Magnetostratigraphy of the Lodève Basin, France: Implications for the Permo-Carboniferous reversed superchron and the geocentric axial dipole

New results from the La Lieude Formation now complete the magneto-stratigraphic coverage of the Permian redbeds preserved in the Lodève Basin of southern France. The majority of the samples yield reversed polarity, with a mean of declination D = 187.4°, inclination I = −0.5° (Fisherian statistics k = 44.2, α 95 = 5.6°, n = 16). Together with previously published results, these data indicate that the entire basin lies within the Permo-Carboniferous Reversed Superchron (PCRS). But the stratigraphically highest sample exhibits normal polarity, suggesting that the transition marking the end of the PCRS may be close. The unusual behaviour of the geodynamo that generates superchrons prompts one to ask if there are concomitant influences on the morphology of the field. The intersecting palaeomeridian method offers a means of pursuing this question. An updated analysis suggests that there are currently no compelling reasons for adding significant higher-order terms to the geocentric axial dipole (GAD) model for the Late Permian.