Fallamiento normal terciario en la Cuenca del Golfo San Jorge, Patagonia Argentina

• Autores: R.E. Giacosa, J.M. Paredes, A. Nillni, Manuel Ledesma, Ferrán Colombo Piñol
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 5, 2003 (Ejemplar dedicado a: V Congreso del Grupo Español del Terciario (Granada, 23-25 de septiembre, 2003)), págs. 89-93
• Idioma: inglés
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• Resumen

  • A structural study in the marine and continental tertiary sediments deposited over the margin of the Golfo San Jorge Basin has been carried out. Tectonic structures are normal faults formed during the last phases of the extensional regime, broadly developed in the continental crust of the South Atlantic passive margin. IT/e present the geometric and kinematics characteristics of the normal faults, their control on tertiary sedimentation and the influence of the fluids on their formation. Two types of normal faults were distinguished: a) major faults, that represents the shallower expression of deep master faults (>3 km long) associated to the development of the basin, and active from the Mesozoic, and b) mesoscopic faults constrain inside the specific depositional sequences in the Chenque Formation, a shallow marine unit of early Miocene age. In agreement to the position in the shallowest part of the upper crust, shear-extensional fracture on intact rocks was the dominant fracture mode, sometimes with fluid control. A thick packages of the Sarmiento Formation, a continental and mostly tuffaceous unit with low-permeability, increased fluid pressure and drives the faults. Consequently, in the continental/marine boundary, hydraulic and crush breccias are present, and veins and stockwork of opal, chalcedony and calcite are common.