A map of the Pacific geomagnetic anomaly during the Brunhes chron

The persistence of an anomaly of the geomagnetic field in the central Pacific Ocean has been suggested by many authors. However, the amplitude and the extent of this feature remain poorly constrained due to insufficient spatial and temporal coverage of the volcanic database. Records from marine sediments are appropriate to document the long-term behavior of the geomagnetic field. We studied 11 piston cores from the central and southwestern Pacific in order to document the anomaly during the past 800 kyr. Ten records were retained after applying selection criteria dealing with physical disturbances, deformations, and any possible sources of inclination errors. The results have been integrated into a new data set for the Pacific Ocean and the eastern Indian Ocean, which combines sedimentary and volcanic records. A strong negative inclination anomaly (≈−10°) in the southwestern Pacific is the main characteristic of the new map. In contrast, the sedimentary records from the Hawaiian area do not indicate any stable feature but rather alternating positive and negative anomalies. The new inclination map of the Brunhes chron bears striking similarities with the configuration of the historical field, particularly the presence of a negative anomaly centered in the eastern Indian Ocean and southwestern Pacific Ocean. Detailed records constraining the archeological period in the southwestern Pacific and documenting the spatial extension of the anomaly are now needed to establish a direct link with the present field.