Paleosecular Variations in the South Atlantic Anomaly Region Over 65–40 ka — Revisiting Site ODP 1233

Abstract The South Atlantic Anomaly (SAA) is the most prominent feature of Earth's magnetic field. Understanding past geomagnetic field variations in the SAA region is crucial for improving our knowledge of the geodynamo. Site Ocean Drilling Program (ODP) 1233, located within the modern SAA and characterized by a high sedimentation rate (∼190 cm/kyr), provides a valuable archive for reconstructing the anomaly's history. Although paleomagnetic data from shipboard and u‐channel measurements spanning the past 70 ka (Lund et al., 2006, 2024) have been reported, they have not been validated by rock magnetic analyses. Notably, during the 65–40 ka interval, which includes the Norwegian‐Greenland Sea and Laschamps excursions, relative paleointensity (RPI) and inclination from site ODP 1233 differ markedly from nearby and global records. SEM–EDS and rock magnetic results show alternating intervals dominated by silicate‐hosted magnetite inclusions, likely associated with reduced supply and partial dissolution of detrital titanomagnetite during Patagonian Ice Sheet retreat, and intervals dominated by detrital titanomagnetite. We therefore applied a log‐transformed RPI normalization that accounts for the magnetic properties of these carriers and rescales amplitudes to a common reference. The resulting RPI curve aligns well with regional and global paleointensity records. When the axial dipole moment was comparable to the present value at ∼57.5 and ∼47 ka, paleointensity minima appear confined to the South Atlantic region, analogous to the present‐day SAA behavior.