Reconstruction of high-resolution paleomagnetic variations in the middle Gauss chronozone, including the upper and lower boundaries of the Mammoth reversed subchronozone

Abstract In this study, we provide paleomagnetic records, including the upper and lower boundaries of the Mammoth reversed subchronozone, reconstructed from a continuous outcrop of the upper marine Pliocene in the southernmost part of the Boso Peninsula, which is more than 200 m thick. In this interval, the Mammoth reversed subchronozone was recognized in an interval of approximately 50 m thickness, including a polarity transition zone at its lower boundary of approximately 10 m thickness. Simultaneously, the upper boundary showed no polarity transition zone and a rapid polarity reversal, suggesting a probable lack of strata. Several significant variations were recognized in the paleomagnetic directions in the middle Gauss chronozone, some of which may qualify as new geomagnetic excursions. The relative paleointensities (RPIs) obtained in this study are consistent in their character of change with those reported from deep-sea cores in the distant Caribbean Sea and the equatorial Pacific, indicating the potential of stratigraphic correlation using RPI. The RPI around the lower Mammoth boundary was significantly attenuated compared to the average of the entire section. On the other hand, the virtual geomagnetic pole (VGP) path of the lower Mammoth boundary shows a rapid shift from the southern hemisphere to the northern hemisphere during transition. This movement passes through regions affected by non-axial dipole fields. Following this, the RPI shows a recovery trend, and the VGP stabilizes in the southern hemisphere, forming clusters that align with records from Italy and Hawaii. This sequence offers significant insights into changes in the axial dipole field during geomagnetic polarity reversals. Graphical Abstract