RÉSUMÉ
Abstract The sandstones of the Furnas Formation in the State of Paraná, south of Brazil, are located in regions with great importance due to the natural heritage found in the rocky forms and associated flora and fauna. This paper presents a detailed analysis of the internal structure of diverse sandstones of the Furnas Formation. X-ray microtomography allowed 3D characterization of the number, pore size and shape distributions of the sandstones. Images with voxel size of 603 µm3 were utilized to evaluate the sandstone's macroporosity. The main results obtained indicate that higher macroporosities were observed in coarser and some types of silicified sandstones. In general, fine sandstones were characterized by the largest number of pores. As a general conclusion the size and shape distribution of pores seem to have a variable relation with genetic factors as grain size and cement (siliceous and/or ferruginous).