Fission-track age of the volcanic ash layer in the Bisan-seto Group around the Bannosu region of the eastern parts of the Seto Inland Sea, Japan

Acheulean artefacts are widely known from archaeological complexes in India and commonly comprise handaxes, picks and cleavers. These provide information on human occupation and evolution across India, and have been the subject of much research on stone technology. In some of these sites, artefacts are associated with a Pleistocene volcanic ash layer derived from the Toba caldera in Sumatra, but various studies have derived a wide range of ages from this deposit leading to differing schools of thought as to the age of the tephra. Recent trace element, fission track and mineralogical studies (since 2011), have enabled accurate recognition of each Toba eruptive unit across their fall out, but these approaches continue to be overlooked in some studies where artefacts and Toba tephra co-exist in India. This leads to significant errors in tephra identification, and thus hampers any derived age interpretations. Most recently, this includes the study by Deo et al. (2021) who, in Geological Society Special Publication 515 (Tiwari et al., 2021), report ages for artefacts and tephra from two sites in the Deccan Volcanic Province which have become pivotal in many arguments, namely Morgaon and Bori. Here we address these issues and reiterate the methods for identification of the three main Toba tephra deposits.

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Fission-track dating data on fresh-water sediments for the study of land connection between the Asiatic continent and Lake Biwa through the Seto Inland Sea.

Proceedings of the Japan Academy Series B ◽

10.2183/pjab.62.377 ◽

1986 ◽

Vol 62 (10) ◽

pp. 377-380 ◽

Cited By ~ 2

Author(s):

Shoji HORIE

Keyword(s):

Fresh Water ◽

Lake Biwa ◽

Fission Track ◽

Seto Inland Sea ◽

Fission Track Dating ◽

The Seto Inland Sea

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Fission-Track Age and Correlation of the Takatsukayama Volcanic Ash Layer Distributed at the Western Foothills of the Rokko Mountains, Western Japan.

The Quaternary Research (Daiyonki-Kenkyu) ◽

10.4116/jaqua.38.411 ◽

1999 ◽

Vol 38 (5) ◽

pp. 411-417 ◽

Cited By ~ 4

Author(s):

Shigehiro Katoh ◽

Hiroshi Sato ◽

Takashi Matsubara ◽

Masayuki Hyodo ◽

Tohru Danhara

Keyword(s):

Volcanic Ash ◽

Fission Track ◽

Ash Layer ◽

Western Japan

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EVALUATION OF MOUNTAIN AREA AS NON-POINT SOURCE OF NITROGEN FOR SETO INLAND SEA: THE NORTHERN SHIKOKU REGION, JAPAN

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.31519/conferencearticle_5b1b9389d98135.84095825 ◽

2017 ◽

Author(s):

Shohei Morisawa ◽

Yukio Komai ◽

Takao Kunimatsu ◽

...

Keyword(s):

Average Concentration ◽

Point Sources ◽

Seto Inland Sea ◽

Mountain Streams ◽

Unit Load ◽

Mountain Areas ◽

Mountain Area ◽

The Seto Inland Sea ◽

Unit Load Method ◽

Important Position

The northern Shikoku region is located in the Western part of Japan and faces towards the Seto Inland Sea. The forest area, which is one of the non-point sources in the Seto Inland Sea watershed, occupies 75% of the land use in the watershed of the northern Shikoku region. The amount of loadings of nutrients and COD in the Seto Inland Sea has been estimated by the unit load method but actually the data has not been investigated. It is however, necessary to know the real concentration of nitrogen in mountain streams to evaluate the role which is the mountain area plays as non-point sources. Therefore, more water samples of mountain streams in the watershed need to be taken and the concentrations of nitrogen analyzed. The mountain streams in the northern Shikoku area were investigated from April, 2015 to November, 2015. The number of sampling sites was 283, in addition to the past data by Kunimatsu et al. The average concentration of nitrate nitrogen in Ehime, Kagawa, and Tokushima was 0.61mg/L, 0.78mg/L and 0.34mg/L, respectively. The environmental standard range for nitrogen in the Seto Inland Sea is from between less than 0.2mg/L and less than 1mg/L. Therefore, the average concentration of nitrogen in these regions was over category II, and those of mountain streams in Kagawa Prefecture exceeded category III. About 20% of mountain streams were more than 1mg/L. It has become clear that mountain areas occupy an important position as non-point sources for the Seto Inland Sea.

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