Paleomagnetism of Pleistocene-Holocene volcanic rocks from Neuquén Province (Argentina)

Investigations of paleosecular variation (PSV) have utilized paleomagnetic records from geological materials. However, the detailed time-averaged field (TAF) structure is limited by the uneven spatio-temporal distribution of paleomagnetic data. These limitations hinder our ability to understand geomagnetic field evolution, especially in assessing the persistence of anomalous field features over the past few million years. We report new paleodirectional records from Quaternary lava flows collected from the Tromen Volcanic System and the Zapala Volcanic Field, both located in Neuquén Province, Argentina. Rock magnetic analysis revealed that titanomagnetite with variable titanium concentrations constitutes the main magnetic carrier, predominantly characterized by vortex domain structures. From the 20 sampled sites corresponding to 19 lava flows, N = 17 paleodirectional sites met the selection criteria with n ≥ 5 and k ≥ 50. After the exclusion of transitional sites using the Vandamme cutoff (53.4°), we obtain a mean direction for N = 16 ( D = 346.9°, I = −54.1° and α 95 = 10.1°), which is statistically indistinguishable from the expected inclination for a geocentric axial dipole (GAD) field ( I GAD = − 56.8 ° ) within the 95% confidence limits. The paleopole (Plat = 80.9°, Plon = 196.5° and A 95 = 12.9°) coincides at the 95% confidence level with the geographic north pole. The estimated inclination anomaly ( ∆ I = 2.7 − 7.4 12.8 ° ) is agreement with zonal TAF models with quadrupole and octupole contributions that are <5.5% of the GAD term for the 0–10 Ma interval. The VGP dispersion obtained ( S B = 26.9 22.3 31.4 ° ) is not statistically consistent with South American datasets at similar latitudes, nor with predictions from PSV models. These results expand the records of anomalous paleofield behavior as observed in other locations in the South America and the South Atlantic regions for the last 10 Myr. • New paleodirection records from Neuquén Province extend the 0–10 Ma database. • High paleomagnetic dispersion suggests anomalous magnetic field behavior. • Positive inclination anomaly indicates non-geocentric axial dipole field structure.