Geomagnetic modulation of the late Pleistocene cosmic-ray flux as determined by Be-10 from Blake Outer Ridge marine sediments

The cosmic-ray flux incident upon the Earth during the late Pleistocene, 20 -60 kyr B.P., was studied by measuring the cosmogenic radionuclide Be-10 fr om a marine sediment core at site CH88-10P on the Blake Outer Ridge. The pa leointensity of the geomagnetic field for this core was determined by vario us methods. The Variance in the concentration of Be-10 in the authigenic fr action of the sediments from Blake Ridge closely correlates with the invers e of the variance in the paleointensity of the geomagnetic field. The Be-10 signal lags, up to 1000 years of sedimentation, the measured paleointensit y of the sediments. In contrast, the data from several other elements, some climatically sensitive, and from beryllium show relationship neither to Be -10 nor to the paleomagnetic data. The relationship between Be-10 concentra tion and the dipole held intensity (M/M-o) as measured in the sediments is consistent with theoretical models. (C) 2000 Elsevier Science B.V. All righ ts reserved.