Petrographic properties of the acidic volcaniclastic deposits in the Omine Belt, western margin of the northern Fossa Magna region, central Japan

The Omine Belt (Kosaka et al. 1979) is lying from Otari to Matsumoto with 65km in length and 5～7km in width along the Itoigawa-Shizuoka Tectonic Line, which is the western manginal fault of the Fossa Magna region. The Omine Belt is burried up by a large amount of non-marine normal clastic and volcaniclastic sediments which ranges in age from Pliocene to early Pleistocene. Plio-Pleistocene strata in the Omine Belt are divided into the Otari and Omine Formations in ascending order. Volcaniclastic sediments of the Otari Formation are andesitic. On the other hand, most of volcaniclastic sediments of the Omine Formation are acidic. In this paper, acidic volcaniclastic sediments are collected and analised in petrographically. 9 samples of the Otari Formation and 64 samples of the Omine Formation are analised. The results are as follows 1) Acidic volcaniclastic sediments in the Omine Belt are made up largely by pumiceous vitric tuff and welded tuff in lithologically. 2) Most of welded tuff beds are rhyolitic petrologically in which biotite occur as main heavy minerals. 3) The Takagariyama tuff I ･ II, which are characterized by a dominance of orthorhombic pyroxene as heavy minerals, are correlative to the Nyukawa Pyroclastic Flow Deposits and Ebisutoge Pyroclastic Deposits in the Takayama Basin, west of Japan Alpus.Article信州大学理学部紀要 33(2): 87-106(1999)departmental bulletin pape

Comparative single-cell genomics of Atribacterota JS1 in the Japan Trench hadal sedimentary biosphere

Deep-sea and subseafloor sedimentary environments host heterotrophic microbial communities that contribute to Earth’s carbon cycling. However, the potential metabolic functions of individual microorganisms and their biogeographical distributions in hadal ocean sediments remain largely unexplored. In this study, we conducted single-cell genome sequencing on sediment samples collected from six sites (7,445–8,023 m water depth) along an approximately 500 km transect of the Japan Trench during the International Ocean Discovery Program Expedition 386. A total of 1,886 single-cell amplified genomes (SAGs) were obtained, offering comprehensive genetic insights into sedimentary microbial communities in surface sediments (<1 m depth) above the sulfate-methane transition zone along the Japan Trench. Our genome data set included 269 SAGs from Atribacterota JS1, the predominant bacterial clade in these hadal environments. Phylogenetic analysis classified SAGs into nine distinct phylotypes, whereas metagenome-assembled genomes were categorized into only two phylotypes, advancing JS1 diversity coverage through a single cell-based approach. Comparative genomic analysis of JS1 lineages from different habitats revealed frequent detection of genes related to organic carbon utilization, such as extracellular enzymes like clostripain and α-amylase, and ABC transporters of oligopeptide from Japan Trench members. Furthermore, specific JS1 phylotypes exhibited a strong correlation with in situ methane concentrations and contained genes involved in glycine betaine metabolism. These findings suggest that the phylogenomically diverse and novel Atribacterota JS1 is widely distributed in Japan Trench sediment, playing crucial roles in carbon cycling within the hadal sedimentary biosphere

Tephrostratigraphy of the Pliocene to Middle Pleistocene Series in Honshu and Kyushu Islands, Japan

The Pliocene to Pleistocene Series in each sedimentary basin or area of Japan has been investigated and described; however, their stratigraphic correlation is difficult because of complex geological structures. Regional stratigraphy has therefore been established using many intercalated tephra beds, i.e. by correlating tephra beds between distant areas. A standardized stratigraphic model of the Pliocene to Middle Pleistocene Series in Japan is put forward in this paper on the basis of tephrostratigraphy, magnetostratigraphy, and biostratigraphy. This stratigraphic model is important for studies of environmental changes and explosive volcanism in this period around the Japanese island-arc