Absolute electron spin resonance (ESR) ages of Pleistocene shells from Hiradoko and Uji shell beds in Noto Peninsula, Central Japan were deduced from the total absorbed dose of natural radiation (TD) and the internal and external radiation dose. The internal dose from inside the shell was assessed using the 238U , 232Th and K contents and newly developed theoretical equation of TD based on uranium-series disequilibrium in a finite medium. The external environmental radiation was measured by thermolumi nescent dosimeter (TLD) of CaSO4(Tm). The ESR ages of around 120,000 years for shells from both shell beds agreed fairly well with coral ages in the same shell beds determined with 230Th/234U dating (OMURA, 1980).
Isamu TOYOKURA2), Kazuo OHMURA2), Fusao ARAI3), Hiroshi MACHIDA4), Nobukazu TAKASE2), Keiji NAKADAIRA2) and Takashi ITO2) A distal tephra laryer occuring in the coastal areas of the Hokuriku district, Central Japan, is characterized and identified with the Sambe Kisuki tephra (SK). It occurs as airfall and water-laid ash associated with overlying drift pumice within the marine terrace deposits. The tephra is characterized by 1) biotite-bearing rhyolitic ash, 2) pumiceous glass with an unusually low refractive index, ranging from 1.494 to 1.498, and with higher concentration of potassium than of sodium, 3) stratigraphic position underlain by the Aso-4 and Kikai-Tozurahara tephra layers. The stratigraphic relationships between SK and well-dated marker tephra layers suggest that the tephra erupted between 80ka and 90ka from Sambe volcano, ca. 400km west of the area. Paleomagnetic measurement of the tephra shows normal polarity, in contrast to the result of NAKAJIMA and MIURA (1983), who demonstrated reversed polarity as evidence of the Blake event. This tephra is recognized as a useful tool for elucidating paleocurrents as well as formation ages of terrace deposits in the Hokuriku area, where no marker had been recognized for the earlier half of Late Pleistocene. (1) The drift pumice balls of SK suggest the presence of an ocean current running eastwards along the Japan Sea coast at that time. (2) The marine terrace deposits distributed at an elevation of 30-40m above sea level in the Hiradoko upland in the Noto peninsula and the Awara sand bed in the Kaetu upland, on the northern part of the Echizen coast, have an age of around 80ka. They can be correlated with the Obaradai terrace deposits in the southern Kanto district. (3) The raised marine terraces intercalating SK and Aso-4 ashes suggest that the rate of uplift may have been higher than was previously considered.
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