CLIMATIC INFLUENCE IN NRM AND 10BE-DERIVED GEOMAGNETIC PALEOINTENSITY DATA

Abstract

One can determine geomagnetic paleointensities from natural remanent magnetizations (NRM) and by inverting production rates of cosmogenic isotopes such as 10Be and 14C. Recently, two independently derived 200-kyr stacks [Y. Guyodo, J.-P. Valet, Relative variations in geomagnetic intensity from sedimentary records: the past 200,000 years, Earth Planet. Sci. Lett. 143 (1996) 23-36; M. Frank, B. Schwarz, S. Baumann, P.W. Kubik, M. Suter, A. Mangini, A 200 kyr record of cosmogenic radionuclide production rate and geomagnetic field intensity from 10Be in globally stacked deep-sea sediments, Earth Planet. Sci. Lett. 149 (1997) 121-129] were compared and the good agreement was suggested to validate the use of sedimentary cores for studies. Both compilations use mainly the astronomically forced and climatically controlled oxygen isotope stratigraphy to date and synchronize the sedimentary records, while this very curve has several coherent features with the supposedly pure geomagnetic records. An NRM relative paleointensity record, which was included in the conventional paleointensity stack, shows correspondence with climatic features, which is explained by an inadequacy in the normalization technique. Therefore, it is possible that the extraction of the pure paleointensity signal from marine sediments has not always been accomplished.