The origin of materials which compose the pedological covering in the Northwestern region of the state of Paraná, Brazil, is provided. Research is based on soil distribution along the slopes and in a special way on the morphological characteristics of detrital grains in Caiuá Sandstone quartz and in pedological covering. Fractions (0.500, 0.125 and 0.053mm) of quartz grains were analyzed by scanning electron microscopy. The grains main morphological features are fissures, fractures, dissolution and reprecipitations are associated with the pedological covering. The more chemically changed quartz grains are found in greater depths in the covering cross-sections and as from the lower third section up to the end of the slopes. It is a segment which is constantly saturated in water for a long time during the year. Roundness and sphericity rates decrease according to the size of detrital grains. The presence of similar features in the quartz grains found in both materials confirm that the pedological covering has originated from the Caiuá Sandstone itself.