The great amount of mineral material with a diameter > 2 mm in soils of the Cerrado biome is an intriguing characteristic that needs highlights the importance of further studies on soil formation, soil classification, land use and management. For a comparison of the morphological, physical, chemical, mineralogical, and micromorphological attributes of such skeletal soils, profiles of Petric Plinthosols and Haplic Cambisols from the eastern Goiás, Brazil, were studied and compared with similar profiles described in the literature. A pit was dug in each of the six soil profiles for morphological description and sampling at two depths (total of twelve soil samples). The petroplinthite nodules in the soil coarse fractions contribute to increase the Fe2O3 content extracted by sulfuric acid of Plinthosols. The Feo/Fed ratios are generally very low, reflecting the high stability of the crystalline Fe forms. The studied Plinthosols and Cambisols presented relatively low Ki and Kr values when compared to other soils of the same classes and with skeletal character in the Cerrado biome. The absence of hematite in the clay fraction of the studied soils results in yellowing of the moister pedoenvironment along the chapada borders. This landscape position is typical for Plinthosols, from where eroded materials contribute to the formation of Cambisol downslope. The hematite occurs only in the sand fraction of Plinthosols, associated with petroplinthite nodules. Magnetite/maghemite were identified in both soils. In the Cambisols, the presence of mica detected by X-ray diffraction analysis of the sand fraction, and the presence of minerals with strong interference colors in the thin sections, besides the higher values of Ki and Kr indices, highlights the less weathered nature of Cambisols as compared to Plinthosols. The small amount of plasma (10 % of the thin section area) indicates the skeletal character of the studied soils. Plinthosols have a dense granular structure, whereas the pore space of the microstructure of pellicular grains of the Cambisols is less connected and dominated by chambers and channels.
petroplinthite; iron oxides; yellowing; concretionary soils
