Construction of long annually-resolved shell-based chronologies using Glycymeris glycymeris (Bivalvia ; Glycymerididae) from the Bay of Brest, France

Abstract : This PhD thesis uses Glycymeris glycymeris, a temperate bivalve in the Glycymerididae family, to reconstruct environmental variability in the Bay of Brest, France. This work comprises of geochemical data archived within shells, compared with several biological and ecological variables. The aims of this study were to assess for potential proxies and expand environmental knowledge prior to local observational records.Thirty-eight live- and dead-collected specimens were used to create a chronology spanning 1891 to 2014. When the standardised growth index was correlated with local environmental factors, it showed that the predominant drivers of growth were Elorn inflow, salinity and suspended particulate matter.Isotopic analysis was undertaken on the juvenile increments of 24 shells. Our results highlight that variations in δ18Oaragonite accurately record local sea surface temperatures, leading to the creation of a 45-year SST reconstruction for the Bay of Brest. Correlations between this and climate forcings show that SSTs in this area are controlled by the subpolar gyre and the East Atlantic Pattern.Five shells (three under the age of 10 and two aged 45) were analysed using a LA-ICP-MS to determine the quantity of strontium and magnesium. Mg and Sr intensities are positively correlated with temperature sub-annually, but on an annual scale there is a negative correlation.This study conveys the potential of G. glycymeris as an archive of climatic and environmental variability in the Bay of Brest. As there are a large number of sub-fossil specimens in the area, this study also provides an anchored base for expansion further back in time.
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Amy Marie Featherstone. Construction of long annually-resolved shell-based chronologies using Glycymeris glycymeris (Bivalvia ; Glycymerididae) from the Bay of Brest, France. Earth Sciences. Université de Bretagne occidentale - Brest, 2017. English. ⟨NNT : 2017BRES0052⟩. ⟨tel-01734881⟩

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