The late Ediacaran to early Cambrian was marked by significant biological and geochemical transformations, including the diversification of animal life, and an enigmatic paleomagnetic record. This study focuses on the Nama Group, a key geological unit for understanding the Ediacaran-Cambrian transition, yet hampered by limited paleogeographic constraints. Previous paleomagnetic studies identified complex remagnetization patterns but lacked a detailed examination of remanence carriers. To address this, we conducted field stability tests and employed advanced rock magnetic techniques on unweathered borehole core samples to complement paleomagnetic data. Thermal demagnetization identified three magnetic components. C1 is a present-day field viscous remanent magnetization (VRM) and was used for borehole core orientation. C2, carried by single domain (SD) pyrrhotite and SD magnetite, aligns with early Paleozoic remagnetization poles from West Gondwanaland and was likely acquired through a thermoviscous magnetization (TVRM) in magnetite and a thermoremanent magnetization (TRM) in pyrrhotite, suggesting regional uplift and cooling between 500-480 Ma. This quasi-synchronous remagnetization is supported by highly clustered paleomagnetic poles and thermochronological data. C3 is an anomalous component with significant inclination variation within the stratigraphy, carried by large pseudo-single domain (PSD) magnetites, possibly of primary, detrital origin. The pattern resembles findings from other cratons, suggesting an unstable geomagnetic field that could have persisted until ca. 540 Ma. This may represent one of the youngest occurrences of such extreme geomagnetic instability in the Ediacaran and provides the first evidence of this behavior in the Kalahari Craton, adding new support for a largely unstable geomagnetic field during this period.

Carbonate rocks frequently undergo remagnetisation events, which can partially/completely erase their primary detrital remanence and introduce a secondary component through thermoviscous and/or chemical processes. Despite belonging to different basins hundreds of kilometres apart, the Neoproterozoic carbonate rocks of South America (over the Amazon and São Francisco cratons) exhibit a statistically indistinguishable single-polarity characteristic direction carried by monoclinic pyrrhotite and magnetite, with paleomagnetic poles far from an expected detrital remanence. We use a combination of classical rock magnetic properties and micro-to-nanoscale imaging/chemical analysis using synchrotron radiation to examine thin sections of these remagnetised carbonate rocks. Magnetic data shows that most of our samples failed to present anomalous hysteresis properties, usually referred to as part of the “fingerprints” of carbonate remagnetisation. Combining scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), highly sensitive X-ray fluorescence (XRF), and X-ray absorption spectroscopy (XAS) revealed the presence of subhedral/anhedral magnetite, or spherical grains with a core-shell structure of magnetite surrounded by maghemite. These grains are within the pseudo-single domain size range (as well as most of the iron sulphides) and spatially associated with potassium-bearing aluminium silicates. Although fluid percolation and organic matter maturation might play an important role, smectite-illitisation seems a crucial factor controlling the growth of these phases. X-ray diffraction analysis identifies these silicates as predominantly highly crystalline illite, suggesting exposure to epizone temperatures. Therefore, we suggest that the remanence of these rocks should have been thermally reset during the final Gondwana assembly, and locked in a successive cooling event during the Early-Middle Ordovician.