Recurring types of variability and transitions in the ∼620 kyr record of climate change from the Chew Bahir basin, southern Ethiopia

Trauth, Martin H.; Asrat, Asfawossen; Cohen, Andrew S.; Duesing, Walter; Foerster, Verena; Kaboth‐Bahr, Stefanie; Kraemer, K. Hauke; Lamb, Henry F.; Marwan, Norbert; Maslin, Mark; Schäbitz, Frank

doi:10.1016/j.quascirev.2020.106777

Cited by 21 publications

(31 citation statements)

References 55 publications

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“…Absorption bands at 1.4 µm are caused by an O-H stretch in molecular water and structural OH. The simultaneous appearance of both absorption bands is a spectral indication of phyllosilicates with a three-layer TABLE 1 | Overview of all spectrally measured CHB14-2 samples with information on sample ID, core depth (midpoint) in meters composite depth (mcd), and potassium counts (normalized counts per 10 s) (Trauth et al, 2020) and interpolated sediment age in ka cal BP (Roberts et al, submitted structure, such as, smectites. These clay minerals are dioctahedral smectites with, primarily Al, but also Mg and Fe ions in octahedral coordination with oxygen and hydroxyl in a sheetlike structure.…”

Section: Results: Spectral Features and Climate Indicatorsmentioning

confidence: 99%

“…), that was determined for all XRF data by dividing the week's measurements by long-term average values of a set of SRM (Standard Reference Materials). Finally, all compositional data sets have been cleaned sub-cm wise by a quality flag system, avoiding coring artifacts, such as, cracks and voids (Trauth et al, 2020).…”

Section: Xrf Scanning Datamentioning

confidence: 99%

“…The potassium (K) content of the sediment has been established as a reliable proxy for dry climate phases in the Chew Bahir Basin, corresponding to increased evaporation, reduced vegetation cover and a lower lake level (Foerster et al, 2012;Trauth et al, 2015Trauth et al, , 2018Trauth et al, , 2020Fischer et al, 2020). Figure 2 displays the variations in potassium (K) content of the composite CHB14-2 core (in normalized counts per second) plotted against age and core depth.…”

Section: Chb Aridity Proxy: Potassiummentioning

confidence: 99%

“…For age-depth control, a Bayesian stratigraphic age model was applied to independent directly dated chronometers including radiocarbon dating of ostracodes, OSL dating of quartz, 40 Ar/ 39 Ar dating of K-feldspar grains from tuffaceous zones, and geochemical correlation of the Konso Silver Tuff (Silver Vitric Tuff, SVT) to a visible tephra unit in the core (Brown and Fuller, 2008;Clark et al, 2003;Brown et al, 2012;Roberts et al, submitted). With a basal age of ∼617 ka BP, and a spatial resolution for XRF elemental proxies of 0.5 cm, the temporal resolution of the CHB14-2 K record averages ∼10 years per data point (Trauth et al, 2020;Roberts et al, submitted) 1 .…”

Section: Chronologymentioning

confidence: 99%

“…For spectral measurements, the samples were filled into aluminum sample cups according to a standardized procedure and placed in the Bruker 513 accessory for the measurement of the bi-directional reflectance. The filling of sample dishes ensures a constant packing texture by testing constant density for FIGURE 2 | Variation in the potassium (K) content of the composite CHB14-2 core from the Chew Bahir Basin (in normalized counts per second) (Trauth et al, 2020) plotted against age (Roberts et al, submitted) and core depth. The potassium content is an established aridity proxy for the CHB sediments (Foerster et al, 2018).…”

Section: Reflectance Spectroscopy Of the Chb Core Samples Experimental Setup And Sample Preparationmentioning

confidence: 99%

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Advanced Hyperspectral Analysis of Sediment Core Samples from the Chew Bahir Basin, Ethiopian Rift, in the Spectral Range from 0.25 to 17 µm: Support for Climate Proxy Interpretation

et al. 2021

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Establishing robust environmental proxies at newly investigated terrestrial sedimentary archives is a challenge, because straightforward climate reconstructions can be hampered by the complex relationship between climate parameters and sediment composition, proxy preservation or (in)sufficient sample material. We present a minimally invasive hyperspectral bidirectional reflectance analysis on discrete samples in the wavelength range from 0.25 to 17 µm on 35 lacustrine sediment core samples from the Chew Bahir Basin, southern Ethiopia for climate proxy studies. We identified and used absorption bands at 2.2 μm (Al–OH), at 2.3 μm (Mg–OH), at 1.16 μm (analcime), and at 3.98 μm (calcite) for quantitative spectral analysis. The band depth ratios at 2.3/2.2 μm in the spectra correlate with variations in the potassium content of the sediment samples, which also reflect periods of increased Al-to-Mg substitution in clay minerals during drier climatic episodes. During these episodes of drier conditions, absorption bands diagnostic of the presence of analcime and calcite support this interpretation, with analcime indicating the driest conditions. These results could be compared to qualitative analysis of other characteristic spectral properties in the spectral range between 0.25 and 17 µm. The results of the hyperspectral measurements complement previous sedimentological and geochemical analyses, allowing us in particular to resolve more finely the processes of weathering in the catchment and low-temperature authigenic processes in the sediment. This enables us to better understand environmental changes in the habitat of early humans.

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Section: Results: Spectral Features and Climate Indicatorsmentioning

confidence: 99%

Section: Xrf Scanning Datamentioning

confidence: 99%