Stalagmite paleomagnetic record of a quiet mid-to-late Holocene field activity in central South America

Speleothems can provide high-quality continuous records of the direction and relative paleointensity of the geomagnetic field, combining high precision dating (with U-Th method) and rapid lock-in of their detrital magnetic particles during calcite precipitation. Paleomagnetic results for a mid-to-late Holocene stalagmite from Dona Benedita Cave in central Brazil encompass similar to 1900 years (3410 BP to 5310 BP, constrained by 12 U-Th ages) of paleomagnetic record from 58 samples (resolution of similar to 33 years). This dataset reveals angular variations of less than 0.06 degrees yr(-1) and a relatively steady paleointensity record (after calibration with geomagnetic field model) contrasting with the fast variations observed in younger speleothems from the same region under influence of the South Atlantic Anomaly. These results point to a quiescent period of the geomagnetic field during the mid-to-late Holocene in the area now comprised by the South Atlantic Anomaly, suggesting an intermittent or an absent behavior at the multi-millennial timescale.

Automated summary

Speleothems can provide continuous and high-quality records of the geomagnetic field. The paleomagnetic records of a mid-to-late Holocene stalagmite from Brazil show small angular variations and relatively steady paleointensity, contrasting with the fast variations observed in younger speleothems from the same region.