Structure and kinematics of Southern San Bernado Fold Belt and this influence on depositional systems, Los Perales Oil field, Golfo de San Jorge Basin

The San Bernardo Fold Belt is developed in the central part of the Golfo de San Jorge Basin, one of the most prolific oil basins in the country with more than 100 years of production history. Historically structural studies were carried out based on E-W seismic lines and structural cross sections, describing N-S striking contractional structures, segmented by E-W minor faults. The present study reviews of all the data available near the Los Perales oil field. Different surface, subsurface and geophysical data sets were integrated to update the structural knowledge of the area. From the surface, multiple geological maps were integrated with well data, gravimetric data, and 2D/3D seismic data. Gravimetric data was used to characterize the basement structural features and the principal fault orientations. Subsequently, using seismic and well data a series of structural cross-sections were constructed, to characterize the principal fault systems, present in the Fold Belt and this kinematics. Using 3D seismic data, was possible to recognize and characterize different fault trends: an N-S and NNE are principal contractional structures, while E-W and ENE trends are occurring across the entire area, mostly composed of extensional faults with decametric displacement. By using, different seismic processing, was possible to identify soft-linkage structures with older basement structures, that were originally formed as half-graben during the rifting stage, and their structural stamp remains through geological time. The detailed structural mapping in the 3D seismic lines shows an extensional context from the Jurassic to the Cretaceous. This is evidenced by a control in the deposition of the Pozo Anticlinal Aguada Bandera Formation (Upper Jurassic-Lower Neocomian) to the basal Lower Bajo Barreal Formation (beginning of Late Cretaceous). Extensional control was observed in the early Cretaceous Seccion Tobacea unit, with extensional wedges showing lateral changes of thickness reaching 200 m, as evidenced by seismic and well data. This thickness is associated with older basement structures showing a structural heritage that controls the distribution of the deformation across the San Bernardo Fold Belt.