ESR age of Pleistocene shells measured by radiation assessment.

Abstract

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 thermoluminescent 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).