BASEMENT GEOMETRY, FROM MAGNETIC AND GRAVITY DATA IN GASTRE TROUGH, CHUBUT, ARGENTINA

A gravimetric and magnetometric study at Gastre Trough, province of Chubut, allowed to reveal its basement geometry. Maps of anomalies show a fractured basement with high and sunk blocks inside the Trough. The minimum anomalous are associated to graben-like depocenters possibly inverted during the Tertiary, while the maximum are linked to basement blocks. Some of these blocks outcropping at the edges of the trough and some others covered by sediments inside. A 3D analytical signal and a gravity horizontal gradient were applied in order to make an appropriate interpretation, associating the maximum magnetic susceptibility changes and density to contacts between different lithologies. Finally, outcropping density values as well as seismic density values allowed to make 2D density models across to the Trough, which showed the presence of a high basement as central Gastre Trough.