The stratigraphy and transitions of sedimentary environments in the latest Pleistocene to Holocene incised valley fills in the Arakawa Lowland are revealed based on sedimentary facies, physical properties and chemical elements contents in the GS-SSS-1 core, Saitama City, Saitama Prefecture.
The sedimentary successions are composed of Pleistocene Shimosa Group (Unit 1), gravelly fluvial deposits (Unit 2), sandy fluvial deposits (Unit 3), salt marsh deposits (Unit 4), inner bay to delta front deposits (Unit 5) and salt marsh to back marsh deposits (Unit 6) in ascending order. The depositional units excepting Unit 1 are the latest Pleistocene to Holocene incised valley fills, indicating a transgression (Unit 2 to the middle part of Unit 5) followed by a regression (the upper part of Unit 5 to Unit 6). In a transverse section, borehole logs correlated with the GS-SSS-1 core show that the gravelly fluvial deposits, sandy fluvial deposits and salt marsh deposits fill the narrow axis of the incised valley under the Arakawa Lowland, the inner bay deposits extend over buried terraces, and the delta front deposits and the salt marsh - back marsh deposits cover the entire lowland.

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The buoyancy weighing-bar method is a new settling method of a particle size distribution measurement. Using this method, we measured the particle size distributions of the test powders standardized by Japanese Industrial Standards. The particle size distributions of the JIS Test Powders 1, class 4 (Talc), class 5 (Fly ash), class 8 (KANTO (Japanese) loam) measured using sodium pyrophosphate solution or ethanol as a dispersed liquid. The particle sizes of the JIS Test Powders 1, class 4 (Talc) and class 8 (KANTO (Japanese) loam) could be measured from 5 to 75μm in 2 h of measuring time. The particle size distribution of JIS Test Powders 1, class 4 (KANTO (Japanese) loam) measured by this method was close to those measured by the other settling methods and the laser diffraction/scattering method. However, the particle size distributions of the JIS Test Powders 1, class 4 (Talc) and the JIS Test Powders 2, No. 4 (White fused alumina) measured by this method were different from those measured by the laser diffraction/scattering method. There is no effect of the particle concentration on the particle size distribution when the particle concentrations of the JIS Test Powders 2, No. 4 (White fused alumina) are 10kg/m³ or less.

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