Vertical distribution of 10Be, 26Al, and 36Cl in the surface soil layer of weathered granite at Abukuma, Japan

Abstract

The northern Abukuma region of Japan is thickly covered by weathered Mesozoic granite. We investigated the vertical distribution of radionuclides (10Be, 26Al, and 36Cl) produced by cosmic irradiation of weathered granitic soil collected from this region at a sampling site located 496 m above sea level, at 37°30′52.6″N, 140°40′13.2″E. We mechanically and chemically separated quartz particles from the weathered granitic soil, and purified them. We also analyzed the vertical distribution of 26Al, 10Be, and 36Cl and estimated a long term averaged erosion rates of 0.019 ± 0.001 mm/y from 26Al, 0.017 ± 0.001 mm/y from 10Be, and not, vert, similar0.01 ± 0.001 mm/y from 36Cl. These cosmogenic erosion rates are comparable to the rate estimated from a geomorphological evolution model and with the observed sedimentary deposition rate at Abukuma.