This paper forms an overview of Japanese tephrochronology with emphasis on the role of distal tephras in Quaternary studies. Recent developments in tephra characterisation techniques and dating methods have provided fruitful results in the correlation and identification of many Japanese tephras. Since the middle 1970s, many distal tephras have been discovered occurring both in the Japan islands and the surrounding seas. This has resulted in the introduction, revision and refinement of regional stratigraphy, the application of tephra in determining the nature and effects of explosive eruptions, and new applications to many aspects of Quaternary studies. Ongoing tephra research is fed into tephra catalogue for the Japan region giving fundamental data for land–sea correlation and for establishment of chronostratigraphic framework for Japanese Quaternary studies.

The stratigraphy, chronology and distribution of distal marker-tephras in and around Japan

Many widespread Quaternary tephras have been identified in and around Japan. Recent developments in tephra characterization and dating methods have provided a regional stratigraphic framework for Quaternary studies as well as for determining the nature and effects of explosive eruptions. This paper stresses on the importance of tephra catalog compilation and shows a simplified example from Japan.

https://www.jstage.jst.go.jp/article/jaqua1957/38/3/38_3_194/_pdf

Quaternary widespread tephra catalog in and around Japan : Recent progress

Summary 1 The influence of tephra (aerially transported volcanic ejecta) on mire vegetation was investigated in a field experiment at Sarobetsu Mire, northern Hokkaido, Japan, which simulated relatively thin, widespread tephras. It was carried out in the centre of a raised part of the mire in a Carex middendorffii ‐ Sphagnum papillosum community. 2 We tested the effects of varying tephra layer thickness, grain size and season of the simulated tephra impact. 3 Vegetation surveys and analyses of the mire pore water were carried out before and 1 and 2 years after tephra application. Redox potential, oxygen saturation and sulphide concentration were measured in the surface layer of selected plots after 10 months. 4 Pore water chemistry and oxygen saturation changed significantly in some treatments. Some plant species disappeared from certain treatments after tephra application, but the majority survived. Colonization by non-mire species played a significant role in only one treatment. Mosses were more strongly affected by the disturbance than vascular plants. 5 Tephra had stronger effects on the vegetation when layers were thicker, were more fine-grained and when applied at the beginning rather than at the end of the growing season. 6 Moderate tephra deposition is unlikely to cause long-term changes in mire development. Subsequent succession depends on properties of the tephra, on the vegetation type (e.g. life-forms) and on the season, but the original vegetation will probably recover even where the moss layer is severely damaged, as Sphagnum spp. can re-establish by growing through tephra at least up to 6 cm thick.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.0022-0477.2004.00901.x

Effects of tephra deposition on mire vegetation: a field experiment in Hokkaido, Japan

Field stratigraphy and macrofossil composition of four mires in Hokkaido, northern Japan, were investigated to test whether tephra deposition induces long-term vegetation shifts. Macroscopic tephras of known origin ranging from 0.5 to > 25 cm in thickness were found in two or more of the study sites, allowing correlation of the stratigraphic development of the mires. Major peat types and position of macroscopic mineral layers were determined in the field, and selected cores were analysed by quantitative macrofossil analysis. Some macrofossil groups and the content of unidentifiable organic matter showed changes in the vicinity of tephra layers, but they did not indicate a clear response pattern of the vegetation or the decomposition dynamics of plant material. Mosses were expected to be most strongly affected by tephra deposition, but even in cases where tephra fell on Sphagnum-dominated vegetation, no fundamental shifts to new plant communities were found. This suggests that disturbance by widespread tep...

F. Arai

Papers

Catalog for late Quaternary marker-tephras in Japan II - Tephras occurring in Northeast Honshu and Hokkaido -