A Proposal for the Study of Geomagnetic Modulation of the Pleistocene Cosmic-Ray Flux by Measurement of 10Be from Blake Outer Ridge Marine Sediment

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The investigators will study the cosmic ray flux incident upon Earth during the Pleistocene epoch. The main effort is to measure the cosmogenic radionuclide 10Be in samples of sea sediment obtained from the Blake Outer Ridge, together with other relevant physical and chemical properties of the sediments. Prior work by the investigators has demonstrated that the concentration of 10Be varies inversely with measures of the paleo magnetic field (paleointensity) of the sediments, and that it is unlikely that this relationship arises from climate forcing. Extension of the high-resolution record will address several problems raised by the earlier work. Specifically, the investigators will concentrate on understanding the Laschamp geomagnetic excursion (41,000 years ago) and the Blake Event (115,000 years ago).