妙高火山山麓における泥炭層の珪藻化石について

概要

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The building process of the Myoko volcano has been clarified by Myoko Research group in 1969. Then, plant remains were collected from the mud flow in the northern foot area in consequence of the breaking on the northern outside slope of the somma (mud II) for the determination of the absolute age by the use of 14C, and the numerical valve of 17,900±450 Y.B.P. years are resulted. In this paper, the analysis of the assemblage of fossil diatom found in eleven samples from the former peat deposit (30 cm in thickness) were treated, and 51 species of 21 genera were totally identified. The dominant and common species in them are Achnanthes lanceolata, Diploneis elliptica, Diatoma vulgaris, Meridion circulare Diatomella balfouriana, and all species showing low frequency in these assemblage may be characterized by rheophilious forms, which have ecological optimum in the running water and distribute comparatively in low water-temprature. From these results, the peat sediment examined are inferred to have been settled at the bottom of the lake or marsh of the low mountainland.
地学団体研究会の論文