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Abstract The early Paleoproterozoic (ca. 2.5–2.2 Ga) represents a critical juncture in Earth history, marking the inception of an oxygenated atmosphere while bearing witness to potentially multiple widespread and severe glaciations. Deciphering the nature of this glacial epoch and its connection with atmospheric oxygenation has, however, proven difficult, hindered by a reliance on disputed stratigraphic correlations given the paucity of direct radiometric age constraints. Nowhere is this more acute than within the South African Transvaal Supergroup: Here, while the loss of oxygen-sensitive mass-independent sulfur isotope fractionation (S-MIF) has been reported from both the Duitschland and Rooihoogte formations, divided opinion surrounding the time-equivalence of these units has prompted authors to argue for vastly different oxygenation trajectories. Addressing this debate, we present a depositional Re-Os age (2443 ± 33 Ma) from diamictite samples preserved in drillcore of the upper Duitschland Formation. The 100-million-year separation between the Duitschland Formation and its previously presumed equivalent reveals at least two isolated disappearances of S-MIF, requiring that the Great Oxidation Event was dynamic and proceeded via discrete oxygenation episodes whose structure remains incompletely understood. Importantly, our revised framework aligns the lower Duitschland diamictite with the low-latitude glacigenic Makganyene Formation, supporting hypotheses of widespread regional, and potentially global, early Paleoproterozoic glaciation. 

Abstract The current morphology of Earth’s time-averaged magnetic field can be approximated to a geocentric axial dipole (GAD), but whether such an approximation remains valid in deep time needs to be investigated. Studies have used paleomagnetic data to reconstruct the ancient field and generally support a GAD morphology since 2 Ga. Recently, the GAD model for mid-Proterozoic time has been challenged, and an alternative model was proposed wherein the mid-Proterozoic field was dominated by a normal-tesseral quadrupole (NTQ) with spherical harmonics of degree l = 2 and order m = 1. We performed forward modeling to quantitatively compare whether a GAD or an NTQ could provide a better fit to mid-Proterozoic paleomagnetic directions. To deal with the ambiguity in plate reconstruction, we first considered data only from Laurentia, and then we expanded the analysis to Baltica by reconstructing its position relative to Laurentia using the geologically based Northern Europe–North America (NENA) configuration. Finally, we included data from Siberia using two reconstruction models. Results showed that in three mid-Proterozoic intervals (1790–1740 Ma, 1485–1425 Ma, 1095–1080 Ma), a GAD morphology gives better, or equally good, fits compared to the NTQ morphology. In addition, a stable NTQ that persisted for hundreds of millions of years is disfavored from a geodynamic perspective. Overall, mid-Proterozoic paleomagnetic directions are more consistent with a dipolar field. We suggest that the GAD remains the most parsimonious model to describe the morphology of the mid-Proterozoic magnetic field. 

Abstract The location of the West African craton (WAC) has been poorly constrained in the Paleoproterozoic–Mesoproterozoic supercontinent Nuna (also known as Columbia). Previous Nuna reconstruction models suggested that the WAC was connected to Amazonia in a way similar to their relative position in Gondwana. By an integrated paleomagnetic and geochronological study of the Proterozoic mafic dikes in the Anti-Atlas Belt, Morocco, we provide two reliable paleomagnetic poles to test this connection. Incorporating our new poles with quality-filtered poles from the neighboring cratons of the WAC, we propose an inverted WAC-Amazonia connection, with the northern WAC attached to northeastern Amazonia, as well as a refined configuration of Nuna. Global large igneous province records also conform to our new reconstruction. The inverted WAC-Amazonia connection suggests a substantial change in their relative orientation from Nuna to Gondwana, providing an additional example of large-magnitude cumulative azimuthal rotations between adjacent continental blocks over supercontinental cycles.