| Project/Area Number |
63420018
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
地質学一般
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| Research Institution | Toyama University |
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Principal Investigator |
TAKEUCHI Akira Associate Professor at College of Liberal Arts, Toyama University, 教養部, 助教授 (20126494)
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| Co-Investigator(Kenkyū-buntansha) |
ASHIDA Kan Assistant Professor at Tritium Research center, Toyama University, トリチウム科学センター, 助手 (70192953)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥18,600,000 (Direct Cost: ¥18,600,000)
Fiscal Year 1989: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1988: ¥16,500,000 (Direct Cost: ¥16,500,000)
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| Keywords | Age determination / Thermoluminescence / Electron spin resonance / Quaternary era / Natural radioactive defects / Gamma-ray detector / Dosimetry / Non-marine sediments |
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| Research Abstract |
Main aim of this study is to establish a method for the Mid to Late Pleistocene age determination of non-marine clastic sediments without any chronological marker fossils for the later Quaternary. Typical inland sediments including volcanic ash, eolian loess, fresh water diatomite, and river and lake deposits are mainly tested. Paleodose accumulated after sedimentation were measured by means of dosimetric signals observed by using thermoluminescence (TL) and electron spin resonance (ESR) techniques.
Dosimetry: After purification for quartz or silica glass, those samples were irradiated by electron beam or X-ray from 6-12MeV linear accelerator. Some samples were annealed before irradiation in order to evaluate saturation in dose. Annual dose rate were measured by using two methods, in-situ dosimetry using TL probes and activity estimation from chemical data of gamma-ray spectrometry.
Experiments for dosimetric dating of 23 specimens was conducted. Among these, a half specimens were succes
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sfully dated ranging from 10Ka to 700Ka B.P. (Ka =10^3 years). Because of almost complete saturation in dose, several samples were failed to get their ages of sedimentation.
Consequently, the following topics and comments are pointed out: (1) Quartz bearing sediments would be most suitable for the dosimetric dating based on a mechanism of sun-light breaching (time zeroing) as well as that of crystallization. (2) Amorphous specimens such as volcanic glass and diatomite could be dated by using low power ESR measurement at liquid nitrogen temperature, if saturation were avoidable during irradiation. (3) High dose rate irradiation over 4.5 Gray/min would change susceptibility and/or sensitivity especially in cases of most sample older than 100Ka. (4) Irradiation by means of lineac electron beam (or X-ray) source is very useful because of its high accuracy of dose control. (5) Precise gamma-ray detector can be put to practical use for direct measurement of dose-rate as well as quantitative analysis for natural radioactive elements (U,Th,K). Less
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