Amazonia in Cambrian times: reconciling discordant paleomagnetic dataset with a geocentric axial dipole?

The paleomagnetic behavior for the Ediacaran to Cambrian periods is problematic with many discordant directions, suggesting a non-uniformitarian Earth's magnetic field during the development of the first complex life on Earth, approximately 540 million years ago. To better understand the global nature of such discrepancies, this study provides new geochronological and paleomagnetic data from the Parauapebas dyke swarm (study area: 6.10°S, 49.76°W), located in the southeastern Amazonian Craton (Carajás Province), Brazil. U-Pb on apatite and Ar-Ar whole rock ages from different dykes agreed for an emplacement of this mafic dyke swarm at ∼522 Ma. Most of the sites revealed a stable characteristic remanent magnetization of Dm = 290.6°, Im = -42.4° (N = 15, k = 8, a95 = 14.4°) yielding a paleomagnetic pole located at 21.8°S and 14.4°E (K = 8.3, A95 = 14.1°) for Amazonia. The primary origin of this pole is confirmed by a positive baked contact, petrography and magnetic mineralogy experiments. Yielding a R-criteria of 6, this is the first reliable pole for Amazonia during the Cambrian. While a persistent anomalous magnetic field since the Ediacaran cannot be dismissed with the available dataset, such discrepancies could be attributed to uncertainties in global reconstructions or data-related issues. Without additional constraints, a Cambrian geocentric axial dipole (GAD) may be considered.