Soil, relief and parent material interactions in the Pau d’Alho Structural High region, Southeastern Brazil

Abstract

Soil-relief relationships, together with information on parent material, have guided soil surveys all over the world. Such contributions can be seen in soil mapping carried out by the Agronomic Institute of Campinas in the State of São Paulo (Southeastern Brazil), whose products are in fact true morphopedological maps. In this context, the aim of this research is to present the interactions among soils, landforms, and parent materials in the Pau D’Alho Structural High located in the Paraná Sedimentary Basin in the State of São Paulo, region in which sandstones, diabase and siltstones are dominant parent materials. To reach this objective, a morphological map was prepared by means of photointerpretation (1:25,000 scale). In addition, field work was carried out to check the geomorphological information, to describe soil profiles, and to collect soil samples for grain-size and chemical analysis. The results indicate that chernozemic A Lithic and Leptic Leptosols, and Inceptisols cover the steepest slopes of ridges and hills. Ultisols and Oxisols (Kandic) occur on top of these geomorphological features. Soil variations are controlled by lithological (parent material) changes. Ultisols, Oxisols (Kandic), and Entisol Quartzipsamments predominate in the hilly landscape supported by sandstones and siltstones. Entisols Aquent and Fluvent are related to colluvial and fluvial deposits occurring in floodplains and wide open valleys of the main streams. This scenario results from the relationships among landforms, parent material, and the pedological cover in the study area. However, these results also point to open issues about the shallow soils covering very gentle surfaces, the influence of Neotectonics on soil development, the origin of closed depressions, and the parent material of the Entisol Quartzipsamments.