Geomagnetic modulation of the late Pleistocene cosmic-ray flux as determined by 10Be 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 10Be from a marine sediment core at site CH88-10P on the Blake Outer Ridge. The paleointensity of the geomagnetic field for this core was determined by various methods. The variance in the concentration of 10Be in the authigenic fraction of the sediments from Blake Ridge closely correlates with the inverse of the variance in the paleointensity of the geomagnetic field. The 10Be signal lags, up to 1000 years of sedimentation, the measured paleointensity of the sediments. In contrast, the data from several other elements, some climatically sensitive, and from beryllium show relationship neither to 10Be nor to the paleomagnetic data. The relationship between 10Be concentration and the dipole field intensity ( M/ Mo) as measured in the sediments is consistent with theoretical models.