Palaeomagnetism of the Lower Cretaceous Sierra De Los Condores Group Cordoba Province Argentina

Measurements are described of the directions of remanent magnetization of 89 samples from nine lava flows and red beds. Stable remanent magnetization was isolated after AC demagnetizing. All the units have normal remanent magnetization, except one lava flow which yields a direction toward the north with positive inclination. From the mean direction of stable remanence, referred to the bedding, of each unit a virtual geomagnetic pole is computed; the mean of eight of these poles is 90·6 °E, 84·2° South, α₉₅= 4·7° and represents the position of the palaeomagnetic pole for the exposures of the Sierra de Los Condores group from El Estrecho-Cerro Libertad. The position of this pole is reasonably close to the positions of the South American Lower Cretaceous palaeomagnetic poles for the Serra Geral and Vulcanitas Cerro Colorado formations and the trachybasaltic dykes from Rio Los Molinos. This supports the interpretations that the South Atlantic Ocean was formed in Lower Cretaceous times and that the Earth's magnetic field was on average similar to that of a geocentric dipole in South America in the Lower Cretaceous, and suggests that there has not been substantial relative movements between Central Argentina and Southern Brazil.