Journal of the Japan Society of Engineering Geology

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5 boring cores were studied by using C/S analysis and ¹⁴C dating techniques, with the aim of elucidating the geological structure and sedimentary environment of Sarobetsu moor in the northern part of Hokkaido. Alluvium was divided into 4 groups, and the distribution of sand and gravel or clay strata with high continuity was estimated. On the basis of these results, the sedimentary environment of Sarobetsu moor was estimated as follows. Braided rivers and lakes were predominant during 10.5∼14.5 kyr BP, and there was a regression at 10.5 kyr BP. Floodplains were predominant during 8∼10.5 kyr BP. Barrier lagoons and tidal flats were predominant during 6.2∼8 kyr BP. Floodplains were predominant after 6.2 kyr BP. Tectonic movement was detected from the displacement of marine sediments. The main area of Sarobetsu moor subsided relative to the hilly area after 6.2 kyr BP. The rate of subsidence might be 1.5 mm/yr at the maximum. The region between the coastal area and the central part of Sarobetsu moor might subside relative to the eastern area during 6∼10 kyr BP.

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