Marine reservoir ages for coastal West Africa

Type Article
Date 2023
Language English
Author(s) Soulet GuillaumeORCID1, Maestrati Philippe2, Gofas Serge2, 3, Bayon Germain1, Dewilde Fabien1, Labonne Maylis4, Dennielou BernardORCID1, Ferraton Franck4, Siani Giuseppe5
Affiliation(s) 1 : Ifremer, Univ Brest, CNRS, Geo-Ocean UMR6538, F-29280, Plouzané, France
2 : Muséum National d’Histoire Naturelle, Paris, DGD-Collections, France
3 : Departamento de Biología Animal, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
4 : MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Montpellier, France
5 : GEOPS, UMR 8148 Université Paris-Saclay, Orsay, France
Source Geochronology (Copernicus GmbH), 2023 , Vol. 5 , N. 2 , P. 345-359
DOI 10.5194/gchron-5-345-2023
Note this preprint is currently under review for the journal GChron.

We measured the 14C age of pre-bomb suspension-feeding bivalves of known-age from coastal West Africa (n = 30) across a latitudinal transect extending from 33° N to 15° S. The specimens are from the collections of the Muséum National d’Histoire Naturelle (Paris, France). They were carefully chosen to ensure that the specimens were alive when collected or died not long before collection. From the 14C-dating of these know-age bivalves, we calculated the marine reservoir age (as ΔR and R values) for each specimen. ΔR values were calculated relative to the Marine20 calibration curve and the R values relative to Intcal20 or SHcal20 calibration curves. Except five outliers, the ΔR and R values were quite homogenous to a mean value of −77 ± 47 14C yrs (1sd, n = 25), and of 400 ± 59 14C yrs (1sd, n = 25), respectively. These values are typical of low latitude marine reservoir age values. Five suspension-feeding species living in five different ecological habitats were studied. For localities were different species were available, the results yielded similar results whatever the specie considered suggesting that the habitat has only a limited impact on the marine reservoir age reconstruction. We show that our measured marine reservoir ages follow the declining trend of the global marine reservoir age starting ca. 1900 AD, suggesting that marine reservoir age of coastal West Africa is driven, at least at first order, by the global carbon cycle and climate rather than by local effects. Each outlier was discussed. Sub-fossil specimens likely explain the older 14C age and thus larger marine reservoir age measured for these samples. Bucardium ringens might not a best choice for marine reservoir age reconstructions.

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