Clumped isotope thermometry in foraminifera - From calibration to Plio-Pleistocene temperature reconstructions in the Indo-Pacific Warm Pool

• Published in: Geochimica et Cosmochimica Acta
• Main Author: Meinicke, Niklas
• Other Authors: orcid:0000-0001-9715-5399
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2021
• Subjects: Pacific; Planktonic foraminifera
• Online Access: https://hdl.handle.net/1956/23042

Clumped isotopes thermometry on foraminifera holds the potential to accurately reconstruct ocean temperatures on million-year timescales. In contrast to most other paleothermometers, clumped isotopes do not rely on prior knowledge regarding ocean chemistry changes thus evading a major source of uncertainty inherent to most other paleothermometers. This thesis aims to amend our understanding of the clumped isotope signal in foraminifera and provide improvements to this paleothermometer for application to ocean sediments (Paper I). The knowledge gained is applied to Plio-Pleistocene sequences from two locations within the Indo-Pacific Warm Pool in order to address discrepancies among other temperature proxies and shed new light on long-standing debates regarding the long-term temperature evolution of this crucial region in the global ocean (Papers II and III). The results displayed in this thesis include a clumped isotope to temperature calibration dataset for planktonic foraminifera that was combined with several existing foraminifer-based calibrations in order to elucidate potential laboratory differences as well as species effects on the paleothermometer (Paper I). Our combined calibration highlights the excellent agreement among various analytical approaches and different foraminifera species. This work thus provides a robust tool to reconstruct past ocean temperatures using various species and on million-year time scales. The results of papers II and III constrain the Plio-Pleistocene temperature evolution of the Indo-Pacific Warm Pool independent of ocean chemistry changes. The knowledge gained can be used to disentangle the influences of these reservoir changes and the temperature signal recorded in other proxies. The paired Mg/Ca and clumped isotope records comprise evidence for the validity of Plio-Pleistocene Mg/Ca-based sea surface temperature reconstructions and argue against a systematic bias of Pliocene Mg/Ca temperature estimates by past Mg/Ca changes of seawater. The long-term temperature evolution ...