Source‐to‐sink response to high‐amplitude lake level rise driven by orbital‐scale climate change: An example from the Pleistocene Lake Malawi (Nyasa) Rift, East Africa
Source‐to‐sink response to high‐amplitude lake level rise driven by orbital‐scale climate change: An example from the Pleistocene Lake Malawi (Nyasa) Rift, East Africa
复制标题
对轨道尺度气候变化驱动的高幅度湖水位上升的源-汇响应：以东非更新世马拉维湖（尼亚萨）裂谷为例
DOI：
10.1111/sed.12909
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发表时间：
2021
期刊：
影响因子：
3.5
通讯作者：
C. Scholz
中科院分区：
文献类型：
--
作者：
M. Tan;C. Scholz
沉积系统在不同的时间尺度上以不同的方式响应环境强迫。马拉维湖（尼亚萨）裂谷是评估轨道或更年轻尺度上湖泊源汇系统整体功能的理想天然实验室。这些封闭的沉积系统表现出高度的时空气候变化，并且评估了它们对两个晚更新世湖面静止状态的响应。粗粒沉积物记录了热带非洲重要气候转变期间发生的从当前湖面以下 350 米到 200 米 (BPLL) 的剧烈海侵。基于数字高程模型和高分辨率单/多道地震剖面的综合分析，流域地貌与汇区的沉积物输送联系起来。每个源-汇系统的粗粒沉积通过沉积物质量计算进行量化。基于蒙特卡罗模拟，考虑温度递减率和地形影响，采用经过修改的经验推导的“BQART”预测器和床载方程来评估沉积物排放。河流流量是通过将集水区与各种气候系统联系起来的特定经验关系来估计的，并使用全球现代河流数据库开发。结果表明，泥沙排放总量从7.53Mt year−1增加到9.50Mt year−1；同样，保存下来的粗粒沉积物也记录了从350米到200米BPLL阶段沉积速率的显着增加，这表明短长度尺度的源-汇系统对气候变化引起的高幅度湖侵敏感。在气候逐渐湿润的情况下，上游缓冲沉积物的体积可能会减少，而缓冲程度则很大程度上受到原有地貌的影响。此外，尽管湖泊水位相对较高，气候稍湿润，但深水泥浆的大量扩散并不发达。这种使用改进的沉积物预测器进行的定量源-汇分析为封闭沉积系统中响应高幅度气候变化的系统功能提供了初步约束。
Sedimentary systems respond to environmental forcings in dissimilar ways over different timescales. The Lake Malawi (Nyasa) Rift is an ideal natural laboratory for evaluating the overall functioning of lacustrine source‐to‐sink systems on orbital or younger scales. These closed sedimentary systems exhibited high spatiotemporal climate variability, and their responses to two late Pleistocene lake‐level stillstands are evaluated. The coarse‐grained deposits documented a dramatic transgression from 350 to 200 m below present lake‐level (BPLL) developed during an important climate transition in tropical Africa. Based on an integrated analysis of a digital elevation model and high‐resolution single/multi‐channel seismic profiles, catchment geomorphology has been linked with sediment delivery in the sink area. The coarse‐grained deposition of each source‐to‐sink system is quantified through a sediment mass calculation. A modified empirically‐derived ‘BQART’ predictor with a bedload equation to assess the sediment discharge is employed based on a Monte Carlo simulation, considering temperature lapse rate and topographic effects. The river discharges are estimated by specific empirical relationships that associate catchment area to various climate systems, developed using a global modern river database. The results show that the total sediment discharge increases from 7.53 to 9.50 Mt year−1; likewise, the preserved coarse‐grained deposits also record a significant increase in deposition rate from 350 to 200 m BPLL stage, indicating that the short length‐scale source‐to‐sink systems are sensitive to the high‐amplitude lake transgression developed from the climate shift. The volume of upstream buffered deposits may decrease within the progressively wetter climate, while the buffering degree was substantially influenced by the pre‐existing landforms. Moreover, the substantial deep‐water mud dispersal is not well‐developed, despite the relatively higher lake‐level and slightly wetter climate. This quantitative source‐to‐sink analysis with the modified sediment predictor yields preliminary constraints for system functioning in response to high‐amplitude climate change in a closed sedimentary system.
DOI：
10.1073/pnas.1512864112
发表时间：
2015-12-22
影响因子：
11.1
作者：
Lyons, Robert P.;Scholz, Christopher A.;Blome, Margaret W.
通讯作者：
Blome, Margaret W.