Kyoto Fission Track Co.

Fujinomiya, Japan

Kyoto Fission Track Co.

Fujinomiya, Japan
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Nakagawa T.,Northumbria University | Gotanda K.,Chiba University of Commerce | Haraguchi T.,Osaka City University | Danhara T.,Kyoto Fission track Co. | And 14 more authors.
Quaternary Science Reviews | Year: 2012

The high potential of the varved sediments of Lake Suigetsu, central Japan, to provide a purely terrestrial radiocarbon calibration model and a chronology of palaeoclimatic changes has been widely recognised for the last two decades. However, this potential has not been fully realised since the only available long sediment core from the lake ('SG93') was extracted from a single bore hole and was therefore interrupted by gaps of unknown duration between successive core sections. In the summer of 2006, a new sediment core ('SG06') was recovered from the lake. Four separate boreholes were drilled and the parallel sets of cores recovered were found to overlap completely, without gaps between segments. This new record provides the ability to test existing atmospheric radiocarbon calibration models, as well as to assess the scale of inter-regional leads and lags in palaeoclimatic changes over the last Glacial-Interglacial cycle. Multi-disciplinary analyses from SG06 are still ongoing, but a reliable description of the sedimentary sequence needs to be provided to the wider science community before major outputs from the project are released, thereby allowing fully-informed critical evaluation of all subsequent releases of data based on the SG06 record. In this paper, we report key litho-stratigraphic information concerning the SG06 sediment core, highlighting changes in the clarity of annual laminations (varves) with depth, and possible implications for the mechanism of the climate change. We also discuss the potential of the SG06 record to meet the fundamental goals of the INQUA-INTIMATE project. © 2010 Elsevier Ltd.


PubMed | Okayama University of Science, 402 1 Fukushima, Max Planck Institute for Evolutionary Anthropology, Mount Kenya University and 12 more.
Type: | Journal: Journal of human evolution | Year: 2016

Most Plio-Pleistocene sites in the Gregory Rift Valley that have yielded abundant fossil hominins lie on the Rift Valley floor. Here we report a new Pliocene site, Kantis, on the shoulder of the Gregory Rift Valley, which extends the geographical range of Australopithecus afarensis to the highlands of Kenya. This species, known from sites in Ethiopia, Tanzania, and possibly Kenya, is believed to be adapted to a wide spectrum of habitats, from open grassland to woodland. The Kantis fauna is generally similar to that reported from other contemporaneous A.afarensis sites on the Rift Valley floor. However, its faunal composition and stable carbon isotopic data from dental enamel suggest a stronger C4 environment than that present at those sites. Although the Gregory Rift Valley has been the focus of paleontologists attention for many years, surveys of the Rift shoulder may provide new perspective on African Pliocene mammal and hominin evolution.


Dirksen O.,Institute of Volcanology and Seismology | van den Bogaard C.,Leibniz Institute of Marine Science | Danhara T.,Kyoto Fission Track Co. | Diekmann B.,Alfred Wegener Institute for Polar and Marine Research
Quaternary International | Year: 2011

Distal volcanic tephras in soil sections and lake sediments in the Dvuh-yurtochnoe (Two-Yurts) lake area, central Kamchatka, were investigated in order to provide a chronological framework for the reconstruction of late Quaternary landscape development. Mineralogical and geochemical data point to sources from 5 volcanoes. Ten tephra layers were identified and correlated to known eruptive events. The ages were corroborated by radiocarbon dating of the soil sections around Two-Yurts lake. These findings allow the reconstruction of regional paleoenvironmental change, recorded in the soil sections around Two-Yurts lake. During the Last Glacial Maximum (LGM) time, the area was affected by glacial advances that produced the glacial moraines at the eastern outlet of the lake. A large landslide, ca. 15,000-18,000 14C BP, dammed the valley and led to formation of Two-Yurts lake. Several more landslide events can be recognized in the Holocene, and one affected Two-Yurts lake ca. 3000 14C BP. This event produced a " tsunami" , documented by poorly sorted deposits with rounded pebbles in the onshore sections around the lake. In contrast to the soil sections, tephras buried in the " soupy" lacustrine sediments of Two-Yurts lake are not well preserved and show inconsistent age-depth relationships compared to those suggested by radiocarbon dating, due to sinking through the lake sediments. Nevertheless, tephrochronological data revealed the strong impact of terrestrial landslides on lake sedimentation. © 2011 Elsevier Ltd and INQUA.


Smith V.C.,University of Oxford | Mark D.F.,Scottish Universities Environmental Research Center | Staff R.A.,University of Oxford | Blockley S.P.E.,Royal Holloway, University of London | And 7 more authors.
Quaternary Science Reviews | Year: 2011

The varved Suigetsu (SG06) sediment core is potentially one of the most important and well-constrained mid-latitude palaeoclimate archives, recording continuous deposition during the last ∼150 kyrs. Numerous visible and non-visible volcanic ash layers form unique age markers within SG06. These ash layers are too fine and crystal-poor to be directly dated using the 40Ar/39Ar technique so the tephra were correlated to proximal volcanic deposits using their glass shard compositions. A high-precision 40Ar/39Ar sanidine age of 10.0 ± 0.3 ka (1σ, n = 34, MSWD = 0.71, p = 0.89) was obtained for the SG06-1288 (U-Oki) proximal tephra (Ulleungdo U4). 40Ar/39Ar yields a precision of ±3% near the younger limit of the method, with improved precision possible for older SG06 samples. Such 40Ar/39Ar ages for tephra layers can provide invaluable tie-points within the Lake Suigetsu SG06 sequence, giving independent verification of the core's varve chronology, allowing for the calibration of cosmogenic nuclide production, and providing a precise chronology beyond the varve limit. © 2011 Elsevier Ltd.


Yuguchi T.,Japan Atomic Energy Agency | Amano K.,Japan Atomic Energy Agency | Tsuruta T.,Japan Atomic Energy Agency | Tsuruta T.,Kumamoto University | And 2 more authors.
Contributions to Mineralogy and Petrology | Year: 2011

The three-dimensional spatial variations in the cooling pattern of the Toki granitic body, a zoned pluton in Central Japan, have been evaluated quantitatively by thermochronology using cooling age determination based on the different closure temperatures for target mineral species. The Toki granite has hornblende K-Ar ages of about 74.3 ± 3.7 Ma (N = 2; closure temperature of 510 ± 25°C), biotite K-Ar ages of 78.5 ± 3.9 to 59.7 ± 1.5 Ma (N = 33; 300 ± 50°C), and zircon fission-track ages of 75.6 ± 3.3 to 52.8 ± 2.6 Ma (N = 44; 240 ± 50°C). The spatial variation in the biotite K-Ar age is similar to that in the zircon fission-track age in samples collected from 11 boreholes and seven outcrop sites in the Toki granite, indicating that cooling was effectively from the roof and also from the northwest margin. This cooling pattern shows a strong correlation with the Alumina Saturation Index (ASI) distribution of the body. Larger ASI values correspond to earlier and more rapid cooling after emplacement and smaller value to slower cooling. Toki granite was effectively cooled from the peraluminous regions where assimilation of country sedimentary rock was most extensive. © 2011 Springer-Verlag.


Sakai H.,Kyoto University | Iwano H.,Kyoto Fission Track Co. | Danhara T.,Kyoto Fission Track Co. | Takigami Y.,Kanto Gakuen University | And 3 more authors.
Island Arc | Year: 2013

In order to decipher the origin and tectonothermal history of the Kuncha nappe, we undertook a geological investigation in the Taplejung window in eastern Nepal, and carried out multichronological analyses of zircon, apatite, and mica of the Kuncha Formation and Taplejung granites. Three granite bodies that intrude into the Kuncha Formation show fission-track (FT) ages of 6.2 to 4.8Ma for zircon and 2.9 to 2.1Ma for apatite, although the granites yielded zircon U-Pb ages of 1852±24Ma and 1877±21Ma, and muscovite 40Ar-39Ar ages of ca 1650Ma. The U-Pb intercept age of detrital zircons from the Kuncha schist is 1888±16Ma, and this age represents a probable depositional age of the lower part of the Kuncha Formation. The FT ages of zircon and apatite from the same schist are found to be 5.4 and 2.5Ma, respectively. No zircon younger than 1.6Ga was identified from any of these samples. It means that the Kuncha nappe has never undergone thermal events after 1.6Ga until the Himalayan orogeny in Miocene. The Kuncha Formation and overlying Kali Gandaki Supergroup as well as the Taplejung granites can be correlated with the Coronation Supergroup and the Hepburn intrusives in the Wopmay orogen, northwest Canada. They are interpreted to be deposits in the basins of continental rift system and subsequent passive-margin settings. All the FT age data of zircon and apatite provide evidence that both the Kuncha nappe and overlying Crystalline nappe seem to have cooled laterally from the nappe front to the north. The FT ages from the front to central part of the nappe in Taplejung suggest that isotherm of 240°C, closure temperature of zircon FT, retreated toward north at about 10mm/y during the middle to late Miocene and Pliocene. © 2013 Wiley Publishing Asia Pty Ltd.


Danhara T.,Kyoto Fission Track Co. | Iwano H.,Kyoto Fission Track Co.
Island Arc | Year: 2013

The authors have developed and demonstrated an independent calibration of zircon fission track dating with the external detector method. During the past two decades, investigations have continued concerning the issues of the absolute age calibration of fission track dating. The derivation of accurate fission track age equations has been made possible by taking into account the relationships between the latent and etched track lengths. Our dating exercise involving 10 zircon reference samples supports our claim that absolute age determinations can be carried out based on the following three parameters: (1) the 238U spontaneous fission decay constant of 8.5×10-17 a-1 (λf) which is recommended by the IUPAC; (2) thermal neutron fluence values based on pre-irradiated IRMM540 dosimeter glass, which is equivalent to the Au and Co metal activation monitors in the 1990 IUGS recommendation; and (3) a [GQR] correction value of 1.35 which has been experimentally determined for the combination of zircon external surfaces irradiated with mica external detectors. Independent measurements of uranium concentration by the fission track method were also tested. A new method of fission track dating that uses mass spectrometry for uranium measurements was simulated with success using our zircon data. We propose that the Fission Track Community reassesses the situation and formulates a new recommendation, in which the established independent method is placed on at least an equal footing with the standard-based method. © 2013 Wiley Publishing Asia Pty Ltd.


Sakai H.,Kyoto University | Iwano H.,Kyoto Fission Track Co. | Danhara T.,Kyoto Fission Track Co. | Hirata T.,Kyoto University | Takigami Y.,Kanto Gakuen University
Island Arc | Year: 2013

A multichronological study of the weakly metamorphosed Early Miocene fluvial Dumri Formation and the overlying Kuncha and Lesser Himalayan Crystalline nappes has helped to clarify the timing and heat source of the metamorphism, as well as the history of emplacement and cooling of the nappes. U-Pb ages of detrital zircons from the Dumri Formation show peaks at ca 1Ga and 500-600Ma, and fission-track dating indicates a thermal imprint on the formation at 11-10Ma. In the Naudanda Quartzite, overlying the Kuncha Formation, reset fission-track detrital zircon ages are 9.5Ma, but the U-Pb ages are older than 1.7Ga. The differences in the U-Pb ages for detrital zircons from the Dumri and Kuncha Formations indicate that the Kuncha nappe was never exposed at the surface during the Early Miocene when the Dumri Formation was deposited. Two-mica garnet schists of the Main Central Thrust (MCT) zone have fission-track detrital zircon ages of 7.8Ma and 40Ar-39Ar muscovite ages of 19Ma, though the zircons have U-Pb ages older than 600Ma. Our interpretation is that the heat for the Dumri Formation metamorphism came from the overlying nappes. The timing of the thermal imprint on the Dumri Formation indicates that the metamorphic nappe reached its present position before ca 10Ma. The Parajul Khola granite in the frontal zone of the Kuncha nappe yields U-Pb zircon ages of 1.89Ga, and it underwent an Early Miocene thermal event, cooling below 240°C at 14.7Ma and below 100°C at 10.3Ma. These thermochronological data suggest that the frontal part of the Kuncha nappe was exposed at the surface around 15-14Ma and cooled immediately, but inner parts of the nappe were still hot during its emplacement. © 2013 Wiley Publishing Asia Pty Ltd.


Smith V.C.,University of Oxford | Staff R.A.,University of Oxford | Blockley S.P.E.,Royal Holloway, University of London | Bronk Ramsey C.,University of Oxford | And 4 more authors.
Quaternary Science Reviews | Year: 2013

The Lake Suigetsu SG06 sedimentary archive from Honshu Island, central Japan, provides a high-resolution palaeoenvironmental record, including a detailed record of explosive volcanism from Japan and South Korea. Thirty visible tephra are recorded within the 73 m-long SG06 core, which spans the last ∼150 ka. Here we describe and characterise these tephras based on major element glass composition, which is useful for the identification and correlation of these tephras and the age models of the records in which they are found. Utilising the large number of radiocarbon measurements (n > 600) from terrestrial plant macrofossils in the Lake Suigetsu SG06 record, we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka. Glass compositional data of some of the largest eruptions from Japan (K-Ah, AT, Aso-4, Aso-A, Aso-D, and Ata; sampled at proximal outcrops) are also presented. These data show that the major element glass chemistry is distinctive for many of the visible SG06 tephra units, and allows some of the layers to be correlated to known eruptions from volcanoes in Japan and South Korea, namely K-Ah (SG06-0967), U-Oki (SG06-1288), AT (SG06-2650), Aso-4 (SG06-4963/SG06-4979), K-Tz (SG06-5181), Aso-ABCD (SG06-5287) and Ata (SG06-5181). The following ages were obtained for the SG06 tephra units: 3.966-4.064 cal. ka BP (95.4% probability range) for the SG06-0588 tephra, 10.242-10.329 cal. ka BP (95.4% probability range) for SG06-1293, 19.487 ± 112 SG062012 ka BP (2 σ) for SG06-1965, 28.425 ± 194 SG062012 ka BP (2 σ) for SG06-2504, 28.848 ± 196 SG062012 ka BP (2 σ) for SG06-2534, 29.765 ± 190 SG062012 ka BP (2 σ) for SG06-2601, 29.775 ± 191 SG062012 ka BP (2 σ) for SG06-2602, 43.713 ± 156 SG062012 ka BP (2 σ) for SG06-3485, 46.364 ± 202 SG062012 ka BP (2 σ) for SG06-3668, 49.974 ± 337 SG062012 ka BP (2 σ) for SG06-3912, 50.929 ± 378 SG062012 ka BP (2 σ) for SG06-3974, and improved ages for two of the most important tephra markers across Japan, the K-Ah (7.165-7.303 cal. ka BP at 95.4% probability range; SG06-0967) and AT tephra (30.009 ± 189 SG062012 ka BP at 2 σ; SG06-2650). © 2013.


Sakata S.,Kyoto University | Hattori K.,Kyoto University | Iwano H.,Kyoto Fission Track Co. | Yokoyama T.D.,Kyoto University | And 2 more authors.
Geostandards and Geoanalytical Research | Year: 2014

We have developed new analytical procedures to measure precise and accurate 238U-206Pb and 235U-207Pb ages for young (~ 1 Ma) zircons using laser ablation-ICP-mass spectrometry. For young zircons, both careful correction for the background counts and analysis of very small Pb/U ratios (i.e., 206Pb/238U < 0.00016 and 207Pb/235U < 0.0001 for 1 Ma zircons) are highly desired. For the correction of the background, the contribution of the background signal intensities for the analytes, especially for the residual signal intensities for 206Pb and 207Pb, was defined through laser ablation of synthesised zircons (ablation blank) containing negligible Pb. The measured signal intensities for 202Hg, 206Pb and 207Pb signals obtained by the ablation blank were slightly higher than those obtained by data acquisition without laser ablation (gas blank). For the wider dynamic range measurements on Pb/U ratios, an attenuator device for the ion detection system was employed to extend the capability to monitor high-intensity signals (i.e., > 3 Mcps). Through the attenuator device, the ion currents were reduced to 1/450 of the signal intensity without the attenuator. Because the switching time for the attenuator was shorter than 1 ms, signal intensities for only specific isotopes could be reduced. With attenuation of the 238U signal, counting statistics on 206Pb and 207Pb isotopes could be improved and counting loss on the 238U signal could be minimised. To demonstrate the reliability of this new analytical technique, 238U-206Pb and 235U-207Pb ages for three young zircon samples (collected from Osaka Group Pink Volcanic Ash, Kirigamine and Bishop Tuff) were measured. The data presented here demonstrate clearly that the present technique could become a major analytical tool for in situ U-Pb age determination of young zircons (~ 1 Ma). © 2014 The Authors.

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