High-resolution Paleosecular Variations from 14 to 70 ka Reconstructed from three Drake Passage Sediment Cores

The present-day geomagnetic field is characterized by low intensities extending from Southern Africa to South America, namely the South Atlantic Anomaly (SAA). The field intensity at the SAA region is currently decreasing and it is controversially discussed whether this may be related to an impending excursion or even reversal of the geomagnetic field. Nevertheless, there is still little known about the history of SAA in the past tens of thousands of years. Here, three sediment cores (PS97/085-03, PS97/084-01, PS97/079-02) recovered from the Drake Passage, Southern Ocean were subjected to detailed rock magnetic and paleomagnetic investigations. The coring sites are close to the southwest edge of the modern SAA region. Age models are based on a combination of two radiocarbon dates, six paleomagnetic excursional tie points, and tuning of high-resolution XRF scanning-derived calcium to titanium ratios as an environmental proxy to Antarctic temperature anomalies. The studied cores are spanning the past 140 ka. However, paleomagnetic data from marine isotope stages 5 and 1 have to be excluded due to unsuitable coarse magnetic grainsize. Thus, only the paleosecular variation from 14 to 70 ka can be reconstructed. The Laschamps and Mono Lake excursions are characterized by low intensities and large deviations of inclinations. The new paleosecular variation records are then compared to global and regional paleomagnetic records and models. In addition to excursions and normal secular variations, anomalous field behavior recorded in studied cores provides new insights into past magnetic field structures resembling the present-day SAA.