Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits
Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits
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DOI：
10.1130/geol.s.12307436.v1
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发表时间：
2020-05
期刊：
影响因子：
5.8
通讯作者：
S. Hage
中科院分区：
文献类型：
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作者：
S. Hage
陆地生物圈颗粒有机碳在海洋沉积物中的埋藏将二氧化碳从大气中移除，在地质时间尺度上调节气候。河流将陆地有机碳输送到海洋，而浊流则将河流沉积物进一步输送到近海。先前的研究表明，大多数有机碳存在于泥质海洋沉积物中。然而，浊流可以携带大量较粗的沉积物，而这些沉积物通常被认为有机碳含量很低。在这里，利用来自加拿大一个峡湾的数据，我们表明，新鲜的木质碎屑可以迅速埋藏在浊流沉积（浊积岩）的砂层中。这些砂层的有机碳含量比上覆泥层高10倍，而且总体而言，木质碎屑占沉积物中保存的有机碳的70%以上。木质碎屑埋藏在被泥盖覆盖的砂层中，减少了它们与氧气的接触，提高了有机碳的埋藏效率。砂质浊流通道在峡湾和深海中很常见；因此我们认为，先前的全球有机碳埋藏预算可能被低估了。
Burial of terrestrial biospheric particulate organic carbon in marine sediments removes CO2 from the atmosphere, regulating climate over geologic time scales. Rivers deliver terrestrial organic carbon to the sea, while turbidity currents transport river sediment further offshore. Previous studies have suggested that most organic carbon resides in muddy marine sediment. However, turbidity currents can carry a significant component of coarser sediment, which is commonly assumed to be organic carbon poor. Here, using data from a Canadian fjord, we show that young woody debris can be rapidly buried in sandy layers of turbidity current deposits (turbidites). These layers have organic carbon contents 10× higher than the overlying mud layer, and overall, woody debris makes up >70% of the organic carbon preserved in the deposits. Burial of woody debris in sands overlain by mud caps reduces their exposure to oxygen, increasing organic carbon burial efficiency. Sandy turbidity current channels are common in fjords and the deep sea; hence we suggest that previous global organic carbon burial budgets may have been underestimated.