Implications of precise 10Be measurements in deep-sea sediments

Precise ¹⁰Be measurements in a vertical profile of a large-diameter gravity core with uniform chemical composition from the central equatorial Pacific have not shown the expected decrease with depth. The decay-corrected ¹⁰Be activities ranged from 5.79 ± 0.21 d.p.m. kg^?1 at the top of the core to 9.88 ± 0.46 d.p.m. kg^?1 at the bottom, with a mean of 7.24 ± 1.18 d.p.m. kg^?1. This variation is attributable to the combined variations in the intensity of cosmic rays and that of the earth's magnetic field during the past ～ 1 Ma.