Evidencias de avances y retrocesos en la deformación a partir del estudio de la anisotropía de susceptibilidad magnética. Grupo Pillahuincó (Sierras Australes, Argentina).

CESARETTI NORA; TOMEZZOLI, R. N; ARZADÚN, G

LatinMag Letters

Universidad Nacional Autónoma de México

Año: 2016 vol. 04 p. 1 - 6

2007-9656

The Sierras Australes of the Buenos Aires province define a fold and thrust belt that trends NW?SE,with decreasing deformation intensity toward the East. Anisotropy of magnetic susceptibility (AMS)studies were carried out on 102 specimens of the Pillahuincó Group (Carbo-Permian; Harrington,1947), with the aim of analyzing the magnitude of the deformation and direction of efforts. Thisgroup crops out at the East of Sierras Australes and was divided into four formations, which are fromthe base to top: Sauce Grande, Piedra Azul, Bonete and Tunas. The AMS results show ellipsoidswith Kmax axes in Northwest-Southeast position, parallel to fold axes. The anisotropy degree showsa decrease toward the youngest formations to the East. The Kmin axes are orientated from horizontalpositions, with Northeast-Southwest orientations, to vertical positions toward the top of the sequence.The fabric is dominantly of tectonic origin, with a maximum effort coming from the Southwest andan attenuation of the deformation to the youngest formations, placed at the East of the basin. Thereis re-activation at the base of Tunas Formation, which would indicate more intense orogenic cyclesin the basin during the Permian, keeping the coaxiability of the efforts. This is a new evidence of theorogenic front migration toward the foreland basin and is consistent with the structural, compaction,AMS and paleomagnetic data.