Initiation of alpine grassland and wet meadow soils on snowy high mountains in central japan : a tephrochronological estimate

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Initiation ages of peaty and mucky soils on snowy high mountains in central and northern Honshu, Japan, were estimated by tephrochronology and radiocarbon dating. Three typical snowy mountains, Chokai, Gassan and Tairappyo, were selected. To identify tephras in such soils, their stratigraphy and lithofacies were investigated. Petrographic characteristics such as mineral composition and refractive indices of volcanic glass shards and phenocrysts of each tephra were also examined. Principal time-marker tephras identified were as follows: the Asama-Kusatsu or the Asama-YP (ca. 16000 cal yr BP), the Kikai-Akahoya (ca. 7200 cal yr BP), the Myoko-Akakura (ca. 6600 cal yr BP), the Myoko-Otagirigawa (ca. 4700 cal yr BP), the Towada-Chuseri (ca. 6300 cal yr BP), etc. The Pleistocene tephra was found only in basal sand and gravel layers underlying upper soils. Conversely, the Holocene tephras were usually identified in upper soils. Samples from the basal part of humic soils were dated as about 11000, 10000 and 7800 cal yr BP. Occurrence of the time marker tephras in these soils and radiocarbon dates indicate that alpine humic soil formation did not occur at the latest stage of the last glacial in the study mountains. Atmospheric warming and humidification after the Younger Dryas termination (ca. 11000 to 10000 cal yr BP) would have caused new formation of such soils. Alpine grassland and wet meadow soils have been formed since the early to mid Holocene.
首都大学東京の論文

Initiation of alpine grassland and wet meadow soils on snowy high mountains in central japan : a tephrochronological estimate

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