CONICET | Buscador de Institutos y Recursos Humanos

An integrated study ofgeological and geophysical data of the Río de la Plata region and its relationto the evolution of the Atlantic passive margin is herein described. Thischaracterization is based on the available geological and geophysical informationand on the correlation of the southern end of the best-known Santa Lucía Basinin Uruguay to the Salado Basin in Argentina, and their connection through theQuilmes Trough. Furthermore, a new Meso-Cenozoic depocenter is characterizedand identified as Recalada Trough, subparallely aligned to the Quilmes Troughand separated from it by the Magdalena-Montevideo High. Both sedimentaryfillings present ENE-WSW trending mainaxes and reach an average thickness of almost 2,000 m. This suggests an evolution from a triple junction whereinterconnected extensional arms developed, which have had common Mesozoictectosedimentary histories related to the early opening of the Atlantic Ocean. Basedon the geophysicaland geological evidence, the previously accepted existence in the Río dela Plata of a first-order structural feature alongthe international border between Argentina and Uruguay, associated to anENE-WSW trending tectonic high, identified as Martín García, is unjustified. The tectonic evolution of the Atlantic margin in front ofthe Río de la Plata estuary is the consequence of a long deformation historystarting in the Precambrian up to recent times.Each Precambrian, Paleozoic, Mesozoic and Cenozoic tectonic scenarioadds different weak trends on the continental crust,which control the evolution of the sedimentary depocenters. The presence ofthese tectosedimentary records influence the bathymetric control of the Río dela Plata and the dynamics of the recent estuarine deposits. TheMeso-Cenozoic sedimentary infill is estimated to comprise considerable rangesof sandstones and conglomerates associated with faulted blocks of thecrystalline basement, with expected petrophysical conditions oscillating in theorder of 12% to 15% of effective porosity and with expected traps of thestratigraphic and combined (closing against faulting) type, and overlapped byfine sediments with excellent quality as seals. The economic significance ofthese sedimentary volumes lies in their yet unexplored potential as natural fluidreservoirs (hydrocarbons and groundwater), of great importance due to their strategic position nearthe large urban areas of Buenos Aires and Montevideo

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