Common controls on Na and Sr in modern and fossil brachiopod shells: Long-term stability of biomineralisation and use for seawater Sr/Ca reconstruction

Ullmann, Clemens V., Lüter, Carsten, Duarte, Luís Vítor, Andrade, Benito, Court, Emma, Bailey, Trevor and Aberhan, Martin 2026. Common controls on Na and Sr in modern and fossil brachiopod shells: Long-term stability of biomineralisation and use for seawater Sr/Ca reconstruction. Chemical Geology , 123752. 10.1016/j.chemgeo.2026.123752

Full text not available from this repository.

Abstract

Robust reconstructions of element cycles are important for a quantitative understanding of the evolution of the Earth system. Fossil shells of marine macroinvertebrates are abundant and constitute valuable archives of past environmental conditions, which can be tied into precise chronostratigraphic schemes. However, complex, species-specific biomineralisation influences on the expression of geochemical proxies in their shells hinder their use for the reconstruction of seawater chemistry. Here, we investigate the variability and co-variation of element/Ca ratios in the shells of modern and Early Jurassic brachiopods belonging to the orders Rhynchonellida, Terebratulida, and Thecideida. We show that within modern and fossil brachiopods of the orders Rhynchonellida and Terebratulida, shells display uniform and strong co-variation of strontium and sodium content. This co-variation is offset and less well expressed in the thecideide Pajaudina atlantica. The coupling of Na/Ca and Sr/Ca in shells of low-Mg calcite secreting taxa can be explained by joint controls on both elements. The comparability of the Nasingle bondSr co-variation in modern and fossil examples suggests that biological controls on the uptake of these elements in Rhynchonellida and Terebratulida have remained essentially unaltered since at least the Early Jurassic. The Sr/Ca ratio of past seawater can be calculated using a Na-corrected Sr distribution coefficient of 0.051 established from modern terebratulide and rhynchonellide brachiopods. Based on this calibration, late Pliensbachian - late Toarcian (c. 185–175 Ma) seawater Sr/Ca ratios of 8.8 mmol/mol to 10.3 mmol/mol with uncertainties of 2 to 15% (95% confidence) are reconstructed.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Earth and Environmental Sciences Schools > Physical, Chemical & Environmental Sciences
Publisher:	Elsevier
ISSN:	0009-2541
Date of Acceptance:	30 September 2026
Last Modified:	06 Oct 2026 11:15
URI:	https://orca.cardiff.ac.uk/id/eprint/190035

Actions (repository staff only)

Edit Item