Paleomagnetic and geochemical studies of Sierra de los Cóndores Group (Lower Cretaceous from Córdoba, Argentina): new PP and stratigraphical interpretation

GEUNA, SILVANA; LAGORIO, SILVIA

Uppsala

Congreso; IAGA 8th Scientific Assembly; 1997

Paleomagnetic and geochemical studies of Early Cretaceous Sierra de LosCóndores Group, Córdoba province (32.3°S, 64.4°W) were carried out. Samplesfrom volcanics and red beds were collected at 65 sites in 17 localities. Threedifferent magnetic components were identified in volcanics: A component wascarried by single or pseudo-single domain magnetite, B component was carried byhematite, and X component, by multidomain magnetite, as deduced from IRM curvesand demagnetization behavior. Only component A passed a conglomerate test, andwas interpreted as a primary magnetization. Site mean directions of componentA, together with revised directions from previous studies, passed both fold andreversal tests. Magnetostratigraphy did not match with geological correlation previouslyproposed, which included two volcanic phases temporally distinct. Polaritiesand geochemical data were more in agreement with a context of gradual change ofchemistry and mineralogy of the volcanics, including great lateral variationbetween localities and diachronisms. The whole Sierra de Los Cóndores Groupappears to be formed during four polarity intervals. A paleomagnetic pole wascomputed: 88.7°S, 82.6°E, A95=4, K= 36, N= 33. This pole includes and supersedes previous ones:Vulcanitas Cerro Colorado and Vulcanitas Rumipalla, both of them carried out onthe same Sierra de Los Cóndores Group.