Mass-spectrometric 10Be dating of deep-sea sediments applying the Zürich tandem accelerator
1984
Abstract We have measured 10 Be in deep-sea sediment cores from the Central North Pacific (GPC-3, 30° N 157° W) and from areas with high biological activity, off West Africa and the South Atlantic near Antarctica. In core GPC-3 we observe a decrease with depth which can be decomposed into three exponentials. Sediment accumulation rates of 2 mm/ka for the upper 2.2 m, 1.1 mm/ka for the section between 2.2 m and 4.7 m and 0.5 mm/ka from 4.7 m to 10 m have been derived. The changes in the accumulation rate occurred at 1.1 Ma and 3.3 Ma BP. In core GPC-3 the 10 Be chronology agrees (20%) with paleomagnetic dating of the uppermost 4.2 m, corresponding to a time range of 2.43 Ma (Matuyama-Gauss Boundary). The average 10 Be flux into the sediments at locality GPC-3 during the past 1.1 Ma is comparable to the assumed depositional flux from the atmosphere. On sediment cores from off West Africa and the South Atlantic we observe, on the contrary, fluxes of 10 Be which exceed more than 10 times the depositional flux. This indicates that the concentration of 10 Be in the open ocean at localities in the proximity of highly productive areas may be strongly modulated by variations of bioactivity throughout time.
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