A (new?)~ 50 Kyr geomagnetic event recorded in a stalagmite from the Bat Cave, Portugal

Stalagmites are potential candidates for high-resolution reconstruction of the Earth’s magnetic field and paleoclimatic variations. Here we provided a pristine record of a geomagnetic event recorded in two stalagmites from the Bat Cave, Central Region of Portugal. SQUID microscopy reveals a high concentration of magnetic particles. FORC diagrams and hysteresis parameters point to non-interacting single-domain magnetite as the main magnetic carrier. Carbon and oxygen isotope compositions are interpreted as primary and provide the record of a Greenland interstadial. Paleomagnetic data show a gradual variation of the magnetic declination and inclination from the normal component to an antipodal reverse component. Return to the normal component is abrupt and is not apparently associated with visible hiatus in the precipitation rate of the stalagmite. Preliminary U-Th dating point to an age of ~50-55 Kyr for the geomagnetic event recorded in both stalagmites. However, owing to the speleothem’s high detrital content and low U concentration, alternative techniques are being explored to improve the uncertainty in radiometric dating. This geomagnetic event can possibly correspond to the Laschamp geomagnetic excursion dated at ~41 Kyr or to a newly discovered ~50 kyr short-lived geomagnetic reversal.

Acknowledgments: This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020- IDL, MIT-EXPL/ACC/0023/2021, and PTDC/CTA-GEO/0125/2021).

How to cite: Font, E., M. Sánchez-Moreno, E., Lima, E., Brás, A. R., Spangenberg, J. E., Edwards, L., Trindade, R., Dimuccio, L., Hasözbek, A., Parés, J., Jiménez Barredo, F., Araujo de Carmo, J., and Feinberg, J.: A (new?) ~50 Kyr geomagnetic event recorded in a stalagmite from the Bat Cave, Portugal, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10068, https://doi.org/10.5194/egusphere-egu23-10068, 2023.