Island Arc最新文献

{"title":"Sulfur-rich mafic magma injection into the felsic magma chamber beneath Asama volcano, central Japan: Records in olivine-hosted melt inclusions from the Itabana and Tenmei eruptions","authors":"Yoshiaki Yamaguchi,&nbsp;Andreas Auer,&nbsp;Isoji Miyagi","doi":"10.1111/iar.12505","DOIUrl":"https://doi.org/10.1111/iar.12505","url":null,"abstract":"<p>Even though no basalts have erupted at Asama volcano, its large, felsic magma chamber standing beneath the summit is frequently replenished by cryptic injections of mafic magma of basalt-basaltic andesite composition. This mafic magma is preserved within melt inclusions trapped in olivine phenocrysts collected from the old Itabana pumice of the Kurofu stage and the Tenmei pumice of the current Maekake stage. The trapped mafic melts provide a detailed and vivid record of cryptic mafic magma injection into the felsic chamber where they admix to erupt andesite magma. The main phenocrysts of plagioclase, orthopyroxene, and clinopyroxene, commonly seen in the erupted products, are derived from the felsic magmas and trapped felsic melts of dacite-rhyolite compositions, containing low sulfur contents (0.3 wt% of SO₃ or less; most are lower than 0.10 wt%). In contrast, the mafic melts, entrapped by olivine phenocrysts, show high concentrations of SO₃, up to 1.06 wt% for Itabana and SO₃ 0.65 wt% for Tenmei. In addition, the olivine phenocryst commonly encloses early crystalline phases precipitated from the sulfur-rich mafic magma, such as Cr-spinel, Mg-rich orthopyroxene, Fe, Cu, and Ni-bearing sulfides, and often Al-rich clinopyroxene. The olivine-hosted mafic melt inclusions always contain numerous vesicles. Furthermore, they are often included as hourglass-shaped trapped melts, exhibiting snapshots of intense foaming and gas phase exsolution during the olivine growth and probably in the process of the cryptic injection into the felsic magma beneath the Asama summit. Our new data contributes to a better understanding of the magmatic system of the Asama volcano but also highlight the importance of the “Excess sulfur problem”, especially concerning the 1783 Tenmai eruption, which was contemporary to the Laki Fires.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138432357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microfungi associated with dying <i>Euphorbia mauritanica</i> in South Africa and their relative pathogenicity.","authors":"S Marincowitz, N Q Pham, B D Wingfield, F Roets, M J Wingfield","doi":"10.3114/fuse.2023.12.04","DOIUrl":"10.3114/fuse.2023.12.04","url":null,"abstract":"<p><p><i>Euphorbia mauritanica</i> is a succulent shrub that is indigenous to South Africa and widely distributed throughout the country. Dying plants have been observed in their natural habitat in the Northern and Western Cape Provinces of South Africa in recent years. Stems displaying lesions were collected and the emerging cultures were identified based on ITS, LSU, <i>ACT</i>, <i>RPB2</i>, <i>TEF1</i> and/or <i>TUB2</i> sequence data. Four filamentous fungi were consistently observed and isolated. One was identified as <i>Alanphillipsia</i> (<i>Ala.</i>) <i>aloes</i>, and the other three were new to science and are described here as <i>Cytospora euphorbiicola sp. nov</i>., <i>Nothomicrosphaeropsis namakwaensis sp. nov</i>. and <i>Austrophoma</i> (<i>Aus</i>.) <i>euphorbiae gen. et sp. nov.</i> These new species and <i>Ala. aloes</i> were the most commonly encountered, and their pathogenicity was tested on <i>E. mauritanica</i> plants in a greenhouse trial. All four species gave rise to lesions that were significantly larger than those associated with the controls, but they were not significantly different to each other. Although the lesions associated with the inoculations were well-developed, they did not give rise to plant death, suggesting that they are not responsible for the large-scale die-off of <i>E. mauritanica</i> in the field. The primary cause of the death of <i>E. mauritanica</i> in the studied area remains unknown and could be due to environmental factors such as has been found with the die-off of <i>Euphorbia ingens</i> in South Africa. <b>Citation:</b> Marincowitz S, Pham NQ, Wingfield BD, Roets F, Wingfield MJ (2023). Microfungi associated with dying <i>Euphorbia mauritanica</i> in South Africa and their relative pathogenicity. <i>Fungal Systematics and Evolution</i> <b>12</b>: 59-71. doi: 10.3114/fuse.2023.12.04.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"10 1","pages":"59-71"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10976952/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80081495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"X-ray computed tomography of deep-sea clay as tools to detect rare earth elements and yttrium enrichment","authors":"Yoichi Usui,&nbsp;Kazutaka Yasukawa,&nbsp;Koichi Iijima,&nbsp;Hideaki Machiyama,&nbsp;Yuji Ichiyama,&nbsp;Erika Tanaka,&nbsp;Koichiro Fujinaga","doi":"10.1111/iar.12503","DOIUrl":"10.1111/iar.12503","url":null,"abstract":"<p>Pelagic clay that contains rare-earth elements and yttrium (REY) at over 2000 ppm (termed “highly REY-rich mud”) has been reported from a few areas in the western North Pacific Ocean through focused geochemical analyses. Those REY are carried by biogenic calcium phosphate, suggesting that the formation of highly REY-rich mud involves enhanced biological productivity. However, detecting REY enrichment in sediment is time-consuming, and the global significance of the formation of REY-rich mud is still under debate. Here we perform x-ray computed tomography (CT) analyses on cores recovered around Minamitorishima Island and demonstrate the positive correlation with highly REY-rich mud and high CT numbers of the sediment. The variation of the CT number matches the wet bulk density. Further quantitative analyses using direct measurements of density and geochemistry suggest that a grain density increase and a porosity decrease due to the REY-carrying biogenic apatite are essential to explain the high CT numbers in the REY-enriched layer. While the chemical composition itself is of minor importance to elevate the CT numbers, our results suggest that x-ray CT can be a proxy for highly REY-rich mud.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135157648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topography, sedimentology, and biochronology of carbonate deposits on seamounts in the JA area, northwestern Pacific Ocean","authors":"Yasufumi Iryu,&nbsp;Hikari Hino,&nbsp;Hideko Takayanagi,&nbsp;Tokiyuki Sato,&nbsp;Nobuyuki Okamoto,&nbsp;Akiko Suzuki,&nbsp;Yuho Fujimaki,&nbsp;Akira Usui","doi":"10.1111/iar.12501","DOIUrl":"https://doi.org/10.1111/iar.12501","url":null,"abstract":"<p>Sedimentological and biochronological analyses were undertaken on carbonate deposits from 20 seamounts belonging to the Marcus–Wake Seamount Group, the Magellan Seamounts, and the Marshall Islands Seamounts in the JA area, northwestern Pacific Ocean. Deposition of carbonates on the JA seamounts varied markedly with age. The oldest carbonate deposits are Lower to middle Cretaceous shallow-water limestones containing mollusks (including rudists), scleractinian corals, and calcareous sponges. Upper Cretaceous and Paleocene carbonates are rare, and no Oligocene carbonates may exist. In contrast, Eocene foraminiferal packstones are widespread, and Miocene–Pleistocene foraminiferal ooze covers the JA seamounts. The limited occurrence of Paleogene carbonate deposits on the JA seamounts is consistent with global observations (i.e., a paucity of Paleogene carbonates). The Cretaceous–Eocene carbonates have been phosphatized, whereas Miocene and later limestones have not. This fact, along with the results of previous studies, suggests that carbonate rocks on seamounts were phosphatized globally during the Oligocene. Upwelling of nutrient-rich bottom waters during this time is likely responsible for the limited occurrence of Oligocene carbonate rocks on the JA seamounts. The thicknesses of the pelagic caps, which consist mainly of Miocene and younger foraminiferal oozes, varies among the seamounts and depends at least partly on the topography of the top of the seamount.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50143244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Cretaceous–Paleogene terrestrial sequence in the northern Kitakami Mountains, Northeast Japan: Depositional ages, clay mineral contents, and vitrinite reflectance","authors":"Atsushi Noda,&nbsp;Kazuya Morimoto,&nbsp;Koji U. Takahashi,&nbsp;Tohru Danhara,&nbsp;Hideki Iwano,&nbsp;Takafumi Hirata","doi":"10.1111/iar.12500","DOIUrl":"https://doi.org/10.1111/iar.12500","url":null,"abstract":"<p>Forearc basin deposits on continental margins contain important information that can be used to reconstruct the tectonic setting, volcanism, and climate at the time of their deposition. Coal-bearing terrestrial to shallow marine strata in Northeast Japan were deposited in a forearc basin along the Eurasian continental margin during the Cretaceous–Paleogene. The rocks exposed in the Kado district, Iwate Prefecture, in the northern Kitakami Mountains include the Upper Cretaceous Yokomichi Formation and the Paleogene Kogawa Group; the latter is known for high-quality refractory clay (kaolin clay). However, their stratigraphy and sedimentological characteristics are not yet fully understood. To reconstruct the formation and filling of the basin, we investigated field observations, U–Pb dating of tuff samples, XRD analysis of tuff and mudstone samples, and vitrinite reflectance of coal samples in this sequence. The U–Pb ages of the Yokomichi Formation and the Kogawa Group are ∼86 Ma and 58–52 Ma, respectively. The U–Pb age of the kaolin-dominated tuffaceous rock (“red rocks”) is 56.1 ± 0.2 Ma. The mean random vitrinite reflectance (VR_r) ranges from 0.37% to 0.53% through the sequence. We propose the following sequence for the formation and filling of the basin. (1) The basin initially formed during the Coniacian–Santonian (Late Cretaceous) and was filled by fluvial–lacustrine sediment. (2) These sediments kept the shallow burial depths during a ∼28 Myr and made a hiatus (86–58 Ma). (3) The basin was reactivated and covered by tuffs during the Thanetian, and the tuffs were altered to kaolin clay during the Paleocene–Eocene Thermal Maximum. (4) The basin was filled rapidly by alluvial fan deposits and subsided &lt;2300 m (assuming a geothermal gradient of &gt;30 K/km). (5) The basin was uplifted and exhumed at a rate of &gt;50 m/Myr faster than the mean exhumation rate of the Kitakami Mountains since the Paleogene.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50141189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation of methane hydrate formation in coarse- to fine-grained sediments in the Nankai Trough, Japan","authors":"Chao Xu,&nbsp;Hitoshi Tomaru","doi":"10.1111/iar.12502","DOIUrl":"https://doi.org/10.1111/iar.12502","url":null,"abstract":"<p>The properties of host sediments and pore water considerably affect both the occurrence and formation processes of methane hydrate. In coarse-grained layers, hydrates are generally concentrated preferentially in the pore space, and their formation is influenced by pore water salinity. To understand how geophysical and geochemical factors control the distribution of methane hydrates, we conducted numerical simulations using a one-dimensional flow model under different reservoir and fluid conditions in the Kumano Forearc Basin, Nankai Trough, Japan. Assuming an estimated range of methane flux between 0.002 and 1.9 kg m⁻² year⁻¹, three flow scenarios were considered. When the methane flux was relatively small, the results coincided with the observed hydrate distribution. In general, a low-methane flux decreases the hydrate saturation upward from the bottom of the methane hydrate stability, whereas a high-methane flux increases the saturation downward. These results also suggest that the sediment structure, such as the fracture distribution, influences the sediment stress conditions and constrains the flow regime. We further examined the effects of permeability changes in the heterogeneous lithological units on the simulation results using typical permeabilities of 10⁻¹³ m² for sand and 10⁻¹⁵ m² for mud. The results showed that hydrate saturation sharply increased and decreased in adjacent high- and low-permeability units, respectively. The consideration of complex stratigraphic conditions and variable fluid configurations provides an understanding of the environmental factors controlling hydrate generation and distribution, which is important for hydrate resource extraction and geohazard prevention.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50152544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of mantle carbonation in trench outer-rise region in the global carbon cycle","authors":"Ikuo Katayama,&nbsp;Keishi Okazaki,&nbsp;Atsushi Okamoto","doi":"10.1111/iar.12499","DOIUrl":"10.1111/iar.12499","url":null,"abstract":"<p>A nearly balanced carbon budget between subduction input and degassing output has likely controlled the long-term surface environment and habitability of Earth throughout geological history. However, the ongoing extensive hydration and carbonation of the mantle in trench outer-rise regions may affect the global carbon budget. In this study, we show that the carbon content of the lithospheric mantle can be inferred from geophysical data and thermodynamic modeling. Based on the seismic velocity anomaly in trench outer-rise regions, we estimated that the total carbon flux due to mantle carbonation is 7–31 Mt C/year, with possible fluid-to-rock mass ratios of 250–1000. These values are similar to the carbon uptake by altered oceanic crust, indicating that mantle carbonation has a significant effect on the subduction carbon budget. Although there are large uncertainties on the estimates of the subduction and degassing carbon fluxes, secular cooling of the mantle leads to the development of outer-rise faults associated with bending of the oceanic lithosphere and increased mantle carbonation, which may disrupt the self-regulating system of the global carbon cycle on geological timescales.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12499","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44466960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The proximal volcaniclastic materials of Fukutoku-Oka-no-Ba in the Izu-Bonin arc show contrasting characteristics to the drift pumice of the 2021 eruption","authors":"Kenta Yoshida,&nbsp;Yoshihiko Tamura,&nbsp;Tomoki Sato,&nbsp;Erika Tanaka,&nbsp;Noriko Tada,&nbsp;Morihisa Hamada,&nbsp;Takeshi Hanyu,&nbsp;Qing Chang,&nbsp;Shigeaki Ono","doi":"10.1111/iar.12498","DOIUrl":"10.1111/iar.12498","url":null,"abstract":"<p>Fukutoku-Oka-no-Ba is a submarine volcano located at 24°17.1′ N/141°28.9′ E in the Izu–Bonin arc, and is one of the most active volcanoes in Japan. This volcano produced an explosive eruption in August 2021 that generated a large amount of volcaniclastic material, some of which drifted westward to Japan and the coastal area of East Asia as a pumice raft. The pumice clasts that drifted for &gt;1000 km were mostly homogeneous and identical to those produced by past historical eruptions. The clasts have trachytic compositions (SiO₂ = 61–63 mass% and Na₂O + K₂O = 8.6–10.0 mass%) and contain augite, plagioclase, olivine (Mg# ~65), and magnetite, along with a small number of mafic enclaves containing diopside and high-Mg olivine (Mg# ~ 92). We undertook a research cruise to investigate the proximal volcaniclastic materials by dredging. The proximal materials include pumice, weakly vesiculated lapilli, and volcanic blocks, which have trachytic composition (SiO₂ contents up to 64.5 mass%). The main minerals in the proximal material are similar to those in the drift pumice, although remnants of mafic magma do not occur in the SiO₂-rich samples. The petrographic and geochemical characteristics of the proximal and drift ejecta from Fukutoku-Oka-no-Ba suggest the magma reservoir was stratified into two parts. The major part experienced magma mixing with a limited volume of mafic magma, whereas the other part was more differentiated. The differentiated high-SiO₂ magma accumulated in the upper part of the magma reservoir and avoided the mixing with and feed of volatile from the mafic magma, then were pushed out from the volcanic vent without extensive bubbling to sunk in the proximal area.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12498","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49394524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metamorphic history of mafic granulite and garnet-bearing amphibolite from the Oki-Dogo Island, Japan","authors":"Mizuki Takahashi,&nbsp;Shunsuke Endo,&nbsp;Atsushi Kamei","doi":"10.1111/iar.12497","DOIUrl":"10.1111/iar.12497","url":null,"abstract":"<p>Oki metamorphic rocks have long been considered as a constituent of the Hida Belt based on their geographic proximity, lithology, and Permo-Triassic metamorphism. However, recent geochronological studies have demonstrated that both para- and ortho-gneisses in the Oki-Dogo Island display Paleoproterozoic protolith formation and two separate phases of metamorphism at 1.85 Ga and 250–230 Ma. Consequently, the Oki metamorphic rocks are closely connected to the Paleoproterozoic massifs in the Korean Peninsula, although little is known about their pressure (P)–temperature (T) history. Here, we provide petrological data on mafic metamorphic rocks in the Oki-Dogo Island. The mafic lithologies are classified into mafic granulite, amphibolitized granulite and amphibolite. In addition, we first discover a garnet-bearing variety of amphibolite from the Oki-Dogo Island. The texture and composition of Ca amphibole suggest these rock types share a common P–T history but the dominant mineral assemblage in each rock type records different stages of metamorphism. The inferred P–T history includes two distinct events. The first event includes a low-P granulite facies stage (~900°C, 0.7–0.8 GPa) and subsequent amphibolite facies retrogression. This event is linked to the continuous compositional change of Ca amphibole from Ti-rich pargasite to hornblende/actinolite. The second event is prograde amphibolite facies metamorphism, which is associated with the formation of tschermakitic hornblende and calcic plagioclase. In high Fe/(Mg + Fe) rocks, garnet was formed at ~550–580°C, 0.45–0.50 GPa in this stage. Depending on the age of the first event, the low-P granulite facies metamorphism is likely to have occurred in a similar tectonic setting as the Paleoproterozoic crustal metamorphism in the Yeongnam Massif or the Permo-Triassic ultrahigh-T metamorphism in the northern Gyeonggi Massif.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45793833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Complex factors contribute to the chemical composition of clastic sediments traveling from rivers to the ocean along island arcs: A case study of the Otsuchi area, Northeast Japan","authors":"Kei Sugiura,&nbsp;Hikaru Sawada,&nbsp;Mutsumi Iizuka,&nbsp;Mana Yasui,&nbsp;Qing Chang,&nbsp;Takafumi Kasaya","doi":"10.1111/iar.12496","DOIUrl":"10.1111/iar.12496","url":null,"abstract":"<p>The chemical composition of coastal sediments and river sediments is influenced by the geological constitution of provenance and fractionation of clastic particles during sedimentary processes. The intricate nature of the geology in active subduction zones has complicated the comprehension of detrital sediments. More geochemical case studies in such areas are necessary to enhance the understanding of the coastal detrital sediments. This study presents the results of a geochemical and particle size analysis of sediment samples from the Sanriku coastal area of Northeast Japan, including inside and outside of Otsuchi Bay and the three rivers that flow into the bay. Otsuchi Bay area is known to have been severely affected by the 2011 off the Pacific coast of the Tohoku Earthquake and tsunami, and tsunami deposits on its seabed have been reported. The present geochemical analysis indicates that the sediments along those three rivers are well explained by the mixing of rocks occurring in their respective provenance. The chemical composition and particle size distribution of the sediments within Otsuchi Bay suggested the removal of coarse-grained quartz. They increased the abundance of fine-grained mafic minerals from Unosumai River having the largest catchment area among the three rivers. During shell debris in the seabed sediment outside of the bay made interpretation of the results was difficult; the sediments collected closer to the bay mouth contained more coarse-grained material with a composition closer to granitoid and sandstone in the provenance. In contrast, offshore sediments consisted of finer grains with a composition closer to mudstone. Notably, the sediments within Otsuchi Bay did not exhibit the characteristic compositional fractionation or particle size distribution associated with tsunami deposits. These findings underscore the importance of considering the geological diversity of provenances and the particle size distribution of minerals in understanding coastal sediments in subduction zones, including tsunami deposits.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47897230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}