Deciphering climate information from authigenic mineral transformations in the Chew Bahir sediment cores: Towards a continuous half-million year climate record from the Southern Ethiopian Rift

解读楚巴赫沉积岩芯中自生矿物转变的气候信息：埃塞俄比亚南部裂谷连续五十万年的气候记录

• 批准号: 398599231
• 负责人: Dr. Verena Foerster
• 金额: --
• 依托单位: Institut für Geographiedidaktik
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/398599231?language=en
• 关键词: Deciphering; climate; information; authigenic; mineral

The Chew Bahir Drilling Project (CBDP) has cored duplicate sediment records from the Chew Bahir basin in southern Ethiopia to test current hypotheses on human-climate interaction during the development of anatomically modern humans and their migrations out of Africa by elucidating the climatic context of critical time periods. However, deciphering paleoclimate from lake sediments is challenging due to the complex and site-specific relationships of climate parameters and sediment composition. Determining and analysing suitable climate proxies that are preserved throughout the core is essential to establishing a high resolution, continuous record on climate change. The project proposed here aims to decipher paleoenvironmental information from authigenic mineral transformations in the Chew Bahir sediment cores in order to contribute meaningful data that could be key to developing a reliable and continuous half million-year climate record from the Southern Ethiopian Rift. In a hydrologically restricted setting, such as Chew Bahir, the composition of authigenic clay minerals and zeolites are strongly controlled by the hydrochemistry of the paleolake, which responds to fluctuations in the precipitation/evaporation ratio. In a pilot study, the Chew Bahir mineral assemblages, especially the abundant clay minerals, have been shown to react sensitively to variations in paleosalinity and alkalinity by finely adjusting their crystallographic composition. Since the ~290-m-long composite core is dominantly comprised of those highly reactive clays, the material has the potential to provide continuous paleohydrochemical and paleoclimatic information through mineralogical and geochemical analyses. This potential dataset could be critical to the success of the project as some other proxies (e.g. pollen and diatoms) are only preserved intermittently. In the first two years of the project, we propose to (1a) identify characteristic mineral assemblages for wet, dry and hyper-arid phases throughout the long core; (1b) determine the precise degree of authigenic alteration in clay minerals and zeolites necessary to derive paleohydrologic data; (2a) link mineralogy (XRD) with geochemistry (µXRF) to show the links between hydroclimatic control, and the formation and preservation of the Chew Bahir proxies; (2b) decipher climatic change on orbital to decadal timescales from previously defined depositional conditions and thresholds; (3) evaluate the impact of different types of climatic change (duration, abruptness, internal variability and magnitude) on the habitat and living conditions of early humans. In summary, the results of the proposed project will form an important contribution to the understanding of complex climate proxy formation, enable continuous paleoclimate information to be deciphered from the Chew Bahir sediment cores, and contribute data that may be essential for testing hypotheses of the impact of climatic change on human evolution and mobility.

Chew Bahir钻探项目（CBDP）从埃塞俄比亚南部的Chew Bahir盆地提取了重复的沉积物记录，以通过阐明关键时期的气候背景来测试当前关于解剖学现代人类发展及其迁移出非洲期间人类-气候相互作用的假设。然而，由于气候参数和沉积物成分之间的复杂和特定的关系，从湖泊沉积物中破译古气候是具有挑战性的。确定和分析保存在整个岩芯中的合适的气候代用指标对于建立高分辨率、连续的气候变化记录至关重要。这里提出的项目旨在从Chew Bahir沉积物岩心的自生矿物转化中破译古环境信息，以便提供有意义的数据，这些数据可能是开发埃塞俄比亚南部裂谷可靠和连续的50万年气候记录的关键。在一个水文限制设置，如Chew Bahir，自生粘土矿物和沸石的组合物强烈控制的水化学的古湖，响应于降水/蒸发比的波动。在一项试点研究中，Chew Bahir矿物组合，特别是丰富的粘土矿物，已被证明反应灵敏的古盐度和碱度的变化，精细调整其晶体组成。由于~290-m长的复合岩心主要由这些高活性粘土组成，该材料具有通过矿物学和地球化学分析提供连续的古水文化学和古气候信息的潜力。这个潜在的数据集可能对项目的成功至关重要，因为其他一些替代物（例如花粉和硅藻）只是间歇性地保存下来。在项目的头两年，我们建议：（1a）确定整个长岩心的湿、干和超干旱阶段的特征矿物组合;（1b）确定获得古水文数据所需的粘土矿物和沸石的自生蚀变的精确程度;（2a）将矿物学（XRD）与地球化学（µXRF）联系起来，以显示水文气候控制与Chew Bahir代用品的形成和保存之间的联系;（2b）根据先前确定的沉积条件和阈值，解读轨道至十年时间尺度上的气候变化;（3）评估不同类型的气候变化（持续时间、快速性、内部变率和幅度）对早期人类生境和生活条件的影响。总之，拟议项目的结果将对理解复杂的气候代用指标的形成作出重要贡献，使连续的古气候信息能够从Chew Bahir沉积物岩心中破译，并提供可能对测试气候变化对人类进化和流动性影响的假设至关重要的数据。