Island Arc最新文献

{"title":"Stratigraphic reconstruction of the lower–middle Miocene Goto Group, Nagasaki Prefecture, Japan","authors":"Shoichi Kiyokawa,&nbsp;Masaru Yasunaga,&nbsp;Takanori Hasegawa,&nbsp;Ayako Yamamoto,&nbsp;Daisaku Kaneko,&nbsp;Yuta Ikebata,&nbsp;Noriko Hasebe,&nbsp;Yukiyasu Tsutsumi,&nbsp;Mami Takehara,&nbsp;Kenji Horie","doi":"10.1111/iar.12456","DOIUrl":"10.1111/iar.12456","url":null,"abstract":"<p>The Goto Islands are located at the westernmost tip of the Japan archipelago, and preserve a lower–middle Miocene sedimentary sequence deposited during rifting of the continental margin and opening of the Sea of Japan. The stratigraphy of the Goto Group and new K–Ar, fission-track, and U–Pb age data were used to determine the initial conditions of rifting in southwest Japan. The thickness of the Goto Group is 2000–3000 m. The lower unit (ca. 22–17.6 Ma) consists of thick, greenish, volcaniclastic rocks with basaltic volcanic material, representing the initial stages of continental rifting. The middle unit (ca. −17.6 Ma) consists of alternating sandstones and shales deposited in lacustrine and meandering fluvial environments in a syn-rift sedimentary basin during a period of volcanic activity. The upper unit (ca. 17.6–16.8 Ma) consists of thick sandstones of fluvial–deltaic facies that were deposited during rapid subsidence at the continental margin. This unit was deposited by a large fluvial system that flowed into the Sea of Japan. These sequences contain relatively cooler to warmer flora (Daijima-type) and record the warm period of the Miocene Climatic Optimum. The Goto felsic volcanic rocks (16.8 ~ 15.4 Ma) unconformably overlie the Goto Group, and granitic magmatism (ca. 16–14.5 Ma) occurred after sedimentation of the Goto Group. The widespread lacustrine, meandering–braided fluvial, and vast deltaic systems of the Goto Group, and felsic volcanism, were formed due to rapid subsidence that produced a horst-and-graben basin during the early stages of rifting of a volcanic arc along the eastern margin of Eurasia. These events occurred from 22.0 to 16.8 Ma before and during the formation of the Sea of Japan.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12456","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45043680","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":"2022 Island Arc Award","authors":"","doi":"10.1111/iar.12451","DOIUrl":"10.1111/iar.12451","url":null,"abstract":"<p><b>Title: A visage of early Paleozoic Japan: Geotectonic and paleobiogeographical significance of Greater South China</b></p><p><b>Author: Yukio Isozaki</b></p><p><b>Reference: <i>Island Arc</i> (2019), <i>28</i>, e12296</b></p><p>Tectonic evolution of Great South China (GSC) during early Paleozoic is fundamental for considering the origin of the Japanese Islands, but has not been fully understood. Nevertheless, zircon U–Pb ages from Paleozoic granitoids and sandstones have provided critical information on the continental margin along which proto-Japan began to grow. Based on currently available dataset of the dating as well as paleogeographic data, Isozaki (2019) reconstructed the early Paleozoic evolution of Japan. He suggested that the tectonic setting changed from a passive continental margin (Stage I) to an active margin (Stage II) during Cambrian when the oldest arc granitoid, high-P/T blueschist, and clastic sediments were formed. The predominant occurrence of Neoproterozoic zircons in Paleozoic rocks indicates that the relevant continental block was a part of South China, which probably formed a northeastern segment of GSC. He estimated that GSC was probably twice as large as the present conterminous South China. In addition, he summarized the faunal characteristics of the Permian marine fauna in Japan, which are in good accordance with the relative position of GSC with respect to the North China block during the late Paleozoic. This extensive summary and novel reconstruction provided clear pictures of the geological history of the Japanese Islands and prospective for future researches to the readers of Island Arc. Therefore, we identified that the paper by Isozaki is suitable for Island Arc Award in 2022.</p><p></p><p>Yukio Isozaki, the Professor Emeritus of the University of Tokyo, has broad expertise in histrorical geology, tectonics, and paleontology. He received his Ph.D from Osaka City University in Geology in 1986. He has worked as an Associate Professor and Professor in Yamaguchi University, Tokyo Institute of Technology, and the University of Tokyo until his retirement in last year. His research started in the analysis of ancient accretionary complexes using microfossils and geochronological dating. By proposing and utilizing the concept/scheme of ocean plate stratigraphy (OPS), he clarified the overall piled nappe structure of Southwest Japan, and synthesized the geological history of the Japanese Islands. His interest expands into the history of life, in particular, on mass extinction events in the past and relevant rapid biodiversification. His main targets include the biggest extinction in history across the Paleozoic-Mesozoic boundary and Cambrian-Ordovician biodiversification. He coined the term “superanoxia” for the long-term oxygen depletion in the Permo-Triassic superocean, a unique C-isotope episode named “Kamura event”, and proposed a possible scenario named “plume winter” for the mass extinction. Considering his ex","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12451","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"62641153","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":"Multistage zircon growth recording polyphase metamorphic evolution caused by pulsed granitoid intrusions into a low-P/T type metamorphic belt: P–T–D–t evolution of migmatites in the Ryoke belt, southwest Japan","authors":"Tetsuo Kawakami,&nbsp;Tomoe Ichino,&nbsp;Keiichi Kazuratachi,&nbsp;Shuhei Sakata,&nbsp;Kota Takatsuka","doi":"10.1111/iar.12454","DOIUrl":"10.1111/iar.12454","url":null,"abstract":"<p>We report contrasting pressure–temperature–time (<i>P–T–t</i>) paths of migmatites developed in the highest-grade metamorphic zone (Grt–Crd zone) and the contact metamorphic zone (Crd–Kfs zone) of the Mikawa area, Ryoke belt, southwest Japan to discuss the complex <i>P–T–D–t</i> evolution of the middle crust that experienced pulsed granitoid intrusions. In the Grt–Crd zone, sillimanite-grade high-<i>T</i> metamorphic condition prevailed from ca. 97 to 87 Ma, followed by cooling to ~500 °C, ~4 kbar. The intrusion of gneissose granitoids below the Grt–Crd zone isobarically reheated the Grt–Crd zone rocks again to the sillimanite-grade high-<i>T</i> condition at ca. 84 Ma. This was followed by ca. 71–70 Ma contact metamorphism. Ductile deformation that formed and folded the foliation of migmatites started before ca. 89 Ma and continued at least until ca. 84 Ma in the Grt–Crd zone. On the other hand, ca. 74 Ma age of the Crd–Kfs zone migmatite developed around the Inagawa Granodiorite in addition to ca. 70 Ma age of a syn-tectonic pegmatite vein revealed that the intrusion of “75–69 Ma granitoids” caused partial melting and locally triggered low-strain ductile deformation in their contact aureoles. Comparison with other areas of the Ryoke belt suggests that plutono-metamorphic evolution of the Mikawa and Aoyama areas are similar with each other in that ca. 80 Ma reheating events (i.e., contact metamorphism) are observed, while absence of separate reheating event postdating peak metamorphism in the Yanai area is a rather uncommon feature in the Ryoke belt.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43734689","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":"Trace-element composition of zircon in Kofu and Tanzawa granitoids, Japan: Quantitative indicator of sediment incorporated in parent magma","authors":"Yusuke Sawaki,&nbsp;Hisashi Asanuma,&nbsp;Shuhei Sakata,&nbsp;Mariko Abe,&nbsp;Takeshi Ohno","doi":"10.1111/iar.12455","DOIUrl":"10.1111/iar.12455","url":null,"abstract":"<p>Zircon is one of the most important minerals in geochronologic research. Isotopic ratios and trace elements in zircons are expected to reflect those of their parent magmas. Many geochemical researchers have proposed various discrimination diagrams for zircon to indicate tectonic setting and to identify source rock. Because most detrital zircons accumulated at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. In our research, we focused on sediment involvement during granitoid formation and tried to identify trace-element compositions in zircon that are sensitive to variation in sediment incorporation. To accomplish this, we examined trace-element compositions of both the granitoids and the included zircons in the Kofu granitic complex and the Tanzawa tonalitic plutons in Japan. Among the high-field-strength elements (Th, U, Ta, Nb, Hf, and rare earth elements), only Nb and Ta concentrations in the granitoids increased as the rate of sediment contribution increased. However, the zircon did not show such trends in Nb and Ta content. Zircon Y and P contents exhibited a positive correlation, indicating that xenotime substitution occurs to some extent. Because P exists as pentavalent ions in igneous systems, its presence likely affects the concentrations of pentads in zircon. When we divided the Nb and Ta contents by the P content, it became clear that zircon Nb/P and Ta/P ratios increase depending on sediment involvement. While some exceptions exist, we found that zircon Yb/Gd ratios also respond to sediment involvement. Our data further demonstrated that zircons in granitoids with significant sediment incorporation are characterized by low Ce/P contents, which is partly attributable to monazite crystallization before zircon saturation. This study demonstrates that combining these element ratios is useful for indicating sediment incorporation.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43120692","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":"Sanbe volcano: Long-term evolution of an arc magmatic system","authors":"Andreas Auer,&nbsp;Atsushi Kamei,&nbsp;Daisuke Endo","doi":"10.1111/iar.12453","DOIUrl":"10.1111/iar.12453","url":null,"abstract":"<p>A suite of samples was studied that represents the major explosive eruptions of Sanbe volcano, SW Japan. We demonstrate how rate of magma flux into the Trans-Crustal Magmatic System (TCMS) presents a major control on the type and style of the subsequently forthcoming eruptions. Erupted products can be separated into two distinct groups. An older group is characterized by highly evolved, high-K, LILE-rich rhyolitic magmas, showing a supressed adakitic trace element signature (otherwise characteristic for the young stratovolcanoes in the SW Japan arc) with low Ca, Sr concentrations and a negative Eu anomaly. In contrast, the younger group (dominantly of andesitic—dacitic composition) displays a strong adakitic trace element signature with characteristic steep REE profiles and high Sr concentrations. An Eu anomaly is generally lacking here. The two groups are also distinct in their petrographic features, with the early group being almost aphyric showing simple log linear crystal size distributions and homogeneous, uniform mineral chemistries. In contrast, products of the younger group show complex crystal size distributions with diverse mineral compositions and abundant disequilibrium features. Our study shows that an initial high melt-production rate allowed dehydration melting of lower crustal rocks leading to the formation of highly evolved K-rich magmas. These magmas intruded into the shallow crust and produced two large Plinian rhyolitic, caldera forming eruptions. Subsequently the primary magma production rate decreased and the lower crust became too refractory for additional dehydration melting by these lower volume magma batches, causing the conventional adakitic magmatism to produced several additional eruptions of smaller magnitude, mainly of Sub-Plinian or Pelean styles.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49616017","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":"Middle Holocene relative sea-level changes and vertical tectonic crustal movements on Shikoku Island near the Nankai Trough, Japan","authors":"Tatsuhiko Yamaguchi,&nbsp;Futoshi Nanayama,&nbsp;Toshimichi Nakanishi,&nbsp;Tomohiro Tsuji,&nbsp;Michiharu Ikeda,&nbsp;Yasuo Kondo,&nbsp;Michiko Miwa,&nbsp;Yohei Hamada","doi":"10.1111/iar.12452","DOIUrl":"10.1111/iar.12452","url":null,"abstract":"<p>The Philippine Sea plate subducts beneath the Eurasia plate at the Nankai Trough, northwestern Pacific, causing crustal deformation, mega-thrust earthquakes, and tsunami events. Shikoku Island, 150 km northwest of the trough, experiences both coseismic and interseismic deformation. Coastal sediments potentially record vertical crustal movements as relative sea level (RSL) changes. We studied sedimentary facies and microfossil ostracodes in core SKM from southwestern Shikoku Island for evidence of middle Holocene tsunami events and deformation. The core sediments included nine event layers corresponding to storm or tsunami events. Using modern analog techniques, we estimated RSLs from the ostracode assemblages of core SKM and 13 other cores from Shikoku Island and the surrounding region. Then, we subtracted RSL changes due to glacio-hydro isostatic adjustment from the estimated RSLs to estimate vertical tectonic movement rates in these cores between 8.6 and 4.7 ka. The inferred RSL changes suggest that the Sukumo site has experienced both uplift and subsidence since 8.6 ka. Before 6.6 ka, rates of tectonic crustal movement were higher than the modern-day rate, and its spatial distribution also differed. After 6.6 ka, tectonic crustal movement showed a similar spatial pattern and occurred at rates close to the modern day interseismic rate. The spatial pattern and rates of tectonic crustal movement could be caused by changes in rupture areas between the Eurasia and the Philippine Sea plates beneath the Shikoku Island and in stress condition of the asthenosphere. Some of the vertical displacements can be explained by the movements of local active faults.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49277730","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":"An obelisk-shaped granitoid tower at Mt. Jizogadake in the Southern Alps of Japan: A 3-D morphological study","authors":"Masahiro Chigira","doi":"10.1111/iar.12449","DOIUrl":"10.1111/iar.12449","url":null,"abstract":"<p>Well-developed tors and associated boulder fields are present in exposed granitoid pluton, but their geomorphological origins have not been fully addressed. Although the tor-like features are commonly attributed to the orthogonal joint system along which weathering proceeds and the weathering materials are removed, the majority of previous studies lack three-dimensional (3-D) morphological observations. One of the well-known granitoid rock towers in Japan, namely, the obelisk at Mt. Jizogadake in the Japanese Southern Alps, was investigated using unmanned air vehicles (UAVs). A 3-D observation of the granitoid obelisk found that it is shaped by columnar joints with an undulation along a long axis and irregularly shaped cross-sections. Because of these features and intersection angles between the rock columns and exposure surfaces, the obelisk exhibits a peculiar morphology appearing as a heap of rock blocks when observed from the ground. The columnar jointing might have occurred in a marginal zone of the granitoid pluton due to faster cooling rates. The 3-D observations also confirmed the columnar joints formation was predated by high-angle, planar joints. The columnar joints divide the rock mass between those planar joints. This may imply that the high-angle joints would have formed probably during cooling under the presence of tectonic and thermal stresses.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"62641144","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":"Microbial influences on manganese deposit formation at Yunotaki Fall, Japan","authors":"Fumito Shiraishi,&nbsp;Ryoji Chihara,&nbsp;Risa Tanimoto,&nbsp;Kazuya Tanaka,&nbsp;Yoshio Takahashi","doi":"10.1111/iar.12448","DOIUrl":"10.1111/iar.12448","url":null,"abstract":"<p>Microorganisms are considered to play an important role in the formation of manganese oxide in natural environments. At Yunotaki Fall in north Japan, manganese-oxidizing bacteria were previously assumed to have oxidized manganese to precipitate birnessite, which relied on oxygen released from algae (i.e., indirect oxidation sensu <i>lato</i>). However, it remained unclear whether larger-scale manganese oxide precipitation was actually occurring under light conditions. This study therefore evaluated the contribution of indirect oxidation using microelectrodes to analyze local water chemistry, in addition to bulk water chemistry and DNA analyses. With the downward flow of hot spring water, pH increases because of CO₂ degassing and causes the saturation index of birnessite to increase downstream. Manganese concentrations in the hot spring water decrease downstream even if it was undersaturated in birnessite, suggesting the dominance of manganese oxide deposition by microorganisms. Indeed, the deposit surface was covered by thick microbial mats, and microscopic observations and DNA analysis of the mats indicate the presence of cyanobacteria, eukaryotic algae (green algae), and manganese-oxidizing bacteria. Microelectrode measurements at the surface of a deposit covered with eukaryotic algae showed that pH and O₂ concentration profiles are characteristic of oxygenic photosynthesis and aerobic respiration. On the other hand, the light and dark conditions show nearly identical Mn(II) concentration profiles decreasing within the algal mats. These results demonstrate that low bulk pH values in the hot spring water hindered indirect oxidation despite the occurrence of active oxygenic photosynthesis and that direct oxidation by manganese-oxidizing bacteria is considered to dominate in the investigated sample.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41942177","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":"Zircon U–Pb ages of the Higo plutonic complex: Implication for migration of Cretaceous igneous activity in Kyushu, southwest Japan","authors":"Yukiyasu Tsutsumi","doi":"10.1111/iar.12446","DOIUrl":"10.1111/iar.12446","url":null,"abstract":"<p>Zircon U–Pb weighted mean ages of seven samples from the Higo plutonic complex (HPC) in Kyushu were determined as follows; Shiraishino granodiorite: 109.3 ± 0.9 Ma and 109.0 ± 1.1 Ma; Kugushima granodiorite: 109.1 ± 1.1 Ma; Miyanohara tonalite: 107.7 ± 1.3 Ma and 108.3 ± 0.9 Ma; Manzaka tonalite: 108.0 ± 0.9 Ma; Joyama tonalite: 112.7 ± 1.2 Ma. The plutonism of batholithic granitoids in the HPC occurred in 109–108 Ma, and granitic intrusions occurred in 113 Ma. The previously reported zircon U–Pb ages range from 107 to 98 Ma in northern Kyushu and concentrate around about 106 Ma in the Chikuhi area in the northern part of central Kyushu. The previously published age data and newly obtained data in this study demonstrate that Cretaceous igneous activity in Kyushu migrated northward from 114 to 98 Ma, accompanied by widespread igneous activity throughout central and northern Kyushu at 106–105 Ma. The HPC situated in the southernmost part of central Kyushu was the origin of this northward migration.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46680672","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":"Relationship among paleosol types, depositional settings, and paleoclimates in Tetori group (Lower Cretaceous, central Japan)","authors":"Kensuke Kuroshima,&nbsp;Masato Fujita,&nbsp;Yoshihiro Kakizaki,&nbsp;Fumito Shiraishi","doi":"10.1111/iar.12445","DOIUrl":"10.1111/iar.12445","url":null,"abstract":"<p>One of the key areas and periods for dinosaur evolution is considered to be Early Cretaceous East Asia, of which paleoclimate, that affected dinosaur diversity, needs to be accurately estimated. This study reconstructed paleoenvironmental information from two paleosol sections of the Lower Cretaceous Tetori Group in Hokuriku province, Japan. Elemental and isotopic compositions indicate that the two sections (Sections K5 and T1) formed under similar mean annual temperature (MAT) and mean annual precipitation (MAP) but exhibit significantly different paleosol colors (red in the Section K5, and gray in the Section T1) and mineralogy of carbonate nodules (dolomite–siderite in the Section K5, and dolomite–calcite in the Section T1). In addition, the oxygen isotopic ratio of carbonate minerals in the Section K5 was significantly low. The differences in sedimentary features and isotopic composition were considered to reflect the differences of seasonal climatic factors (e.g., monsoon) and local settings (e.g., drainage condition) despite the two sections exhibiting similar MAT and MAP. The results of this study suggest that the northeastern margin of East Asia, where the Tetori Group was deposited, had temperate and humid climate with monsoonal contrast in humidity during Aptian to Albian.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46707247","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}