A new look at old carbon in active margin sediments
A new look at old carbon in active margin sediments
复制标题
DOI：
10.1130/g25351a.1
复制
发表时间：
2009-03
期刊：
影响因子：
5.8
通讯作者：
N. Drenzek;K. Hughen;D. Montluçon;J. Southon;G. Santos;E. Druffel;L. Giosan;T. Eglinton
中科院分区：
文献类型：
--
作者：
N. Drenzek;K. Hughen;D. Montluçon;J. Southon;G. Santos;E. Druffel;L. Giosan;T. Eglinton
最近的研究表明，在构造活动大陆边缘沉积物中埋藏的有机碳（OC）中，多达一半可能是化石页岩风化的产物。这些估计依赖于这样的假设，即维管植物碎屑花很少的时间隔离在中间水库，如土壤，淡水沉积物和河流三角洲，因此只有最低限度地有助于在相邻的货架上经常观察到的总有机物的古老的14C年龄。在这里，我们通过测量个体高等植物蜡脂肪酸的Δ 14 C和δ 13 C值以及从鳗鱼河边缘（加州）分离的可提取烷烃的δ 13 C值来测试这种范例。长链脂肪酸的同位素特征表明，维管植物材料在沉积之前已经被隔离了几千年。用于重新评估沉积碳收支的耦合分子同位素质量平衡表明，化石成分的丰度低于先前的估计，而不是由相当大比例的所有有机物组成的前年龄的陆地物质。如果这些发现是其他大陆边缘的特点，靠近小型山区河流，那么在海洋沉积物中的成岩有机碳埋藏的重要性可能需要重新评估。© 2009美国地质学会。
Recent studies suggest that as much as half of the organic carbon (OC) undergoing burial in the sediments of tectonically active continental margins may be the product of fossil shale weathering. These estimates rely on the assumption that vascular plant detritus spends little time sequestered in intermediate reservoirs such as soils, freshwater sediments, and river deltas, and thus only minimally contributes to the extraneously old 14C ages of total organic matter often observed on adjacent shelves. Here we test this paradigm by measuring the Δ14C and δ13C values of individual higher plant wax fatty acids as well as the δ13C values of extractable alkanes isolated from the Eel River margin (California). The isotopic signatures of the long chain fatty acids indicate that vascular plant material has been sequestered for several thousand years before deposition. A coupled molecular isotope mass balance used to reassess the sedimentary carbon budget indicates that the fossil component is less abundant than previously estimated, with pre-aged terrestrial material instead composing a considerable proportion of all organic matter. If these findings are characteristic of other continental margins proximal to small mountainous rivers, then the importance of petrogenic OC burial in marine sediments may need to be reevaluated. © 2009 The Geological Society of America.