Distribution, Source, and Burial of Sedimentary Organic Carbon in Kermadec and Atacama Trenches
Distribution, Source, and Burial of Sedimentary Organic Carbon in Kermadec and Atacama Trenches
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DOI：
10.1029/2020jg006189
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发表时间：
2021-04
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通讯作者：
Yunping Xu;Xinxin Li;M. Luo;Wenjie Xiao;Jiasong Fang;H. Rashid;Yongbo Peng;Wenpeng Li;F. Wenzhöfer;A. Rowden;R. Glud
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作者：
Yunping Xu;Xinxin Li;M. Luo;Wenjie Xiao;Jiasong Fang;H. Rashid;Yongbo Peng;Wenpeng Li;F. Wenzhöfer;A. Rowden;R. Glud
对深海海沟（最深的海洋领域）中沉积有机碳（OC）的了解还很初步。在这里，我们对总OC（TOC），稳定和放射性碳同位素（δ 13 C和Δ 14 C）以及生物标志物（例如，正构烷烃、正构烷醇和正构脂肪酸）的12个沉积物岩心中的正构烷烃、正构烷醇和正构脂肪酸，这些沉积物岩心是从Kermadec海沟（西南太平洋）和Atacama海沟（东南太平洋）区域的深渊（海沟轴）和非深渊（深海平原和斜坡）环境中收集的。研究结果表明，阿塔卡马海沟区的TOC（0.86% ± 0.69%）显著高于克马德克海沟区（0.29% ± 0.08%），这可能与不同的表层初级生产力有关。在这两个海沟区，与非超深源地点相比，超深源地点通常具有更负的δ 13 C，更高的TOC/TN比值以及相似或更高的陆源/海相生物标志物丰度比，这表明超深源海沟轴处选择性地保存了陆源生物源/化石OC。非超深渊沉积物芯中14 C年龄随沉积物深度的线性增加反映了稳定的沉积条件，而八分之七的超深渊沉积物芯显示14 C年龄逆转，可能是由于偶尔的质量输送沉积。我们的研究结果表明：（1）海沟之间和每个海沟内部的沉积有机碳特征具有很强的不均匀性;（2）克马德克海沟（0.35 ± 0.04 g m−2 yr−1）和阿塔卡马海沟（1.4 ± 0.5 g m−2 yr−1）中陆源有机碳的累积速率相对较高。因此，超深槽似乎代表了深海陆源碳沉积的重要环境。
Knowledge of sedimentary organic carbon (OC) in hadal trenches, the deepest ocean realm, is rudimentary. Here, we conducted a comprehensive analysis of total OC (TOC), stable and radio‐carbon isotopes (δ13C and Δ14C), and biomarkers (e.g., n‐alkanes, n‐alkanols and n‐fatty acids) in 12 sediment cores collected from hadal (trench axis) and non‐hadal (abyssal plains and slopes) settings of the Kermadec Trench (Southwestern Pacific) and Atacama Trench (Southeastern Pacific) regions. Our results show that the TOC in the Atacama Trench region (0.86% ± 0.69%) is significantly higher than that of the Kermadec Trench region (0.29% ± 0.08%), likely related to different surface primary productivity. In both trench regions, the hadal sites are generally characterized by more negative δ13C, higher TOC/TN ratio, and similar or higher abundance ratio of terrigenous/marine biomarkers as compared to the non‐hadal sites, suggesting the selective preservation of terrigenous biogenic/fossil OC at the hadal trench axis. The linear increase in 14C age with sediment depth in non‐hadal cores reflects steady depositional conditions, whereas seven out of eight hadal sediment cores show 14C age reversals presumably due to occasional mass‐transport deposits. Our results suggest (1) a strong heterogeneity in sedimentary OC characteristics between trenches and within each trench and (2) relatively high accumulation rates of terrigenous OC in both the Kermadec Trench (0.35 ± 0.04 g m−2 yr−1) and the Atacama Trench (1.4 ± 0.5 g m−2 yr−1). Thus, hadal trenches appear to represent an important environment for terrigenous carbon deposition in the deep ocean.