Geomagnetic paleosecular variation from 42000 to 5000 cal years BP in southern Brazil: preliminary results

Understanding the Earth's magnetic field on centennial to millennial scales is essential to improve the knowledge about the geodynamo mechanism. However, paleomagnetic data on these timescales are abundant in the northern hemisphere, and only a few data are available for the southern hemisphere. Here we present new paleomagnetic secular variation and relative paleointensity records spanning 37 ka, from 42000 to 5000 cal years BP. The magnetic records were obtained from sedimentary samples of a marine core collected in the south coast of Brazil (29.2S, 47.3W). The age model was based on four radiocarbon ratings obtained by accelerator mass spectrometry (AMS) and five oxygen isotopes tie-points using the LR04 stack model. Magnetic remanence was studied using AF demagnetization of discrete samples measured on the 755-1.65 DC SQUID magnetometer (2G Enterprises) housed in a magnetically shielded room at Laboratório de Paleomagnetismo of Universidade de São Paulo (USPMag). The amplitude of inclinations vary from -40° to -70° and are similar to those predicted by the SHA.DIF.14k model from 14000 to 5000 cal years BP. A noticeable variation in inclination accompanied by a significant decrease in relative intensity is observed around 40000 cal years BP, which may be related to the Laschamp geomagnetic excursion. The improvement of the age model and the addition of complementary paleomagnetic measurements will be necessary to improve the first paleosecular variation curve for southern Brazil over the past 50 ka.