沉积物
地质学
海床
总有机碳
淤泥
大陆架
海洋学
锰
沉积岩
海底扩张
河流
地球化学
地貌学
环境化学
构造盆地
有机化学
化学
作者
Moutusi Roy,James McManus,Miguel A. Goñi,Zanna Chase,Jeffry C. Borgeld,Robert A. Wheatcroft,Jesse M Muratli,Meghan Megowan,Alan C. Mix
标识
DOI:10.1016/j.csr.2012.12.012
摘要
We examined the spatial distribution of sedimentary reactive iron (FeR) and manganese (MnR) along the continental shelf near the mouth of the Umpqua River, Oregon (USA). A well-defined muddy (silt+clay) depocenter of fluvial origin characterizes this part of the Oregon margin. Reactive Fe and Mn contents are elevated within the silt-rich landward edge of the depocenter. Away from this depocenter, sediments are predominantly sandy both along the inner-shelf (<∼100 m depth) and mid-shelf (∼100–150 m depth) and have lower concentrations of reactive metals compared to the depocenter. Sediments are also muddy along the slope (>∼150 m depth) and have elevated FeR and MnR. Based on their correlation with sediment grain size, it appears that FeR and to a lesser extent MnR, are associated with mud size sediments. Reactive metal concentration is also positively correlated with organic carbon (OC) content, indicating a potentially common source. Seabed sediments from five other small, mountainous river systems (Klamath, Eel, Navarro, Russian, and Salinas) located south of Umpqua show the same general relationship between FeR and OC. Although both FeR and MnR exhibit similar relationships to grain size and OC, the relationships with MnR exhibit considerable scatter. Comparison of Umpqua River suspended sediment data with the seabed data suggests that MnR is more prone to loss from sediment particles during transit to the seabed as compared to FeR, and this difference explains why FeR maintains a reasonably tight relationship with organic carbon and particle size along the seafloor relative to MnR.
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