Selective preservation of organic matter in marine environments; processes and impact on the sedimentary record
Selective preservation of organic matter in marine environments; processes and impact on the sedimentary record
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DOI：
10.5194/bg-7-483-2010
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发表时间：
2009-07
期刊：
影响因子：
4.9
通讯作者：
K. Zonneveld;G. Versteegh;S. Kasten;T. Eglinton;K. Emeis;C. Huguet;B. Koch;G. Lange;J. D. Leeuw-J.
中科院分区：
文献类型：
--
作者：
K. Zonneveld;G. Versteegh;S. Kasten;T. Eglinton;K. Emeis;C. Huguet;B. Koch;G. Lange;J. D. Leeuw-J.
摘要。本文是由德国研究基金会（DFG）研究中心/卓越集群MARUM“地球系统中的海洋”、欧洲近岸过程国际研究生院（EUROPROX）以及阿尔弗雷德·韦格纳极地与海洋研究所赞助的一次研讨会的成果。该研讨会汇聚了有机物降解以及基于替代指标的环境重建方面的专家。本文围绕研讨会的主题展开，即理解海洋沉积物中有机物（OM）的选择性降解/保存对化石记录解释的影响。特别关注以下方面：（A）有机物的分子组成相对于生物和物理沉积环境的影响，包括测定复杂有机生物分子的新方法；（B）有机物的选择性保存对海洋古海洋学和古气候重建替代指标解释的影响；（C）过去的海洋生产力以及沉积物中的选择性保存。似乎大多数影响有机物保存的因素已被确定，但它们起作用的许多机制只是部分地，甚至是零碎地被理解。有些因素甚至没有被仔细考虑。对有机物分解的这种不完全理解阻碍了对当前和过去碳循环的正确评估，以及对基于有机物的替代指标和受有机物分解影响的替代指标的解释。为了实现更好的基于替代指标的重建，需要考虑替代指标形成后与搬运和成岩作用相关的分子和原子变化的“变形函数”。一些新出现的有机物降解替代指标可能会阐明这种变形函数。将孢粉形态浓度和组合成分的选择性变化用作有机物生产和保存的模型，可以纠正由于选择性降解导致的偏差。这种对有机物降解的定量评估可能会导致对过去生产力和底层水含氧量更准确的重建。鉴于古气候研究中获取沉积岩芯的项目以及生成替代指标记录所涉及的成本和工作量，为这些记录的解释建立详细的沉积学和成岩背景似乎是明智的。关于后者，同时获取能说明替代指标特征保真度并揭示潜在成岩偏差的数据将具有明显的价值。
Abstract. The present paper is the result of a workshop sponsored by the DFG Research Center/Cluster of Excellence MARUM "The Ocean in the Earth System", the International Graduate College EUROPROX, and the Alfred Wegener Institute for Polar and Marine Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments. It appears that most of the factors influencing OM preservation have been identified, but many of the mechanisms by which they operate are partly, or even fragmentarily, understood. Some factors have not even been taken carefully into consideration. This incomplete understanding of OM breakdown hampers proper assessment of the present and past carbon cycle as well as the interpretation of OM based proxies and proxies affected by OM breakdown. To arrive at better proxy-based reconstructions "deformation functions" are needed, taking into account the transport and diagenesis-related molecular and atomic modifications following proxy formation. Some emerging proxies for OM degradation may shed light on such deformation functions. The use of palynomorph concentrations and selective changes in assemblage composition as models for production and preservation of OM may correct for bias due to selective degradation. Such quantitative assessment of OM degradation may lead to more accurate reconstruction of past productivity and bottom water oxygenation. Given the cost and effort associated with programs to recover sediment cores for paleoclimatological studies, as well as with generating proxy records, it would seem wise to develop a detailed sedimentological and diagenetic context for interpretation of these records. With respect to the latter, parallel acquisition of data that inform on the fidelity of the proxy signatures and reveal potential diagenetic biases would be of clear value.