Towards an understanding of climate proxy formation in the Chew Bahir basin, southern Ethiopian Rift
- 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 theDeciphering 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 (similar to 15-5 ka) or high-latitude controlled climate events such as the Younger Dryas (similar to 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 pXRF-derived aridity proxy K and provides a better paleohydrological understanding of complex climate proxy formation.…
Author details: | Verena FoersterORCiD, Daniel M. Deocampo, Asfawossen AsratORCiD, Christina GünterGND, Annett JungingerORCiD, Kai Hauke KrämerORCiD, Nicole A. StroncikORCiD, Martin H. TrauthORCiDGND |
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DOI: | https://doi.org/10.1016/j.palaeo.2018.04.009 |
ISSN: | 0031-0182 |
ISSN: | 1872-616X |
Title of parent work (English): | Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences |
Publisher: | Elsevier |
Place of publishing: | Amsterdam |
Publication type: | Article |
Language: | English |
Date of first publication: | 2018/04/18 |
Publication year: | 2018 |
Release date: | 2021/10/29 |
Tag: | Authigenic mineral transformation; Illitization; Paleoclimatology; Potassium; Zeolites |
Volume: | 501 |
Number of pages: | 13 |
First page: | 111 |
Last Page: | 123 |
Funding institution: | German Research Foundation (DFG) through the Priority Program SPP 1006 ICDP [TR 419/8, TR 419/9, SCHA 472/13, SCHA 472/18]; German Research Foundation (DFG) through the CRC 806 Research Project "Our way to Europe" [TR 419/8, TR 419/9, SCHA 472/13, SCHA 472/18]; NSF grantNational Science Foundation (NSF) [EAR-1349599] |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Geowissenschaften |
DDC classification: | 5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften |
Peer review: | Referiert |