Wavelet analysis of relative geomagnetic paleointensity at ODP Site 983

We performed spectral analysis of the record of relative geomagnetic paleoi ntensity obtained at ODP Site 983, covering the time interval 0-1.1 Ma. The results confirm the presence of significant power at frequencies correspon ding to the earth orbital parameters (eccentricity, obliquity, precession). The construction of the evolutionary spectrum allowed us to establish the non-stationarity of the signal at those frequencies. The subsequent use of wavelet techniques made it possible to demarcate the time intervals over wh ich orbital frequencies are present in the record. For those intervals, the paleointensity record shows some coherency with the isothermal remanent ma gnetization, normalizer of the natural remanent magnetization, and the rati o anhysteretic remanent magnetization/k. These results suggest that the orb ital frequencies embedded in the paleointensity record are the expression o f lithologic variations, and probably not a characteristic of the geodynamo itself. Extracting (filtering) these wavelet components from the Site 983 paleointensity record indicates, however, that this secondary overprint is of sufficiently low level that it has a minor effect on the overall charact er of the record. (C) 2000 Elsevier Science B.V. All rights reserved.