Assessing elemental ratios as a paleotemperature proxy in the calcite shells of patelloid limpets

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 465; pp. 376 - 385
• Main Authors: Graniero, L.E., Surge, D., Gillikin, D.P., Briz i Godino, I., Álvarez, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2017
• Subjects: Carbon isotopes; Elemental ratios; Oxygen isotopes; Paleoceanography; Paleotemperature; Patelloid limpets; Paleotemperature; Paleoceanography; Elemental ratios; Oxygen isotopes; Carbon isotopes; Patelloid limpets
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2016.10.021

Archaeological shell and fish middens are rich sources of paleoenvironmental proxy data. Patelloid limpet shells are common constituents in archaeological middens found along European, African, and South American coastlines. Paleotemperature reconstructions using oxygen isotope ratios of limpet shells depend on the ability to constrain the oxygen isotope ratio of seawater; therefore, alternative proxies are necessary for coastal localities where this is not possible. The study evaluates whether Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li ratios are reliable proxies of sea surface temperature (SST) in the calcite layer of shells of the patelloid limpets, Patella vulgata and Nacella deaurata. We compare Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li ratios to the seasonal variations in contemporaneous δ18Oshell values, which primarily record seasonal changes in SST. Elemental ratios (Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li) show no significant correlations with reconstructed SST in P. vulgata and N. deaurata shells, nor do they show sinusoidal cycles expected from a SST proxy. In addition, shell δ13C values show no significant ontogenetic trends, suggesting that these limpets exhibit little change in metabolic carbon incorporation into the shell with increasing ontogenetic age. Although shell growth rate exhibits a logarithmic decrease with age based on calculated linear extension rates, growth rate does not correlate with elemental profiles in these limpets. Overall, elemental ratios are not reliable recorders of paleotemperature in patelloid limpets. •No apparent trends between SST and elemental ratios recorded in limpet shells.•Elemental ratios are not reliable paleotemperature proxies in patelloid limpets.•Factors controlling elemental ratios remain elusive, yet unrelated to temperature.