Potential geomagnetic instability during the Last Deglaciation: High-resolution paleomagnetic evidence from the South China Sea

Abstract

The Last Deglaciation has been marked by numerous reports of geomagnetic excursions, though controversies persist due to uncertainties in their timing and the inconclusiveness of supporting evidence. In this study, we present new paleomagnetic data from ultra-high sedimentation rate core (up to 834 cm/kyr) from the South China Sea, which may reflect geomagnetic instability during this period. Based on 12 AMS ¹⁴C dates, we identify multiple intervals of reversed inclination between 14.5 and 11.5 ka. Our detailed rock magnetic and sedimentological analyses, in conjunction with the presence of shallow inclination anomalies in nearby records, suggest that these deviations likely represent genuine geomagnetic signals linked to excursion events. The observed transient and discontinuous directional changes, along with the geographically concentrated nature of our dataset, lead us to hypothesize that the sedimentary low-pass filter effect and the regionally confined occurrence of excursions contribute to the enigmatic nature of these anomalies in previous studies. The rapid and frequent directional shifts observed highlight the severe instability of the geomagnetic field during this period, potentially driven by non-dipole components. Nevertheless, further investigations are essential to confirm the validity of these hypotheses and to deepen our understanding of geomagnetic instability during this period.