The competition between coastal trace metal fluxes and oceanic mixing from the 10Be/9Be ratio: Implications for sedimentary records
The competition between coastal trace metal fluxes and oceanic mixing from the 10Be/9Be ratio: Implications for sedimentary records
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DOI：
10.1002/2017gl074259
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发表时间：
2017-08
影响因子：
5.2
通讯作者：
Hella Wittmann;F. Blanckenburg;M. Mohtadi;M. Christl;Anne Bernhardt
中科院分区：
文献类型：
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作者：
Hella Wittmann;F. Blanckenburg;M. Mohtadi;M. Christl;Anne Bernhardt
在智利近海37°S的一个海洋边缘地点，我们使用大气宇宙成因10Be/9Be比值来追踪由于与海水交换而引起的陆地颗粒组成的变化。我们分析了沿海岸垂直样带的表层沉积物中的海洋自生阶段，并将其与河流来源的样品进行了比较。我们发现了自生环通过共沉淀而不是可逆吸附生长的证据，这些自生环包含了距离海岸仅30公里的深海10Be/9Be特征，覆盖了陆地10Be/9Be特征。随着10Be/9Be比值的增加，颗粒结合铁浓度增加，这归因于沉积物中边界交换过程中富铁孔隙水的释放。在沉积记录中使用10Be/9Be进行古剥蚀通量重建的意义如下：在靠近海岸的地点，自生记录可能会保存不受与海水交换影响的当地河流比率，而在混合良好的海水下的地点将保存全球通量特征。
At an ocean margin site 37°S offshore Chile, we use the meteoric cosmogenic 10Be/9Be ratio to trace changes in terrestrial particulate composition due to exchange with seawater. We analyzed the marine authigenic phase in surface sediments along a coast‐perpendicular transect and compared to samples from their riverine source. We find evidence for growth of authigenic rims through coprecipitation, not via reversible adsorption, that incorporate an open ocean 10Be/9Be signature from a deep water source only 30 km from the coast, overprinting terrestrial 10Be/9Be signatures. Together with increasing 10Be/9Be ratios, particulate‐bound Fe concentrations increase, which we attribute to release of Fe‐rich pore waters during boundary exchange in the sediment. The implications for the use of 10Be/9Be in sedimentary records for paleodenudation flux reconstructions are the following: in coast‐proximal sites the authigenic record will likely preserve local riverine ratios unaffected by exchange with seawater, whereas sites beneath well‐mixed seawater will preserve global flux signatures.