The basalts of the Posadas Formation were extruded during the huge continental volcanism that affected the Paraná Basin in the Lower Cretaceous. We have carried out a paleomagnetic and rock-magnetic study on samples collected along a basalt outcrop section in Misiones, Argentina and determined that rocks classified as tholeiitic basalts and andesi-basalts are characterized by a low to intermediate content of Ti. Paleomagnetic and rockmagnetic studies suggest that the main magnetic mineral is low-Ti titanomagnetite of superparamagnetic (SP) to single-domain (SD) sizes, and very low amounts of multi-domain (MD) particles. The stable magnetic remanence enabled us to define characteristic remanent magnetizations (ChRMs) with a maximum angular deviation (MAD) <5• in most cases; and in all the cases, a MAD <10• . The sequence has registered at least two polarity reversions, starting from a normal polarity at the base. The calculated virtual geomagnetic poles (VGPs) present an elongated distribution similar to other distributions of VGPs published for the Paraná Magmatic Province. The elongated distribution of the VGPs could be a real feature of the geomagnetic field at a time of frequent changes of polarity.

S U M M A R YA paleomagnetic study was carried out on recent volcanic rocks exposed on Deception Island (63.0• S, 60.6• W), Antarctica. Sampling comprised all stratigraphic units exposed on the island, which include basaltic, andesitic and trachytic lavas, basaltic dykes and pyroclastic flows. Following stepwise thermal and alternating field demagnetization procedures, consistent characteristic remanence directions were determined at 21 sites, using principal-component analysis. The overall mean remanence direction for the Deception Island rocks is dec. 348.8• , inc. −73.7• , α 95 = 4.4• , N = 21, and is consistent within error with the geocentric axial dipole direction at the study locality. All of the studied rocks show normal polarity, indicating a Brunhes Chron age. The only available radiometric date of 153 ± 46 kyr agrees with this and suggests a minimum chronostratigraphic span of 100 kyr for the sampled rocks. The site mean directions show a Fisherian distribution and dispersion values compatible with current palaeosecular variation models. No evidence of the far-sided or right-handed effect is found in our data.