TY  - JOUR
A1  - Trauth, Martin H.
A1  - Foerster, Verena
A1  - Junginger, Annett
A1  - Asrat, Asfawossen
A1  - Lamb, Henry F.
A1  - Schäbitz, Frank
T1  - Abrupt or gradual?
BT  - Change point analysis of the late Pleistocene-Holocene climate record from Chew Bahir, southern Ethiopia
JF  - Quaternary research : an interdisciplinary journal
N2  - We used a change point analysis on a late Pleistocene-Holocene lake-sediment record from the Chew Bahir basin in the southern Ethiopian Rift to determine the amplitude and duration of past climate transitions. The most dramatic changes occurred over 240 yr (from similar to 15,700 to 15,460 yr) during the onset of the African Humid Period (AHP), and over 990 yr (from similar to 4875 to 3885 yr) during its protracted termination. The AHP was interrupted by a distinct dry period coinciding with the high-latitude Younger Dryas stadial, which had an abrupt onset (less than similar to 100 yr) at similar to 13,260 yr and lasted until similar to 11,730 yr. Wet-dry-wet transitions prior to the AHP may reflect the high-latitude Dansgaard-Oeschger cycles, as indicated by cross-correlation of the potassium record with the NorthGRIP ice core record between similar to 45-20 ka. These findings may contribute to the debates regarding the amplitude, and duration and mechanisms of past climate transitions, and their possible influence on the development of early modern human cultures.
KW  - Late Pleistocene
KW  - Holocene
KW  - Change point analysis
KW  - Principal component analysis
KW  - Paleoclimatology
KW  - Southern Ethiopian Rift
KW  - African Humid Period
KW  - Younger Dryas
KW  - Dansgaard-Oeschger cycles
Y1  - 2018
U6  - https://doi.org/10.1017/qua.2018.30
SN  - 0033-5894
SN  - 1096-0287
VL  - 90
IS  - 2
SP  - 321
EP  - 330
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
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  -