Variability of organic δC and C/N in the Mersey Estuary, U.K. and its implications for sea-level reconstruction studies |
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| Authors: | Graham P Wilson Angela L Lamb Melanie J Leng Silvia Gonzalez David Huddart |
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| Institution: | aSchool of Biological and Earth Sciences, Liverpool John Moores University, Liverpool L3 3AF, UK;bNERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK;cSchool of Geography, University of Nottingham, Nottingham NG7 2RD, UK;dSchool of Outdoors, Leisure and Food, Liverpool John Moores University, Liverpool L17 6BD, UK |
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| Abstract: | Microfossil analysis (e.g. diatoms, foraminifera and pollen) represents the cornerstone of Holocene relative sea-level (RSL) reconstruction because their distribution in the contemporary inter-tidal zone is principally controlled by ground elevation within the tidal frame. A combination of poor microfossil preservation and a limited range in the sediment record may severely restrict the accuracy of resulting RSL reconstructions. Organic δ13C and C/N analysis of inter-tidal sediments have shown some potential as coastal palaeoenvironmental proxies. Here we assess their viability for reconstructing RSL change by examining patterns of organic δ13C and C/N values in a modern estuarine environment. δ13C and C/N analysis of bulk organic inter-tidal sediments and vegetation, as well as suspended and bedload organic sediments of the Mersey Estuary, U.K., demonstrate that the two main sources of organic carbon to surface saltmarsh sediments (terrestrial vegetation and tidal-derived particulate organic matter) have distinctive δ13C and C/N signatures. The resulting relationship between ground elevation within the tidal frame and surface sediment δ13C and C/N is unaffected by decompositional changes. The potential of this technique for RSL reconstruction is demonstrated by the analysis of part of an early Holocene sediment core from the Mersey Estuary. Organic δ13C and C/N analysis is less time consuming than microfossil analysis and is likely to provide continuous records of RSL change. |
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| Keywords: | δ 13C C/N ratios saltmarsh relative sea-level Holocene Mersey Estuary |
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