北八甲田山における更新世末期以降の火山灰層序と植生変遷

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Ten characteristic tephras since Latest Pleistocene time were recognized in the North Hakkoda Mountains. Tephras HK-a, -b, -f, -i and -j of them were correlated to the previous reported Tomakomai ash (Tm), the upper fall unit of Towada-a ash fall (To-a), Chuseri pumice(Cu), Hachinohe pumice(HP) respectively. Tephra HK-i was correlated to the pumice-flow tuff(HPf) of the upper part of HP. The local pollen assemblage zones in four sites, Yachi, Tashiro and Kenashitai moors and Jigokunuma, were identified and correlated based on their stratigraphy and chronology. In ca. 12, 000-8, 500 years B. P., two transitional forest stages from the Latest Pleistocene subarctic coniferous to the Holocene cool-temperate Fagus forests, i.e., the Betula or Alnus forest stage and the deciduous broad-leaved forest one mainly characterized by plentiful Quercus (Lepidobalanus) in ascending order. In the latter half of the Betula or Alnus forest stage, a temporary expansion of the subarctic conifers was recognized. Fagus spread out rapidly since ca. 8, 500 years B. P. In the altitudes over ca. 1, 100m, subarctic Abies mariesii began to expand in ca. 5, 000 years B. P.
日本第四紀学会の論文