The samples for diatom assemblage were selected at nine horizons from GC01 and GC04, respectively. The sediment treatment, slide preparation, and diatom counting were carried out at Jeonbuk National University. The quantitative analysis of the diatom slides was performed according to the procedure described in Scherer (1994). The absolute abundance was calculated as follows:Abundance = ((number of specimens counted × area of the settling chamber) / (number of microscope fields of view × area of the field of view)) ÷ sample mass. Chaetoceros resting spores were not included in specimen counting.