SUMMARY
The study area is located on southeastern boundary of the intracratonic Paraná Basin, in the northeastern region of Rio Grande do Sul State, Brazil. The study of organic matter characterization and its distribution in relation to the sequence stratigraphy method is of great importance for the identification of possible target or inappropriate areas for exploration on the eastern border of this basin. Three boreholes were analysed in this work and sample sets were collected from the sedimentary section covering a Permian stratigraphic interval, from sequences II, III and IV (between the base of Rio Bonito Formation and the top of Teresina Formation). Results of this work evidence that: the concentration and composition of the dispersed organic matter (DOM) in the sedimentary package is associated with production, dilution, preservation and degradation of the organic matter; the organic fragments preserved in sedimentary rocks are predominantly composed of a mixture of particles of the inertinite group and lesser amounts from the vitrinite group, both derived from terrestrial plants; consequently, the hydrogen and oxygen indexes are low; since the kerogen type is II and IV, it does not contribute to the generation of oil. The organic matter distribution within the analysed sequence stratigraphic shows the following general trend or behaviour: 1) total organic carbon, hydrogen index and vitrinite group contents are relatively high in the rocks of the transgressive system but are lower in rocks of the lowstand and highstand systems; 2) the Inertinite group contents show the opposite trend, with the highest concentrations in the rocks of the lowstand and the highstand systems. The results of this work also evidence that in the upper strata of Rio Bonito Formation the OM is immature but should have reached the oil window (catagenesis) in the strata located below this formation.