2023年04月, 文部科学大臣表彰「科学技術賞」研究部門, 上総層群における松山—ブリュン地磁気逆転の系統的研究, 文部科学省
岡田 誠・菅沼悠介
国内学会・会議・シンポジウム等の賞

2021年12月, 水戸市文化栄誉賞, 学術研究分野, 水戸市
岡田 誠
その他の賞

2021年09月, 日本地質学会表彰, 千葉セクションにおける日本初のGSSP認定, 日本地質学会
千葉セクションGSSP提案チーム

2021年06月, 日本第四紀学会学術賞, 房総半島の海成第四系を中心とした古地磁気層序に関する一連の研究, 日本第四紀学会
岡田 誠

2021年06月, 田中舘賞, 上総層群における松山−ブリュン地磁気逆転の系統的研究, 地球電磁気・地球惑星圏学会
岡田 誠;菅沼悠介

2020年12月, つくば賞, 我が国初の地質時代名称「チバニアン」承認の礎となった地磁気逆転および古海洋変動復元に関する研究, 茨城県科学技術振興財団
岡田 誠・菅沼悠介・羽田裕貴
出版社・新聞社・財団等の賞

2020年11月, 茨城県特別功労賞, 日本初の地質年代名「チバニアン」承認（提案チーム代表）, 茨城県
岡田 誠
その他の賞

2020年10月, 茨城大学学長学術特別表彰, 国立大学法人 茨城大学
岡田 誠・菅沼悠介・羽田裕貴
出版社・新聞社・財団等の賞

2020年08月, 日本第四紀学会功労賞, 日本初のGSSP認定, 日本第四紀学会
チバニアンGSSP提案グループ
国内学会・会議・シンポジウム等の賞

2016年09月, 日本地質学会 小藤文次郎賞, 一般社団法人日本地質学会
菅沼悠介・岡田 誠・堀江憲路・竹原真美・木村純一・羽田裕貴・風岡 修
学会誌・学術雑誌による顕彰

2006年09月, 日本地質学会論文賞, 一般社団法人日本地質学会
辻 隆司・宮田雄一郎・岡田 誠・三田 勲・中川 洋・佐藤由理・中水 勝
国内学会・会議・シンポジウム等の賞

Orbital Scale Kuroshio Current Variations of the Northwestern Pacific Ocean in the Early Pleistocene (Marine Isotope Stage 40–36) Based on Calcareous Nannofossil Records
Daisuke Kuwano; Koji Kameo; Yoshimi Kubota; Masayuki Utsunomiya; Kanako Mantoku; Makoto Okada, ラスト(シニア)オーサー, Abstract

The Quaternary period was marked by distinct glacial‐interglacial climate cycles driven by orbital forcing, which are closely linked to marine environmental change. In the northwestern Pacific Ocean, the subtropical Kuroshio Current and subarctic Oyashio Current play crucial roles in global climate modulation. Despite their significance, paleoceanographic studies with high temporal resolutions are scarce. Here, we investigated calcareous nannofossil assemblages of the Kazusa Group to reconstruct the sea‐surface conditions around the Japanese Archipelago during the marine isotope stage (MIS) 40–36, providing an important climatic record prior to the mid‐Pleistocene transition. A time‐series analysis of nannofossil floral changes revealed orbital scale Kuroshio Current variability as well as Kuroshio Front migrations, suggesting that the Kuroshio Current variations were linked to the variability of the North Pacific subtropical gyre. Moreover, orbital‐scale southward migrations of the Kuroshio Front during the glacial periods may be correlated with the displacement of the intertropical convergence zone caused by the northern hemisphere climate changes. Finally, spectral and wavelet analyses of calcareous nannofossil abundance showed a periodicity of ∼20 Kyr, indicating that these variabilities in the Kuroshio Current are predominantly controlled by high‐latitude climate forcings. Therefore, the results obtained in this study suggest that Kuroshio Current variations are related to climatic changes from low to high latitudes during the MIS 40–36., American Geophysical Union (AGU)
Paleoceanography and Paleoclimatology, 2025年02月17日, ［査読有り］

Seasonal Sea Surface Temperature Variations at the Northern Limit of the Kuroshio Current in Marine Isotope Stage 20–18
Hiroto Kajita; Yusuke Suganuma; Yuki Haneda; Makoto Okada; Masanobu Yamamoto; Osamu Seki; Naohiko Ohkouchi, Abstract

This study presents a high time‐resolution alkenone unsaturation ratios (U^K'₃₇) in the Chiba composite section, a marine sedimentary sequence formed in the Kazusa forearc basin in the northwestern Pacific under the influence of the Kuroshio and Oyashio currents. The U^K'₃₇ reflects summer sea surface temperature (SST) and records glacial‐interglacial to sub‐millennial‐scale variations spanning the marine isotope stage (MIS) 19, an analog of our Holocene interglacial. At the glacial‐interglacial scale, summer U^K'₃₇‐SST and previously published winter SST fluctuations are in tandem with East Asian Summer and Winter monsoon variabilities, respectively. Millennial‐scale U^K'₃₇‐SST variations correspond to meltwater events in the North Atlantic. Summer temperature amplitudes maybe half those in winter, suggesting the stable dominance of the Kuroshio Current during the summer and significant winter cooling caused by the Oyashio Current intrusion. Our study reveals the unique seasonally different atmosphere‐ocean coupling system during MIS 19 at the subarctic front in the northwestern Pacific., American Geophysical Union (AGU)
Geophysical Research Letters, 2025年02月01日, ［査読有り］

Reconstruction of high-resolution paleomagnetic variations in the middle Gauss chronozone, including the upper and lower boundaries of the Mammoth reversed subchronozone
Akihiro Tanimoto; Makoto Okada; Ryota Hayashi, Abstract

In this study, we provide paleomagnetic records, including the upper and lower boundaries of the Mammoth reversed subchronozone, reconstructed from a continuous outcrop of the upper marine Pliocene in the southernmost part of the Boso Peninsula, which is more than 200 m thick. In this interval, the Mammoth reversed subchronozone was recognized in an interval of approximately 50 m thickness, including a polarity transition zone at its lower boundary of approximately 10 m thickness. Simultaneously, the upper boundary showed no polarity transition zone and a rapid polarity reversal, suggesting a probable lack of strata. Several significant variations were recognized in the paleomagnetic directions in the middle Gauss chronozone, some of which may qualify as new geomagnetic excursions. The relative paleointensities (RPIs) obtained in this study are consistent in their character of change with those reported from deep-sea cores in the distant Caribbean Sea and the equatorial Pacific, indicating the potential of stratigraphic correlation using RPI. The RPI around the lower Mammoth boundary was significantly attenuated compared to the average of the entire section. On the other hand, the virtual geomagnetic pole (VGP) path of the lower Mammoth boundary shows a rapid shift from the southern hemisphere to the northern hemisphere during transition. This movement passes through regions affected by non-axial dipole fields. Following this, the RPI shows a recovery trend, and the VGP stabilizes in the southern hemisphere, forming clusters that align with records from Italy and Hawaii. This sequence offers significant insights into changes in the axial dipole field during geomagnetic polarity reversals.

Graphical Abstract, Springer Science and Business Media LLC
Earth, Planets and Space, 2024年12月26日, ［査読有り］

Paleomagnetic study of the 30 ka Aira caldera-forming eruption and 60–45 ka Iwato pyroclastic flow deposits, southern Kyushu, Japan
Takeshi Hasegawa; Nobutatsu Mochizuki; Hidetoshi Shibuya; Ayumu Nishihara; Chie Kusu; Shohei Shibata; Makoto Okada; Kuniaki Nishiki; Yuki Sato, Abstract

To constrain the age and duration of large-scale caldera-forming eruptions, we measured paleomagnetic directions of pyroclastic deposits from the 30 ka Aira caldera eruption sequence, and the 60–45 ka Iwato pyroclastic flow deposits around Aira caldera in southern Kyushu, Japan. The 30 ka Aira caldera eruption sequence consists of Osumi pumice fall (OS), Tarumizu pyroclastic flow deposit (TM), Ito ignimbrite (IT) and co-ignimbrite ash (AT), in ascending order. Oriented samples were collected by drilling for OS, TM and welded ignimbrites, and by cubing for non-welded (unconsolidated) pyroclastic flow deposit. We systematically sampled Ito ignimbrite with the degree of welding as: non-welded (IT1), moderately welded (IT2), and strongly welded (IT3) facies that is limitedly distributed in north of Aira caldera. Mean paleomagnetic directions of OS, TM, IT1 and IT2 are consistent with those previously reported for AT and welded facies of IT. Although OS samples were collected from multiple pumice clasts at proximal locations, we obtained well-defined mean paleomagnetic directions corresponding to those of co-eruptive pyroclastic flow (TM). This suggests that even clast-supported and non-welded pumice fall can retain thermoremanent magnetization at the time of deposition. Significance tests for our mean paleomagnetic directions showed that of all sequential units of the Aira caldera-forming eruption deposits, only IT3 has a different paleomagnetic direction. Based on reported paleosecular variation changing rates in Japan, and on the angular difference associated with error of the two paleosecular directions, we estimate the time gap between IT3 and IT2, to be 24.3 ± 16.3 years. A conductive cooling model explains this time difference as due to differences in cooling time between quickly, and slowly cooled parts of a thick single ignimbrite unit. Although the possibility that multiple flow units occurred within tens of years of each other cannot be excluded, there are no observations of clear flow unit boundaries in the Ito ignimbrite to support the suggestion that the Aira caldera-forming eruption sequence was deposited within a shorter time than years. In addition, the age of Iwato pyroclastic flow deposit, which has been situated between 60 and 45 ka, was estimated by calculating the angular distance between the mean paleomagnetic direction and the modeled secular variation curve from the GGF100 ka. As the result, we determine the most probable age to be around 56 ka.

Graphical abstract, Springer Science and Business Media LLC
Earth, Planets and Space, 2024年12月18日, ［査読有り］

Application of a recently developed method of oriented drill coring to accumulative tephra layers: identification of the Matuyama-Brunhes geomagnetic reversal in Akan caldera-forming eruption deposits
Takeshi HASEGAWA; Chie Kusu; Makoto Okada; Aoi Hiratsuka; Kuniaki Nishiki; Yuki Sato; Masaru Koshigai; Takuya Matsuzaki; Yuhji Yamamoto
Earth, Planets and Space, 2024年11月, ［査読有り］

Paleomagnetic Field Variability and Revised Chronostratigraphy of Bering Sea (IODP Expedition 323) Deep‐Sea Sediments During MIS 6–7 (130–144 ka)
Steve Lund; Emily Mortazavi; Joe Stoner; Makoto Okada, Abstract

We have developed replicate paleomagnetic secular variation (PSV) records for MIS 6–7 (130–244 ka) from IODP Ex. 3 23 Sites 1,343, 1,344, and 1,345 (Bering Sea). We can correlate the PSV at all three sites and identify 90 inclination features and 64 declination features. We have developed relative paleointensity records for all three sites by normalizing the demagnetized natural remanence to magnetic susceptibility. Paleointensity highs/lows can be tied to the PISO‐1500 global oxygen‐isotope‐dated paleointensity record. This provides a significant increase in chronostratigraphic resolution for these sites. Only one excursion is recorded in the MIS 6–7 sediments of the Bering Sea—the Iceland Basin Excursion (∼196 ± 3 ka). Replicate records of the inclinations and declinations both flip quickly to reversed polarity directions, stay there for several hundred years and then flip quickly back to normal polarity directions. However, the inclination flips occur without significant declinations changes and visa versa. A statistical PSV study was carried out by averaging the data in 3 ky and 9 ky windows. There is a distinctive bimodal pattern to the angular dispersions with most time spent with low angular dispersion values (∼10°–15°), but there is an interval of more than 30 ky (185–220 ka) with angular dispersions averaging two to three times higher amplitudes (∼25°–35°). This interval also has low paleointensities and the Iceland Basin Excursion. This same, coupled pattern of high angular dispersion, low paleointensity, and excursions is noted synchronously in the central North Atlantic Ocean and may indicate a global pattern to the geomagnetic field., American Geophysical Union (AGU)
Journal of Geophysical Research: Solid Earth, 2024年10月23日, ［査読有り］

On the relationship between paleomagnetic secular variation and excursions – Records from MIS 11 and 12 – ODP Leg 172, western North Atlantic Ocean
Steve Lund; Gary Acton; Brad Clement; Makoto Okada; Lloyd Keigwin, Elsevier BV
Physics of the Earth and Planetary Interiors, 2024年09月18日, ［査読有り］

Paleomagnetic secular variation and revised chronostratigraphy of Bering Sea (IODP expedition 323) deep-sea sediments (MIS 5)
Steve Lund; Makoto Okada; Emily Mortazavi, Elsevier BV
Deep Sea Research Part I: Oceanographic Research Papers, 2024年06月, ［査読有り］

Paleomagnetism and paleomagnetic dating to large volcanic bombs: an example from the historical eruption of Azuma–Jododaira volcano, NE Japan
Takeshi Hasegawa; Bunta Kikuchi; Shibata Shohei; Yuhji Yamamoto; Takumi Imura; Masao Ban; Kae Tsunematsu; Chie Kusu; Makoto Okada; Tsukasa Ohba, Abstract

Vulcanian activity is one of the most common eruption styles of arc andesitic volcanism on Earth. It ejects and deposits volcanic bombs around the source crater. Although paleomagnetic studies of volcanic bombs are limited, such studies can potentially provide more opportunities for high-resolution paleomagnetic dating of volcanic activity. In this study, paleomagnetic dating was applied to large (> 1 m) volcanic bombs around active craters in the Azuma volcano group, NE Japan. Oriented samples were collected from the interior parts of five large volcanic bombs situated on gentle slopes, a few hundred meters from the source crater. More than six core samples were collected from each bomb and all samples were subjected to a range of rock magnetic experiments, including anisotropy of magnetic susceptibility (AMS) and thermal/alternating field demagnetization (THD/AFD) analyses. The Characteristic Remanent Magnetization (ChRM) directions for specimens from all bombs were well-defined, have small α₉₅ (< 2.5º), and are in close agreement with each other. Comparing our measured overall mean direction (D_m = 355.5º, I_m = 49.8º, α₉₅ = 1.6º) with modeled geomagnetic field estimates and a reference secular variation curve for this area (using MATLAB-based archaeomagnetic dating tool), we suggest that the volcanic bombs were produced in the historical Meiji period (1893–1895 CE) eruption. In addition, a combination of the data of ChRM, AMS, thermomagnetic analyses, hysteresis measurement, and XRF analysis indicates that the volcanic bombs were derived from a plug of lava in the conduit under the solidification point (ca. 800 °C), but above the Curie point of the titanomagnetite remanence carrier (around 300 °C). We show that volcanic bombs can be powerful for paleomagnetic dating if certain sampling conditions, such as quantity, situation, size and portion are satisfied.

Graphical Abstract, Springer
Earth, Planets and Space, 2023年11月16日, ［査読有り］

古地磁気層序とテフラ層序に基づく房総半島南部の下部更新統千倉層群と同半島東部の上総層群の対比
小西拓海,宇都宮正志,岡田 誠,田村糸子, 日本地質学会
地質学雑誌, 2023年10月31日, ［査読有り］

福島県，吾妻—浄土平火山の1893年明治噴火はマグマ放出を伴っていた：燕沢火口列周辺に分布する巨大な火山弾の古地磁気年代測定による推察
長谷川 健; 菊池 文太; 柴田 翔平; 井村 匠; 伴 雅雄; 常松 佳恵; 山本 裕二; 大場 司; 鈴木 和馬; 戸丸 淳晴; 楠 稚枝; 岡田 誠
火山, 2023年09月30日, ［査読有り］

Multi-method constraints on the age and timescale of silicic small-volume eruptions of Puketerata Volcanic Complex, Taupō Volcanic Zone, New Zealand
Szabolcs Kósik; Takeshi Hasegawa; Martin Danišík; Károly Németh; Makoto Okada; Bjarne Friedrichs; Axel K. Schmi, Abstract

Accurate dating of young eruptions from explosive volcanoes is essential for forecasting future eruptions and for defining the hazardscape of volcanic fields. However, precise dating of Quaternary eruptions is often challenging due to limited number of applicable dating methods or lack of datable eruptive phases. Moreover, small volume eruptions (e.g., monogenetic type), despite their significance on regional scale, have traditionally deserved less attention than their large volume counterparts. Puketerata is a maar-lava dome complex in the central Taupō Volcanic Zone (New Zealand), encompassing mafic and silicic phreatomagmatic eruptions with well-preserved pyroclastic deposits sourced from closely spaced vents. Its most recent activity is estimated to ca. 16 ka based on medial and distal stratigraphic surveys. Here, we carried out two independent age determinations and an additional paleomagnetic analysis on the volcanic succession of the Puketerata maar-lava dome complex with an aim to unravel the timing of volcanic activity. Combined U-Th disequilibrium and (U-Th)/He dating of zircon from two lava domes yielded eruption ages of 11.3 ± 2.6 ka and 11.3 ± 1.7 ka, which are concordant with the radiocarbon ages of 11.3–11.7 ka obtained on charcoal from the base of the pyroclastic sequence. Paleomagnetic data on the lavas from the two lava domes suggest at least ~ 100 years difference between their emplacements. Our geochronological results and new stratigraphic observations suggest that the volcanic/magmatic history of the Puketerata is complex with multiple eruptions within a small, confined area, where the most recent eruptions occurred only at ca. 11.5 ka, which is significantly younger than previously thought. This provides an additional datum for volcanic hazards assessment and stratigraphic correlations in New Zealand.

Graphical Abstract, Springer Science and Business Media LLC
Earth, Planets and Space, 2023年07月12日, ［査読有り］

Rotated Transtensional Basins Formed During Back-Arc Spreading in Japan: Simultaneous Rapid Tectonic Rotation and Basin Subsidence
Hosoi; J.; Tanii; Y.; Okada; M.; Haneda; Y, John Wiley & Sons, Inc.
Tectonics, 2023年06月27日, ［査読有り］

Paleomagnetic constraint of the age and duration of the Taupō Eruption, New Zealand
Takeshi Hasegawa; Annika Greve; Darren M. Gravley; Chie Kusu; Yasuaki Kaneda; Shohei Shibata; Makoto Okada; Szabolcs Kósik; Nobutatsu Mochizuki; Gillian Turner
Earth, Planets and Space, 2023年02月, ［査読有り］

On the relationship between paleomagnetic secular variation and excursions – Records from MIS 9 and 10 - ODP Leg 172
Steve Lund; Gary Acton; Brad Clement; Makoto Okada; Lloyd Keigwin, Elsevier
Physics of the Earth and Planetary Interiors, 2022年03月26日, ［査読有り］

Millennial-scale oscillations in the Kuroshio– Oyashio boundary during MIS 19 based,on the radiolarian record from the Chiba composite section, central Japan
Takuya Itaki; Sakura Utsuki; Yuki Haneda; Kentaro Izumi; Yoshimi Kubota; Yusuke Suganuma; Makoto Okada, ラスト(シニア)オーサー, Marine isotope stage (MIS) 19 is considered to be the best orbital analog for the present interglacial. Consequently, clarifying the climatic features of this period can provide us with insights regarding a natural baseline for assessing future climate changes. A high-resolution radiolarian record from 800 to 750 ka (MIS 20 to MIS 18) was examined from the Chiba composite section (CbCS) of the Kokumoto Formation, including the Global Boundary Stratotype Section and Point for the lower–middle Pleistocene boundary on the Boso Peninsula on the Pacific side of central Japan. Millennial-scale oscillations in the Kuroshio warm and Oyashio cold currents were revealed by the Tr index, which is estimated using a simple equation based on radiolarian assemblages. The estimated Tr values ranged between 0.1 and 0.8 for MIS 18 through MIS 19, with minimum and maximum values corresponding to values observed off present day Aomori (41°N) and the Boso Peninsula (35°N), respectively. The observed patterns tended to be synchronous with the total radiolarian abundance associated with their production. Multiple maxima in radiolarian abundance occurred during periods of the Oyashio expanded mode before 785 ka and during periods of Kuroshio extension after 785 ka in MIS 19. Such increases in radiolarian abundance with the Kuroshio extension during MIS 19 are likely related to improvements in nutrient and photic environments with the development of a two-layer structure along the Kuro- shio–Oyashio boundary zone. A similar pattern of millennial-scale climatic changes was also recognized in a precipita- tion record from the Sulmona Basin in central Italy, suggesting a close relationship with the CbCS record as a result of a large-scale climate system similar to the Arctic Oscillation in the northern hemisphere., Springer Science and Business Media LLC
Progress in Earth and Planetary Science, 2022年01月12日, ［査読有り］

Paleoceanography and dinoflagellate cyst stratigraphy across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the Chiba composite section, Japan
Eseroghene J. Balota; Martin J. Head; Makoto Okada; Yusuke Suganuma; Yuki Haneda, A dinoflagellate cyst record from the highly resolved Chiba composite section in Japan has been used to reconstruct sea-surface paleoceanographic changes across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the global stratotype, constituting the first detailed study of this microfossil group from the Pleistocene of the Japanese Pacific margin. Cold, subarctic water masses from 794.2 ka gave way to warming and rapid retreat of the Subpolar Front at 789.3 ka, ~ 2000 years before the end of Marine Isotope Stage (MIS) 20. Throughout the fully interglacial conditions of MIS 19c, assemblages are consistent with warm sea surface temperatures but also reveal instability and latitudinal shifts in the Kuroshio Extension system. The abrupt dominance of Protoceratium reticulatum cysts between 772.9 and 770.4 ka (MIS 19b) registers the influence of cooler, mixed, nutrient-rich waters of the Kuroshio–Oyashio Interfrontal Zone resulting from a southward shift of the Kuroshio Extension. Its onset at 772.9 ka serves as a local ecostratigraphic marker for the Chibanian Stage Global Boundary Stratotype Section and Point (GSSP) which occurs just 1.15 m (= 1300 years) below it. An interval from 770.1 ka to the top of the examined succession at 765.8 ka (MIS 19a) represents warm, presumably stratified but still nutrient-elevated surface waters, indicating a northward shift of the Kuroshio Extension ~ 5 kyrs after the termination of full interglacial conditions on land., Springer Science and Business Media LLC
Progress in Earth and Planetary Science, 2021年12月, ［査読有り］

Paleoceanography of the northwestern Pacific across the Early–Middle Pleistocene boundary (Marine Isotope Stages 20–18)
Yoshimi Kubota; Yuki Haneda; Koji Kameo; Takuya Itaki; Hiroki Hayashi; Kizuku Shikoku; Kentaro Izumi; Martin J. Head; Yusuke Suganuma; Makoto Okada, ラスト(シニア)オーサー, The fluctuating position of the boundary between the Kuroshio (warm) and Oyashio (cold) currents in the mid-latitude western North Pacific affects both heat transport and air–ocean interactions and has significant consequences for the East Asian climate. We reconstruct the paleoceanography of Marine Isotope Stages (MIS) 20–18, MIS 19 being one of the closest astronomical analogues to the present interglacial, through multiple proxies including microfossil assemblage data, planktonic foraminiferal isotopes (δ¹⁸O and δ¹³C), and foraminiferal Mg/Ca-based temperature records, from the Chiba composite section (CbCS) exposed on the Boso Peninsula, east-central Japan. Principal component analysis (PCA) is used to capture dominant patterns of the temporal variation in these marine records, and shows that the relative abundances of calcareous nannofossil and radiolarian taxa are consistent with the water mass types inferred from geochemical proxies. The leading mode (36.3% of total variance) mirrors variation in the terrestrial East Asian winter monsoon (EAWM), reflecting seasonal trends dominated by the winter monsoon system. In the CbCS, this mode is interpreted as reflecting the interplay between the warm Kuroshio and cold Oyashio waters, which is likely related to the latitudinal shift of the subtropical–subarctic gyre boundary in the North Pacific. The second mode (15.4% of total variance) is closely related to subsurface conditions. The leading mode indicates that MIS 19b and 19a are represented by millennial-scale stadial/interstadial oscillations. Northerly positions for the gyre boundary during late MIS 19c, the interstadials of MIS 19a, and early MIS 18 are inferred from the leading mode, which is consistent with a weak EAWM and consequent mild winter climate in East Asia. Nonetheless, the northerly positions for the gyre boundary during late MIS 19c and early MIS 19a were not associated with subsurface warming presumably due to the suppressed gyre circulation itself caused by the weak Aleutian Low. Intermittent southerly positions for the gyre boundary are inferred for the stadials of MIS 19b and 19a. Regional sea surface temperature (SST) comparisons in the western North Pacific reveal that the moderate SSTs during MIS 19a through early MIS 18 were restricted to the mid- to high latitudes, influenced by the weak EAWM. Comparison between MIS 20–18 and MIS 2–1 suggests that glacial MIS 20 and 18 had significantly milder winters than MIS 2, likely related to the relatively weak EAWM., Springer Science and Business Media LLC
Progress in Earth and Planetary Science, 2021年12月, ［査読有り］

A tephra-based approach to calibrating relative geomagnetic paleointensity stacks to absolute values
Nobutatsu Mochizuki; Satomu Fujii; Takeshi Hasegawa; Yuhji Yamamoto; Tadahiro Hatakeyama; Daisuke Yamashita; Makoto Okada; Hidetoshi Shibuya, Relative paleointensity (RPI) stacks provide a relative, global paleointensity variation, which reflects variations in the geocentric axial dipole moment. Previous calibrations of an RPI stack rely on adjusting a mean RPI to a mean of virtual axial dipole moments (VADMs), which are selected from absolute paleointensity (API) databases. To achieve more quantitative calibration of an RPI stack into absolute values, we propose a novel approach that compares (1) tephra-derived APIs and (2) the same tephras' horizons, in the oxygen isotope stratigraphy, tied RPIs (hereafter termed the "TA-TOR" approach). For the TA-TOR approach, APIs were newly determined for welded tuffs of 15 pyroclastic flow deposits in Japan. Eight of the 15 new APIs and 2 previously reported APIs have tephra horizons in the oxygen isotope stratigraphy. Based on the 10 data of the TA-TOR approach, combined with 4 data of the transitional field, VADMs calculated from the APIs (VADM(API)) were compared with isochronous RPIs from two RPI stacks, PISO-1500 and Sint-2000. The 14 data points in RPI vs. VADM(API) diagrams show a linear relationship with correlation coefficients of 0.83-0.89. Using the observed linear relationships, the two RPI stacks were reliably calibrated to VADM values (VADM(RPI)) for the period since 1.1 Ma. Compared with the VADMs calibrated by the previous studies, the present calibration provides a 12-13% smaller median/mean and a larger dispersion as represented by a 15-53% larger standard deviation for the two RPI stacks. The similarities between the cumulative distributions of VADM(RPI) from the two stacks and those of VADMs selected from the API database indicate the reliability of the present calibration. These results show that the present calibration, which relies on the TA-TOR approach, accurately converts a RPI stack into VADM(RPI) values and will contribute to studies on time variations in the geocentric axial dipole moment, sedimentary RPI, and cosmogenic radionuclides. Variations in VADM(RPI) for the past 1.1 Myr, obtained from PISO-1500 and Sint-2000 via the present calibration, can be used as standard geocentric axial dipole variations for this period. (C) 2021 Elsevier B.V. All rights reserved., Elsevier BV
Earth and Planetary Science Letters, 2021年10月, ［査読有り］

A record of the lower Mammoth geomagnetic polarity reversal from a marine succession in the Boso Peninsula, central Japan
Yuki Haneda; Makoto Okada,
Palaeomagnetic records from geological archives provide significant information about the nature of geomagnetic polarity reversals; however, there are few detailed palaeomagnetic records of pre-Pleistocene reversals. The lower Mammoth Subchron boundary (late Pliocene) is recorded in a 10-m interval of a marine succession deposited at high accumulation rates (9–66 cm/kyr) in the Boso Peninsula, central Japan. Here, we report a continuous palaeomagnetic record of the lower, normal to reverse boundary interval of the Mammoth Subchron, including the geomagnetic field direction and relative palaeointensity, with an average temporal resolution of ca 800 years. A hybrid method of thermal demagnetization at 200° C and progressive alternating field demagnetization were used to effectively extract the primary palaeomagnetic component, which is carried by magnetite. The lower Mammoth transition is characterized by palaeomagnetic direction of instability and decay of the relative palaeointensity, and occurred from late Marine Isotope Stage MG3 (3351 ka) to MG2 (3336 ka) or MG1 (3331 ka), spanning 15–20 kyr. Virtual geomagnetic poles (VGPs), calculated from primary palaeomagnetic directions, rapidly rebounded twice from southern latitudes to northern latitudes within the transition. In contrast to the complex lower Mammoth reversal behavior recorded in the Boso Peninsula succession, records from a lava sequence in O'ahu (Hawai'i) reveal a rebound following a 180° directional change, and those from a marl succession in Sicily (Italy) indicate a single rapid directional change. Diverse geomagnetic field evolution among these three sections is reflected resolution difference among the records likely in combination with an influence of non-axial dipole field., Oxford University Press (OUP)
Geophysical Journal International, 2021年09月02日, ［査読有り］

Formal ratification of the Global Boundary Stratotype Section and Point (GSSP) for the Chibanian Stage and Middle Pleistocene Subseries of the Quaternary System: the Chiba Section, Japan†
Yusuke Suganuma; Makoto Okada; Martin J. Head; Koji Kameo; Yuki Haneda; Hiroki Hayashi; Toshiaki Irizuki; Takuya Itaki; Kentaro Izumi; Yoshimi Kubota; Hiroomi Nakazato; Naohisa Nishida; Masaaki Okuda; Yasufumi Satoguchi; Quentin Simon; Yoshihiro Takeshita, The Executive Committee of the International Union of Geological Sciences on January 17, 2020 ratified the Global Boundary Stratotype Section and Point (GSSP) defining the base of the Chibanian Stage/Age and Middle Pleistocene Subseries/Subepoch at the Chiba section of the Chiba composite section, Japan. The Chiba composite section is a continuous and expanded marine sedimentary succession in the east-central Japanese archipelago facing the Pacific Ocean. It contains well-preserved pollen, marine micro-and macrofossils, a tightly-defined Matuyama-Brunhes (M-B) paleomagnetic polarity boundary, two geomagnetic field paleointensity proxies, and numerous tephra beds, allowing the establishment of a robust and precise chronostratigraphic framework. Its open-ocean continental slope setting has captured both terrestrial and marine environmental signals from upper Marine Isotope Stage (MIS) 20 to lower MIS 18. The M-B reversal serves as the primary guide for the Lower-Middle Pleistocene boundary, yield ing an astronomical age of 772.9 ka. The GSSP is positioned 1.1 m below the directional midpoint of the reversal, at the base of a regional lithostratigraphic marker, the OntakeByakubi-E (Byk-E) tephra bed, in the Chiba section. The GSSP has an astronomical age of 774.1 ka and occurs immediately below the top of Marine Isotope Substage 19c., International Union of Geological Sciences
Episodes, 2021年09月01日, ［査読有り］

On the relationship between paleomagnetic secular variation and excursions – Records from MIS 6 and 7 - ODP Leg 172
Steve Lund; Gary Acton; Brad Clement; Makoto Okada; Lloyd Keigwin, Elsevier BV
Physics of the Earth and Planetary Interiors, 2021年09月, ［査読有り］

関東平野西部毛呂山丘陵と川島コアから発見された第四系最下部の指標テフラ
納谷友規; 岡田 誠; 古澤 明; 水野清秀, Tokyo Geographical Society
Journal of Geography (Chigaku Zasshi), 2021年06月25日, ［査読有り］

Rock magnetic variability of quaternary deep-sea sediments from the Bering Sea and their environmental implications
Steve Lund; Emily Mortazavi; Ellen Platzman; Matt Kirby; Joe Stoner; Makoto Okada, Elsevier BV
Deep Sea Research Part I: Oceanographic Research Papers, 2021年06月, ［査読有り］

On the relationship between palaeomagnetic secular variation and excursions—records from MIS 8–ODP Leg 172
Steve Lund; Gary Acton; Brad Clement; Makoto Okada; Lloyd Keigwin,
Palaeomagnetic secular variation (PSV) and excursion data obtained across MIS 8 (243–300 ka) from the western North Atlantic Ocean ODP (Ocean Drilling Program) sites 1060–1063 show composite high-resolution PSV records (both directions and relative palaeointensity) developed for each site and intercompared. Two methods of chronostratigraphy allow us to date these records. First, we used published results that compared the calcium carbonate records of ODP Leg 172 sediments and tuned them with Milankovich cyclicity. We also compared our palaeointensity records with the PISO-1500 global palaeointensity record that was dated with oxygen isotope stratigraphy. We prefer the PISO-1500 record to date our cores. Two excursions are preserved in our PSV records—Excursions 8α and 9α. Our revised age estimates for both excursions are 8α (236.7–239.8 ka) and 9α (283.7–286.9 ka). We have compared shipboard measurements of the two excursions with u-channel measurements of selected excursion intervals. Excursion 8α is interpreted as a ‘Class II’ excursion (local reversal) with in-phase inclination and declination changes; Excursion 9α is a ‘Class I’ excursion with 90° out-of-phase inclination and declination changes. Averaged directions (after removal of true excursional directions) and relative palaeointensity in 3 and 9 ka overlapping intervals show significant PSV directional variability over 104 yr timescales that is regionally correlatable among the four sites. A notable pattern of angular dispersion variability involves most time spent with low (∼10°) dispersion, with three shorter intervals of high (∼25°) dispersion. The relative palaeointensity variability also shows significant variability over 104 yr timescales with three notable intervals of low palaeointensity in all four records and a direct correspondence between the three low-palaeointensity intervals and the three intervals of high angular dispersion. The two magnetic field excursions occur in two of the three low-palaeointensity/high-dispersion intervals. This suggests that the geomagnetic field operates in two states between reversals, one with regular to high palaeointensity and low directional variability and one with low palaeointensity and significantly higher directional variability and excursions., Oxford University Press (OUP)
Geophysical Journal International, 2021年03月11日, ［査読有り］

Multiproxy sedimentological and geochemical analyses across the Lower–Middle Pleistocene boundary: chemostratigraphy and paleoenvironment of the Chiba composite section, central Japan
Kentaro Izumi; Yuki Haneda; Yusuke Suganuma; Makoto Okada; Yoshimi Kubota; Naohisa Nishida; Moto Kawamata; Takuya Matsuzaki, The Chiba composite section (CbCS) in the Kokumoto Formation, Kazusa Group, central Japan is a thick and continuous marine succession that straddles the Lower–Middle Pleistocene boundary and the well-recognized Matuyama–Brunhes paleomagnetic polarity boundary. Although recent studies extensively investigated the CbCS, its chemostratigraphy, particularly around the Lower–Middle Pleistocene boundary, is poorly understood. Therefore, in this study, we performed multiproxy sedimentological and geochemical analyses of the CbCS, including the Chiba section, which is the Global Boundary Stratotype Section and Point for defining the base of the Middle Pleistocene Subseries. The aim of these analyses is to establish the high-resolution chemostratigraphy and to reconstruct the paleoenvironments of its sedimentary basin in detail. We used the K/Ti ratio as a broad proxy for the clastic material grain size of the sediments. Although the K/Ti ratio generally varies throughout the studied interval, the K/Ti ratio especially during Marine Isotope Stage (MIS) 19a shows a variation pattern like those of the foraminiferal oxygen isotope (δ¹⁸O) records. The records of the C/N ratio of bulk samples and carbon isotope ratio of the organic carbon (δ¹³C_org) suggest that the organic matter in the CbCS sediments during MIS 19c mostly originated from marine plankton, whereas the organic matter during MIS 18 and 19a was characterized by a mixture of marine plankton and terrestrial plants. These records are clearly indicative of changes in mixing ratio of marine vs. terrestrial organic matter in association with glacial–interglacial cycles from the late MIS 20 to the early MIS 18. In addition, we calculated the mass accumulation rates (MARs) of organic carbon, biogenic carbonate, and terrigenous material for quantitative interpretations on the paleoenvironmental changes. MAR calculations revealed that the contribution of marine organic carbon relative to terrestrial organic carbon increased during MIS 19c, and that the contribution of the terrigenous material relative to biogenic carbonate decreased during MIS 19c. Furthermore, we observed relatively large variations in the total organic carbon and total nitrogen contents during MIS 19a. These variations were probably caused by the relative decrease in bottom-water oxygen level, which is also supported by our trace-fossil data, although it is not certain whether the increase in organic-carbon flux at ~ 760 ka was due to the synchronous increase in biogenic productivity in surface water. Such a relative decrease in bottom-water oxygen level was partly due to the increased ocean stratification because of the northward displacement of the Kuroshio Extension Front., Springer Science and Business Media LLC
Progress in Earth and Planetary Science, 2021年01月22日, ［査読有り］

Correction to: Calcareous nannofossil biostratigraphy of the Lower–Middle Pleistocene boundary of the GSSP, Chiba composite section in the Kokumoto Formation, Kazusa Group, central Japan, and implications for sea-surface environmental changes (Progress in Earth and Planetary Science, (2020), 7, 1, (36), 10.1186/s40645-020-00355-x)
Koji Kameo; Yoshimi Kubota; Yuki Haneda; Yusuke Suganuma; Makoto Okada, In the original publication of this article (Kameo et al. 2020), a reference article is missing in the reference list. The missing reference should be referenced at the location in the main body of the article below where “Hole U1427” is referred to. Main Text: Their occurrences suggest that the influence of coastal water near the coast of the Japanese islands may have increased along with the Kuroshio Current after the full interglacial during MIS 19. In Japan Sea, subtropical Tsushima Warm Current radiolarian species were rapidly decreased in Hole U1427 (Sagawa et al. 2018). Sagawa et al. (2018) suggested that shallowing the Tsushima strait due to lowering sea-level prevented the Tsushima Warm Current from flowing into Japan Sea after interglacial maxima. The missing reference: Sagawa T, Nagahashi Y, Satoguchi Y, Holbourn A, Itaki T, Gallagher SJ, Saavedra-Pellitero M, Ikehara K, Irino T, Tada R (2018) Integrated tephrostratigraphy and stable isotope stratigraphy in the Japan Sea and East China Sea using IODP Sites U1426, U1427, and U1429, Expedition 346 Asian Monsoon. Prog Earth Planet Sci 5:18. https://doi.org/10.1186/s40645- 018-0168-7, Springer
Progress in Earth and Planetary Science, 2020年12月01日

Calcareous nannofossil biostratigraphy of the Lower–Middle Pleistocene boundary of the GSSP, Chiba composite section in the Kokumoto Formation, Kazusa Group, central Japan, and implications for sea-surface environmental changes
Koji Kameo; Yoshimi Kubota; Yuki Haneda; Yusuke Suganuma; Makoto Okada, Springer Science and Business Media LLC
Progress in Earth and Planetary Science, 2020年12月, ［査読有り］

A full sequence of the Matuyama-Brunhes geomagnetic reversal in the Chiba composite section, Central Japan
Haneda, Y; Okada, M; Suganuma Y; Kitamura, T, Springer
Progress in Earth and Planetary Science, 2020年09月01日, ［査読有り］

A paleomagnetic record of the early Matuyama chron including the Réunion subchron and the onset Olduvai boundary: High-resolution magnetostratigraphy and insights from the transitional geomagnetic fields
Konishi, T; Okada, M, 責任著者, Springer
Progress in Earth and Planetary Science, 2020年08月08日, ［査読有り］

Millennial-scale hydrographic changes in the northwestern Pacific during marine isotope stage 19: teleconnections with ice melt in the North Atlantic
Haneda, Y; Okada, M; Kubota, Y; Suganuma, Y
Earth and Planetary Science Letters, 2020年01月, ［査読有り］

High-resolution 10Be and paleomagnetic recording of the last polarity reversal in the Chiba composite section: Age and dynamics of the Matuyama–Brunhes transition
Simon, Q; Suganuma, Y; Okada, M; Haneda, Y; ASTER Team, Elsevier
Earth and Planetary Science Letters, 2019年08月, ［査読有り］

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications
Haneda, Y; Okada, M, Springer
Progress in Earth and Planetary Science, 2019年01月21日, ［査読有り］

千葉セクション:下部‐中部更新統境界の国際境界模式層断面とポイントへの提案書(要約)
菅沼悠介; 菅沼悠介; 羽田裕貴; 林広樹; 本郷美佐緒; 堀江憲路; 兵頭政幸; 五十嵐厚夫; 石塚治; 入月俊明; 板木拓也; 泉賢太郎; 亀尾浩司; 川又基人; 川村賢二; 木村純一; 小島隆宏; 久保田好美; 中里裕臣; 西田尚央; 岡田誠; 荻津達; 奥田昌明; 奥野淳一; 里口保文; 仙田量子; SIMON Quentin; 末吉哲雄; 紫谷築; 菅谷真奈美; 竹下欣宏; 竹原真美; 渡邉正巳; 八武崎寿史; 吉田剛
地質学雑誌, 2019年01月15日, ［査読有り］

Corrigendum to “Paleoclimatic and paleoceanographic records through Marine Isotope Stage 19 at the Chiba composite section, central Japan: A key reference for the Early–Middle Pleistocene Subseries boundary” (Quaternary Science Reviews (2018) 191 (406–430), (S0277379117302251) (10.1016/j.quascirev.2018.04.022))
Suganuma, Y.; Haneda, Y.; Kameo, K.; Kubota, Y.; Hayashi, H.; Itaki, T.; Okuda, M.; Head, M.J.; Sugaya, M.; Nakazato, H.; Igarashi, A.; Shikoku, K.; Hongo, M.; Watanabe, M.; Satoguchi, Y.; Takeshita, Y.; Nishida, N.; Izumi, K.; Kawamura, K.; Kawamata, M.; Okuno, J.; Yoshida, T.; Ogitsu, I.; Yabusaki, H.; Okada, M.
Quaternary Science Reviews, 2019年

Paleoclimatic and paleoceanographic records through Marine Isotope Stage 19 at the Chiba composite section, central Japan: A key reference for the Early–Middle Pleistocene Subseries boundary
Yusuke Suganuma; Yuki Haneda; Koji Kameo; Yoshimi Kubota; Hiroki Hayashi; Takuya Itaki; Masaaki Okuda; Martin, J. Head; Manami Sugaya; Hiroomi Nakazato; Atsuo Igarashi; Kizuku Shikoku; Misao Hongo; Masami Watanabe; Yasufumi Satoguchi; Yoshihiro Takeshita; Naohisa Nishida; Kentaro Izumi; Kenji Kawamura; Moto Kawamata; Jun’ichi Okuno; Takeshi Yoshida; Itaru Ogitsu; Hisashi Yabusaki; Makoto Okada, ラスト(シニア)オーサー, Marine Isotope Stage (MIS) 19 is an important analogue for the present interglacial because of its similar orbital configuration, especially the phasing of the obliquity maximum to precession minimum. However, sedimentary records suitable for capturing both terrestrial and marine environmental changes are limited, and thus the climatic forcing mechanisms for MIS 19 are still largely unknown. The Chiba composite section, east-central Japanese archipelago, is a continuous and expanded marine sedimentary succession well suited to capture terrestrial and marine environmental changes through MIS 19. In this study, a detailed oxygen isotope chronology is established from late MIS 20 to early MIS 18, supported by a U-Pb zircon age and the presence of the Matuyama-Brunhes boundary. New pollen, marine microfossil, and planktonic foraminiferal delta O-18 and Mg/Ca paleotemperature records reveal the complex interplay of climatic influences. Our pollen data suggest that the duration of full interglacial conditions during MIS 19 extends from 785.0 to 775.1 ka (9.9 kyr), which offers an important natural baseline in predicting the duration of the present interglacial. A Younger Dryas-type cooling event is present during Termination IX, suggesting that such events are linked to this orbital configuration. Millennial- to multimillennial-scale variations in our delta O-18 and Mg/Ca records imply that the Subarctic Front fluctuated in the northwestern Pacific Ocean during late MIS 19, probably in response to East Asian winter monsoon variability. The climatic setting at this time appears to be related to less severe summer insolation minima at 65N and/or high winter insolation at 50N. Our records do not support a recently hypothesized direct coupling between variations in the geomagnetic field intensity and global/regional climate change. Our highly resolved paleoclimatic and paleoceanographic records, coupled with a well-defined Matuyama-Brunhes boundary (772.9 ka; duration 1.9 kyr), establish the Chiba composite section as an exceptional climatic and chronological reference section for the Early-Middle Pleistocene boundary. (C) 2018 The Authors. Published by Elsevier Ltd., Elsevier BV
Quaternary Science Reviews, 2018年07月, ［査読有り］

Paleomagnetic direction and paleointensity variations during the Matuyama–Brunhes polarity transition from a marine succession in the Chiba composite section of the Boso Peninsula, central Japan
Makoto Okada; Yusuke Suganuma; Yuki Haneda; Osamu Kazaoka, 筆頭著者, Springer Science and Business Media LLC
Earth, Planets and Space, 2017年12月, ［査読有り］

Chronostratigraphy of the Pliocene-Pleistocene boundary in forearc basin fill on the Pacific side of central Japan: Constraints on the spatial distribution of an unconformity resulting from a widespread tectonic event
Masayuki Utsunomiya; Chie Kusu; Ryuichi Majima; Yuichiro Tanaka; Makoto Okada, ラスト(シニア)オーサー, The upper Ikego Formation (Pliocene) and the Urago Formation (Pliocene to Lower Pleistocene) have been examined for their lithostratigraphy, calcareous nannofossil biostratigraphy, and magneto-stratigraphy. Both formations are forearc basin fills exposed on the Miura Peninsula on the Pacific side of central Japan. The boundary between these formations has been previously treated as the western extension of the Kurotaki Unconformity, which was considered to be related to widespread tectonic change at ca. 3 Ma in the Japanese forearc region. However, the presence of the unconformity on the Miura Peninsula remains unclear due to sparse lithostratigraphic and chronostratigraphic data around the boundary between the both formations. In the study area, the Ikego Formation consists mainly of sandy mudstone and the Urago Formation of sandstone and muddy sandstone; both formations contain numerous tuff beds. Key tuff beds and the last appearance of Discoaster tamalis have been identified in the upper Ikego Formation and the lower Urago Formation, allowing these formations to be considered conformable. The following continuous stratigraphic markers were identified (in ascending order): top of the Mammoth Subchronozone (3.21 Ma); base (3.13 Ma) and top (3.05 Ma) of the Kaena Subchronozone; last appearance of Discoaster tamalis (2.76 Ma); the widespread tuff bed KGP (ca. 2.5 Ma); and the last appearance of Discoaster pentaradiatus (2.41 Ma). Sedimentation rates are almost constant among these age-controlled horizons, which indicates continuous sedimentation from 3.2 to 2.4 Ma. The results indicate that the Kazusa Group conformably overlies the Miura Group on the Miura Peninsula, which provides a well-established continuous stratigraphic section for analyses of regional paleoenvironmental and tectonic evolution in the Japanese forearc region. (C) 2017 Elsevier Ltd and INQUA. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
QUATERNARY INTERNATIONAL, 2017年10月, ［査読有り］

Millennial-scale northern Hemisphere Atlantic-Pacific climate teleconnections in the earliest Middle Pleistocene
Masayuki Hyodo; Balazs Bradak; Makoto Okada; Shigehiro Katoh; Ikuko Kitaba; David L. Dettman; Hiroki Hayashi; Koyo Kumazawa; Kotaro Hirose; Osamu Kazaoka; Kizuku Shikoku; Akihisa Kitamura, Suborbital-scale climate variations, possibly caused by solar activity, are observed in the Holocene and last-glacial climates. Recently published bicentennial-resolution paleoceanic environmental records reveal millennial-scale high-amplitude oscillations postdating the last geomagnetic reversal in the Marine Isotope Stage (MIS) 19 interglacial. These oscillations, together with decoupling of post-reversal warming from maximum sea-level highstand in mid-latitudes, are key features for understanding the climate system of MIS 19 and the following Middle Pleistocene. It is unclear whether the oscillations are synchronous, or have the same driver as Holocene cycles. Here we present a high resolution record of western North Pacific submarine anoxia and sea surface bioproductivity from the Chiba Section, central Japan. The record reveals many oxic events in MIS 19, coincident with cold intervals, or with combined cold and sea-level fall events. This allows detailed correlations with paleoceanic records from the midlatitude North Atlantic and Osaka Bay, southwest Japan. We find that the millennial-scale oscillations are synchronous between East and West hemispheres. In addition, during the two warmest intervals, bioproductivity follows the same pattern of change modulated by bicentennial cycles that are possibly related to solar activity., NATURE PUBLISHING GROUP
SCIENTIFIC REPORTS, 2017年08月, ［査読有り］

CONNECTING MARINE AND ON-LAND PALEOINITENSITY STUDIES
Hidetoshi Shibuya; Nobutatsu Mochizuki; Takeshi Hasegawa; Makoto Okada, Geological Society of America
Geological Society of America Abstracts with Programs, 2017年

Stephanodiscus akutsui, a new fossil diatom species from the Middle Pleistocene Miyajima Formation, Shiobara Group, Tochigi Prefecture, central Japan
Kojima; T; Saito-Kato; M; Okada; M, 日本珪藻学会
Diatom, 2016年12月31日, ［査読有り］

A record of the upper Olduvai geomagnetic polarity transition from a sediment core in southern Yokohama City, Pacific side of central Japan
Chie Kusu; Makoto Okada; Atsushi Nozaki; Ryuichi Majima; Hideki Wada, Springer Science and Business Media LLC
Progress in Earth and Planetary Science, 2016年12月, ［査読有り］

Calcareous nannofossil biochronology from the upper Pliocene to lower Pleistocene in the southernmost Boso Peninsula, central part of the Pacific side of Japan
K. Kameo; M. Okada, The calcareous nannofossil biostratigraphy in the southernmost Boso Peninsula, central part of the Pacific side of Japan, was examined to calibrate nannofossil biohorizons to an existing oxygen isotope stratigraphy for the northwestern Pacific. Five nannofossil biohorizons were detected in the uppermost Pliocene and the lower Pleistocene Mera and Minamiasai Formations. Each biohorizon can be correlated with a previously presented magnetic reversal and a corresponding marine isotope stage (MIS) in both formations. They are from bottom to top: last occurrence (LO) of Discoaster asymmetricus (MIS G8-G9 transition), LO of Reticulofenestra minutula var. B (MIS G8-G9 transition), LO of Discoaster tamalis (MIS G7-G8 transition), LO of Discoaster surculus (MIS 100), and LO of Discoaster pentaradiatus (MIS 95). Based on a comparison with previous studies, most of these biohorizons are traceable events, although the degree of synchrony varies depending on the biohorizons. Moreover, the LO of R. minutula var. B, an abrupt disappearance event of larger Reticulofenestra specimens in the lower part of the Minamiasai Formation, is also traceable to other regions. (C) 2016 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
JOURNAL OF ASIAN EARTH SCIENCES, 2016年11月, ［査読有り］

Sedimentary processes and depositional environments of a continuous marine succession across the Lower–Middle Pleistocene boundary: The Kokumoto Formation, Kazusa Group, central Japan
Nishida, N; Kazaoka, O; Izumi, K; Suganuma, Y; Okada, M; Yoshida, T; Ogitsu, I; Nakazato, H; Kameyama, S; Kagawa, A; Morisaki, M; Nirei, H, The Chiba composite section of the Kokumoto Formation in central Japan is a remarkable, thick marine succession and is a candidate for formal recognition as the Global Boundary Stratotype Section and Point (GSSP) for the base of the Middle Pleistocene stage. Although there have been numerous studies of the Kokumoto Formation, the sedimentology of the formation, particularly in the Chiba composite section, has been unclear. We use field observations and laboratory analyses to elucidate the sedimentary processes and depositional environments of the formation. The Chiba composite section includes the Matuyama-Brunhes paleomagnetic reversal, which is the primary guide for the Lower-Middle Pleistocene boundary, along with multiple tephra deposits that provide isochronous correlational tie points. One bed, Byk-E (also known as Ontake-Byakubi Tephra), immediately underlies the paleomagnetic reversal and hence provides a useful widespread marker for the boundary. The predominant silty beds of the Chiba composite section are intensely bioturbated and lack evidence of episodic deposition such as slumps or muddy turbidites. However, minor sandy beds intercalated within the silty section, particularly in its lower part, are either (1) fining upward sequences with faint planar or ripple laminations and an erosional base, or (2) sequences containing abundant mud clasts in a poorly sorted sand matrix with a sharp base and an irregular top surface. The silty beds are interpreted to be hemipelagite formed by deposition of fine-grained suspended material under stable and calm bottom-water conditions. The sandy deposits are interpreted to be sediment gravity-flow deposits (i.e., turbidites and debrites). These sedimentary processes and the trace fossil assemblage indicate that the Chiba composite section was formed in a continental slope environment. The depositional environments of the Chiba composite section, together with tephrostratigraphy, make it suitable for high-resolution studies on the paleoenvironment, paleoclimate, and paleoceanography of the northwest Pacific Ocean across the Lower-Middle Pleistocene boundary; it is therefore a suitable candidate to become the GSSP for the Middle Pleistocene. (C) 2015 Elsevier Ltd and INQUA. All rights reserved., Elsevier Ltd and INQUA
Quaternary International, 2016年03月, ［査読有り］

High resolution stratigraphy across the early-middle Pleistocene boundary from a core of the Kokumoto Formation at Tabuchi, Chiba Prefecture, Japan
Masayuki Hyodo; Shigehiro Katoh; Akihisa Kitamura; Kenta Takasaki; Hayato Matsushita; Ikuko Kitaba; Ikuko Tanaka; Masakazu Nara; Takuya Matsuzaki; David L. Dettman; Makoto Okada, We present a detailed stratigraphy of the lithology, sedimentary facies, magnetic susceptibility, and chemical composition of a 54-m thick core sequence drilled adjacent to the Chiba section, a candidate for the Global Boundary Stratotype Section and Point of the early-middle Pleistocene boundary. Siltstones rich in trace fossils are dominant throughout the core, except for the lowermost sand beds. The Byakubi tephra is divided into three units, of which the uppermost (39.54-39.49 m core depth) is identified as a primary bed showing evidence of fallout. The preliminary Matuyama-Brunhes magnetic polarity boundary lies 1 m above the top of the fallout unit. Maximum and minimum susceptibility axes for anisotropy of magnetic susceptibility have shallow (<11 degrees) and steep (>73 degrees) inclinations, respectively, throughout the core. The results suggest that sedimentary structures formed in calm environments remain undisturbed in the sediment. Clustered maximum axis directions indicate the influence of a persistent NW-SE contour current. The homogeneous depositional environment for the siltstone interval is supported by relatively smooth variations in magnetic susceptibility and chemical composition. Stratigraphic correlation with published oxygen isotope data indicates that the depositional age of the core may extend from the end of marine oxygen isotope stage (MIS) 20 to just after mid-MIS 19, from which an average sedimentation rate of 2-2.5 m/ky is estimated. These results suggest that the Chiba section has a high potential to provide an excellent stratotype for the early-middle Pleistocene boundary. (C) 2015 Elsevier Ltd and INQUA. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
QUATERNARY INTERNATIONAL, 2016年03月, ［査読有り］

Paleomagnetic field variability and chronostratigraphy of Brunhes-Chron deep-sea sediments from the Bering Sea: IODP Expedition 323
Steve Lund; Joseph Stoner; Makoto Okada; Emily Mortazavi, IODP Expedition 323 recovered six complete and replicate records of Brunhes-Chron paleomagnetic field variability (0-780,000 years BP) in 2820 m core depth below sea floor (CSF) of deep-sea sediments. On shipboard, we made more than 220,000 paleomagnetic measurements on the recovered sediments. Since then, we have u-channel sampled more than 300 m of Brunhes Chron sediments to corroborate our shipboard measurements and improve our paleomagnetic and rock magnetic understanding of these sediments. Several intervals of distinctive paleomagnetic secular variation (PSV) have been identified that appear to be correlatable among sites 1343, 1344, and 1345. One magnetic field excursion is recorded in sediments of sites 1339, 1343, 1344, and 1345. We identify this to be excursion 7 alpha/Iceland Basin Event (192,000 years BP), which is also seen in the high-latitude North Atlantic Ocean (Channell et al., 1997). We have verified in u-channels the placement of the Brunhes/Matuyama boundary (780,000 years BP) at sites 1341 and 1343. Finally, we have developed a medium-quality relative paleointensity record for these sediments that is correlatable among the sites, even though it is still biased by large amplitude environmental variability. On the basis of these observations we have built a magnetic chronostratigraphy of Expedition 323 sediments suitable for regional correlation and dating over the last 1 million years, and compared this with oxygen-isotope chronostratigraphy from sites U1339 and U1345. (C) 2016 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 2016年03月, ［査読有り］

Quantitative paleoclimate reconstruction based on a 130 ka pollen record from the C9001C core off NE Japan
Manami Sugaya; Masaaki Okuda; Makoto Okada, ラスト(シニア)オーサー, Although monsoons are an important climatic factor in the Indo-Pacific region, the mechanism responsible for monsoon variations is not fully understood, particularly at the 105 year-scale, which includes the Milankovitch orbital cycles. Here, we provide a palynological result from the C9001C marine core drilled in the NW Pacific off the Shimokita Peninsula, eastern Japan. Based on the parallel delta O-18 record, the pollen record covers the past 130,000 years. During the interglacial periods (MIS1 and 5e), the C9001C core is dominated by cool temperate pollen of Fagus (beech) and Quercus subgenus Lepidobalanus (deciduous oak) that is similar to the present-day Shimokita vegetation. However, during the glacial periods (MIS2-4), the pollen spectra are dominated by subarctic elements of Betula (birch) and Picea (spruce), similar to the vegetation of Sakhalin and northern Hokkaido. These fossil pollen data are converted into quantitative climate variables by using the modern analog technique. Of the reconstructed paleoclimate variables, the mean annual temperature (Tann) correlates with the parallel delta O-18 record. By contrast, reconstructed precipitation in the summer (Psum) shows a similar pattern to the northern insolation variations particularly during MIS5, though the phase relation between the two curves requires further studies. (C) 2015 Elsevier Ltd and INQUA. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
QUATERNARY INTERNATIONAL, 2016年03月, ［査読有り］

Stratigraphy of the Kazusa Group, Boso Peninsula: An expanded and highly-resolved marine sedimentary record from the Lower and Middle Pleistocene of central Japan
Osamu Kazaoka; Yusuke Suganuma; Makoto Okada; Koji Kameo; Martin J. Head; Takeshi Yoshida; Manami Sugaya; Shun Kameyama; Itaru Ogitsu; Hisashi Nirei; Nobuyuki Aida; Hisao Kumai, Major climatic reorganizations, including changes in the nature of glacialeinterglacial cycles through the Pleistocene, are a key issue for improving the understanding of Earth's climate system. Highly resolved marine sedimentary records are essential to reconstruct the details of these past climatic changes and investigate the mechanisms responsible for them. The Kazusa Group, located in the central part of the Japanese island chain, is well-exposed and contains a remarkably continuous and thick, deep-and shallow-water marine sedimentary succession. This group also contains well-preserved marine micro-fossils, pollen, paleomagnetic reversal events, geochemical signatures, and a large number of tephra beds. These features allow us to establish a robust chronological and stratigraphic framework for the Kazusa Group, and provide a rare opportunity to study oceanic and terrestrial climatic and environmental changes at high resolution especially through the Lower and lower Middle Pleistocene. In the Boso Peninsula, Chiba Prefecture, the Kazusa Group is deeply incised, yielding spectacular river-cut exposures. The Matuyama-Brunhes paleomagnetic reversal is observed immediately above the widespread Byakubi-E (Byk-E) tephra in the Chiba composite section within the Kokumoto Formation (Kazusa Group). Because the Matuyama-Brunhes boundary customarily serves as the primary guide for the Lower-Middle Pleistocene Subseries boundary, the Chiba composite section is considered an excellent candidate for its global boundary stratotype section and point (GSSP). This study reviews the published data for the Kazusa Group (hitherto almost exclusively in Japanese) in order to place the Chiba composite section within its broader depositional and chronostratigraphic context. (C) 2015 Elsevier Ltd and INQUA. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
QUATERNARY INTERNATIONAL, 2015年10月, ［査読有り］

オホーツク海底の表層堆積物における花粉群の平面分布
菅谷真奈美; 奥田昌明; 岡田 誠; 坂本竜彦, 日本地質学会
地質学雑誌, 2015年10月, ［査読有り］

Early to Middle Miocene rotational tectonics of the Ou Backbone Range, northeast Japan
Jun Hosoi; Makoto Okada; Tomohiro Gokan; Kazuo Amano; Andrew James Martin, It is well known that a counterclockwise rotation occurred in the Miocene in northeast Japan. However, the detailed timing and mechanism of the rotation has been debated. Moreover, there has been no research about the relationship between rotational tectonics and the evolution of sedimentary basins. We carried out paleomagnetic and rock magnetic analyses in Nishiwaga Town, Iwate Prefecture, northeast Japan, where the stratigraphy and sedimentary basin formation have previously been clarified. We found that there was a counterclockwise rotational movement of about 45 degrees at about 15 Ma. From our results and previous studies on the tectonics and sedimentary basin development, we are able to ascertain the following tectonic history and sedimentary basin evolution in this area: (i) before the rotational movement, sandstone and mudstone were deposited in a tranquil environment with no volcanic activity coupled with slow tectonic subsidence; (ii) between 16.4-15.1 Ma and 14 Ma, a counterclockwise rotation occurred with rapid tectonic subsidence and continuous explosive volcanism; (iii) at about 14Ma, the counterclockwise rotation ended and there was a reduction in both subsidence and volcanism. This result shows the impact that rotational tectonics can have on sedimentary basin formation., WILEY-BLACKWELL
ISLAND ARC, 2015年09月, ［査読有り］

Age of Matuyama-Brunhes boundary constrained by U-Pb zircon dating of a widespread tephra
Yusuke Suganuma; Makoto Okada; Kenji Horie; Hiroshi Kaiden; Mami Takehara; Ryoko Senda; Jun-Ichi Kimura; Kenji Kawamura; Yuki Haneda; Osamu Kazaoka; Martin J. Head, The youngest geomagnetic polarity reversal, the Matuyama-Brunhes boundary (MBB), provides an important datum plane for sediments, ice cores, and lavas. Its frequently cited age of 780 ka is based on orbital tuning of marine sedimentary records, and is supported by Ar-40/Ar-39 dating of Hawaiian lavas using recent age calibrations. Challenging this age, however, are reports of younger astrochronological ages based on oxygen isotope stratigraphy of high-sedimentation-rate marine records, and cosmogenic nuclides in marine sediments and an Antarctic ice core. Here, we present a U-Pb zircon age of 772.7 +/- 7.2 ka from a marine-deposited tephra just below the MBB in a forearc basin in Japan. U-Pb dating has a distinct advantage over Ar-40/Ar-39 dating in that it is relatively free from assumptions regarding standardization and decay constants. This U-Pb zircon age, coupled with a newly obtained oxygen isotope chronology, yields an MBB age of 770.2 +/- 7.3 ka. Our MBB age is consistent with those based on the latest orbitally tuned marine sediment records and on an Antarctic ice core. We provide the first direct comparison between orbital tuning, U-Pb dating, and magnetostratigraphy for the MBB, fulfilling a key requirement in calibrating the geological time scale., GEOLOGICAL SOC AMER, INC
GEOLOGY, 2015年06月, ［査読有り］

安房層群安野層の古地磁気ー酸素同位体複合年代層序
羽田 裕貴; 岡田 誠, 一般社団法人 日本地質学会
日本地質学会学術大会講演要旨, 2015年

三浦半島北部の上総層群中部（下部更新統）で掘削されたコアの堆積相とオルドバイ正磁極亜帯の上限
楠 稚枝; 野崎 篤; 岡田 誠; 和田秀樹; 間嶋隆一
地質学雑誌, 2014年02月, ［査読有り］

前期〜中期中新世における東北日本弧内テクトニクス
細井 淳; 岡田 誠; 後閑友裕; 天野一男, 日本堆積学会
堆積学研究, 2013年12月, ［査読有り］

房総半島南端千倉層群における鮮新統−更新統境界層準の古地磁気-酸素同位体複合層序
岡田 誠; 所 佳実; 内田剛行; 荒井裕司; 斉藤敬二, 筆頭著者, 古地磁気および底生有孔虫化石の酸素同位体データを基に，房総半島南端に分布する鮮新－更新統境界を含む千倉層群の中部層準における詳細な編年を行った．その結果，検討層準がKaena逆磁極亜帯を含むGauss正磁極帯上部から松山逆磁極帯下部に，LR04酸素同位体標準カーブにおける海洋同位体ステージ（MIS）G16～93の間に対応することがそれぞれ判明した．またLR04タイムスケールでMIS 104とされていたMatuyama/Gauss境界は，MIS 103に相当することがわかった．この結果は，ATNTS2004で採用されている地中海の腐泥層序で見られる同境界の層位学的位置と一致する．, The Geological Society of Japan
地質学雑誌, 2012年02月, ［査読有り］

Coupled organic and inorganic carbon cycling in the deep subseafloor sediment of the northeastern Bering Sea Slope (IODP Exp. 323)
Laura M. Wehrmann; Nils Risgaard-Petersen; Heather N. Schrum; Emily A. Walsh; Youngsook Huh; Minoru Ikehara; Catherine Pierre; Steven D'Hondt; Timothy G. Ferdelman; Ana Christina Ravelo; Kozo Takahashi; Carlos Alvarez Zarikian, We studied microbially mediated diagenetic processes driven by carbon mineralization in subseafloor sediment of the northeastern Bering Sea Slope to a depth of 745 meters below seafloor (mbsf). Sites U1343, U1344 and U1345 were drilled during Integrated Ocean Drilling Program (IODP) Expedition 323 at water depths of 1008 to 3172 m. They are situated in the high productivity "Green Belt" region, with organic carbon burial rates typical of the high-productivity upwelling domains on western continental margins. The three sites show strong geochemical similarities. The downward sequence of microbially mediated processes in the sediment encompasses (1) organoclastic sulfate reduction, (2) anaerobic oxidation of methane (AOM) coupled to sulfate reduction, and (3) methanogenesis. The sediment contains two distinct zones of diagenetic carbonate formation, located at the sulfate-methane transition zone (SMTZ) and between 300 and 400 mbsf. The SMTZ at the three sites is located between 6 and 9 mbsf. The upward methane fluxes into the SMTZ are similar to fluxes in SMTZs underlying high-productivity surface waters off Chile and Namibia. Our Bering Sea results show that intense organic carbon mineralization drives high ammonium and dissolved inorganic carbon (DIC) production rates (>4.2 mmol m(-3) y(-1)) in the uppermost 10 mbsf and strongly imprints on the stable carbon isotope composition of DIC, driving it to a minimum value of -27%. (VPDB) at the SMTZ. Porewater calcium and magnesium profiles demonstrate formation of diagenetic Mg-rich calcite in the SMTZ. Below the SMTZ, methanogenesis results in C-13-enrichment of pore-water DIC, with a maximum value of + 11.9%.. The imprint of methanogenesis on the DIC carbon isotope composition is evident down to a depth of 150 mbsf. Below this depth, slow or absent microbially mediated carbon mineralization leaves DIC isotope composition unaffected. Ongoing carbonate formation between 300 and 400 mbsf strongly influences porewater DIC and magnesium concentration profiles. The linked succession of organic carbon mineralization and carbonate dissolution and precipitation patterns that we observe in the Bering Sea Slope sediment may be representative of passive continental margin settings in high-productivity areas of the world's ocean. (C) 2011 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
CHEMICAL GEOLOGY, 2011年05月, ［査読有り］

IODP Expedition 323—Pliocene and Pleistocene Paleoceanographic Changes in the Bering Sea
Takahashi, K; Ravelo, A.C; Alvarez Zarikian, C.A; the Expeditio; Scientists, High-resolution paleoceanography of the Plio-Pleistocene is important in understanding climate forcing mechanisms and the associated environmental changes. This is particularly true in high-latitude marginal seas such as the Bering Sea, which has been very sensitive to changes in global climate during interglacial and glacial or Milankovitch time scales. This is due to significant changes in water circulation, land-ocean interaction, and sea-ice formation. With the aim to reveal the climate and oceanographic history of the Bering Sea over the past 5 Ma, Integrated Ocean Drilling Program (IODP) Expedition 323 cored a total of 5741 meters of sediment (97.4% recovery) at seven sites covering three different areas: Umnak Plateau, Bowers Ridge, and the Bering slope region. Four deep holes range from 600 m to 745 m spanning in age from 1.9 Ma to 5 Ma. The water depths (819 m to 3173 m) allow characterization of past vertical water mass distribution such as the oxygen minimum zone (OMZ). The results highlight three key points. (1) The first is an understanding of long-term evolution of surface-water mass distribution during the past 5 Ma including past sea-ice distribution and warm and less eutrophic subarctic Pacific water mass entry into the Bering Sea. (2) We characterized relatively stagnant intermediate water mass distribution imprinted as laminated sediment intervals that have been ubiquitously encountered. Today, the OMZ impinges upon the sediments at ~700-1600 m water depths. In the past, the OMZ appears to have occurred mainly during interglacial periods. Changes in low oxygen-tolerant benthic foraminiferal faunas clearly concur with this observation. (3) We also characterized significant changes between glacial episode of terrigenous sedimentary supply and interglacial episode of diatom flux.
Scientific Drilling, 2011年03月, ［査読有り］

Expedition 323 summary
K.Takahashi; A.C.Ravelo; C.A.Zarikaian; the Expeditio; Scientists; Ivano Aiello; Hirofumi Asahi; Gretta Bartoli; Beth Caissie; Muhong Chen; Elena Colmenero-Hidalgo; Mea Cook; Kelsie Dadd; Gilles Guèrin; Katrine Husum; Akira Ijiri; Sev Kender; Douglas LaVigne; Tanzhuo Liu; Steve Lund; Christian März; Alan Mix; Maheswar Ojha; Makoto Okada; Yusuke Okazaki; Jonaotaro Onodera; Taou␣k Radi; Tatsuhiko Sakamoto; David Scholl; Zuzanna N. Stroynowski
Proc. IODP, 2011年, ［査読有り］

Description of basement volcanic sequences in Holes U1342A and U1342D on Bowers Ridge in the Bering Sea
H. Kawabata; K. Sato; Y. Tatsumi; D.W. Scholl; K. Takahashi; the Expeditio; Scientists
Proc. IODP, 2011年, ［査読有り］

Data report: site surveys in the Bering Sea for Integrated Ocean Drilling Program Expedition 323 (as part of IODP Proposal 477)
T. Sakamoto; K. Takahashi; K. Iijima; Y. Kido; F. Yamamoto; T. No; T. Tsuru; U. Suzuki; M. Okada; Y. Okazaki; H. Tokuyama; A. Taira
Proc. IODP, 2011年

Age model, physical properties and paleoceanographic implications of the middle Pleistocene core sediments in the Choshi area, central Japan
Koji Kameo; Makoto Okada; Moamen El-Masry; Toshio Hisamitsu; Saneatsu Saito; Hiroomi Nakazato; Naohiko Ohkouchi; Minoru Ikehara; Hisato Yasuda; Hiroshi Kitazato; Asahiko Taira, A continuous, well-preserved core was obtained from the Choshi area, on the Pacific side of Japan, to investigate paleoceanographic and paleoclimatic changes around the northwestern Pacific region during the middle Pleistocene. Siliciclastic sequences in the core are divided into five formations - the Obama, Yokone, Kurahashi and Toyosato Formations in the Inubo Group and the Katori Formation, in ascending order. Examination of calcareous nannofossils and magnetic polarities detected four datums in the core sediments of the Inubo Group: the top of Reticulofenestra asanoi, the base of Helicosphaera inversa, the top of Pseudoemiliania lacunosa and the Brunhes-Matuyama boundary. Fourteen marine isotope stages (MIS24-MIS11) were identified in the delta O-18 and delta C-13 records based on detected datums and the graphic correlation with the standard stack oxygen isotope curve. Magnetic susceptibility and gamma-ray attenuation porosity evaluator density were also measured and low values characterize the glacial intervals. Biogenic sedimentation by primary production may be larger during the glacial periods because of invasions of nutrient-rich northern surface-waters related to the southward shift of the Kuroshio front in the Choshi area., WILEY-BLACKWELL
ISLAND ARC, 2006年09月, ［査読有り］

Magnetostratigraphy of the Miocene Chiang Muan Formation, northern Thailand: Implication for revised chronology of the earliest Miocene hominoid in Southeast Asia
Y. Suganuma; T. Hamada; S. Tanaka; M. Okada; H. Nakaya; Y. Kunimatsu; H. Saegusa; S. Nagaoka; B. Ratanasthien, A paleomagnetic study has been conducted on the Miocene Chiang Muan Formation in northern Thailand, in order to provide a chronology for the earliest large-bodied Miocene hominoid in Southeast Asia. The Chiang Muan Formation is mainly composed of clay, silt and sand beds, indicating lacustrine and fluvial environments. Paleomagnetic samples were collected from 124 horizons along an approximately 150 m thick section from the Chiang Muan Formation at the opencast Chiang Muan Mine. Rock magnetic experiments and stepwise thermal demagnetizations revealed that the main carrier of the magnetization of the sediments is magnetite and the samples have stable magnetization. Exceptionally, stable magnetization is also carried by hematite, which is represented by red colored sediments. Characteristic remanent magnetization (ChRM) directions, calculated by the principal component analysis, revealed normal or reversed polarities of magnetization, which allow the application of the reversal test of McFadden and McElhinny [McFadden, P.L., McElhinny, M.W., 1990. Classification of the reverse test in paleomagnetism. Geophys. Int. 103, 725-729]. The mean paleomagnetic directions of the normal and reversed polarities passed the reversal test with a classification C, indicating that the Chiang Muan Formation preserved the primary magnetization. in total, five normal and four-reversed polarity zones are recognized from the studied section. Based on paleontological age constraints, this magnetostratigraphic column of the Chiang Muan Formation correlates best with Chron C5AAn-C5n of the geomagnetic polarity time scale (GPTS) from the geological time scale (GTS2004) developed by Gradstein et al. [Gradstein, F., Ogg, J., Smith, A. (Eds.) 2004. A Geological Time Scale 2004. Cambridge Univ. Press, Cambridge, UK, p. 589]. This correlation revealed that sedimentation of the Chiang Muan Formation began approximately at 13 Ma and continued until 9.8 Ma with a mean sedimentation rate of approximately 4.2 cm/ky. The age of the earliest Southeast Asian hominoid is between 12.4 and 13.0 Ma. (c) 2006 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY, 2006年09月, ［査読有り］

The variations of stable carbon isotope ratio of land plant-derived n-alkanes in deep-sea sediments from the Bering Sea and the North Pacific Ocean during the last 250,000 years
NP Ratnayake; N Suzuki; M Okada; M Takagi, Two piston cores, one located far from the continents (The North Pacific Ocean: ES core), and another located comparatively closer to the continents (The Bering Sea: BOW-8a core) were investigated to reconstruct environmental changes on source land areas. The results show significant contribution of terrestrial organic matter to sediments in both cores. The delta C-13 values of n-C-27, n-C-29, and n-C-31 alkanes in sediments from the North Pacific ES core show significant glacial to interglacial variation whereas those from the Bering Sea core do not. Variations of delta C-13 values of land plant n-alkanes are related to the environmental or vegetational changes in the source land areas. Environmental changes, especially, aridity, rainfall, and pCO(2) during glacial/interglacial transitional periods can affect vegetation, and therefore C-3/C-4 plant ratios, resulting in 6 13C changes in the preserved land plant biomarkers. Maximum values of delta C-13 as well as maximum average chain length values of long chain n-alkanes in the ES core occur mostly at the interglacial to glacial transition zones reflecting a time lag related to incorporation of living organic matter into soil and transportation into ocean basins via wind and/or ability of C-4 plants to adapt for a longer period before being replaced by C-3 plants when subjected to gradual climatic changes. Irregular variations with no clear glacial to interglacial trends in the BOW-8a core may result from complex mixture of aerosols from westerly winds and riverine organic matter from the Bering Sea catchments. In addition, terrestrial organic matter entering the Bering Sea could originate from multiple pathways including eolian, riverine, and ice rafted debris, and possibly be disturbed by turbidity and other local currents which can induce resuspension and re-sedimentation causing an obliterated time relation in the Bering Sea biomarker records. (c) 2005 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
CHEMICAL GEOLOGY, 2006年04月, ［査読有り］

Congener-specific carbon isotopic analysis of 18 PCB products using two dimensional GC/IRMS
Y Horii; G Petrick; M Okada; K Amano; T Katase; T Gamo; N Yamashita, lit this study, we developed a new approach of compound-specific carbon isotopic analysis using a two-dimensional gas chromatograph (2DGC) with a combustion furnace (C) isotope ratio mass spectrometer (IRMS), and applied it for the "congener-specific" carbon isotopic analysis of polychlorinated biphenyls (PCBs). It was clarified that the 2DGC system enables a better separation of individual PCB congeners than a single column. Accurate values of δC-13 were obtained for some congeners without co-elution. At the same time, a decrease of an undesirable organic carbon source from an impurity in the sample and column breed into the second column separation resulted in a significant improvement of detection limit. The estimated sensitivity of carbon using 2DGC/C/IRMS was less than 7 ng. Totally, thirty-one PCB congeners were measured in 18 PCB products: Kanechlors, Aroclors, Clophens, Phenoclors, Sovol, Trichlorodiphenyl including two PCB products from Eastern Europe (Delors, Chlorofen). Observed (δC-13 values of individual PCB congeners front 2DGC/C/IRMS ranged from -34.4 (CP180,. Delor-106) to -22.0%. (CB70/76, Sovol). These values are comparable to VC value expected for industrial chemicals ,made of shell oil. However, we found a specific trend of a decrease in the isotope compositions according to increasing chlorine number in each PCB product. Increased chlorine number caused increased C-13 depletion in all PCBs. It is worth mentioning that Delors and Chlorofen had a completly different range of δC-13 values for other PCB products, and could be identified by isotopic compositions. The wide range of isotopic compositions between the PCB products and individual congeners may prove to be a powerful tool in the determining the source of PCBs in the environment. This technique may, have wide applications in environmental chemistry., JAPAN SOC ANALYTICAL CHEMISTRY
BUNSEKI KAGAKU, 2005年05月, ［査読有り］

二次元ガスクロマトグラフ/同位体比質量分析計を用いた18種ポリ塩素化ビフェニル製剤の異性体別炭素同位体比分析
堀井 勇一; Gert Petrick; 岡田 誠; 天野 一男; 片瀬 隆雄; 蒲生 俊敬; 山下 信義, 世界各国から収集した18種類のPCB製品を，二次元GC/C/IRMSを用いて異性体別の炭素同位体分析を行い，その同位体比分布とPCB組成との関係を明らかにし，産出国による同位体比分布の違いを見いだした。担当部分：同位体分析法および同位体比と組成の関係に関する議論の指導
BUNSEKI KAGAKU, 2005年, ［査読有り］

房総半島に分布する下部更新統上総層群大田代層と梅が瀬層の高精度堆積年代ー石油公団研究井TR-3コアの酸素同位体比・古地磁気・石灰質ナンノ化石に基づく年代層序
辻 隆司; 宮田雄一郎; 岡田 誠; 三田 勲; 中川 洋; 佐藤由理; 中水 勝, 石油公団によって，房総半島上総層群梅ヶ瀬層下部〜大田代層で掘削された堆積岩コアの古地磁気・酸素同位体測・石灰質ナノ化石層序・火山灰層序により，詳細年代層序を構築した．これにより，梅ヶ瀬層下部がMIS27-28にあたり，大田代層の最上部がMIS29の間氷期にあたることがわかった．担当部分：古地磁気層序, 日本地質学会
地質学雑誌, 2005年01月, ［査読有り］

Chronostratigraphy of sediment cores from the Bering Sea and the subarctic Pacific based on paleomagnetic and oxygen isotopic analyses
M Okada; M Takagi; H Narita; K Takahashi, 筆頭著者, The chronostratigraphy of six piston cores collected from the Bering Sea and one piston core from the subarctic Pacific is reported. Age models are primarily based on oxygen isotope data from Cores BOW-8A and ES in conjuction with relative paleointensity proxy records, biogenic opal data, and a radiolarian datum from other cores whose sediments mainly consist of diatom microfossils and poorly preserved calcium carbonate. The records, the first paleointensity proxy reported from the Bering Sea, show that characteristic paleointensity lows at similar to 40, similar to 60 and similar to 100 ka, which have been well documented in other paleointensity records. Those features can be correlated to standard paleointensity curves with the aid of biogenic opal data and a radiolarian datum. The mean sedimentation rates of the diatom-rich cores collected in the eastern Bering Sea range from 10 to 20 cm kyr(-1). In contrast, the mean sedimentation rate of Core BOW-8A, from the western edge of the Bowers Ridge, is only similar to 3 cm kyr(-1), which is comparable to Core ES from the pelagic realm in the subarctic Pacific. These results suggest that biological productivity has been quite high during the late Pleistocene in the eastern part of the Bering Sea, but low over the western edge of the Bowers Ridge. (c) 2005 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 2005年, ［査読有り］

Characteristics of bottom surface sediments in relation to wind and wave action in Lake Kitaura, central Japan
T. Naya; K. Amano; M. Okada; R. Nakazato; F. Kumon; H. Nirei, 茨城県北浦湖底118地点で表層堆積物試料を採取し，粒度，全有機炭素量，全窒素量の分析を行い，風による波浪影響の強い浅い湖沼における堆積モデルを提唱した．担当部分：堆積物試料の採取，処理指導および堆積物組成に関する議論の一部．, 日本地質学会
The Journal of Geological Society of Japan, 2004年, ［査読有り］

Concentrations and fluxes of chloronaphthalenes in sediment from Lake Kitaura in Japan in past 15 centuries
Y Horii; J Falandysz; N Hanari; P Rostkowski; T Puzyn; M Okada; K Amano; T Naya; S Taniyasu; N Yamashita, The concentrations of 63 congeners of chloronaphthalene (CN; polychlorinated naphthalenes, PCNs) in dated on similar to500 B.C. to 2000 sediment core from the Lake Kitaura in Japan have been quantified by HRGC/HRMS after double column HPLC fractionation. Sediment from the Lake Kitaura showed a time-dependent pattern in distribution of CNs since the similar to500 B.C. Starting from the 1910s the total CNs content increased accelerating from the 1960s, and in parallel, the pattern of CN congeners has changed with a substantial increase in contribution from the penta, hexa, hepta, and octaCN. The total CNs content normalized to dry weight of sediment peaked out in the layer dated on 1984-1985, and next nearly two-fold decreased with further gradually decreasing concentration in 1987-2000. An occurrence of tri and tetraCNs in deep sediment layers corresponded to preindustrial synthesis and use of CNs seems to be connected to relatively greater water solubility and mobility in the pore water of those CN homologue groups. Based on CN congener pattern and results of multivariate analysis three main layers were separated in the sediment core. Starting from 1981 the emission sources related to combustion marker congeners become substantial contributors to flux of annually deposited CNs, while relative significance of the evaporative source marker congeners decreased after 1985. The annual flux of CNs into sediments of the Lake Kitaura was 0.073-0.31 pg/cm(2) before 1926, increased to 5.5-14pg/cm(2) in 1963-1970 and next sharply increased to 50-107 pg/ cm(2) in 1971-1985, and after that decreased to 17 Pg/Cm-2 in 1997-2000., MARCEL DEKKER INC
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A-TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING, 2004年, ［査読有り］

Diatom assemblage and productivity changes during the last 340,000 years in the subarctic Pacific
K Katsuki; K Takahashi; M Okada, Diatoms represent the major part of the microfossils preserved in the subarctic Pacific sediments. During the warm climate intervals the diatom accumulation rate (DAR) tended to increase, whereas it tended to decrease during the cold intervals. Principal component (PC) analysis of the fossil diatom assemblages in Piston Core KH99-3 ES samples from the subarctic Pacific was carried out to investigate the paleoceanographic conditions of the area. PC1 (59.9% of the total variance) was represented by Neodenticula seminae, a characteristic species representing the high nutrient concentrations, which dominated during the interglacial periods. The DAR and PC changes can be attributed to a global origin that is influenced by the nutrient change due to intermediate water change and to a local one that is explained by the change of upwelling region. The analysis of PC2 (17.1% of the total variance) indicates the change of water mass in the western subarctic Pacific. During Marine Isotope Stages (MIS) 2 and 3, the western subarctic Pacific region was significantly influenced by the sea-ice, which may have been derived from the coastal region or a proximal marginal sea., TERRA SCIENTIFIC PUBL CO
JOURNAL OF OCEANOGRAPHY, 2003年10月, ［査読有り］

Carbonate dissolution and planktonic foraminiferal assemblages observed in three piston cores collected above the lysocline in the western equatorial Pacific
K Kimoto; H Takaoka; M Oda; M Ikehara; H Matsuoka; M Okada; T Oba; A Taira, Planktonic foraminiferal assemblages were analyzed in three piston cores recovered from depths above the recent sedimentary lysocline (3.5 km) in the western Pacific Ocean for the purposes of (1) evaluating the effects of carbonate dissolution on fossil assemblages and (2) the impact of dissolution on paleoceanographic reconstructions for the past 300 kyr. We used the perfect test ratio (PTR) of Globorotalia menardii as an indicator of carbonate dissolution. Down-core variations of the PTR indicate that significant dissolution occurred during reglaciation steps represented by isotope stages 7-6, 5-4, and 3-2. The results of principal component analysis (PCA) based on the relative abundances of dominant species of planktonic foraminifera indicate that down-core changes in factor 1 loadings correlate with variations in PTR and with variations in the percentage of coarse fraction (> 63 mum) present in the sediments. These correlations indicate that foraminiferal assemblages were apparently altered by dissolution events despite the fact that they were deposited at water depths shallower than the modern lysocline. We also estimated variations in paleo-sea surface temperature (palco-SST) using the transfer function FP-12E. A negative correlation was found in communality as calculated from PCA and factor I loadings; this trend is distinct for the case of communality lower than 0.9. Thus, we conclude that estimated paleo-SST values based upon analysis of planktonic foraminifera are biased by carbonate dissolution. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
MARINE MICROPALEONTOLOGY, 2003年03月, ［査読有り］

千倉層群下部の石灰質ナンノ化石群集に基づく本邦中部太平洋側海域の後期鮮新世表層海洋環境
亀尾浩司・斎藤敬二・小竹信宏・岡田 誠, 房総半島南端部に分布する上部鮮新統千倉層群より産出する石灰質ナンノ化石群集を検討し，後期更新世の房総沖における海洋表層環境の変遷を考察した．担当部分：古地磁気層序による地層の詳細な年代決定に関する議論．, 日本地質学会
地質学雑誌, 2003年, ［査読有り］

Paleomagnetic overprints in ocean sediment cores and their relationship to shear deformation caused by piston coring
GD Acton; M Okada; BM Clement; SP Lund; T Williams, [1] We use paleomagnetic data from cores collected at Ocean Drilling Program Site 1062 on the Bahama Outer Ridge, as well as observations from prior cruises, to quantify the nature and to assess the causes of drilling overprints. The largest overprint arises from an isothermal remanent magnetization that is imparted to the core during coring or core retrieval. A second type of overprint is apparent only in soft sediments collected with a piston corer and has coercivities and unblocking temperatures that completely overlap those of the primary remanent magnetization, which means it cannot be removed by standard demagnetization methods. This demagnetization-resistant overprint can produce significant biases in paleomagnetic observations, particularly those from split core sections. We hypothesize that shearing, which occurs as a result of friction on the inside wall of the piston corer as it rips through sediments and cuts a core, deflects the ancient magnetization. We develop and test a model that predicts how shear deformation can rotate remanence-carrying grains and deflect the paleomagnetic remanence of a split core section. Using the shear model predictions and directions measured on split core sections and U channel samples from the undeformed core center, we estimate the average deformation sustained and then correct the split core data for biases caused by shear deformation. The reduction in the deviations between corrected split core data and U channel data is statistically significant, indicating that the shear model is capable of accounting for a significant portion of the systematic biases observed in paleomagnetic observations obtained from piston cores., AMER GEOPHYSICAL UNION
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2002年04月, ［査読有り］

茨城県北浦における柱状底質試料中の塩素化ナフタレン・ダイオキシン類異性体別分析　　　　　　　　　　　　　　　
堀井勇一; 岡田 誠; 天野一男; 羽成修康; 谷保佐知; 山下信義, 堆積物に含まれる塩素化ナフタレン(PCNs)やダイオキシン状物質の分離および異性体別分析を高精度で行う手法を確立した．さらに茨城県北浦湖底堆積物試料を用い，PCNs汚染の歴史復元を行った．担当部分：テーマ設定，堆積物試料採取指導，年代決定の議論．
分析化学, 2002年, ［査読有り］

タイ北部 Chian Muan に分布する第三系 Mae Moh 層群の古地磁気層序（予報）　　　　　　　　　　　　　　　
菅沼悠介; 岡田 誠; 長岡信治, 東南アジア初の中新世大型類人猿化石が発見されたタイ北部に分布する Mae Moh層群の年代を古地磁気層序学的手法で調査し，11Ma前後であることを初めて明らかにした．担当部分：古地磁気分析およびデータ処理の指導，年代決定の議論．
霊長類研究, 2002年, ［査読有り］

Records of the Cobb Mountain Subchron from the Bermuda Rise (ODP LEG 172)
Z Yang; BM Clement; GD Acton; SP Lund; M Okada; T Williams, Duplicate records of the Cobb Mountain Subchron were obtained from two holes (Holes 1063B at 33 degrees 41.204'N, 57 degrees 36'W and 1063C at 33 degrees 41.181'N, 57 degrees 36'W) drilled in a sediment drift at Ocean Drilling Program (ODP) Site 1063 on the northeast Bermuda Rise. We sub-sampled the cores from both holes using U-channels (up to 1.5 m long samples with 2 X 2 cm cross-section) focusing on continuous sampling through the late Matuyama interval containing the Cobb Mountain Subchron. Results of standard progressive alternating field demagnetization experiments reveal that these sediments generally have a stable characteristic component after removal of a low-coercivity drilling overprint. Additional discrete samples ( similar to 7 cm(3) oriented cubes) used in progressive thermal demagnetization studies display similar behavior. By taking duplicate sets of U-channels, we were able to identify and remove several measurement artifact, such as edge effects that affect measurements made near the ends of the U-channel samples. The upper normal-to-reverse polarity transition was not obtained because of a coring gap or an interval of coring deformation. After removing measurement artifacts, the records from the two holes were stacked to obtain a composite record. Virtual geomagnetic poles (VGPs) computed from the composite record follow a path through the central Pacific during the lower polarity transition, very similar to VGP paths from Cobb Mountain Subchron records from other sites around the world. Furthermore, the VGPs cluster near southern Africa early in the reversal process and then group in a nearly antipodal patch in the north Pacific late in the reversal. Taken together, these records indicate that the transitional field remained nearly dipolar through the polarity reversal, or at least during the beginning and end of the reversal when the field was dominated by an axial dipole tilted about 20-40 degrees to the spin axis. If a tilted dipole is an inherent part of the initiation and ending of a reversal, it may help explain why many sediment recorders, which are thought to smooth the field, record antipodal VGP paths through many reversals. (C) 2001 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
EARTH AND PLANETARY SCIENCE LETTERS, 2001年12月, ［査読有り］

Paleomagnetism and fission-track ages of Oki-Dogo Island in Southwest Japan
T Kojima; M Okada; H Ohira; K Tokieda; H Komuro; K Amano, 責任著者, Zircon fission-track (F.T.) ages and paleomagnetic directions were measured on the Neogene series of the Oki-Dogo Island. The results of F.T. dating on the the Tokibariyama Formation show ages of 23.7 +/- 1.3 and 20.0 +/- 2.3 Ma, indicating the early Early Miocene. Paleomagnetic measurements of the Tokibariyama, Kori Formations (24-17 Ma) and the Oki Trachyte-Rhyolite (6.8 Ma) were done to reveal the movement of Oki-Dogo Island during the Japan Sea opening. The Tokibariyama and Kori Formations show an average declination of 39.9 degrees. The Oki Trachyte-Rhyolite has the same average geomagnetic direction as the present day value. These results show that a clockwise rotation of 40 degrees +/- 15 degrees of the Oki-Dogo Island occurred between 17 and 6.8 Ma which is similar to the main land of southwest Japan., TERRA SCIENTIFIC PUBL CO
EARTH PLANETS AND SPACE, 2001年, ［査読有り］

Brunhes chron magnetic field excursions recovered from Leg 172 sediments
S.P.Lund; T.Williams; G.D.Acton; B.Clement; M.Okada, 国際深海掘削計画第172節航海 (ODP Leg172) によって採取された西大西洋の海底堆積物コアの古地磁気記録から最後の地磁気逆転以降の期間である過去78万年間に数多くの地磁気エクスカーションが起こっていたことを明らかにした．担当部分：試料の古地磁気測定およびデータ解析に関する議論．
Proceedings of the Ocean Drilling Program, Scientific Results, 2001年, ［査読有り］

Paleomagnetic records of Stage 3 excursions, Leg 172
S.P.Lund; G.D.Acton; B.Clement; M.Okada; T.Williams, 国際深海掘削計画第172節航海 (ODP Leg172) によって採取された堆積物コアに，酸素同位体ステージ３においてLaschamp Excursionに対応する地磁気エクスカーションが記録されていることを明らかにした．担当部分：試料の古地磁気測定およびデータ解析に関する議論．
Proceedings of the Ocean Drilling Program, Scientific Results, 2001年, ［査読有り］

Sulfur isotope records around Livello Bonarelli (northern Apennines, Italy) black shale at the Cenomanian-Turonian boundary
N Ohkouchi; K Kawamura; Y Kajiwara; E Wada; M Okada; T Kanamatsu; A Taira, Sulfur isotope ratios for carbonate-hosted sulfate show a rapid increase (+6 parts per thousand to +9 parts per thousand/m.y.) across the Livello Bonarelli black shale (Marche-Umbrian Apennines of Italy), which was deposited at the Cenomanian-Turonian boundary in the middle Cretaceous (93.5 hla). The increase suggests that rates of pyrite burial increased substantially over the event, resulting in a decrease of 9%-27% in the oceanic reservoir of SO42-. The enhanced pyrite burial mag have significantly increased the flux of oxygen to the atmosphere (9-27 x 10(18) mol/m.y.). Furthermore, removal of the large amount of iron associated,vith this process might have had a profound effect on iron cycle., GEOLOGICAL SOC AMER, INC
GEOLOGY, 1999年06月, ［査読有り］

Further application of the deconvolution method of post-depositional DRM to the precise record of the Matuyama-Brunhes reversal in the sediments from the Bose Peninsula, Japan
H Tsunakawa; M Okada; N Niitsuma, The Matuyama-Brunhes geomagnetic reversal was continuously recorded in the massive siltstones of the Bose marine sediments in Japan with the time resolution better than 9 years. However the Bose sediments probably have the post-depositional detrital remanent magnetization (pDRM) depressing short-period variations due to the convolution of the geomagnetic field. The previous application of the deconvolution method of pDRM to the 900 year records gave the half fixing depth of 21 cm. Further application of this fixing depth to the 4100 year record clearly shows nearly 100 year variations in both of the inclination and declination., TERRA SCIENTIFIC PUBL CO
EARTH PLANETS AND SPACE, 1999年, ［査読有り］

Quaternary geomagnetic field intensity: Constant periodicity or variable period?
T Sato; H Kikuchi; M Nakashizuka; M Okada, Paleomagnetic results are presented from a core, KH 90-3-5, in the Melanesia basin and are correlated with the previously obtained results from two cores, KH 73-4-7, KH 73-4-8, in the same basin in a period between 0.04 Ma and 1.1 Ma. The sediments in the three cores are composed mostly of calcareous ooze. It has been shown that the variation in the saturation isothermal remanent magnetization (SIRM) in the two cores is caused neither by deposition-rate variation of magnetic minerals nor by rock-magnetic inhomogeneity but almost solely by variations in CaCO3 dissolution. A close similarity between the variation in the SIRM in the two cores and the variation in the initial susceptibility (K) in KH 90-3-5 has enabled us to correlate among the cores, and also means negligible rock-magnetic inhomogeneity in the core. A time versus depth correlation has been established from the delta(18)O record of KH 90-3-5. The relative paleointensity record estimated from the natural remanent magnetization (NRM) normalized by kappa in KH 90-3-5 and those records in the other two cores are remarkably similar, implying that the records faithfully reflect variations in relative paleointensity of the geomagnetic field for the past 1.1 Ma. We examined on the periodicity of the paleointensity records with wavelets. It is shown that periods of major changes in the records reveal continuous shifts between about 50 Ka and 140 Ka over time. We offer an alternative viewpoint about the periodicity of the paleointensity in which periods of major changes shifted continuously within the time range instead of constant periodicities., AMER GEOPHYSICAL UNION
GEOPHYSICAL RESEARCH LETTERS, 1998年06月, ［査読有り］

Deconvolution of paleomagnetic directions from marine sediments in the Boso Peninsula, Japan, and its implications for the Matuyama-Brunhes transition field
H Tsunakawa; M Okada; N Niitsuma, The method of deconvolution of post-depositional DRM (detrital remanent magnetization) is applied to the paleomagnetic directions of continuous sedimentary sections from two sites in the Bose Peninsula, Japan. These sections have different accumulation rates and cover a time span of about 1000 years that includes the Matuyama-Brunhes reversal. Since the remanences are thought to be of the postdepositional DRM origin, a new deconvolution method with an exponential fixing function is applied. The deconvolution restores relative intensities of three components in the original fields from the remanence directions. As a result, the half-fixing depth is estimated to be 21 cm and the three-dimensional plot of the relative intensity is given. In the diagram of X and Z components, the polarity change in the geocentric axial dipole field with some additional field is recognized during the main reversal, while there seems to be no correlation between X and Y. After the deconvolution, the VGP path during the main reversal does not show longitudinal confinement, but does show longitudinal drift near the equator., TERRA SCIENTIFIC PUBL CO
JOURNAL OF GEOMAGNETISM AND GEOELECTRICITY, 1996年, ［査読有り］

Detailed variation of geomagnetic field intensity during the late Pleistocene at Site 882　　　　　　　　　　　　　　　
Ocean Drilling Program
Proceedings of the Ocean Drilling Program, Scientific Results, 1995年08月, ［査読有り］

WAS DEEP-WATER FORMED IN THE NORTH PACIFIC DURING THE LATE QUATERNARY - CADMIUM EVIDENCE FROM THE NORTHWEST PACIFIC
N OHKOUCHI; H KAWAHATA; M MURAYAMA; M OKADA; T NAKAMURA; A TAIRA, A benthic foraminifera Cd/Ca record, dating from the last glacial period to the Holocene, for a high sedimentation rate core recovered from the northwest Pacific is reported. It shows that the deep water (water depth of 2700 m) cadmium concentration was about 50% lower in the last glacial period than in the Holocene. At 15 kyr B.P., the beginning of deglaciation, a minimum Cd/Ca is recorded which is almost the same as that of the modern North Atlantic. Considering previously obtained cadmium records from the northwesternmost and western equatorial Pacific, a steep gradient in the deep-water cadmium concentration between the western equatorial Pacific and the northwest Pacific from the last glacial to deglacial periods has been estimated. In contrast to cadmium records, benthic foraminifera deltaC-13 records in these regions showed similar increasing trends during this time span and no large difference in deltaC-13 can be observed between these two regions. This discordance between these two nutrient tracers may come from the change in the deltaC-13-phosphate relationship in the ocean during the Late Quaternary. Although we cannot absolutely rule out other possibilities, we suggest that there was a convection cell in the northwest Pacific during the last glacial period and at the beginning of deglaciation period the turnover rate of this cell increased and cadmium concentration in the northwest Pacific significantly decreased., ELSEVIER SCIENCE BV
EARTH AND PLANETARY SCIENCE LETTERS, 1994年06月

DETAILED PALEOMAGNETIC RECORDS DURING THE BRUNHES-MATUYAMA GEOMAGNETIC REVERSAL, AND A DIRECT DETERMINATION OF DEPTH LAG FOR MAGNETIZATION IN MARINE-SEDIMENTS
M OKADA; N NIITSUMA, 筆頭著者, ELSEVIER SCIENCE BV
PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 1989年07月, ［査読有り］

チバニアン GSSP サイトと陸化した前弧海盆上総層群の層序
岡田 誠,羽田裕貴
地質学雑誌, 2023年04月06日, ［査読有り］, ［招待有り］
筆頭著者

千葉複合セクションのn-アルカン分析による海洋酸素同位体ステージ19の陸上気候・植生変動復元
梶田 展人; 関 宰; 山本 正伸; 大河内 直彦; 岡田 誠; 羽田 裕貴; 菅沼 悠介
日本地球化学会第69回年会講演要旨集, 2022年11月

チバニアンGSSPの特徴と、その学術上の意義
岡田 誠
学術の動向, 2022年11月01日, ［招待有り］
筆頭著者

上総層群黄和田層上部の微化石分析に基づく北西太平洋の前期更新世海洋変動
桑野太輔; 土屋祐貴; 亀尾浩司; 林広樹; 宇都宮正志; 久保田好美; 万徳佳菜子; 大浦佑馬; 岡田誠
日本地質学会学術大会(Web), 2022年

ニュージーランド,タウポ噴火の古地磁気年代測定
長谷川健; GREVE Annika; GRAVLEY Darren; 楠稚枝; 岡田誠; KOSIK Szabolcs; 望月伸竜; 金田泰明
日本火山学会講演予稿集, 2021年

「チバニアン」と地質学
岡田 誠
環境管理 = Environmental management, 2019年06月, ［招待有り］

未来技術の旗手たち 地層の古地磁気から読み解いた地質時代"チバニアン"
小川 明; 岡田 誠
商工ジャーナル, 2019年05月

地球磁場極性逆転年代の高精度化 (総特集 第四紀研究における年代測定法の新展開 : 最近10年間の進展(3)相対年代と古環境の高精度復元) -- (古地磁気層序学とその応用)
菅沼 悠介; 岡田 誠; 堀江 憲路
号外地球, 2014年

広域テフラに対比される溶結凝灰岩による絶対古地磁気強度測定:相対古地磁気強度との対比と絶対値較正
藤井哲夢; 望月伸竜; 長谷川健; 岡田誠; 渋谷秀敏
地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 2013年

地球磁場極性逆転年代の高精度化
菅沼悠介; 岡田誠; 堀江憲路
月刊地球号外, 2013年

Geomagnetic field excursions occurred often during the last million years
LUND S. O.
EOS Trans. AGU, 1998年08月

Paleomagnetic and tephrochronological analyses of a sediment core from Lake Kitaura(jointly worked)
Okada M.; Amano; K.; Kikuchi; Y.; Itoda; C
Publication of Itako Hydrobiological Station, 1997年10月
筆頭著者

BENTHIC FORAMINIFERA CADMIUM RECORD FROM THE WESTERN EQUATORIAL PACIFIC
N OHKOUCHI; H KAWAHATA; M OKADA; M MURAYAMA; E MATSUMOTO; T NAKAMURA; A TAIRA
MARINE GEOLOGY, 1995年09月

北太平洋における新生代の古海洋学的変遷 ーODP Leg145の成果ー
岡田 誠; ODP Leg; 乗船研究者一同
月刊海洋,海洋出版, 1993年08月
筆頭著者

最新 地学事典　　　　　　　　　　　　　　　
地学団体研究会 編, 分担執筆
平凡社, 2024年03月21日
9784582115086

古生物学の百科事典　　　　　　　　　　　　　　　
日本古生物学会 編; 西 弘嗣 編集委員長, 分担執筆
丸善出版, 2023年02月01日
9784621307588

チバニアン誕生 : 方位磁針のN極が南をさす時代へ
岡田, 誠, 単著
ポプラ社, 2021年06月
9784591170342

地球・惑星・生命 = The earth, planets, and life
日本地球惑星科学連合, 分担執筆
東京大学出版会, 2020年05月
9784130637152

海洋底科学の基礎　　　　　　　　　　　　　　　
日本地質学会「海洋底科学の基礎」編集委員会編, 共著
共立出版, 2016年09月15日
9784320047297

フィールドジオロジー２ 層序と年代　　　　　　　　　　　　　　　
長谷川四郎; 中島 隆; 岡田 誠, 共著
共立出版, 2006年01月25日
432004682X

プロフェッショナル英和辞典スペッドテラ 物質・工学編　　　　　　　　　　　　　　　
堀内克明,蟹江幸博,他編, 分担執筆
小学館, 2004年07月20日
409506711X

房総半島南端地域に分布する海成層の第四系基底部付近におけるボーリングコアを用いた超高時間解像度を持つ古地磁気-酸素同位体複合層序構築の試み　　　　　　　　　　　　　　　
柚原 涼花; 岡田 誠; 長友 大輝; 菅沼 悠介
日本地質学会第131年学術大会, 2024年09月09日
20240908, 20240910

房総半島南端に分布する千倉層群から得られた中期鮮新世温暖期末期の古地磁気-酸素同位体複合層序　　　　　　　　　　　　　　　
谷元 瞭太; 岡田 誠
日本地質学会第131年学術大会, 2024年09月09日
20240908, 20240910

複数の地層群から復元した同一地磁気逆転周辺の古地磁気変動記録の比較　　　　　　　　　　　　　　　
小西 拓海; 岡田 誠; 小塚 大輝
日本地質学会第131年学術大会, 2024年09月09日
20240908, 20240910

房総半島南端に分布する海成更新統の2.17Ma付近の層準で検出された地磁気エクスカーション記録　　　　　　　　　　　　　　　
岡田 誠; 前田 郷; 小塚 大輝; 小西 拓海
日本地質学会第131年学術大会, 2024年09月09日
20240908, 20240910

鬼界カルデラの海底カルデラ壁で掘削したボーリングコアの岩相と岩石磁気学的特徴　　　　　　　　　　　　　　　
西来 邦章; 佐藤 勇輝; 羽生 毅; 宮崎 隆; Tejada Maria Luisa; 上木 賢太; 臼井 洋一; 金子 克哉; 清杉 孝司; 鈴木 桂子; 中岡 礼奈; 長谷川 健; 岡田 誠
JpGU 2024年大会, 2024年05月31日
20240524, 20240531

Piacenzian oxygen isotope-magnetostratigraphy constrained by U-Pb;dating of tephra beds from a marine;sucession in central Japan　　　　　　　　　　　　　　　
羽田 裕貴; 岩野 英樹; 檀原 徹; 平田 岳史; 細井 淳; 久保田 好美; 中谷 是崇; 岡田 誠
JpGU 2024年大会, 2024年05月29日
20240524, 20240531

房総半島南端に分布する海成層の第四系基底部における定方位ボーリング コアを用いた古地磁気−酸素同位体複合層序　　　　　　　　　　　　　　　
柚原 涼花; 岡田 誠; 長友 大輝; 菅沼 悠介
JpGU 2024年大会, 2024年05月28日
20240524, 20240531

房総半島南端に分布する海成更新統の松山逆磁極帯下位層準で検出された地磁気エクスカーション　　　　　　　　　　　　　　　
岡田 誠; 前田 郷; 小塚 大輝; 小西 拓海
JpGU 2024年大会, 2024年05月28日
20240524, 20240531

SQUID顕微鏡による微小領域磁気分析を利用した二次磁化キャリアの推 定の試み　　　　　　　　　　　　　　　
谷元 瞭太; 小田 啓邦; 岡田 誠
JpGU 2024年大会, 2024年05月27日
20240524, 20240531

Rotated Transtensional Basins Formed During Back-arc Spreading in Japan: Simultaneous Rapid Tectonic Rotation and Basin Subsidence　　　　　　　　　　　　　　　
Jun Hosoi; Yurie Tanii; Makoto Okada; Yuki Haneda
米国地球物理学会 2023年秋期大会, 2023年12月12日
20231209, 20231213

Continuous Relative paleointensity records for the C2An.3n-C2An.2n period from the marine succession in the southernmost part of the Boso Peninsula, central Japan　　　　　　　　　　　　　　　
Akihiro Tanimoto; Makoto Okada
米国地球物理学会 2023年秋期大会, 2023年12月12日
20231209, 20231213

房総半島南端地域に分布する海成上部鮮新統千倉層群布良層における層序学的研究　　　　　　　　　　　　　　　
谷元 瞭太,岡田 誠,柴田 翔平
日本地質学会第130年京都大会, 2023年09月19日, 日本地質学会
20230917, 20230919

南房総海成鮮新−更新統の第四系基底部における定方位ボーリングコアを用いた超高時間解像度を持つ古地磁気−酸素同位体複合層序構築の試み　　　　　　　　　　　　　　　
岡田 誠,柚原 涼花,長友 大輝,菅沼 悠介
日本地質学会第130年京都大会, 2023年09月19日, 日本地質学会
20230917, 20230919

古地磁気層序とテフラ層序に基づく房総半島南端の下部更新統千倉層群と同半島東部の上総層群の対比　　　　　　　　　　　　　　　
小西 拓海,岡田 誠,宇都宮 正志,田村 糸子,小塚 大輝
日本地質学会第130年京都大会, 2023年09月19日, 日本地質学会
20230917, 20230919

房総半島南端に分布する海成更新統の約1.9-2.2Maの年代区間における詳細な古地磁気－酸素同位体複合層序　　　　　　　　　　　　　　　
小塚 大輝,岡田 誠,小西 拓海,江部 裕太
日本地質学会第130年京都大会, 2023年09月19日, 日本地質学会
20230917, 20230919

Paleomagnetic and oxygen isotopic analyses on a boring core drilled through the base of Quaternary from the marine sedimentary succession Chikura Group in the southern Boso Peninsula, Japan　　　　　　　　　　　　　　　
Makoto Okada; Joan Songeons; Daiki Nagatomo; Yusuke Suganuma
第21回国際第四紀学連合ローマ大会, 2023年07月18日, 国際第四紀学連合
20230714, 20230720

Paleomagnetic and 10Be records across the Pleistocene and Pliocene geomagnetic polarity transitions from the Boso Peninsula, central Japan　　　　　　　　　　　　　　　
Yuki Haneda; Yusuke Suganuma; Hiroto Kajita; Masayuki Utsunomiya; Makoto Okada
第21回国際第四紀学連合ローマ大会, 2023年07月17日, 国際第四紀学連合
20230714, 20230720

Coupled terrestrial and oceanic variability during marine isotope stage 19 reconstructed from biomarkers in the Chiba Composition Section　　　　　　　　　　　　　　　
Hiroto Kajita; Osamu Seki; Masanobu Yamamoto; Makoto Okada; Yuki Haneda; Naohiko Ohkouchi; Yusuke Suganuma
第21回国際第四紀学連合ローマ大会, 2023年07月15日, 国際第四紀学連合
20230714, 20230720

南房総に分布する海成更新統を用いた地磁気逆転イベントと海洋同位体層序との精密対比　　　　　　　　　　　　　　　
岡田 誠,小塚 大輝,小西 拓海,江部 裕太
日本地球惑星科学連合2023年大会, 2023年05月26日, 日本地球惑星科学連合
20230521, 20230526

北西太平洋における後期鮮新世の酸素同位体ー古地磁気複合層序と古気候復元　　　　　　　　　　　　　　　
羽田 裕貴,岡田 誠,久保田 好美,本郷 美佐緒,中谷 是崇
日本地球惑星科学連合2023年大会, 2023年05月26日, 日本地球惑星科学連合
20230521, 20230526

海成鮮新-更新統千倉層群における第四紀開始境界付近の年代層序　　　　　　　　　　　　　　　
長友 大輝,岡田 誠,Sngeons Joan
日本地球惑星科学連合2023年大会, 2023年05月26日, 日本地球惑星科学連合
20230521, 20230526

房総半島南端に分布する千倉層群布良層から得られたMammoth逆磁極亜帯周辺の古地磁気記録　　　　　　　　　　　　　　　
谷元 瞭太,岡田 誠
日本地球惑星科学連合2023年大会, 2023年05月26日, 日本地球惑星科学連合
20230521, 20230526

北海道東部，阿寒カルデラ噴出物ボーリングコア中に認められたMatuyama-Brunhes逆転境界　　　　　　　　　　　　　　　
長谷川 健,楠 稚枝,岡田 誠,平塚 葵,西来 邦章,佐藤 勇輝
日本地球惑星科学連合2023年大会, 2023年05月26日, 日本地球惑星科学連合
20230521, 20230526

房総半島に分布する鮮新－更新統の堆積岩に記録された残留磁化の構成成分のSQUID顕微鏡を用いた予察的分析　　　　　　　　　　　　　　　
谷元 瞭太,小田 啓邦,岡田 誠,福與 直人
日本地球惑星科学連合2023年大会, 2023年05月24日, 日本地球惑星科学連合
20230521, 20230526

チバニアンGSSPの批准とその年代層序学的意義　　　　　　　　　　　　　　　
岡田 誠
日本地質学会第129年学術大会, 2022年09月05日, 一般社団法人日本地質学会, ［招待有り］
20220904, 20220906

第四紀更新世における地質年代境界決定の現状　　　　　　　　　　　　　　　
岡田 誠
日本地質学会第129年学術大会, 2022年09月05日, 一般社団法人日本地質学会, ［招待有り］
20220904, 20220906

房総半島の海成鮮新ー更新統における古地磁気ー同位体複合層序の構築とその意義
岡田 誠
日本第四紀学会 2021年日本第四紀学会学会賞・学術賞受賞記念 第2回講演会, 2022年06月04日, 日本第四紀学会, ［招待有り］
20220604, 20220604

南房総海成鮮新ー更新統の第四系基底部における定方位ボーリングコアの予察的古地磁気研究
岡田 誠・Songeons; Joan
日本地球惑星科学連合2022年大会, 2022年05月22日, 日本地球惑星科学連合
20220522, 20220602

チバニアン GSSP の特徴と、その学術上の意義
岡田 誠
日本学術会議公開シンポジウム「チバニアン、学術的意義とその社会的重要性」, 2022年05月24日, 日本学術会議, ［招待有り］
20220524, 20220524

GSSP, Chibanian ,and Geology of Boso Peninsula　　　　　　　　　　　　　　　
Makoto Okada
Development of Joint Research between Mongolia and Japan on Geological Information, Natural Resources, and Analytical Technologies of Geological Samples, 2022年03月02日, 産業技術総合研究所・さくらサイエンスプログラム, ［招待有り］
20220301, 20220302

房総の地質と松山-ブリュン境界,～チバニアン前夜～
岡田 誠・菅沼悠介
2021年度 田中舘賞受賞講演, 2021年11月03日, 地球電磁気・地球惑星圏学会, ［招待有り］
20211102, 20211104

チバニアン認定と，その古生物学・古環境学への貢献
岡田 誠
日本古生物学会第170回例会 シンポジウム１「南関東の前弧海盆堆積物に記録された古環境変遷ー年代層序と化石記録からー, 2021年02月05日, 日本古生物学会, ［招待有り］
20210205, 20210207

チバニアンと古環境学 −陸上地質のススメ−
岡田 誠
地球環境史学会2020年大会, 2020年11月07日, 地球環境史学会, ［招待有り］
20201107, 20201107

第四紀 “千葉時代”（チバニアン）の決定とその意義　　　　　　　　　　　　　　　
岡田 誠
日本第四紀学会普及講演, 2020年08月29日, 日本第四紀学会, ［招待有り］
20200829, 20200829

房総半島およびその周辺に分布する海成鮮新ｰ更新統に記録された過去4.5Maに起こった地磁気逆転
岡田 誠
JpGU-AGU Joint Meeting 2020, 2020年07月13日, JpGU（日本地球惑星科学連合）, ［招待有り］
20200712, 20200715

日本最初の地質時代名称チバニアンと最後の地磁気逆転
岡田 誠
JpGUトップセミナー, 2020年07月12日, JpGU（日本地球惑星科学連合）, ［招待有り］
20200712, 20200712

千葉複合セクションの有孔虫同位体記録によるMIS 19の数千年スケール古海洋変動
羽田 裕貴; 岡田 誠; 久保田 好美; 菅沼 悠介
日本地質学会学術大会講演要旨, 2019年, 一般社団法人 日本地質学会
2019, 2019

千葉セクションにおける地磁気逆転記録　　　　　　　　　　　　　　　
岡田 誠
産業技術総合研究所 海外卓越研究院招聘事業成果発表会「地球惑星科学における磁場逆転と磁性物質」, 2019年03月14日, 産業技術総合研究所, ［招待有り］
20180314

千葉複合セクションの有孔虫同位体記録によるMIS 19の数千年スケール古海洋変動
羽田 裕貴; 岡田 誠; 久保田 好美; 菅沼 悠介
日本地質学会学術大会講演要旨, 2018年, 一般社団法人 日本地質学会
2018, 2018

房総半島に分布する下部更新統千倉層群上部および上総層群下部における古地磁気変動対比
小西 拓海; 岡田 誠; 丸岡 亨; 宇都宮 正志
日本地質学会学術大会講演要旨, 2017年, 一般社団法人 日本地質学会
2017, 2017

千葉セクションにおけるM-B極性反転境界付近の高解像度古地磁気－酸素同位体比記録
岡田 誠; 羽田 裕貴; 菅沼 悠介; 風岡 修
日本地質学会学術大会講演要旨, 2015年, 一般社団法人 日本地質学会
2015, 2015

本邦太平洋側とその周辺海域における新第三系・第四系石灰質ナノ化石基準面
亀尾 浩司; 岡田 良昭; 千代延 俊; 岡田 誠
日本地質学会学術大会講演要旨, 2015年, 一般社団法人 日本地質学会
2015, 2015

安房層群安野層の古地磁気ー酸素同位体複合年代層序
羽田 裕貴; 岡田 誠
日本地質学会学術大会講演要旨, 2015年, 一般社団法人 日本地質学会
2015, 2015

過去500万年間のベーリング海気候変動―海氷出現と寒冷化―IODP Expedition323掘削成果
高橋孝三; 岩崎晋弥; 兼松芳幸; 小野寺丈尚太郎; 岡崎裕典; 須藤斎; 朝日博史; 池上隆仁; 坂本竜彦; 池原実; 関宰; 堀川恵司; 岡田誠; 井尻暁; RAVELO A.C; ZARIKIAN ALVAREZ C
日本海洋学会大会講演要旨集, 2012年09月01日
20120901, 20120901

岩手県西和賀町周辺奥羽脊梁山脈の前期～中期中新世テクトニクス
細井 淳; 岡田 誠; 天野 一男
日本地質学会学術大会講演要旨, 2012年, 一般社団法人 日本地質学会
2012, 2012

房総半島南端部に分布する鮮新統／更新統千倉層群の浮遊性有孔虫化石層序と表層海洋環境変遷
濱田 早苗; 亀尾 浩司; 林 広樹; 岡田 誠
日本地質学会学術大会講演要旨, 2012年, 一般社団法人 日本地質学会
2012, 2012

三浦半島, 三浦-上総層群における新第三紀と第四紀の境界
宇都宮 正志; 楠 稚枝; 中村 章子; 間嶋 隆一; 田中 裕一郎; 岡田 誠
日本地質学会学術大会講演要旨, 2012年, 一般社団法人 日本地質学会
2012, 2012

O-1 銚子ボーリングコアの年代層序(1. 前弧海盆堆積体のテクトニクス・古海洋・堆積・生物 : 南関東上総層群相当層を例として)
岡田 誠; 亀尾 浩二; 中里 裕臣; 大河内 直彦; 久光 敏夫; 北里 洋
日本地質学会学術大会講演要旨, 2004年, 日本地質学会
2004, 2004

O-144 銚子掘削コアの化学分析による後期更新世海洋環境変動の復元(13. 海洋地質(液晶有),口頭発表,一般講演)
岡田 誠; 丸田 佳奈
日本地質学会学術大会講演要旨, 2002年, 日本地質学会
2002, 2002

P-114 古地磁気に基づく東北日本の中新世テクトニクス(19. テクトニクス,ポスターセッション,一般発表)
小島 健; 岡田 誠; 天野 一男
日本地質学会学術大会講演要旨, 2000年, 日本地質学会
2000, 2000

O-144 南部フォッサマグナ島弧多重衝突テクトニクスにおける東部御坂山地の位置付け
田中舘 宏橘; 天野 一男; 岡田 誠
日本地質学会学術大会講演要旨, 1999年, 日本地質学会
1999, 1999

南部フォッサマグナにおける被衝突地塊の回転運動
天野 一男; 石田 高; Andrew James Martin; 田中舘 宏橘; 納谷 友規; 鈴木 久美子; 菅沼 悠介; 岡田 誠
日本地質学会学術大会講演要旨, 1998年, 一般社団法人 日本地質学会
1998, 1998

古地磁気から見た日本海形成時における隠岐島後の挙動
小島 健; 岡田 誠; 時枝 克安; 小室 裕明; 天野 一男
日本地質学会学術大会講演要旨, 1998年, 一般社団法人 日本地質学会
1998, 1998

13 房総半島南端千倉層群の古地磁気層序
斉藤 敬二; 岡田 誠; 亀尾 浩二; 小竹 信宏
日本地質学会学術大会講演要旨, 1997年, 日本地質学会
1997, 1997

555 南房総千倉層群畑層の古地磁気層序(地域地質)
斉藤 敬二; 岡田 誠; 小竹 信宏; 亀尾 浩司
日本地質学会学術大会講演要旨, 1996年, 日本地質学会
1996, 1996

554 地磁気エクスカーションを用いた上総層群梅ヶ瀬層と豊房層群神余層の対比(地域地質)
郡谷 順英; 岡田 誠; 亀尾 浩司; 高山 俊昭; 天野 一男
日本地質学会学術大会講演要旨, 1996年, 日本地質学会
1996, 1996

571 タービダイト相と海水準変動 : 上総層群梅ヶ瀬層〜大田代層の例(堆積)
辻 隆司; 佐藤 由理; 三田 勲; 内田 英一; 岡田 誠; 宮田 雄一郎; 中水 勝
日本地質学会学術大会講演要旨, 1996年, 日本地質学会
1996, 1996

45. 房総南端に分布する鮮新-更新統境界付近の古地磁気および生層序
斉藤 敬二; 岡田 誠; 亀尾 浩司
日本地質学会学術大会講演要旨, 1995年, 日本地質学会
1995, 1995

2010年05月 - 現在, 地球環境史学会

2000年04月 - 現在, 日本第四紀学会

1991年04月 - 現在, アメリカ地球物理学会(American Geophysical Union)

1989年08月 - 現在, 日本地質学会

1986年10月 - 現在, 地球電磁気・地球惑星圏学会

地磁気逆転現象が気候・生態系に対して与えた影響の検証
基盤研究(S)
茨城大学
2024年04月 - 2029年03月

磁気顕微鏡による地球内核形成前後の地球磁場復元と地球生命史への影響の解明
基盤研究(A)
国立研究開発法人産業技術総合研究所
2021年04月 - 2025年03月

水蒸気噴火の推移予測法の開発：物質科学的特徴から探る熱水ーマグマ系プロセス
科学研究費助成事業：基盤研究（B)
茨城大学大学院理工学研究科
2021年04月 - 2024年03月

〔主要な業績〕過去400万年間に起こった地磁気逆転の年代確定と生物相・気候に対する影響の検証
基盤研究(A)
茨城大学
2019年04月 - 2023年03月

80万年前に東南アジアで起きた小天体衝突の位置、規模、様式特定と環境への影響評価
国際共同研究加速基金(国際共同研究強化(B))
2018年10月 - 2022年03月

火山灰層の古地磁気方位を利用した巨大噴火同時発生イベントの検証
基盤研究(C)
2016年04月 - 2020年03月

複数指標の組み合わせに基づく上総層群国本層の古環境変動の高精度復元
研究活動スタート支援
千葉大学
2017年08月 - 2019年03月

〔主要な業績〕松山－ブルン地磁気逆転境界年代の決定と地質年代の総合的キャリブレーション
基盤研究(B)
茨城大学
2016年04月 - 2019年03月

北西太平洋地域における石灰質ナノ化石基準面の総括：本邦上部新生界による検証
基盤研究(C)
千葉大学
2014年04月 - 2017年03月

急激な温暖化における太平洋高緯度海洋の役割～過去１１回の温暖化アーカイブの構築
基盤研究(A)一般
2011年04月 - 2014年03月

地磁気逆転期における寒冷化イベントの発生 原因の解明
基盤研究(B)一般
神戸大学
2010年04月 - 2013年03月

フィリピンから産出する化学合成化石群集の成立条件の解明
基盤研究(B)海外
横浜国立大学
2011年04月 - 2012年03月

現世および化石カキ礁の形成過程から解明する古環境とカキ類の古生態変遷
基盤研究(B)
茨城大学
2010年 - 2012年

〔主要な業績〕房総半島に分布する海成堆積層を用いた，鮮新統〜更新統における高精度基準層序の確立
基盤研究(C)一般
茨城大学
2008年04月 - 2011年03月

光ルミネッセンス年代決定法を用いた極域寒冷圏の高分解能古海洋変動解析
基盤研究(A)一般
独立行政法人海洋研究開発機構
2008年04月 - 2011年03月

東北日本の蝦夷堆積盆における白亜紀-古第三紀古環境変動
基盤研究(C)
茨城大学
2005年 - 2007年

〔主要な業績〕地層褶曲等による堆積物変形が残留磁化方位に及ぼす影響の評価
萌芽研究
茨城大学
2003年04月 - 2006年03月

〔主要な業績〕古地磁気学的アプローチによる房総−三浦地域における第三紀テクトニクスの解明
その他
茨城大学
2000年04月 - 2002年03月

北海道の白亜系-第三系境界のシーケンス層序と化石相の変遷
基盤研究(C)
茨城大学
1998年 - 2001年

チョーク層連続分析による温室地球から寒冷地球への環境変遷史の研究
基盤研究(A)
東京大学
1998年 - 2000年

深海掘削試料解析・孔内計測による海洋底の構造と進化の研究
国際学術研究
東京大学
1994年 - 1996年

掘削試料の解析と孔内計測による世界の深海底の比較研究
国際学術研究
東京大学
1992年 - 1993年

地質年代チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
一般社団法人 建設コンサルタンツ協会, 令和４年度地質技術勉強会, 2022年07月23日 - 2022年07月23日

チバニアンズガイド講座 房総の地質の特徴とチバニアン　　　　　　　　　　　　　　　
講師
NPO法人チバニアンズ, チバニアンズガイド講座, 2022年07月10日 - 2022年07月10日

千葉県立中央博 特別講演会「親子で学ぶチバニアン 〜地層の声をきこう！〜」
講師
千葉県立中央博物館, 2022年07月03日

千葉の自然シリーズ 地層の声を聴け！〜チバニアンから探る地球の歴史〜
講師
千葉市科学館, 大人が楽しむ科学教室2022, 2022年07月03日

チバニアンと房総半島
講師
mihorin企画, 安房の魅力とさかなクン〜東京湾と館山〜, 2022年06月26日

2022年度いきいき大学教養文化教室,チバニアン 〜千葉の名前が地球の歴史に〜　　　　　　　　　　　　　　　
講師
いきいき大学, 2022年度いきいき大学教養文化教室, 2022年04月25日

蛍雪時代2022年4月増刊号 全国大学学部・学科案内号 理学部系統 地学分野　　　　　　　　　　　　　　　
寄稿
蛍雪時代2021年4月増刊号 全国大学学部・学科案内号, 2022年03月30日

NPOチバニアンズガイド講習会 ラボ見学会
講師
NPO法人チバニアンズ, ガイド講習会, 2021年12月16日 - 2021年12月16日

石から見える世界,〜鉄道でいこう！１００万年前の深海への旅〜
講師
ちば子ども大学, 2021年度 ちば子ども大学講座, 2021年12月14日 - 2021年12月14日

茨城大学図書館土曜アカデミー 新著を語る「チバニアン誕生」　　　　　　　　　　　　　　　
講師
茨城大学図書館, 土曜アカデミー 新著を語る, 2021年11月06日

地質時代チバニアンと房総の地質　　　　　　　　　　　　　　　
講師
市原市加茂公民館, 講演会, 2021年10月16日

チバニアンとは? ~千葉時代と地磁気の逆転~　　　　　　　　　　　　　　　
講師
土木学会関東支部, 土木学会関東支部談話会, 2021年10月05日

チバニアン 〜千葉の名前が地球の歴史に〜　　　　　　　　　　　　　　　
講師
いきいき大学, 2021年度いきいき大学教養文化講座, 2021年08月17日

チバニアン見学会　　　　　　　　　　　　　　　
講師
mihorin企画, 2021年07月11日

チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
かわさき市民アカデミー, 講座４「広がる生命科学の世界」, 2021年04月26日

小湊鉄道と房総の地質　　　　　　　　　　　　　　　
講師
いきいき大学, 2021年度いきいき大学教養文化教室, 2021年04月26日

日本初の地質時代名称「チバニアン」誕生とその意義　　　　　　　　　　　　　　　
講師
一般社団法人日本外科学会, 第121回定期学術集会 特別講演, 2021年04月10日

蛍雪時代2021年4月増刊号 全国大学学部・学科案内号 理学部系統 地学分野　　　　　　　　　　　　　　　
寄稿
蛍雪時代2021年4月増刊号 全国大学学部・学科案内号, 2021年03月30日

第四紀“千葉時代”（チバニアン）の決定とその意義　　　　　　　　　　　　　　　
講師
日本第四紀学会, 普及講演, 2020年12月27日

チバニアンズ ガイド講座　　　　　　　　　　　　　　　
講師
NPO法人 チバニアンズ, 2020年12月17日

チバニアンと地層のでき方　　　　　　　　　　　　　　　
講師
NPO法人ひと・まちねっとわーく, いばらき子ども大学デリバリー事業, 2020年12月14日

チバニアン見学会　　　　　　　　　　　　　　　
講師
一般社団法人 学士会, 2020年11月08日

地質時代「チバニアン」　　　　　　　　　　　　　　　
講師
市原市加茂公民館, 講演会, 2020年10月17日

地層学から見た地球温暖化と気候変動「チバニアンの発見と研究から見えてきた新たな気候学」　　　　　　　　　　　　　　　
講師
一般社団法人 茨城県環境管理協会, 第3回エコ・カレッジ職域コース, 2020年09月25日

「チバニアン」から読み解く地球の謎　　　　　　　　　　　　　　　
講師
毎日新聞千葉支局, 企業人大学9月講座, 2020年09月16日

チバニアンの全て〜最後の地磁気逆転はどのように起こったのか　　　　　　　　　　　　　　　
講師
一般社団法人 学士会, 夕食会講演, 2020年09月07日

新地質年代・チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
鉄道・運輸機構東京支社, 第16回業務研究発表会 特別講演, 2020年08月25日

日本最初の地質時代名称チバニアンと最後の地磁気逆転　　　　　　　　　　　　　　　
講師
公益社団法人 日本地球惑星科学連合, トップセミナー, 2020年07月12日

蛍雪時代2020年4月増刊号 全国大学学部・学科案内号 理学部系統 地学分野　　　　　　　　　　　　　　　
寄稿
蛍雪時代2020年4月増刊号 全国大学学部・学科案内号, 2020年03月30日

理学部系統 地学分野　　　　　　　　　　　　　　　
寄稿
蛍雪時代2020年4月増刊号 全国大学学部・学科案内号, 2020年03月30日

「チバニアン」と地質時代　　　　　　　　　　　　　　　
講師
深田地質研究所, 第196回深田研談話会, 2019年12月13日

地質時代「チバニアン」ー地質学で探る地球の歴史ー　　　　　　　　　　　　　　　
講師
城里町教育委員会, 東茨城郡教育振興大会, 2019年11月12日

チバニアンと地質時代　　　　　　　　　　　　　　　
講師
千葉県生涯大学校, 千葉県生涯大学校京葉学園講座, 2019年10月31日

チバニアンと地質時代　　　　　　　　　　　　　　　
講師
茨城大学, 茨城大学創立70周年記念講演会, 2019年10月26日

チバニアンについて学ぶ　　　　　　　　　　　　　　　
講師
東海大浦安高等学校, サイエンスクラス講座, 2019年10月18日

チバニアンからひもとく地球の歴史　　　　　　　　　　　　　　　
講師
茨城高等学校, 1 day キャンパス in 茨城高校, 2019年09月22日

千葉セクションから読み解く地球史　　　　　　　　　　　　　　　
講師
市原市田淵町会, 田淵ガイド養成講座, 2019年08月22日

「チバニアン」から学ぶ地質学 GSSPと地質時代　　　　　　　　　　　　　　　
講師
2019年 茨城大学高校生公開講座, 2019年08月08日

「チバニアン」と地質学　　　　　　　　　　　　　　　
講師
いきいき大学, いきいき大学教養文化教室, 2019年05月13日

地磁気の逆転とチバニアン　　　　　　　　　　　　　　　
講師
兵庫県立大学大学院地域資源マネジメント研究科, サイエンスカフェRRM, 2019年05月12日

蛍雪時代2019年4月増刊号 全国大学学部・学科案内号 理学部系統 地学分野　　　　　　　　　　　　　　　
寄稿
蛍雪時代2019年4月増刊号 全国大学学部・学科案内号, 2019年03月30日

理学部系統 地学分野　　　　　　　　　　　　　　　
寄稿
蛍雪時代2019年4月増刊号 全国大学学部・学科案内号, 2019年03月30日

「チバニアン」と地磁気逆転　　　　　　　　　　　　　　　
講師
放送大学茨城学習センター, 放送大学ライブラリー講演会, 2018年12月15日

チバニアンと地質学　　　　　　　　　　　　　　　
講師
東京私立中学高等学校協会, 理数系教科研究会（理科・地学）講演会, 2018年12月07日

チバニアン現地巡検　　　　　　　　　　　　　　　
講師
茨城県高等学校教育研究会, 平成30年度茨城県高等学校教育研究会地学部地区合同研修会, 2018年11月28日

房総地質巡検　　　　　　　　　　　　　　　
講師
(株)建築技術研究所, 平成30年度CTIグループ地質部門 地質巡検, 2018年08月30日 - 2018年08月31日

チバニアン　　　　　　　　　　　　　　　
出演
NHK ETV放送, サイエンスZERO特別編 ５７５でカガク！, 2018年08月26日

「チバニアン」と地学・地質学教育　　　　　　　　　　　　　　　
講師
京都大学防災研究所, 京大防災研研究集会「地学教育の展望ー来たるべき南海トラフ地震に備えてー」, 2018年08月25日

「チバニアン」と地質時代　　　　　　　　　　　　　　　
講師
全国私立幼稚園連合会, 関東大会記念講演会, 2018年08月21日

チバニアンと地質学　　　　　　　　　　　　　　　
講師
地学団体研究会, 2018年度総会記念講演会, 2018年08月19日

「チバニアン」と地質時代　　　　　　　　　　　　　　　
講師
一般社団法人総合科学研究機構, CROSS2018総合科学市民公開講座 太陽系と地球誕生の謎に迫る, 2018年08月18日

「チバニアン」から探る地球の歴史　　　　　　　　　　　　　　　
講師
茨城新聞社, 茨城新聞政経懇話会講演会, 2018年07月26日

“チバニアン”って何だろう？　　　　　　　　　　　　　　　
講師
千葉県立佐倉高等学校, 佐倉高校SSH講演会, 2018年07月17日

「チバニアン」から探る地球の歴史　　　　　　　　　　　　　　　
講師
ひたちなか市, 平成30年度ひたちなか市民大学 基調講演, 2018年06月22日

地質学で地球の歴史を探る　　　　　　　　　　　　　　　
講師
所沢市民大学, 第26期所沢市民大学講座, 2018年06月11日

チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
慶應学術事業会, 慶應MCC夕学50講, 2018年05月17日

チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
水戸ロータリークラブ, 水戸ロータリークラブ卓話, 2018年04月30日

「チバニアン」と地質学　　　　　　　　　　　　　　　
講師
明治大学博物館友の会, 友の会講演会, 2018年04月26日

チバニアン現地見学会　　　　　　　　　　　　　　　
講師
よみうりカルチャー船橋ららぽーと, 地層のふしぎ「チバニアン」を知ろう 公開講座, 2018年03月31日

チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
里山会（千葉市）, 里山トークリレー, 2018年03月30日

地質時代とはなにか？ 地磁気逆転ってなんだろう？　　　　　　　　　　　　　　　
講師
よみうりカルチャー船橋ららぽーと, 地層のふしぎ「チバニアン」を知ろう 定期講座, 2018年03月30日

GSSP申請と千葉セクション　　　　　　　　　　　　　　　
講師
千葉県立中央博物館, 中央博記念事業 「誕生なるか！チバニアン」講演会, 2018年03月18日

知りたい！チバニアン 地層が語る地球の歴史　　　　　　　　　　　　　　　
講師
毎日新聞社, 毎日新聞メディアカフェ, 2018年01月22日

地球最後の地磁気逆転を記録した「千葉セクション」の研究とその意義　　　　　　　　　　　　　　　
講師
日本技術士会応用理学部会, 日本技術士会応用理学部会講演会, 2017年12月16日

チバニアンと地磁気逆転　　　　　　　　　　　　　　　
講師
放射線医学総合研究所, 放射線医学総合研究所創立60周年記念講演会, 2017年11月27日

最後の地磁気逆転が記録された“千葉セクション”の国際標準模式層への認定(チバニアン)と想定される地学教育への貢献　　　　　　　　　　　　　　　
講師
東京大学地震研究所, 東大地震研共同研究集会「地震・火山現象を含む学校地学教育の現状とそのイノベーション」, 2017年11月11日