Meteoric 10Be as a tracer of terrestrial denudation in marine sediments: A feasibility study offshore central Chile

海洋沉积序列往往保存了从大陆到世界海洋的沉积物通量的长期和相对连续的档案。现在已有新的定量方法，使用原地和大气宇宙成因同位素，可应用于这些矿床，并有可能提供近海大陆边陆源沉积物的现代侵蚀速率。原位10Be，记录强大的空间平均侵蚀速率在陆上河流沉积物，迄今为止还没有被应用到海洋记录，由于缺乏足够的砂大小的石英在海洋沉积物芯。另一方面，流星体10Be由于吸附在沉积物颗粒上而带有侵蚀信号，与特定的样品矿物学无关，可以方便地在少量细粒沉积物上进行测量。然而，与海水的交换和海洋环境中的10Be清除需要测试该方法。在这项研究中，我们将进行第一个小规模的测试，跟踪现代陆地侵蚀信号保存在海洋沉积物中使用宇宙成因核素为基础的10 Be。首先，我们将确定现代的侵蚀速率在智利中部的两个流域，其沉积物最终排入海洋，通过使用原位和流星10 Be。然后，我们将比较这些陆上率与海洋领域的侵蚀记录，通过测量大气10Be从海洋表层沉积物。通过这种方式，我们试图建立流星10Be作为现代陆地侵蚀的一阶示踪剂在智利中部近海的海洋环境。

Marine sedimentary successions often preserve long and relatively continuous archives of sediment flux from the continents to the worlds oceans. New quantitative methods using in situ and meteoric cosmogenic isotopes are now available that can be applied to these deposits and will potentially provide modern erosion rates from terrigenous sediment deposited offshore continental margins. In situ 10Be, which records robust spatially averaged erosion rates in onshore fluvial sediment, has so far not been applied to marine records due to the lack of sufficient amounts of sand-sized quartz in marine sediment cores. Meteoric 10Be on the other hand, which carries a signal of erosion from its adsorption to sediment particles, is independent from the particular sample mineralogy and can be conveniently measured on small amounts of fine-grained sediment. However, exchange with seawater and 10Be scavenging in the marine environment necessitates testing of this method. In this study, we will conduct the first small-scale test of tracing the modern terrestrial erosion signal preserved in marine sediments by using cosmogenic nuclide-based 10Be. First, we will determine modern erosion rates for two drainage basins in central Chile, whose sediment is ultimately discharged into the ocean, by using in situ and meteoric 10Be. We will then compare these onshore rates with a record of erosion in the marine realm by measuring meteoric 10Be from surface ocean sediment. This way, we attempt to establish meteoric 10Be as a first-order tracer of modern terrestrial erosion in marine environments offshore central Chile.