Paleomagnetismo de unidades del Jurásico Superior y Cretácico Inferior de la Cuenca de Somuncurá - Cañadón Asfalto (Chubut): Evidencia de bloques rotados

GEUNA, SILVANA; SOMOZA, RUBÉN; VIZAN, HAROLDO; FIGARI, EDUARDO; RINALDI, CARLOS

Salta

Congreso; Congreso Geológico Argentino; 1999

We report paleomagnetic data from a widespread distribution of sites ofUpper Jurassic to Cretaceous volcanic and sedimentary rocks in the Somuncura -Cañadón Asfalto basin, central Patagonia. Monocomponent and multicomponentmagnetizations were observed during both thermal and AF demagnetizationprocedures. The resulting time-averaged paleomagnetic vector of each localitywas compared with the expected Late Jurassic ? Cretaceous paleofield for SouthAmerica. Despite problems with the accurate definition of the apparent polarwander path of this continent, the paleodeclinations of the Upper Jurassic -Lower Cretaceous rocks suggest the widespread occurrence of vertical axisrotations. In contrast, the unconformable overlying Mid-Cretaceous rocks in theregion do not show paleomagnetic evidence of vertical axis rotations. Thisindicates that most tectonic rotations detected in rocks of the Somuncura- CañadónAsfalto basin are closely related to a new extensional-transtensional stressfield that generated superposed depocenters in Hauterivian times.