Sedimentary accumulation and vertical mixing of diatom valves in coastal marine sediments in Omura Bay, western Japan

概要

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Taphonomic process of diatom valves was investigated with samples from a surface sediment core and a sediment trap above it in Omura Bay, western Japan. Extremely weak diatom valves of a coastal marine diatom, Chaetoceros affinis Lauder was considerably observed in the sediment core, whereas the other Chaetoceros species with weak valves like C. affinis rarely occurred even though they were found in trap samples. Biweekly sediment trap experiments revealed the season when each Chaetoceros species bloomed and deposited on seafloor. The observation suggests that the latest bloomed Chaetoceros valves (younger than 7-8 months) were preserved in the sediments. Vertical mixing of loose sediments by seawater movement and burrowing invertebrates seems to work within the depth of 5cm of surface deposits according to observation of sedimentary structures and stratigraphical distribution of C. affinis in the core. The diatom valves are well mixed in this layer within 4 weeks.
日本堆積学会の論文