A new method for amino acid geochronology of the shell of the bivalve mollusc Arctica islandica

Martina L.G. Conti*, Paul G. Butler, David J. Reynolds, Tamara Trofimova, James D. Scourse, Kirsty E.H. Penkman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The bivalve mollusc Arctica islandica can live for hundreds of years, and its shell has provided a valuable resource for sclerochronological studies and geochemical analyses for understanding palaeoenvironmental change. Shell specimens recovered from the seabed need to be dated in order to aid sample selection, but existing methods using radiocarbon dating or cross-dating are both costly and time-consuming. We have investigated amino acid geochronology (AAG) as a potential alternative means of providing a less costly and more efficient range-finding method. In order to do this, we have investigated the complex microstructure of the shells, as this may influence the application of AAG. Each of the three microstructural layers of A. islandica have been isolated and their protein degradation examined (amino acid concentration, composition, racemization, and peptide bond hydrolysis). The intra-crystalline protein fraction was successfully extracted following oxidation treatment for 48ĝ€¯h, and high-Temperature experiments at 140ĝ€¯°C established coherent breakdown patterns in all three layers, but the inner portion of the outer shell layer (iOSL) was the most appropriate component due to practicalities. Sampling of the iOSL layer in Holocene shells from early and late ontogeny (over 100-400 years) showed that the resolution of AAG is too low in A. islandica for within-shell age resolution. However, analysis of 52 subfossil samples confirmed that this approach could be used to establish a relative geochronology for this biomineral throughout the whole of the Quaternary. In the late Holocene the temporal resolution is g1/41500-2000 years. Relative dating of 160 dredged shells of unknown age was narrowed down using AAG as a range finder, showing that a collection of shells from Iceland and the North Sea covered the middle Holocene, late Holocene, later and post-medieval (1171-1713ĝ€¯CE), and modern day. This study confirms the value of A. islandica as a reliable material for range finding and for dating Quaternary deposits.

Original languageEnglish
Pages (from-to)175-198
Number of pages24
JournalGeochronology
Volume6
Issue number2
DOIs
Publication statusPublished - 23 May 2024

Bibliographical note

© Author(s) 2024.

Funding Information:
North Sea radiocarbon dates were funded by the European Union Fifth Framework HOLSMEER project (EVK2-CT-2000-00060) and the United Kingdom Natural Environment Research Council standard research grant (NER/A/S/2002/00809).

Funding Information:
Collection of the Easton Wood shells was funded by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant no. 865222). We thank Dustin White, Richard Preece, Tim Holt-Wilson, and Matthew Jeffries for collecting the shells from Easton Wood.

Funding Information:
Iceland radiocarbon dates were funded by the EU Framework 6 MILLENNIUM Integrated Project \u201CEuropean climate of the last millennium\u201D (SUSTDEV-2004-3.1.4.1, 017008-2).

Funding Information:
United Kingdom Natural Environment Research Council standard research grant (NER/A/S/2002/00809)

Funding Information:
The SEACHANGE Synergy Project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant no. 856488).

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