Geochemical Implications of the Hanam Riverine Sediments during the Last 2 ka in the NW South Korea(<Featured Article>Earth Surface Processes, Natural Disasters and Historical Environmental Changes)

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In Hanam area near the Han River of mid Gyeonggi province of NW South Korea, undisturbed core sediments of 1.65 m in length were chosen to know the geochemical implications by variations and characteristics of major oxides and rare earth elements (REE) during the last 2 ka. In stratigraphy, the sediments can be divided into three sections of unit 5, 6, and 7-surface soil, among which unit 5 of black peat can reflect the swamp environment. They reveal the ages of 1,990 to 1,660 yr BP by radiocarbon (<14>^C) data in unit 5, belonging to the Late Holocene. In XRD results, mineral constituents of them are quartz, plagioclase, k-feldspar, kaolinite, chlorite, illite and so on, which could be supplied from the basement rocks by primary or secondary except zircon. In variation of oxides, they show generally increasing or decreasing trends at lower and middle sections, which might be caused by small differences of constituent mineral contents, and generally no variations at upper one. Chemical index of alteration (CIA) for the sediments show the intensively weathered degree of 83.31-86.72. In molar A-CN-K and A-CNK-FM, they show densely plotted domains near apex A and A-FM, respectively. Chondrite-normalized REE patterns show enriched LREE and depleted HREE distribution with parallel and uniform trends. The geochemical implications can suggest that the sediments might have been derived mainly from the sedimentary processes by relatively homogeneous mixings of intensively altered material transported from the surrounding rocks in the area.
日本地形学連合の論文
2012-04-25

Geochemical Implications of the Hanam Riverine Sediments during the Last 2 ka in the NW South Korea(<Featured Article>Earth Surface Processes, Natural Disasters and Historical Environmental Changes)

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