Diagenetic Processes and Authigenic Mineral Formation in Amazon Shelf Sediments

这项研究是AmasSeds项目（一个多- 亚马逊大陆架沉积物研究），该研究旨在 了解物理，化学和地质过程， 影响亚马逊大陆架上的粒子通量，或受其影响。 高颗粒通量发生在亚马逊大陆架上的结果， 来自亚马逊河的大量沉积物 潮汐作用下细颗粒陆架沉积物的广泛再悬浮 流程. 本研究的这一部分检查了铁和锰 发生在亚马逊内陆架泥浆中的还原反应。 的 Fe和Mn反应明显优于SO 4反应 结果是低有机碳， 中等富铁颗粒和大量非稳态 沉积和海底物理改造。 这些 性能促进非硫化物自生 矿物（铁碳酸盐，铁，铝硅酸盐）更典型的低 SO 4沉积物，强烈影响出口和储存， 成岩再活化过程中的微量/微量元素 铁载体相沉淀，抑制底栖生物群落 和含壳动物群，并有重大后果， 保存下来的沉积记录的性质。 这些 这些特征表明亚马逊大陆架可能与 铁矿石或绿砂形成的古老环境。 影响这些过程的变量之间的关系 将在亚马逊大陆架和三角洲大陆架地区进行调查。 通过了解化学相的形成过程， 沉积物沉积在这个河口，其他河流/海洋系统 可以更好地描述。 特别是铁和锰的减少， 发生在亚马逊内陆架泥浆的反应取决于 低有机碳、内陆架泥浆之间的平衡取决于 低有机碳、中等富铁颗粒、 大规模非稳态沉积和物理改造的 海底 原位沉淀物进入 历史地质记录将在亚马逊进行调查 陆架区和三角洲陆架区。

This research is part of the AmasSeds Project (A Multi- disciplinary Amazon Shelf Sediment Study), which seeks to understand the physical, chemical and geological processes that affect, or are affected by, particle fluxes on the Amazon shelf. High particulate fluxes occur on the Amazon shelf as a result of the enormous sediment discharge from the Amazon River and the extensive resuspension of fine-grained shelf sediment by tidal processes. This component of the research examines Fe and Mn reduction reactions occurring in Amazon inner shelf muds. The dominance of Fe and Mn reactions over SO4 reactions apparently results from a favorable balance between low organic C, moderately Fe-rich particles, and massive nonsteady-state deposition and physical reworking of the seabed. These properties promote the formation of nonsulfidic authigenic minerals (Fe-carbonates, Fe, Al-silicates) more typical of low SO4 deposits, strongly influence export and storage of minor/trace elements during diagenetic remobilization/ precipitation of Fe carrier phases, inhibit benthic communities and shell-bearing fauna, and have major consequences for the nature of the preserved sedimentary record. These characteristics suggest the Amazon shelf may be an analogue to ancient environments of ironstone or greensand formation. Relationships between the variables affecting these processes will be investigated in the Amazon shelf and delta-shelf region. By understanding the processes by which chemical phases of sediment are deposited in this estuary, other river/ocean systems can be better characterized. In particular, Fe and Mn reduction reactions occurring in Amazon inner shelf muds depend upon a balance between low organic C, inner shelf muds depend upon a balance between low organic C, moderately Fe-rich particles, massive nonsteady-state deposition and physical reworking of the seabed. The processes by which in situ precipitates enter the historical geological record will be investigated in the Amazon shelf and delta-shelf region.