Latosols from the lobo creek basin (Brotas; Itirapina-SP): I. Granulometry

Abstract

The latosol profiles from the Lobo creek basin, in the region of São Carlos, Brotas and Itirapina, State of São Paulo, initially classified by the SOIL COMMISSION (I960) and re-classifield by FREIRE et alii (1978), were sampled and studied through granulometric analysis by employing the statistical parameters proposed by FOLK & WARD (1957). The main objectives of this study were to characterize these soils, to elucidate their genesis and evolution, and to check the apparent morphological uniformity manifested by the classification of FREIRE et alii (1978). The results obtained revealed that the profiles under study two distinct categories: one showing a tendency to shift to the side of the coarser fractions, the modal fraction consists of fine sand and has symmetric freguency distribution size curves, and the other, where the modal fraction consists of medium sand with a clay content 30 to 40% higher than that of the first, has asymmetrical frequency distribution size curves. Probable occurrences of lithological discontinui ties were not indicated by the results obtained, but the degree of selection values, degree of asymmetry and curtosis suggest such discontinuities. However, these data are not conclusive.