An analysis of geomagnetic field reversals supports the validity of the Geocentric Axial Dipole (GAD) hypothesis in the Precambrian

The Geocentric Axial Dipole (GAD) hypothesis has been regarded as the cornerstone of paleomagnetism for decades, and disputes on its applicability have mostly dealt with the Precambrian data. One way to analyze the zonal harmonics of the geomagnetic field and the validity of GAD hypothesis is based on the angular difference between the normal and reversed polarities, also referred to as reversal asymmetry. For this purpose, a comprehensive compilation of the reversals of Archaean and Proterozoic geomagnetic field has been done, using a novel paleomagnetic database with 3246 entries globally. Given the uncertainties prevailing in this type of analysis, results from 106 reversal records show no dependence of the reversal asymmetry on paleolatitude, thus supporting the outcome of our inclination frequency analysis of the Precambrian field. In addition to the inclination asymmetry, the non-antiparallelity between N and R also involves a declination asymmetry, which is more difficult to determine and deals with the non-zonal features of the field. Based on our dual polarity data, we propose that the Geocentric Axial Dipole (GAD) is a viable approximation of the geomagnetic field throughout the Precambrian. (c) 2013 Elsevier B.V. All rights reserved.