An improved system for measuring refractive index using the thermal immersion method

Danhara, Tohru; Yamashita, Tohru; Iwano, Hideki; Kasuya, Masao

doi:10.1016/1040-6182(92)90013-r

Cited by 100 publications

(40 citation statements)

References 3 publications

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“…The 63-to 125-μm fraction was mounted on glass slides, and the bulk grain composition and heavy-mineral composition were determined under a microscope. Refractive indices of hornblende crystals were measured individually using a refractive index measurement system (RIMS) analyzer (56). In the absence of volcanic glass, hornblende refractive indices (controlled by the content of oxides with high specific refractivity) were used to distinguish tuffs, as in the cataloged data for tuffs in Japan (57).…”

Section: Methodsmentioning

confidence: 99%

High-resolution record of the Matuyama–Brunhes transition constrains the age of Javanese Homo erectus in the Sangiran dome, Indonesia

Hyodo

Matsu’ura

Kamishima

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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A detailed paleomagnetic study conducted in the Sangiran area, Java, has provided a reliable age constraint on hominid fossilbearing formations. A reverse-to-normal polarity transition marks a 7-m thick section across the Upper Tuff in the Bapang Formation. The transition has three short reversal episodes and is overlain by a thick normal polarity magnetozone that was fission-track dated to the Brunhes chron. This pattern closely resembles another highresolution Matuyama-Brunhes (MB) transition record in an Osaka Bay marine core. In the Sangiran sediments, four successive transitional polarity fields lie just below the presumed main MB boundary. Their virtual geomagnetic poles cluster in the western South Pacific, partly overlapping the transitional virtual geomagnetic poles from Hawaiian and Canary Islands' lavas, which have a mean 40 Ar/ 39 Ar age of 776 ± 2 ka. Thus, the polarity transition is unambiguously the MB boundary. A revised correlation of tuff layers in the Bapang Formation reveals that the hominid last occurrence and the tektite level in the Sangiran area are nearly coincident, just below the Upper Middle Tuff, which underlies the MB transition. The stratigraphic relationship of the tektite level to the MB transition in the Sangiran area is consistent with deep-sea core data that show that the meteorite impact preceded the MB reversal by about 12 ka. The MB boundary currently defines the uppermost horizon yielding Homo erectus fossils in the Sangiran area.paleomagnetism | marine isotope stage 19 | magnetostratigraphy | geochronology

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Section: Methodsmentioning

confidence: 99%

High-resolution record of the Matuyama–Brunhes transition constrains the age of Javanese Homo erectus in the Sangiran dome, Indonesia

Hyodo

Matsu’ura

Kamishima

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…The refractive index of volcanic glass shards, which is useful for identifying widespread tephras in Japan Co., Ltd.). The RIMS system measures volcanic glass shards to an accuracy of ±0.0002 (Danhara et al 1992). The major element compositions were analyzed by energy-dispersive spectrometry using an electron probe microanalysis (EPMA) system (Horiba Emax Energy EX-250) at the FURUSAWA Geological Survey.…”

Section: Tephra Analysismentioning

confidence: 99%

Historical and paleo-tsunami deposits during the last 4000 years and their correlations with historical tsunami events in Koyadori on the Sanriku Coast, northeastern Japan

Ishimura

Miyauchi

2015

Prog. in Earth and Planet. Sci.

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Large tsunamis occurring throughout the past several hundred years along the Sanriku Coast on the Pacific coast of northeastern Japan have been documented and observed. However, the risk of large tsunamis like the tsunami generated by the 2011 off the Pacific coast of Tohoku earthquake could not be evaluated from previous studies, because these studies lacked evidence of historical and paleo-tsunami deposits on the coastline. Thus, we first identified event deposits, which are candidates for tsunami deposits, from excavating surveys conducted on the coastal marsh in Koyadori on the Sanriku Coast, northeastern Japan. Second, we determined the physicochemical sediment properties of the deposits (roundness of grains, color, wet and dry densities, and loss on ignition) and established their geochronology by radiocarbon dating and tephra analysis. Third, we identified event deposits as tsunami deposits, based on their sedimentary features and origin, sedimentary environment, paleo-shoreline, and landowner interviews. In this study, we report 11 tsunami deposits (E1-E11) during the past 4000 years, of which E1, E2, E3, and E4 were correlated with the 2011 Tohoku-oki tsunami, the 1896 Meiji Sanriku tsunami, the 1611 Keicho Sanriku tsunami, and the 869 Jogan tsunami, respectively. From age data and the number of tsunami deposits in the trench, we estimated that tsunamis larger than the 1896 Meiji Sanriku tsunami occur and hit the study area on average every 290-390 years. However, historical tsunami correlations revealed variable tsunami occurrence, indicating diverse tsunami generation and/or the combination of several types of large earthquakes from different sources around the Japan Trench.

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“…Coupling the refractive index of the glass shards with the glass morphology and heavy and light mineral compositions is a popular method characterizing tephras in and around Japan. The thermal immersion method (e.g., Danhara et al 1992) is usually used to measure refractive index. There are some datasets on the refractive indices of glass shards and some heavy minerals for Japanese tephras (e.g., Machida and Arai 2003).…”

Section: Identification and Correlation Of Tephramentioning

confidence: 99%

Marine tephra in the Japan Sea sediments as a tool for paleoceanography and paleoclimatology

Ikehara

2015

Prog. in Earth and Planet. Sci.

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Tephra is a product of large and explosive volcanic events and can travel thousands of kilometers before deposition. Consequently, tephra deposits are common in terrestrial, lacustrine, marine, and glacial environments. Because tephra deposition is a geologically synchronous event, tephras constitute important isochrones in the Quaternary sequence, not only in Japan but also throughout the northwest Pacific and its marginal seas. As a result, establishing the chronostratigraphic order of tephra deposits is an effective tool for assessing local and regional stratigraphies and for correlating events among sites. For example, tephrostratigraphy can provide precise chronological constraints for other stratigraphic data, such as magneto-and biostratigraphic data. Spatiotemporal variability in the occurrence and geochemistry of tephras can also be used to trace the magmatic evolution of island arcs and their relationships to regional tectonics. In a paleoclimatic context, tephra deposits allow the correlation of past climate events among terrestrial, lacustrine, and marine environments. Tephrochronology is also a fundamental element used in reconstructing the marine reservoir effect, where the ages of tephra in marine and terrestrial settings are compared. Therefore, tephra is a valuable tool not only in stratigraphy, chronology, and volcanology but also in paleoceanography and paleoclimatology.

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An improved system for measuring refractive index using the thermal immersion method

Cited by 100 publications

References 3 publications

High-resolution record of the Matuyama–Brunhes transition constrains the age of Javanese Homo erectus in the Sangiran dome, Indonesia

High-resolution record of the Matuyama–Brunhes transition constrains the age of Javanese Homo erectus in the Sangiran dome, Indonesia

Historical and paleo-tsunami deposits during the last 4000 years and their correlations with historical tsunami events in Koyadori on the Sanriku Coast, northeastern Japan

Marine tephra in the Japan Sea sediments as a tool for paleoceanography and paleoclimatology

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