Testing novel archives of seawater chemistry in biogenic carbonate

Year
2026
Primary Supervisor
Robert Newton <[email protected]>
Institution
University of Leeds (School of Earth and Environment)
Possibility of becoming a CASE project
No
Collaborative Project
Yes
Academic Supervisors
Crispin Little <[email protected]> (University of Leeds, School of Earth and Environment), James Witts <[email protected]> (Natural History Museum London), Lorna Kearns <[email protected]> (University of Leeds, School of Earth and Environment)
Research Themes
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Project Partners
None
Research Keywords
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Relevant Degree Courses
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Understanding how seawater chemistry has evolved over geological time is essential for reconstructing Earth’s environmental history and carbon cycling. Surprisingly, key components such as calcium and sulfate remain poorly constrained through time, despite their central role in regulating surface processes.

This PhD project will explore the potential of fossil calcifiers—including bivalves, belemnites, and foraminifera—as archives of past seawater chemistry. While foraminifera have been widely used to reconstruct environmental conditions, recent studies suggest that the sulfur, barium, and sodium content of their shells may serve as proxies for carbonate, sulfate, and calcium ion concentrations. Extending this approach to other fossil groups could unlock new records spanning the last 540 million years.

Research Approach

The project will begin by analyzing bivalve samples from selected intervals across the Cenozoic, comparing results with existing records from foraminifera and halite fluid inclusions. The last 16 million years (mid-Miocene to present) offer a particularly rich archive due to well-documented changes in seawater chemistry.

Belemnites, abundant and well-preserved in Jurassic and Cretaceous deposits, will also be studied. The Late Cretaceous is a key interval where foraminifera, bivalves, and belemnites co-occur, providing a unique opportunity for cross-group comparison.

Analytical techniques will include:

  • ICP-MS and wet chemistry for elemental analysis (initial focus on Na/Ca ratios)
  • SEM, EBSD, and microprobe to assess spatial distribution of elements
  • Stable isotope analysis and SEM imaging to evaluate preservation

All analyses will be conducted in the School’s state-of-the-art laboratory facilities.

Training and Environment

The successful candidate will receive full training in a wide range of geochemical and analytical techniques. No prior lab experience is required, though familiarity with lab work is beneficial. In addition to specialist skills, the PhD will develop transferable competencies in data analysis, scientific communication, and project management.

You will join a vibrant research community within the Earth Surface Science Institute, and the Cohen Geochemistry and Palaeo@Leeds groups—offering a collaborative and supportive environment for idea exchange and interdisciplinary research.

Impact

This project will pioneer the use of underutilized fossil archives to reconstruct seawater chemistry, potentially revealing changes on much shorter timescales than previously possible. The research is expected to lead to several high-impact publications and contribute significantly to our understanding of ocean chemistry and Earth system evolution.

References

Weldeghebriel, M.F. et al. (2022), EPSL, 594, p. 117712. Available at: https://doi.org/10.1016/j.epsl.2022.117712

Zhou, X. et al. (2021), GCA, 305, pp. 306–322. Available at: https://doi.org/10.1016/j.gca.2021.04.012