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Importance of coarse sedimentation events for maintaining back-barrier salt-marshes resilience to sea-level rise
An improved understanding of the resilience capacity of salt-marsh environments, which are recognized as one of the most vulnerable yet valuable coastal morpho-sedimentary systems is important for enhancing adaptation to ongoing and future sea-level rise. The aim of this study is to provide a long-term (multi-centennial) context to the capacity of response of saltmarsh environments to relative sea-level rise and extreme wave events by reconstructing the accretion histories of two microtidal back-barrier (one aggradational and one transgressive) saltmarshes in the Bay of Gaspé (Québec, Eastern Canada) over the last centuries. Particular emphasis is put on coarse minerogenic sedimentation and the role it played in the response of the two marshes to relative sea-level changes. To do so, lithostratigraphic, geochronological, and geochemical analyses are carried out on sedimentary cores taken in the back-barrier marsh areas. The accretion histories and the chronology of coarse deposition upon the marshes are reconstructed and yield the following two main results: (1) Coherent yet contrasting records of coarse sedimentation histories are obtained for the two sites, which relate to the distinct configurations and functioning of the fronting barrier systems. The coarse sedimentation time-series of both marshes carry pluri-decadal periodicities typical of atmospheric and intra-oceanic modes of variability, as well as periodicities of 18.0 to 18.5 years, which are interpreted as the expressions of the influence of the 18.6-year nodal tidal cycle. (2) We observe intra- and inter-site variations in the accretionary behavior of the two systems as well as in their respective histories of coarse minerogenic deposition. We show that coarse sedimentation at the surface of the two marshes has been crucial for maintaining accretion rates both in minerogenic and organogenic environments, and thus for allowing saltmarshes to build a resilience capacity in a regime of relative sea-level rise.
saltmarshes, sea level, storminess, washover, accretion, resilience
49.138648N, 48.407378S, -63.824701E, -64.989252W
Datasheet correspond to the data used for the analyses presented in Goslin et al. (2022). Data in the spreadsheet are for the two main cores from Penouille site (PEN-ST-3-1) and Sandy Beach site (SB-ST-M1).
Colmun 1 is the sampling depth in core. Column 2 gives the ages produced by the age-depth model. Col. 4 is the D90 grain size at each sampling depth in µm, col.5 is dry bulk density. Col.6 is Loss-on-ignition (LOI, in %) data produced after combustion at 150°C and 550°C. Col. 7 and 8 are the organic and mineral contents of the sediment at each sampling depth, determined using the LOI. Col. 9 show sediment accretion rates (in mm.yr-1, calculated using a layer thickness of 10mm and the age difference between two layers) and col. 10 show deposition rates (in Kg.m-2.yr-1, calculated using bulk density). Col. 11 and 12 are Relative sea-level data from Barnett et al. 2019. Col.14 and 15 show respective mineral and organic deposition rates as calculated by dividing the deposition rates by the organic and mineral content. Col. 16 show the percentage of minerogenic deposition that is explained by the deposition of coarse sedimentary fractions.
Data that served at reconsctructing last centuries coarse sedimentation events and accretion history in two saltmarsh of the Bay of Gaspé (Canada)
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