Bulletin of the Geological Survey of Japan Top Page

Bulletin of the Geological Survey of Japan Vol.74 No.3 (2023)

Cover photograph | Table of Contents | Abstract

Cover photograph

North edge of the Hida Mountain Range seen from the Toyama Plain, Toyama Prefecture

　The Hida Mountain Range consist of Paleozoic and Mesozoic formations such as the Hida Belt, and contain high summits. The left summit in the photograph is Mt. Tsurugi (alt. 2,999 m) and the right summit is Mt. Dainichi (alt. 2,501 m). A series of hills is distributed between the Hida Mountain Range and the Toyama Plain. These hills are composed of marine sediments from the time when the Sea of Japan was formed in the Early Miocene. The Toyama Plaine has been supplied with an enormous amount of coarse-grained sediments originating from erosion of the uplifted Hida Mountain Range, leading to the development of a fan delta. (Photographing location: 36°43' 53.6" N, 137°20' 15.7" E)

(Photograph and Caption by NAGAMORI Hideaki)

Table of Contents

All the pages PDF ： 74_03_full.pdf ［17MB］

Title	Author	PDF
Article
14C ages for the Gotenba and Mabusegawa Debris Avalanche Deposits in the eastern foot of Fuji Volcano, Japan	YAMAMOTO Takahiro and KOBAYASHI Makoto (p107-118)	74_03_01.pdf [5.2MB]
Stratigraphic correlation of the Higashibessho, Tenguyama and Otokawa formations in the central to eastern area of Toyama Prefecture, central Japan	NAGAMORI Hideaki and WATANABE Mahito (p119-131)	74_03_02.pdf［2.1MB］
Report
Cumulative volume step-diagram for eruptive magmas of Towada Volcano	KUDO Takashi (p133-153)	74_03_03.pdf［8.3MB］
Constraint on the spatial distribution of the Early and Middle Jurassic units within the Nakatsugawa Complex of the North Kitakami Belt by detrital zircon U–Pb dating	OSAKA Masashi, AOKI Shogo, UCHINO Takayuki and FUKUYAMA Mayuko (p155-166)	74_03_04.pdf［4MB］

Abstract

¹⁴C ages for the Gotenba and Mabusegawa Debris Avalanche Deposits in the eastern foot of Fuji Volcano, Japan

YAMAMOTO Takahiro and KOBAYASHI Makoto

 We examined ¹⁴C dating and correlation of exotic tephra for newly obtained samples in the eastern foot of Fuji Volcano. Wood samples in the Gotenba Debris Avalanche Deposit (OYM201 and OYM201b) yielded ages of 2,490 ± 20 BP and 2,510 ± 20 BP, respectively, black soil immediately below the S-13 Pyroclastic Deposit (OYM202) were 2,860 ± 30 BP, black soil at the base of the Fuji Black Soil Layer (OYM203) yielded 8,520 ± 30 BP, and a wood chip in Mabusegawa Debris Avalanche Deposit (OYM205) were dated as 16,270 ± 50 BP. Felsic glass shards in the soil layer above the Mabusegawa Debris Avalanche Deposit were correlated with the Tachikawa Upper Glassy Ash. Based on the results, the Gotenba Debris Avalanche occured around 800 cal BC, and the Mabusegawa Debris Avalanche took place around 18,000 cal BC.

Stratigraphic correlation of the Higashibessho, Tenguyama and Otokawa formations in the central to eastern area of Toyama Prefecture, central Japan

NAGAMORI Hideaki and WATANABE Mahito

 The Cenozoic strata, excluding terrace deposits and alluvium, in the eastern area of the Hokuriku sedimentary basin, central Japan, consists of the Nirehara, Iwaine, Kurosedani, Higashibessho, Tenguyama, lower Otokawa, upper Otokawa, Mita and Kurehayama formations in ascending order. In this study, the stratigraphic correlations among the Higashibessho, Tenguyama and Otokawa formations in the Yatsuo area are examined in terms of the type area and the strata present in east of Yatsuo area. Nineteen samples for diatom fossil analysis were collected from the Kushida, Kitayama, Kurokawa and Hieda areas. The Shakusenji Formation in the Kurokawa and Kiyayama areas is correlated with the Denticulopsis lauta Zone (NPD4A). On the other hand, diatom fossils are not found in the Otokawa Formation．The following conclusions are obtained in this study. The Higashibessho Formation is correlated with the Shakusenji, Sasagawa and lower Sazen formations. The Tenguyama Formation is contemporaneous with the upper Sazen Formation, but heterotopic facies. The Lower Otokawa Formation is correlated with the Takabatake Formation but is not distributed east of Yatsuo area to the Kurokawa area. The Upper Otokawa Formation extends to the Hayatsuki River, but not further north.

Cumulative volume step-diagram for eruptive magmas of Towada Volcano

KUDO Takashi

 The cumulative volume step-diagram for eruptive magmas of Towada Volcano was prepared. The eruptive volume and age data were compiled from previous studies, and the deficiencies were supplemented in this report. Specifically, each eruptive volume and age of the distal tephras from the precaldera to the early caldera-forming stage was estimated using the author's original stratigraphic data and the isopach maps by previous research. This report shows the dataset for the cumulative volume stepdiagram for eruptive magmas of Towada Volcano and describes the precautions to be paid when using this dataset and the future tasks for improving this diagram.

Constraint on the spatial distribution of the Early and Middle Jurassic units within the Nakatsugawa Complex of the North Kitakami Belt by detrital zircon U–Pb dating

OSAKA Masashi, AOKI Shogo, UCHINO Takayuki and FUKUYAMA Mayuko

 Previous detrital zircon U–Pb and fossil studies of the terrigenous rocks in the southwestern unit (Nakatsugawa Complex) of the North Kitakami Belt have suggested that the unit was formed during the Early to Middle Jurassic. In this study, we additionally performed detrital zircon U–Pb dating of two sandstones in the southwest part of the Nakatsugawa Complex (sample OM-07 and OM-06) for constraining the spatial distribution of the Early and Middle Jurassic units of the complex. As a result, those two samples showed youngest cluster ages of the middle and late Early Jurassic (183.3 ± 1.0 Ma in OM-07 and 176.7 ± 1.6 Ma in OM-06), respectively. Combining data from this and previous studies, we conclude that the unit from the southwestern margin to the location of OM-06 in the complex was formed during the Early Jurassic, while its northeastern part was formed during the Middle Jurassic. Moreover, it seems that the Nakatsugawa Complex has been formed without a significant age gap.