Abstract: Samples obtained from a gravity core from Prydz Bay were pretreated by the removal of biogenic silica. Sediment grain size and volume percentages of particles of different sizes were measured; results between treated and untreated samples were compared. Main grain size distribution of biogenic silica in the sediments of Prydz Bay is <3Φ, 5.25—7.25Φ, and 8.75—9.75Φ. We conducted a correlation analysis on the grain size parameters and the percentage content of each component obtained from the two sets of experiments, and inferred that biogenic silica has little influence on the average particle size, sand, silt and clay fractions in the sediment, but has a clear influence on the sorting, skewness and kurtosis of grain size distribution; as a result, in untreated samples, measured particle size is larger than actual particle size. Study results indicate that removal of biogenic silica from sediments is a prerequisite for grain size studies and provenance analyses in polar regions.

Key words: Grain size, Biogenic silica, Pretreatment methods, Prydz Bay