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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 information.

Arnold, Gabriele and Szczech, Claudia and Asfawossen, Asrat and Cohen, A.S. and Foerster, Verena and Schäbitz, F. and Lamb, H. and Trauth, M. (2020) 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 information. EGU General Assembly 2020, 4. May - 8. May 2020, online. doi: 10.5194/egusphere-egu2020-5233.

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Official URL: https://meetingorganizer.copernicus.org/EGU2020/EGU2020-5233.html

Abstract

This paper reports on the application of advanced hyperspectral analysis to support the nondestructive study of samples from long sediment cores (up to 280 m coring depth) collected under the Hominin Sites and Paleolake Drilling Program (HSPDP) in the Chew Bahir region of southern Ethiopia. For this purpose, the bidirectional reflectance of 35 core samples from different core depths in the wavelength range from 0.25 to 17 µm was measured. It can be directly compared with spectral remote sensing data of the corresponding land surface areas. We examined the relationship between the derived mineralogical and geochemical properties of the core samples to test for linkage to the hydroclimate history of the region. Using XRD and µXRD methods, it has been shown that an illitization of the smectites and an octahedral Al-to-Mg substitution occurs in the phyllosilicate materials present during phases that have been associated with increased salinity and alkalinity due to enhanced evaporation (Foerster et al., 2018). These processes are found to be accompanied by potassium fixation and they are associated with the increase of the layer charge due to the authigenic changes of the octahedral composition. Reflection spectroscopy is a suitable method for studying such mineralogical properties. We investigated the spectral properties over a wide spectral range from UV to MIR. This enables detection of absorption bands of crystal field transitions of transition metal ions in the UV/VIS range and to detect the characteristic bands of OH, H2O, M-OH lattice vibrations in the NIR. It also allows the study of the fundamental vibration bands as well as other typical MIR features like the Christiansen band or transparency features of silicates and thus helps to reconstruct weathering paths. The results show that the main mineralogical components are clays of the smectite group. The samples are rich in montmorillonite and show variable concentrations of calcite. The clays are composed of tetrahedral coordinated, corner-connected SiO4 for which Si is partially substituted by Al and of edge-linked Al (OH)6 octahedrons in which part of the Al is substituted by Mg and which are layered by OH and H2O groups. Thus all reflectance spectra show the characteristic absorption bands at 1.4 µm (OH), 1.9 µm (H2O), 2.2 µm (Al-OH), and 2.3 µm (Mg-OH). Their band depth ratios derived from continuum removed spectra have been used to characterize the clay structure within different climate periods. The results support the model of illitization and potassium fixation during dry climate intervals. In addition, the spectral indicators determined in the MIR can be used to specify the mineralogical properties of silicates and other materials in terms of their geochemical composition. In summary, the method is suitable for examining the main mineralogical components of Chew Bahir core samples and enables confirmation of climate driven wet and dry weathering processes in the formation of phyllosilicates.

Item URL in elib:https://elib.dlr.de/138622/
Document Type:Conference or Workshop Item (Poster)
Title: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 information.
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Arnold, GabrieleGabriele.Arnold (at) dlr.deUNSPECIFIED
Szczech, ClaudiaClaudia.Szczech (at) dlr.deUNSPECIFIED
Asfawossen, AsratInstitute of Geography Education, University of Cologne, Cologne, GermanyUNSPECIFIED
Cohen, A.S.University of Arizona, Department of Geosciences, Tucson AZ, USAUNSPECIFIED
Foerster, VerenaInstitute of Geography Education, University of CologneUNSPECIFIED
Schäbitz, F.University of Cologne, Institute of GeographyUNSPECIFIED
Lamb, H.Aberystwyth University, Department of Geography and Earth Sciences, UKUNSPECIFIED
Trauth, M.University of Potsdam, Institute of Geosciences, Potsdam, GermanyUNSPECIFIED
Date:2020
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
DOI :10.5194/egusphere-egu2020-5233
Page Range:EGU2020-5233
Status:Published
Keywords:Hyperspectral lab studies, remote sensing, sediment core samples, Chew Bahir
Event Title:EGU General Assembly 2020
Event Location:online
Event Type:international Conference
Event Dates:4. May - 8. May 2020
Organizer:EGU General Assembly
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Exploration of the Solar System
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Leitungsbereich PF
Deposited By: Arnold, Dr. Gabriele
Deposited On:30 Nov 2020 14:12
Last Modified:08 Dec 2020 03:00

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