Geomagnetic excursions: a critical assessment of the evidence as recorded in sediments of the Brunhes Epoch

Abstract

Geomagnetic excursions have tantalized geophysicists since the earliest suggestion of their occurrence over 15 years ago. Either as large-scale geomagnetic secular variation, geomagnetic reversals of short duration or aborted reversals, they held great promise of providing new insights into the nature of the origin of the geomagnetic field. Unfortunately the evidence for geomagnetic excursions from the palaeomagnetic record of Brunhes age sediments is not as compelling as the theoretical arguments. A critical assessment of the available data indicates that the Gothenburg excursion is unlikely to have occurred and the Erieau excursion is very unlikely. The Mono Lake excursion probably occurred, but its absence in nearby contemporaneous sites creates profound problems. The Blake Event appears to be an actual short reversal of complex character, but confirmation of its global nature may be quite difficult.