Modern Sedimentation and Authigenic Mineral Formation in the Chew Bahir Basin, Southern Ethiopia: Implications for Interpretation of Late Quaternary Paleoclimate Records
Modern Sedimentation and Authigenic Mineral Formation in the Chew Bahir Basin, Southern Ethiopia: Implications for Interpretation of Late Quaternary Paleoclimate Records
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DOI：
10.3389/feart.2021.607695
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发表时间：
2021-04-30
影响因子：
2.9
通讯作者：
Asrat, Asfawossen
中科院分区：
文献类型：
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作者：
Gebregiorgis, Daniel;Deocampo, Daniel M.;Asrat, Asfawossen
我们提出了新的矿物学和地球化学数据，从现代沉积物中的Chew Bahir盆地和集水区，埃塞俄比亚。我们的目标是更好地了解现代沉积过程中的化学代用品形成的作用，在Chew Bahir古湖，一个新的研究古气候档案，提供人类进化和扩散的环境背景。在目前干燥的干盐湖湖底之外的现代沉积物具有较高的SiO2和Al 2 O3（50-70重量%）与泥滩样品相比。平均而言，泥滩沉积物样品富含Mg、Ca、Ce、Nd和Na等元素，表明可能在化学风化过程中富集（例如，粘土形成）。在上游湖查莫蒸发水的热力学建模产生的方解石，方沸石，和富含镁的自生伊利石粘土矿物的自生矿物组合，与普遍的环境增强蒸发浓度的Chew Bahir盆地。与样品的基础上全岩MgO/Al 2 O3，Ba/Sr和自生粘土矿物三角洲O-18值的丘巴希尔沉积物岩心的比较表明：现代沉积物中沉积的含盐泥滩丘巴希尔干涸的湖床类似于古沉积物沉积在干燥时期，如在末次冰期最大和新仙女木stadial。来自现代碎屑上游来源的沉积物更类似于湿润时期沉积的沉积物，如全新世早期非洲湿润时期。
We present new mineralogical and geochemical data from modern sediments in the Chew Bahir basin and catchment, Ethiopia. Our goal is to better understand the role of modern sedimentary processes in chemical proxy formation in the Chew Bahir paleolake, a newly investigated paleoclimatic archive, to provide environmental context for human evolution and dispersal. Modern sediment outside the currently dry playa lake floor have higher SiO2 and Al2O3 (50-70 wt.%) content compared to mudflat samples. On average, mudflat sediment samples are enriched in elements such as Mg, Ca, Ce, Nd, and Na, indicating possible enrichment during chemical weathering (e.g., clay formation). Thermodynamic modeling of evaporating water in upstream Lake Chamo is shown to produce an authigenic mineral assemblage of calcite, analcime, and Mg-enriched authigenic illitic clay minerals, consistent with the prevalence of environments of enhanced evaporative concentration in the Chew Bahir basin. A comparison with samples from the sediment cores of Chew Bahir based on whole-rock MgO/Al2O3, Ba/Sr and authigenic clay mineral delta O-18 values shows the following: modern sediments deposited in the saline mudflats of the Chew Bahir dried out lake bed resemble paleosediments deposited during dry periods, such as during times of the Last Glacial Maximum and Younger Dryas stadial. Sediments from modern detrital upstream sources are more similar to sediments deposited during wetter periods, such as the early Holocene African Humid Period.