman, C.T., Peck, J.A., Allen, J.R., King, J.W., Appleby, P.G.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01-12-1997; Elsevier
• Subjects: 137Cs; 210Pb; Brackish; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochronology; Isotope geochemistry. Geochronology; Marine; Marine and continental quaternary; Massachusetts (U.S.A.); radiocarbon; salt marsh; sea-level rise; sedimentation rates; storms; Surficial geology; North Atlantic; United States; Massachusetts; Northwest Atlantic; New England; ANW, USA, Massachusetts, Cape Cod, Eastham, Nauset Marsh; Massachusetts (U.S.A.); 210Pb; sea-level rise; radiocarbon; sedimentation rates; storms; salt marsh; 137Cs; eustacy; time variations; Atlantic Ocean; Cs-137; marshes; feldspar; Pb-210; North America; inlets; accretion; C-14; modern; silicates; spatial variations; framework silicates; magnetic susceptibility; landform evolution
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1006/ecss.1997.0236

Sediment accumulation rates were determined at several sites throughout Nauset Marsh (Massachusetts, U.S.A.), a back-barrier lagoonal system, using feldspar marker horizons to evaluate short-term rates (1 to 2 year scales) and radiometric techniques to estimate rates over longer time scales (137Cs,210Pb,14C). The barrier spit fronting theSpartina-dominated study site has a complex geomorphic history of inlet migration and overwash events. This study evaluates sediment accumulation rates in relation to inlet migration, storm events and sea-level rise. The marker horizon technique displayed strong temporal and spatial variability in response to storm events and proximity to the inlet. Sediment accumulation rates of up to 24mm year−1were recorded in the immediate vicinity of the inlet during a period that included several major coastal storms, while feldspar sites remote from the inlet had substantially lower rates (trace accumulation to 2·2mm year−1). During storm-free periods, accumulation rates did not exceed 6·7mm year−1, but remained quite variable among sites. Based on137Cs (3·8 to 4·5mm year−1) and210Pb (2·6 to 4·2mm year−1) radiometric techniques, integrating sediment accumulation over decadal time scales, the marsh appeared to be keeping pace with the relative rate of sea-level rise from 1921 to 1993 of 2·4mm year−1. At one site, the210Pb-based sedimentation rate and rate of relative sea-level rise were nearly similar and peat rhizome analysis revealed thatDistichlis spicatarecently replaced this onceS. patenssite, suggesting that this portion of Nauset Marsh may be getting wetter, thus representing an initial response to wetland submergence. Horizon markers are useful in evaluating the role of short-term events, such as storms or inlet migration, influencing marsh sedimentation processes. However, sampling methods that integrate marsh sedimentation over decadal time scales are preferable when evaluating a systems response to sea-level rise.