Towards an understanding of climate proxy formation in the Chew Bahir basin, southern Ethiopian Rift

Verena Foerster, Daniel M. Deocampo, Asfawossen Asrat, Christina Günter, Annett Junginger, Kai Hauke Krämer, Nicole A. Stroncik, Martin H. Trauth

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Deciphering paleoclimate from lake sediments is a challenge due to the complex relationship between climate parameters and sediment composition. Here we show the links between potassium (K) concentrations in the sediments of the Chew Bahir basin in the Southern Ethiopian Rift and fluctuations in the catchment precipitation/evaporation balance. Our micro-X-ray fluorescence and X-ray diffraction results suggest that the most likely process linking climate with potassium concentrations is the authigenic illitization of smectites during episodes of higher alkalinity and salinity in the closed-basin lake, due to a drier climate. Whole-rock and clay size fraction analyses suggest that illitization of the Chew Bahir clay minerals with increasing evaporation is enhanced by octahedral Al-to-Mg substitution in the clay minerals, with the resulting layer charge increase facilitating potassium-fixation. Linking mineralogy with geochemistry shows the links between hydroclimatic control, process and formation of the Chew Bahir K patterns, in the context of well-known and widely documented eastern African climate fluctuations over the last 45,000 years. These results indicate characteristic mineral alteration patterns associated with orbitally controlled wet-dry cycles such as the African Humid Period (~15–5 ka) or high-latitude controlled climate events such as the Younger Dryas (~12.8–11.6 ka) chronozone. Determining the impact of authigenic mineral alteration on the Chew Bahir records enables the interpretation of the previously established μXRF-derived aridity proxy K and provides a better paleohydrological understanding of complex climate proxy formation.

Original languageEnglish
Pages (from-to)111-123
Number of pages13
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Publication statusPublished - Jul 15 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology


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