A record of the δ44/40Ca and [Sr] of seawater over the last 100 million years from fossil elasmobranch tooth enamel

Alliya A. Akhtar, Lauren M. Santi, Michael L. Griffiths, Martin Becker, Robert A. Eagle, Sora Kim, László Kocsis, Yair Rosenthal, John A. Higgins

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The global geochemical cycles of calcium and strontium in seawater link the chemical composition of the oceans to the global carbon cycle and Earth's climate through the precipitation, diagenetic alteration, and sedimentary recycling of marine carbonate minerals. Here we present a record of calcium isotopic composition and [Sr] of seawater over the last 100 million years using measurements from modern and fossil shark teeth. Although there is significant variability in modern elasmobranch tooth enamel associated with physiology and diet, our record suggests a first-order increase in the average calcium isotopic composition of seawater by 0.5‰ and a decline in Sr/Ca ratios of ∼40% over the last 100 million years. These observations are in agreement with trends seen in other archives. We propose that the observed changes in both the calcium isotopic composition and Sr concentration of seawater can be explained by changes in the partitioning of the global carbonate sink associated with the development of a deep-sea carbonate reservoir in the mid-Mesozoic.

Original languageEnglish (US)
Article number116354
JournalEarth and Planetary Science Letters
StatePublished - Aug 1 2020

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


  • Calcium isotopes
  • Sr/Ca
  • elasmobranch teeth
  • marine calcium cycle
  • seawater chemistry


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