Holocene sedimentary history of some coastal plains in Hokkaido,Japan IV. Diatom assemblages in the sediments from Kushiro moor (2) |
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Authors: | Shigeru Kumano Masashi Ihira Yasuo Maeda Misako Yamauchi Eiji Matsumoto Isao Matsuda |
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Affiliation: | (1) Department of Biology, Faculty of Science, Kobe University, 657 Kobe, Japan;(2) Laboratory of Biology, Chiben Gakuen High School, 637 Gojo, Japan;(3) Department of Science Education, Faculty of Education, Yamagata University, 990 Yamagata, Japan;(4) The Yomiuri Press, 530 Osaka, Japan;(5) Water Research Institute, Nagoya University, 464 Nagoya, Japan;(6) Shiretoko Museum, 0999-41 Shari-cho, Japan |
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Abstract: | Diatom assemblages of sediments obtained from three sites on Kushiro Moor were analyzed to investigate the Holocene sedimentary history. The results showed that: 1) The Takkobu site was originally at the bottom of the paleo-Kushiro Bay, and after-wards the paleo-Takkobu Lagoon developed, became sealed off, and changed to a freshwater lake. The succession to peat moor probably began about 2000 yr B.P. at the Takkobu site. 2) The Tsurui site was originally at the bottom of the paleo-Kushiro Bay, then changed to the paleo-Kushiro Lagoon and became peat moor as a result of the first Holocene regression, which finished about 3600 yr B.P. The site then returned to a brackish lake again, probably due to the second Holocene transgression between 3600 and 3000 yr B.P., thereafter passing through brackish lake and freshwater lake stages, and eventually becaming peat moor at about 2000 yr B.P., 3) At the Chuo site, the second paleo-Kushiro Bay developed again as a result of the second Holocene transgression, which finished about 3000 yr B.P. Thereafter, brackish or freshwater lakes, rivers, and then peat moor developed in the central area of Kushiro Moor. 4) The second marine diatom zone (MD2 Zone), which indicates the second Holocene transgression, complete by about 3000 yr B.P., is detected only at the Chuo site in the central area of Kushiro Moor. |
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Keywords: | Diatom assemblages Holocene transgression Kushiro Moor Second marine diatom zone Sedimentary history |
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