EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

A comparison study of Mg/Ca-, alkenone- and TEX86-derived temperatures for the Brazilian Margin during Marine Isotope Stages 6–5

André Bahr1, Andrea Jaeschke2, Alicia Hou1,3, Christiano M. Chiessi4, Ana Luiza Spadano Albuquerque5, Janet Rethemeyer2, and Oliver Friedrich1
André Bahr et al.
  • 1Heidelberg University, Institute of Earth Sciences, Heidelberg, Germany (
  • 2Institute of Geology and Mineralogy, University of Cologne, Cologne, Germany
  • 3Institute of Oceanography, NTU, Taipei, Taiwan (ROC)
  • 4School of Arts, Sciences and Humanities, University of São Paulo, Brazil
  • 5Departamento de Geoquímica, Universidade Federal Fluminense, Niterói, RJ, Brazil

The reconstruction of accurate sea-surface temperatures (SST) is of utmost importance due to the central role of the ocean in the global climate system. Yet SST-proxies might be influenced by a number of environmental processes that may potentially bias the accurate reconstruction of the target variable. Here, we investigate the fidelity of SST reconstructions for the Western Tropical South Atlantic (WTSA) for Marine Isotope Stages (MIS) 6–5, utilizing a core collected off eastern Brazil at ~20°S. This interval was selected as previous SST estimates based on Mg/Ca ratios of planktic foraminifera suggested a peculiar pooling of warm surface waters in the WTSA during MIS 6 despite glacial boundary conditions. To ground-truth the Mg/Ca-based SST data we generated SST reconstructions from the same core using both, alkenone and TEX86 paleothermometers. Comparison with alkenone-based temperature estimates corroborate the previous Mg/Ca-based SST reconstructions, supporting the presumed warm-water anomaly during MIS 6. In contrast, while core top samples indicate that TEX86-derived temperatures represent annual mean SST, the TEX86-derived paleo-temperatures are up to 6°C colder than Mg/Ca- and alkenone-based SST reconstructions. We interpret the periods of anomalously cold TEX86-temperatures as a result of a vertical migration of the TEX86 producers (heterotrophic marine Thaumarchaeota) to deeper water depths in response to an increase in food availability during phases of enhanced fluvial suspension input.

How to cite: Bahr, A., Jaeschke, A., Hou, A., Chiessi, C. M., Spadano Albuquerque, A. L., Rethemeyer, J., and Friedrich, O.: A comparison study of Mg/Ca-, alkenone- and TEX86-derived temperatures for the Brazilian Margin during Marine Isotope Stages 6–5, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5912,, 2023.