著者

石塚 利孝 鹿島 薫

出版者

公益社団法人 日本地理学会

雑誌

地理学評論 Ser. A (ISSN:00167444)

巻号頁・発行日

vol.59, no.4, pp.205-212, 1986-04-01 (Released:2008-12-25)

参考文献数

4

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Lake Ogawara is located in the eastern part of Aomori Prefecture, north Japan. The authors obtained the Holocene lake sediments by all-cored borings at two sites of lake-side lowland, and presumed the Holocene water level changes of Lake Ogawara through diatom analysis of the sediments. At the Loc. A near the Chushi (I) shell-mound site formed early to middle Jomon period, the succession of three diatom zones can be subdivided. Zone I (-1.8_??_+1.0m); marine species constitute about 90%, and Paralia sulucata, Diploneis smithii are dominant. Zone II (+1.0_??_+2.6m); the rate of marine species decreases from lower to upper horizon, and Cyclotella striata v. subsalina, which lives in brackish lagoon, is dominant. Zone III (+2.6_??_+5.0m); fresh water species accounts for more than 90%, and marine species cannot be observed. Navicura radiosa, Fragilaria construens and Eunotia veneris are dominant. At the Loc. B near Futatsumori shell-mound site formed early to middle Jomon period, the succession of three diatom zone can be subdivided. Zone I (-0.5_??_-0.0m); Cyclotella striata v. subsalina accounts for about 50%. Zone II (0.0_??_+3.0m); fresh water species constitute more than 90%. Navicula radiosa, Melosira ambigua, which live in fresh-water pond, are dominant. Zone III (+3.0_??_+5.0m); fresh water species constitute more than 90%. But Eunotia veneris, which lives in a boggy environment, is dominant. On the basis of the result of diatom analysis, 14C date and tephrochronology, water level of Lake Ogawara was 2m higher than that of present about 4, 500_??_5, 000 y. 8. P., and it had lowered to the same level as present till 3, 500 y. B. P.. Since then water level has been stable.