Immediate propagation of deglacial environmental change to deep-marine turbidite systems along the Chile convergent margin
Immediate propagation of deglacial environmental change to deep-marine turbidite systems along the Chile convergent margin
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DOI：
10.1016/j.epsl.2017.05.017
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发表时间：
2017-09
影响因子：
5.3
通讯作者：
A. Bernhardt;W. Schwanghart;D. Hebbeln;J. Stuut;M. Strecker
中科院分区：
文献类型：
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作者：
A. Bernhardt;W. Schwanghart;D. Hebbeln;J. Stuut;M. Strecker
了解地球表面过程如何对过去的气候扰动作出反应，对于预测气候变化对沉积物通量的未来影响至关重要。沉积记录提供了档案推断这些过程，但他们的解释是妥协的，我们不完全了解沉积路由系统如何响应千年尺度的气候cycles.We分析了七个沉积物岩心从海洋浊积岩沉积网站沿着智利大陆边缘。这些地点跨越明显的干旱到潮湿梯度，地形起伏不定，陆地和海洋环境的相关沉积物连通性也各不相同。这些地点使我们能够研究从末次盛冰期到现在的不同气候和地貌环境中与事件相关的沉积过程。这三个地点揭示了冰消期浊流沉积的急剧下降。海平面的高速率上升滞后于浊流沉积的下降。与古气候代用指标的比较表明，时空沉积格局反映了冰消期湿度的下降和伴随的变暖，没有可分辨的滞后时间。这个信号通过高度连接的系统迅速传播到智利中北部的海洋水槽。相反，在智利中南部，安第斯侵蚀带和河流转移带之间的连通性可能突然减少沉积物截留在皮埃蒙特湖泊有关的冰川消退，导致突然减少沉积物供应到海洋。此外，减少水分供应可能有助于浊流沉积的快速下降。这些不同的原因导致了海盆中相似的沉积模式。我们的结论是，浊流地层可能构成可靠的记录器的气候变化在广泛的气候带和地貌条件。然而，在接收器中的类似信号表现的根本原因可能不同，范围从维持高系统连接到突然的连接丢失。
Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment fluxes. Sedimentary records provide the archives for inferring these processes, but their interpretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles.We analyzed seven sediment cores recovered from marine turbidite depositional sites along the Chile continental margin. The sites span a pronounced arid-to-humid gradient with variable relief and related sediment connectivity of terrestrial and marine environments. These sites allowed us to study event-related depositional processes in different climatic and geomorphic settings from the Last Glacial Maximum to the present day. The three sites reveal a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise postdate the decline in turbidite deposition. Comparison with paleoclimate proxies documents that the spatio-temporal sedimentary pattern rather mirrors the deglacial humidity decrease and concomitant warming with no resolvable lag times.Our results let us infer that declining deglacial humidity decreased fluvial sediment supply. This signal propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chile, connectivity between the Andean erosional zone and the fluvial transfer zone probably decreased abruptly by sediment trapping in piedmont lakes related to deglaciation, resulting in a sudden decrease of sediment supply to the ocean. Additionally, reduced moisture supply may have contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata may constitute reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss.