LA DORSAL ASUNCIÓN - RÍO GRANDE: UN ALTOFONDO REGIONAL ENTRE LAS CUENCAS PARANÁ (BRASIL, PARAGUAY Y URUGUAY) Y CHACOPARANAENSE (ARGENTINA)

Abstract

THE DORSAL ASUNCIÓN - RÍO GRANDE: A REGIONAL UPLIFT BETWEEN THE PARANÁ (BRAZIL, PARA- GUAY AND URUGUAY) AND CHACOPARANENSE (ARGENTINA) BASINS The Dorsal Asunción-Río Grande (DARG) is a first magnitude tectonic megastructure that constitutes a regional depositional uplift responsible for the partitioning of the post- Permian-Triassic sedimentation of the Paraná (Brazil, Paraguay and Uruguay) and Llanura Chacoparanense (Argentina) basins. The northern end of the DARG, in Paraguay, is represented by the Asunción High materialized by an outcrop of the crystalline basement (Tebicuary Craton) plunging toward the SSE and fringed by Paleozoic and Mesozoic sedimentary sequences. Contrarily, the southern extreme of the DARG is constituted by the Rio Grande High, located in the Río Grande do Sul State, Brazil; and it is equally characterized by an outcrop of crystalline basement fringed by Paleozoic and Mesozoic sequences, but plunging toward the NNW. The intermediate tract, in the territories of the Argentina and Uruguay, is less exposed and required a regional correlation by means of subsurface information. The DARG separates two huge tectonosedimentary environments that correspond to the ad- jacent Paraná Basin, toward the east, better exposed and the different sedimentary basins covered by the Llanura Chacoparanense, toward the west. On the basis of geographical disposition, kinematics and chronology of its evolution, the DARG´s origin can be correlated with the convergent tectonics of the Late Paleozoic that structured the Sierras Australes of Buenos Aires (Argentina). Finally, the evaluation of the influence of the DARG contributes to the understanding of the tectonosedimentary mechanisms that exhibit the sequence constituting the infill of the basins of the Llanura Chacoparanense and Paraná