Shallow architecture of Fuegian Andes lineaments based on Electrical Resistivity Tomography (ERT). Evidences of transverse extensional faulting in the central Beagle Channel area

BRAN, DONALDO MAURICIO; TASSONE, ALEJANDRO ALBERTO; MENICHETTI, MARCO; CERREDO, MARÍA ELENA; LOZANO, JORGE GABRIEL; LODOLO, EMANUELE; VILAS, JUAN FRANCISCO

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Año: 2018 vol. 45 p. 1 - 34

0718-7092

The southern foothills of the Fuegian Andes are bounded by the Beagle Channel (BC), a conspicuousE-W longitudinal basin, controlled by a large transcurrent fault system, which extends from the Atlantic to the PacificOcean. The northern shore of the Beagle Channel?s central segment is characterized by several E-W oriented valleys,parallel to the main basin, which are interspersed with a series of oblique NW trending lineaments that extend across themountain belt. A geoelectrical survey was carried out in order to investigate the shallow architecture of such sets of linear morphologies. The principal E-W lineament system was characterized by conspicuous sub-vertical resistivity contrasts,interpreted as fractured zones associated with fault strands of the main strike-slip Beagle Channel system, whereas theoblique NW-SE trending set of lineaments revealed slightly different resistivity patterns, with vertical displacementsand less abrupt contrasts. These resistivity patterns, in combination with the widespread occurrence of normal faultingin the area, allowed to infer an extensional control over the oblique depressions. These morphological features wererelated to oblique transverse faults that segment two sub parallel E-W fault systems. The oblique faults were probablydeveloped along inherited structural anisotropies and can be extended well beyond the BC shoreline to the NW. Bothgeophysical and field evidence suggest a post-glacial deformation along the area.