Paleomagnetismo del Grupo Sierra de Los Cóndores (Cretácico Inferior de Córdoba): correlación magnetoestratigráfica local, y sus consecuencias en la interpretación geológica.

GEUNA, SILVANA

REVISTA DE LA ASOCIACIÓN GEOLÓGICA ARGENTINA

Asociación Geológica Argentina

Lugar: Buenos Aires; Año: 1998 vol. 53 p. 69 - 82

0004-4822

A paleomagnetic study was carried out on continental beds of the Early Cretaceous Sierra de los Cóndores Group, Córdoba province (32,3ºS; 64,4ºW). Samples from volcanics and red beds were collected at 65 sites in 17 localities. Detailed AF demagnetization permitted the identification of three different magnetic components in volcanics: A component was carried by single or pseudo-single domain magnetite, B component was carried by hematite, and X component, by multidomain magnetite, as deduced from IRM curves and demagnetization behavior. Only component A had a positive conglomerate test, and was interpreted as a primary magnetization. Components B and X were interpreted  to be of  recent origin. Site mean directions of component A, together with revised directions from previous studies, passed both fold and reversal tests. Magnetostratigraphy did not match with geological correlation previously proposed, which included two volcanic phases temporally distinct. Magnetic properties were more in agreement with a context of gradual change of chemistry and mineralogy of the volcanics, including great lateral variation between localities. A paleomagnetic pole was computed: 88,7ºS, 85,4ºE, A95 = 4,2; K= 37, N= 33, coincident with an Early Cretaceous reference pole for South America, Serra Geral. No block rotations about vertical axes were detected.