Caracterização granulométrica e mineralógica de três perfis de solos desenvolvidos do arenito Bauru no Estado de São Paulo

The pedogenesis of eutrophic Red-Yellow Podzolic soils found overlying Bauru sandstone in the Monte Alto Municipality, was studied by means of two well developed profiles (P1 and P2) and a less developed profile (P3). Pedogenic interpretations were based on morphological, particle size distribution and micromorphological determinations. The more developed soil (P1 and P2 profiles) has an argillic horizon 105 cm thick and the less develped (P3) a thin B horizon (27 cm); colour, texture (sandy to sandy loam in the superficial horizons and sandy clay loam in the Bt horizon) and structure remained practically constants. The particle size distribution showed redistribution of the soil particles: clay content increased in the B horizon in relation to the A; fine sand and very fine sand fractions dominated in the less developped soil, and in the more developed profiles the fine fraction (silt+clay) was dominant, showing the weathering of the very fine sand to the clay fraction as the development increased from P3 to the other profiles; sand fraction showed the dominance of stable minerals like quartz, opaques (magnetite and illmenite), zircon and tourmaline, and feldspars also, which occurred in lower amount in the more developed soils; the content of feldspars decreased from the rock toward the surface of the soil; zircon/tourmaline relation showed the presence of heterogeneous material in the P1 and P3. Micromorphological studies indicated that as the soil profile goes through development, illuvial argilans content tend to increase, as well as the mosepic plasma to a weakly insepic one