Palaeomagnetism of the Lower Cretaceous Vulcanitas Cerro Colorado Formation of the Sierra de los Cóndores Group province of Córdoba, Argentina

• Main Author: Valencio, Daniel Alberto
• Language: unknown
• Published: 1972
• Subjects: Argentina; Geomagnetic Pole
• Online Access: https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0012821X_v16_n3_p370_Valencio; https://hdl.handle.net/20.500.12110/paper_0012821X_v16_n3_p370_Valencio

Measurements are described of the directions of magnetization of 101 samples from six lava flows, one dyke and redbeds from the Lower Cretaceous Sierra de los Cóndores Group, Argentina. The magnetic remanence of the lowest basaltic flow (Embalse Río Tercero Formation) was unstable. Primary remanent magnetizations of the other five lava flows, the dyke and redbeds (Vulcanitas Cerro Colorado Formation) were isolated after detailed A.C. and thermal cleaning; all these units have reversed magnetization. On the basis of the mean direction, referred to the bedding, of cleaned remanent magnetization of each unit a virtual geomagnetic pole is computed; the mean of these virtual geomagnetic poles, SAK2, is: 14°E 81°S, α95 = 13°; we think that SAK2 is a geomagnetic pole. The position of the pole for the Vulcanitas Cerro Colorado Formation (118.5 ± 6 my) is reasonably close to the Serra Geral Formation pole (115-125 my); this supports the interpretation that South America and Africa were separated in Lower Cretaceous time and suggests that the earth magnetic field was, on average, similar to that of a geocentric dipole in the Lower Cretaceous. The reversed remanent magnetization and the K-Ar age (118.5 ± 6 my) of the Vulcanitas Cerro Colorado Formation define the existence of a previously unrecognized period of reversed polarity at the Lower Cretaceous. © 1972. Fil:Valencio, D.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.