TY  - JOUR
A1  - Foerster, Verena
A1  - Deocampo, Daniel M.
A1  - Asrat, Asfawossen
A1  - Günter, Christina
A1  - Junginger, Annett
A1  - Krämer, Kai Hauke
A1  - Stroncik, Nicole A.
A1  - Trauth, Martin H.
T1  - Towards an understanding of climate proxy formation in the Chew Bahir basin, southern Ethiopian Rift
JF  - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2  - 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 (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.
KW  - Paleoclimatology
KW  - Authigenic mineral transformation
KW  - Potassium
KW  - Illitization
KW  - Zeolites
Y1  - 2018
U6  - https://doi.org/10.1016/j.palaeo.2018.04.009
SN  - 0031-0182
SN  - 1872-616X
VL  - 501
SP  - 111
EP  - 123
PB  - Elsevier
CY  - Amsterdam
ER  -