ASYMMETRICAL SAW-TOOTH PATTERN OF THE GEOMAGNETIC-FIELD INTENSITY FROM EQUATORIAL SEDIMENTS IN THE PACIFIC AND INDIAN OCEANS

A record of relative paleointensity from marine sediments in the equatorial Indian Ocean spanning the last 4 Ma completes a previous dataset from Ocean Drilling Program (ODP) Leg 138 sites in the equatorial Pacific [1]. The timescale was defined with a precision better than 20 kyr with different and independent methods. Most of the features present in the record from the equatorial Pacific are confirmed: the overall saw-tooth pattern is observed across every field reversal and the short-term fluctuations superimposed on the slow intensity decrease preceding the reversals appear to be similar at both sites. The global character of these features reinforces their interpretation in terms of changes in dipole field intensity and provides new important constraints on models of the geodynamo. A synthetic curve of field intensity changes during the last 4 Ma is proposed as a first paleointensity timescale for future stratigraphic studies.