Using end-member analysis to determine sediment dispersal and depositional processes on the Heuksan mud belt, southwest Korean shelf

Abstract

Due to the large volume of the Heuksan mud belt (HMB), the source of the mud and the depositional processes involved have been controversially discussed over the past two decades. To illuminate the issue, an end-member analysis (EMA) was applied to the grain-size data of 74 surficial samples in order to determine the sediment dispersal pattern on the HMB. In addition, a sedimentary facies analysis was carried out to serve an interpretation of depositional processes. Five grain-size end-members (EMs) were identified. Their dominant modes are 1.4 (EM1), 2.4 (EM2), 3.9 (EM3), 5.6 (EM4), and 7.3 ϕ (EΜ5). The EM3 and EM4 are mainly found on the inner shelf, their distribution decreasing from proximal to distal. On the middle shelf, where tidal rhythmites are found, the end-member scores show a mixture of EM4 and EM5, implying that these are good proxies for tidal influence. The distribution of EM4 decreases gradually from proximal to distal, whereas the finest end-member (EM5) increases toward the distal region. It indicates the outcome of progressive size-sorting with distance from the source area. As such, EM4 and EM5 can be interpreted to have been derived from Korean rivers. Previous geochemical and clay mineral studies suggested that sediments were partly supplied from Chinese rivers. The differences between the sedimentological and geochemical results suggest that the sediments may have been redistributed by tidal currents. Consequently, the end-member modeling of grain-size distributions of sediments from the western shelf of Korea has allowed the identification of the main sediment dispersal and depositional mechanisms.