Effects of climate and the cosmic-ray flux on the 10Be content of marine sediments

Abstract 10 Be from Blake Outer Ridge (BOR) marine sediments at Leg 72, site 1061 from 35 to 160 ka B.P. was measured in order to obtain a record of the cosmic-ray flux incident upon the Earth. The variations in the concentration of 10 Be per gram of sediment in BOR sediments and that of the oxygen isotope record of the North Atlantic are strikingly similar highlighting the effects of climate on the deposition of 10 Be in marine sediments. In addition, the long-term trends of 9 Be and 10 Be concentrations, both source dependent, are shown to be inversely correlated and thus the 10 Be/ 9 Be normalization is ambiguous at best. The effects of climate on 10 Be deposition were best removed by normalization of 10 Be to the mass of the authigenic fraction of the sediment in which it was contained. The 10 Be content of the sediments at site 1061 was correlated to another site on the Blake Outer Ridge, CH88-10P, and to a site in the Gulf of California Leg 64, site 480. 10 Be normalized to the authigenic mass at these sites show that the 10 Be concentrations within the sea fall within a range consistent with the expected secular variations of the Earth's dipole field.