Estimation of aeolian dust flux on Cheju Island, Korea, during the Mid- to Late Holocene

摘要

Aeolian dust flux was estimated from a maar sediment with bimodal grain-size distribution on Cheju Island, Korea, during the Mid- to Late Holocene. The bimodal grain-size distributions of chemically isolated aeolian quartz and lithogenic minerals were partitioned into fine and coarse components by a Weibull-function fitting method, and fine and coarse aeolian dust fluxes were estimated. Estimates of coarse dust flux (ECDF) during the last 6500 years varied from 2 to 14 mg/cm~2/yr and averaged 7 mg/cm~2/yr. ECDF were low during the period 6500-4000 cal yr BP, increased from 4000 to 2000cal yr BP, and decreased again from 2000 to 1000cal yr BP, indicating a millennial-scale variation. The estimates of fine dust flux (EFDF) varied from 1 to 11 mg/cm~2/yr with an average of 3 mg/cm~2/yr. The variation of EFDF was characterized by centennial-scale fluctuations. These results demonstrate that aeolian dust sediments in downwind areas, including Korea and Japan, were a mixture of fine and coarse dust components transported by the westerlies and winter monsoon surface winds, respectively. This suggests that these aeolian dust sediments should be interpreted in view of two dust components and two transporting winds.