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

海洋沉积序列通常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。现在有了使用原位和大气宇宙成因同位素的新的定量方法，可以应用于这些沉积物，并可能提供近岸大陆边缘沉积的陆源沉积物的现代侵蚀速率。In situ 10Be记录了陆上河流沉积物中强劲的空间平均侵蚀速率，但由于海洋沉积物岩心中缺乏足够数量的沙粒大小的石英，迄今尚未应用于海洋记录。另一方面，大气中的be由于吸附在沉积物颗粒上而携带着侵蚀的信号，它与特定的样品矿物学无关，可以方便地在少量细粒度沉积物上进行测量。然而，与海水交换和在海洋环境中清除10Be需要对该方法进行测试。在本研究中，我们将利用宇宙成因核素基10Be进行第一次小范围追踪海洋沉积物中保存的现代陆地侵蚀信号试验。首先，我们将利用原位和大气10Be确定智利中部两个流域的现代侵蚀速率，这些流域的沉积物最终被排放到海洋中。然后，我们将通过测量海洋表层沉积物的大气10Be，将这些陆上的侵蚀速率与海洋领域的侵蚀记录进行比较。通过这种方式，我们试图将大气10Be作为智利中部近海海洋环境中现代陆地侵蚀的一级示踪剂。

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.