Sediment geochemistry data for the publication: “10Be/9Be ratios reveal marine authigenic clay formation”

As reverse weathering has been shown to impact long-term changes in atmospheric CO2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio (10Be/9Be) recorded in marine clay-sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders-of-magnitude difference in 10Be/9Be ratios between continental Be and Be dissolved in seawater. On riverine and marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay-sized sediment fraction. We compare the riverine and marine 10Be/9Be ratio of this fraction. Moreover, we compare the elemental and mineralogical composition and the Nd and Sr-isotopic composition of these samples. 10Be/9Be ratios increase four-fold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10Be/9Be from dissolved biogenic opal, which also serves as a Si-source for the precipitation of marine authigenic clays. 10Be/9Be ratios thus sensitively track reverse-weathering reactions forming marine authigenic clays.

鉴于已有研究表明逆风化作用（reverse weathering）会影响大气二氧化碳的长期变化，开发定量工具以重建海洋自生黏土（marine authigenic clay）的形成过程至关重要。本研究探讨了海洋黏土级沉积物（clay-sized sediment）中记录的铍（Be）同位素比值（10Be/9Be）示踪自生黏土新形成过程的潜力。该代用指标（proxy）的有效性依赖于陆源铍与海水中溶解铍之间10Be/9Be比值的数量级差异。针对沿智利陆缘断面采集的河流源与海洋沉积物样品，我们通过化学方法提取了活性组分，并分离出黏土级沉积物组分。我们对比了该组分的河流源与海洋沉积物10Be/9Be比值。此外，我们还对比了这些样品的元素与矿物组成，以及钕（Nd）和锶（Sr）同位素组成。从河流源沉积物到海洋沉积物，10Be/9Be比值提升了四倍。我们将这一升高归因于源自溶解态生物成因蛋白石（biogenic opal）的、具有高10Be/9Be比值的铍的掺入——该蛋白石同时也是海洋自生黏土沉淀的硅源。因此，10Be/9Be比值可灵敏示踪形成海洋自生黏土的逆风化反应过程。