Departmental Bulletin Paper 秋田県北部峰浜地域に分布する上部鮮新統〜下部更新統の浮遊性有孔虫化石層序
Upper Pliocene to lower Pleistocene planktic foraminiferal biostratigraphy from Minehama area in the northern part of Akita Prefecture, Japan

山﨑, 誠  ,  小松, 優子  ,  福永, 里実  ,  佐藤, 時幸  ,  YAMASAKI, Makoto  ,  KOMATSU, Yuko  ,  FUKUNAGA, Satomi  ,  SATO, Tokiyuki

36pp.9 - 14 , 2015-10 , 秋田大学大学院工学資源学研究科
Planktic foraminiferal biostratigraphy of the upper Pliocene to lower Pleistocene Tentokuji and SasaokaFormations distributed in the Minehana area located in the northern part of Akita Prefecture, Japan, is described indetail. Totally 44 samples were analyzed for this study. Based on calcareous nannofossil and plankticforaminiferal assemblages, the studied section includes the horizon of global cooling that was resulted fromNorthern hemisphere galaciation in the latest Pliocene. Globigerina bulloides and Globigerina quinquelobaoccurred throughout the studied section. Cold-water planktic foraminifera were generally observed in the middleto upper part of studied section. Especially, a polar to subpolar dweller, Neogloboquadrina pachyderma (sinistralcoiling variety), was found commonly just after global cooling at latest Pliocene while dextral coiling variety of thisspecies, which thrived in warmer water, were rare in the middle to upper part of the studied section. On the otherhand, tropical to subtropical species such as Globigerinoides ruber were also found at the upper part of the studiedsection. It indicates that the studied area seems to be covered by warm water in the early Pleistocene.

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