Bulletin of the Geological Survey of Japan Top Page

Bulletin of the Geological Survey of Japan Vol.75 No.2 (2024)

Cover photograph | Table of Contents | Abstract

Cover photograph

Felsic tuff of the Shittakazawa Formation and a coral fossil in the Onimaru Formation, lower Carboniferous, South Kitakami Belt

The lower Carboniferous in the South Kitakami Belt consists mainly of mafic and felsic pyroclastic rocks interbedded with sandstone and mudstone in the lower to middle part, and coral-bearing limestone in the upper part. The former rocks show large regional differences in terms of lithology and thickness, whereas the limestone is of similar lithology throughout the belt. The main photograph shows felsic tuff (ca. 5 m thick) and underlying sandy mudstone of the Shittakazawa Formation in the lower part of the lower Carboniferous (location: Kashiwari in the Setamai area, Sumida Town, Iwate Prefecture). Zircons from this tuff have been dated at ca. 340 Ma (early Visean) (see this issue). The photograph at lower left shows a fossil Kueichouphyllum sp., indicating a late Visean age for limestone of the Onimaru Formation in the upper part of the lower Carboniferous (location: Yukisawa in the Yahagicho area, Rikuzentakata City, Iwate Prefecture). The lens cap for scale is 4 cm across.

(Photograph and Caption by UCHINO Takayuki and KAWAMURA Toshio)

Table of Contents

All the pages PDF ： 75_02_full.pdf ［16MB］

Title	Author	PDF
Report
Zircon U–Pb age constraints on the history of Carboniferous volcanism in the South Kitakami Belt, Northeast Japan	KAWAMURA Toshio and UCHINO Takayuki (p.61-72)	75_02_01.pdf [13MB]
"Ask AnyOne" Researcher Collaboration System: Design, Implementation, and Future Prospects	SHIRO Masanori, MIYAKAWA Ayumu, FUJITA Tsukasa, OCHI Masanao, IWASAKI Yuichi and YASUTAKA Tetsuo (p.73-81)	75_02_02.pdf［811KB］

Abstract

Zircon U–Pb age constraints on the history of Carboniferous volcanism in the South Kitakami Belt, Northeast Japan

KAWAMURA Toshio and UCHINO Takayuki

 Carboniferous strata of the South Kitakami Belt in Northeast Japan contain large volumes of volcaniclastic rocks that indicate intense volcanism. We conducted zircon U–Pb dating on samples collected from two stratigraphic horizons: coarse felsic tuff from the middle part of the lower Carboniferous Shittakazawa Formation, and sandy tuff from the middle part of the upper Carboniferous Kidoguchi Formation. The samples yielded weighted mean ages of 339.5 ± 2.6 Ma (middle Visean) and 313.6 ± 2.3 Ma (early Moscovian), respectively. The former age is more tightly constrained and slightly younger than the late Tournaisian age previously determined using fossil biostratigraphy and lithostratigraphic correlations. The latter age indicates that volcanism was ongoing throughout the late Carboniferous. Taking into account the occurrence of late Carboniferous granitic rocks and earliest Permian andesitic tuff in the South Kitakami Belt, our results suggest that igneous activity lasted from the Carboniferous to early Permian.

"Ask AnyOne" Researcher Collaboration System: Design, Implementation, and Future Prospects

SHIRO Masanori, MIYAKAWA Ayumu, FUJITA Tsukasa, OCHI Masanao, IWASAKI Yuichi and YASUTAKA Tetsuo

 This study proposes a new system, "Ask AnyOne", that aims to facilitate collaboration among researchers with diverse specializations within research organizations. This system enables researchers embarking on studies in new fields to ask questions about fields outside their expertise easily and receive responses from relevant experts quickly, thereby minimizing their burden. Recognizing the importance of collaboration among researchers with diverse specializations within research organizations and the need to address temporal and psychological costs, we focus on improving the shortcomings of existing systems. We analyzed the problems with existing systems and designed a system that allows collaboration through questions and answers. Subsequently, we verified the effectiveness and utility of the system through operational tests in a small-scale organization. In particular, we analyzed the trends of questions and answers and considered the effectiveness and prospects of the system. Our findings indicate that this system has the potential to facilitate communication and collaboration among researchers, thereby enhancing the quality and efficiency of research.