Formation ages of Late Quaternary alluvial fans in the southern Korean Peninsula

초록

The alluvial fans, Quaternary fluvial landforms, are formed on various scales in the southern Korean Peninsula, and large alluvial fans with an area of more than 2 km2 are distributed at 34 sites. The alluvial fans in mid-latitude moist climate areas, such as the southern Korean Peninsula, are mainly caused by flash floods and landslides caused by heavy rains and typhoons. As a result of analyzing the formation period of the 38 sites where OSL (optically stimulated luminescence) age dating was performed in the southern Korean Peninsula, the main periods of the alluvial fan formation appeared in 28~32 (late MIS (marine oxygen isotope stage) 3), 42~48 (early MIS 3), 66~74 (early MIS 4), 86~91 (MIS 5b), and 110~117 (MIS 5d), and the peak ages were 28, 48, 70, 90, and 114 ka. This period generally corresponds to the period of cool and temperature drop. The time ineterval of the peak age of the alluvial fan formation has a 20~24 ka, which coinsides with the fluctuation cycle of East Asia summer monsoon of 23 ka. In addition, peak ages generally coincide with the period of increase in the intensity of the East Asian summer monsoon. Therefore, it is estimated that the late Quaternary formation period of the alluvial fans in the southern Korean Peninsula is closely related to the increase in the intensity of the East Asian summer monsoon, which can cause strong flash floods and landslides.

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