The Permian System in Eastern Paraguay, Chacoparaná Basin
Lovecchio, Juan Pablo1 and Gebhard, Irene
The onshore Chacoparaná basin is an intracratonic basin covering an area of 2 MM km2. The infill of the basin is mainly siliciclastic and in Eastern Paraguay occurred in six cycles spanning from Ordovician to Cretaceous. Although mostly unexplored, the basin holds evidences of oil and gas-prone active petroleum systems in Brazil. Gas occurrences are associated with the Devonian shales while oil shales and tar sands relate to Permian source rocks assigned to the Iratiacute; formation.
The Upper Paleozoic column of the Chacoparaná basin records a glacial episode in Late Carboniferous – Early Permian times and a post-glacial transgression throughout the Early Permian (San Miguel formation in eastern Paraguay), followed by continentalization and aridization of the environment starting in the Middle Permian and probably lasting until early Triassic (Tacuary formation in the study area).
This work involved sedimentologic description of 450m of continuous core, as well as palynological and geochemical characterization of Permian strata. A detailed sequence stratigraphic interpretation using numerous wells in the area allowed the correlation with the sequences in Brazil. Paleogrographic maps were built for each of the defined sequences. Finally, a summary chronostratigraphic chart was prepared.
In eastern Paraguay, six sequences were defined within the Permian, equivalent to the brazilian Rio Bonito, Palermo, Iratiacute;, Serra Alta, Teresina and Rio do Rasto respectively. As in Brazil, the sequence equivalent to Iratiacute; was identified as a potential source rock level. This sequence consists of marine shales with calcareous contribution, deposited in a restricted shallow marine environment, during the Late Artinskian.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013