scholarly journals 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

2021 ◽  
Vol 9 ◽  
Author(s):  
Gabriele E. Arnold ◽  
Verena Foerster ◽  
Martin H. Trauth ◽  
Henry Lamb ◽  
Frank Schaebitz ◽  
...  
Keyword(s):  
Sediment Core ◽  
Spectral Range ◽  
Environmental Changes ◽  
Southern Ethiopia ◽  
Ethiopian Rift ◽  
Absorption Bands ◽  
Climate Proxy ◽  
Core Samples ◽  
Reflectance Analysis ◽  
Band Depth

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.

scholarly journals 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

2020 ◽  
Author(s):  
Gabriele Arnold ◽  
Claudia Szczech ◽  
Asfawossen Asrat ◽  
Andrew S. Cohen ◽  
Verena Foerster ◽  
...  
Keyword(s):  
Spectral Range ◽  
Transition Metal Ions ◽  
Ethiopian Rift ◽  
Absorption Bands ◽  
Geochemical Composition ◽  
Climate Proxy ◽  
Potassium Fixation ◽  
Core Samples ◽  
Geochemical Properties ◽  
Mineralogical Properties

<p>This paper reports on the application of advanced hyperspectral analysis to support the non-destructive 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.</p><p>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, H<sub>2</sub>O, 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.</p><p>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 SiO<sub>4</sub> for which Si is partially substituted by Al and of edge-linked Al (OH)<sub>6</sub> octahedrons in which part of the Al is substituted by Mg and which are layered by OH and H<sub>2</sub>O groups. Thus all reflectance spectra show the characteristic absorption bands at 1.4 µm (OH), 1.9 µm (H<sub>2</sub>O), 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.</p><p><br>Foerster, V. et al., (2018) Towards an understanding of climate proxy formation in the Chew Bahir basin, southern Ethiopian Rift. Palaeogeography, Palaeoclimatology, Palaeoecology, 501, 111-123.</p>

Human responses to hydroclimate fluctuations over the last 200 kyr in Ethiopia

2020 ◽  
Author(s):  
Frank Schäbitz ◽  
Verena Foerster ◽  
Asfawossen Asrat ◽  
Andrew S. Cohen ◽  
Melissa S. Chapot ◽  
...  
Keyword(s):  
Climate Change ◽  
Environmental Change ◽  
Environmental Changes ◽  
Homo Sapiens ◽  
Human Mobility ◽  
Regional Scale ◽  
Eastern Africa ◽  
Southern Ethiopia ◽  
Ethiopian Rift ◽  
Mobility Patterns

<p><span>Humans </span><span>have been adapting to more demanding habitats in the course of their evolutionary history</span><span>. </span><span>Nevertheless</span><span>, environmental changes coupled with overpopulation naturally limit competition for resources. In order to find such limits, reconstructions of climate and </span><span>population changes </span><span>are increasingly used for the continent of our origin, Africa.</span> <span>However, </span><span>continuous and high-resolution records of climate-human interactions are still scarce. </span></p><p><span>Using a 280 m sediment core from Chew Bahir*, a wide tectonic basin in southern Ethiopia,</span> <span>we reconstruct the paleoenvironmental conditions during the development of <em>Homo sapiens.</em> The complete multiproxy record of the composite core covers the last ~600 ka </span><span>, allowing tests of hypotheses about the influence of climate change on human evolution and technological innovation from the Late Acheulean to the Middle/Late Stone Age, and on dispersal within and out of Africa</span><span>. </span></p><p><span>Here we present results from the uppermost 100 meters of the Chew Bahir core, spanning the last 200 kiloyears (ka). </span><span>The record shows two modes of environmental change that are associated with two types of human mobility. The first mode is a long-term trend towards a more arid climate, overlain by precession-driven wet-dry alternation. Through comparison with the archaeological record, humid episodes appear to have led to the opening of ‘green’ networks between favourable habitats and thus to increased human mobility on a regional scale. The second mode of environmental change resembles millennial-scale Dansgaard-Oeschger and Heinrich events, which seem to coincide with enhanced vertical mobility from the Ethiopian rift to the highlands, especially in the time frame between ~65–21 ka BP. The coincidence of climate change and human mobility patterns help to define the limiting conditions for early <em>Homo sapiens</em> in eastern Africa.</span></p><p><span>___________________</span></p><p><span>*</span> <span>cored in the context of HSPDP (<em>Hominin Sites and Paleolakes Drilling Project</em>) and CRC </span><span>(<em>Collaborative Research </em><em>Centre</em>) 806 “<em>Our way to Europe</em>”</span></p>

scholarly journals 46 000 years of alternating wet and dry phases on decadal to orbital timescales in the cradle of modern humans: the Chew Bahir project, southern Ethiopia

2014 ◽  
Vol 10 (2) ◽  
pp. 977-1023 ◽  
Author(s):  
V. Foerster ◽  
A. Junginger ◽  
A. Asrat ◽  
H. F. Lamb ◽  
M. Weber ◽  
...  
Keyword(s):  
Human Evolution ◽  
High Latitude ◽  
Environmental Changes ◽  
Climatic Variability ◽  
Southern Ethiopia ◽  
Ethiopian Rift ◽  
Environmental Response ◽  
Climate Shifts ◽  
Decadal Climate ◽  
Abrupt Shifts

Abstract. Rapid changes in environmental conditions are considered to be an important driver for human evolution, cultural and technological innovation, and expansion out of Africa. However, the nature of these environmental changes, their amplitude and correlation with steps in human evolution is the subject of current debates. Here we present a high-resolution (~3–12 yr) and well-dated (32 AMS 14C ages) lake-sediment record of the last 46 000 yr from the Chew Bahir basin in the southern Ethiopian Rift. The record was obtained from six cores along a NW–SE transect across the basin, which has been selected as the drilling location within the ICDP Hominin Sites and Paleolakes Drilling Project (HSPDP). Multi-proxy data and the comparison between the transect coring sites provide initial insight into intra-basin dynamics and major mechanisms controlling the sedimentation of the proxies that was used to develop a basic proxy concept for Chew Bahir for the last two wet-dry cycles. The environmental response to orbitally induced sinusoidal insolation changes is usually nonlinear, as climate changes abruptly compared to changes in the forcing, or gradual but punctuated by multi-decadal intervals of drier conditions. The second major control on the environment is millennial-scale climate variability lasting ~1500 yr, similar in duration to the high-latitude Dansgaard–Oeschger cycles and Heinrich events including the Younger Dryas cold reversal at the end of the last glacial, mostly causing abrupt shifts from extreme arid to wet conditions. The duration and character of orbitally induced, high-latitude controlled, and multi-decadal climate shifts provides important constraints for the adaptation of humans to the changing environment. Therefore, Chew Bahir is a perfect site to study and understand climatic variability on different timescales.

Pesticides and heavy metals in sediment core samples from a coastal area in Japan

2017 ◽  
Vol 51 (6) ◽  
pp. 525-536
Author(s):  
Chikumbusko Chiziwa Kaonga ◽  
Kazuhiko Takeda ◽  
Hiroshi Sakugawa ◽  
Hideo Yamazaki
Keyword(s):  
Heavy Metals ◽  
Sediment Core ◽  
Coastal Area ◽  
Core Samples

Penguin occupation in the Vestfold Hills

2008 ◽  
Vol 21 (2) ◽  
pp. 131-134 ◽  
Author(s):  
Tao Huang ◽  
Liguang Sun ◽  
Yuhong Wang ◽  
Renbin Zhu
Keyword(s):  
Sediment Core ◽  
Environmental Changes ◽  
Sediment Cores ◽  
East Antarctica ◽  
Before Present ◽  
The Holocene ◽  
History Of ◽  
Vestfold Hills ◽  
Free Area ◽  
Ornithogenic Sediment

AbstractDuring CHINARE-22 (December 2005–March 2006), we investigated six penguin colonies in the Vestfold Hills, East Antarctica, and collected several penguin ornithogenic sediment cores, samples of fresh guano and modern penguin bone and feather. We selected seven penguin bones and feathers and six sediments from the longest sediment core and performed AMS14C dating. The results indicate that penguins occupied the Vestfold Hills as early as 8500 calibrated years before present (cal. yrbp), following local deglaciation and the formation of the ice free area. This is the first report on the Holocene history of penguins in the Vestfold Hills. As in other areas of Antarctica, penguins occupied this area as soon as local ice retreated and the ice free area formed, and they are very sensitive to climatic and environmental changes. This work provides the foundation for understanding the history of penguins occupation in Vestfold Hills, East Antarctica.

scholarly journals The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared – Part 2: Accurate calibration of high spectral-resolution infrared measurements of surface solar radiation

2016 ◽  
Vol 9 (9) ◽  
pp. 4673-4686 ◽  
Author(s):  
Andreas Reichert ◽  
Markus Rettinger ◽  
Ralf Sussmann
Keyword(s):  
Water Vapor ◽  
Spectral Range ◽  
High Spectral Resolution ◽  
Spectral Radiance ◽  
Transfer Model ◽  
Water Vapor Absorption ◽  
Absorption Bands ◽  
Model Calculations ◽  
Infrared Measurements ◽  
Vapor Absorption

Abstract. Quantitative knowledge of water vapor absorption is crucial for accurate climate simulations. An open science question in this context concerns the strength of the water vapor continuum in the near infrared (NIR) at atmospheric temperatures, which is still to be quantified by measurements. This issue can be addressed with radiative closure experiments using solar absorption spectra. However, the spectra used for water vapor continuum quantification have to be radiometrically calibrated. We present for the first time a method that yields sufficient calibration accuracy for NIR water vapor continuum quantification in an atmospheric closure experiment. Our method combines the Langley method with spectral radiance measurements of a high-temperature blackbody calibration source (<  2000 K). The calibration scheme is demonstrated in the spectral range 2500 to 7800 cm−1, but minor modifications to the method enable calibration also throughout the remainder of the NIR spectral range. The resulting uncertainty (2σ) excluding the contribution due to inaccuracies in the extra-atmospheric solar spectrum (ESS) is below 1 % in window regions and up to 1.7 % within absorption bands. The overall radiometric accuracy of the calibration depends on the ESS uncertainty, on which at present no firm consensus has been reached in the NIR. However, as is shown in the companion publication Reichert and Sussmann (2016), ESS uncertainty is only of minor importance for the specific aim of this study, i.e., the quantification of the water vapor continuum in a closure experiment. The calibration uncertainty estimate is substantiated by the investigation of calibration self-consistency, which yields compatible results within the estimated errors for 91.1 % of the 2500 to 7800 cm−1 range. Additionally, a comparison of a set of calibrated spectra to radiative transfer model calculations yields consistent results within the estimated errors for 97.7 % of the spectral range.

Late Quaternary Vegetational Changes in a Marsh Forest in Southeastern Brazil with Comments on Prehistoric Human Occupation

Radiocarbon ◽  
2015 ◽  
Vol 57 (5) ◽  
pp. 737-753 ◽  
Author(s):  
Walter Mareschi Bissa ◽  
Mauro B de Toledo
Keyword(s):  
Sediment Core ◽  
Environmental Changes ◽  
Human Impacts ◽  
Late Quaternary ◽  
Southeastern Brazil ◽  
Pollen Record ◽  
Important Indicator ◽  
Climate Conditions ◽  
Ams Radiocarbon Dating ◽  
Se Brazil

This article presents a palynological study carried out on a sediment core from a peat deposit in Serra de Botucatu, in SÃo Paulo State, southeastern Brazilian Plateau. This region has been covered by grassland vegetation and forest patches throughout the recorded period. AMS radiocarbon dating plus palynological analysis of 27 samples from the sediment core allowed the recognition of several environmental changes that took place during the last 33,000 yr recorded in the core. The relationship between sedimentation rates and changes in the abundance of plants recognized through their pollen record, particularly a few important indicator species, provided the paleoenvironmental history for the Serra de Botucatu region, allowing the identification of changes in climate conditions and comparison with other regions in Brazil. One of the most remarkable features of this record is the cold and humid conditions during the Last Glacial Maximum, which diverges from previous interpretations for southeastern and southern Brazil but is in good agreement with paleoclimatic data from trace elements from cave stalagmites in SE Brazil. No indications of human impacts on the vegetation were found in this record.

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