Estimation of groundwater retention time by carbon-14 in the sedimentary rocks at the Horonobe study site

Murakami, Hiroaki  ; Amano, Yuki   ; Kokubu, Yoko   ; Iwatsuki, Teruki  

C in sedimentary rocks were measured to understand the residence time of groundwater at Horonobe area, Japan. Wakkanai Formation and Koetoi Formation are distributed at the study area. Groundwater samples were collected at -140m and -250m (GL). C concentration in groundwater samples are range from 0.39 to 1.04 pMC. Results of calculations, C in samples are not contamination. Although the C ages are about 40,000 year BP by simply calculation, correlation from influence of dead carbon is necessary.