• Journal of the Korean Geographical Society
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• v.39 no.3
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• pp.425-443
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• 2004

Fluvial terraces is poorly developed along Bukhan River in Central Korea. Altitude from riverbed of T1 terraces are 18-29m, T2 terraces 2539m, respectively. Rubification index of T2 is 0.66, T1 is 0.54, and thickness of gravel weathering rind on gneiss of T2 are 14.0mm, granites of T2 are $\infty$, gneiss of T1 are 5.0mm and granites of T2 are 8.0mm, because weathering in deposits of T2 terraces, older than T1, is severer than T1 terraces. Since deposits in T2 have more active and longer weathering than T1, SiO$_2$/Al$_2$O$_3$ is 3.32 in T2 and 4.06 in T1, and SiO$_2$/R$_2$O$_3$ is 2.64 in T2 and 3.19 in T1. CIA(Chemical Index of Alteration) is 87.85％ in T2 and 85.88％ in T1. Kaolinite and halloysite are founded in deposits of T2 indicating high weathering, and are founded gibbsite made tv eluviation of kaolinite. However, deposits of T1 have no kaolinite, and are found plagioclase, weak mineral in weathering process. Comparing to previous researches by estimated age as altitude from riverbed, rubification index, thickness of gravel weathering rind, element contents and mineral composition, forming age of T2 terraces in Bukhan River are estimated in marine oxygen isotope stage 6 (130-190ka), and T1 terraces are marine oxygen isotope stage 4(59-74ka).

• Journal of the Korean Geographical Society
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• v.39 no.1
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• pp.27-44
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• 2004

Upper reach of Soyang River at the northernmost area around Taebaek Mountains in South korea is profitable area to understand paleo-environment during the Quaternary such as tectonic process and climate change in the Korean Peninsula. This study explained paleo-environment affect to channel development by geomorphic distribution and characteristics of terrace surfaces, and analysis of deposits at 58 fluvial terraces in upper reach of Soyang River. Fluvial terraces were classified from T1 to T6. Most terraces are distributed on the point bar in meandering channel and one side along river valley. Terraces tend to decrease in number and superficial dissection rate to be higher and channel slope to be steeper if it takes long time from T1 to 6. The paleo-channel of Soyang River is supposed to be stronger meandering in period of T2 than T3. The weathering rind of gravel is generally thicker in older terrace, however, differs by contents of water and air in deposits. Based on the data of stratigraphy, grain size analysis, pollen analysis and rubification index in deposit, formation age of T5 terrace in Soyang River are estimated in MIS(Marine Oxygen Isotope Stage) 10, and T2 terrace are estimated in MIS 6.