CAMBISOLS AND RELATED SOILS IN NORTH-CENTRAL PORTUGAL - THEIR GENESISAND CLASSIFICATION

This study was undertaken as a preliminary investigation on the genesi s of the most extensive soils in north-central Portugal. Six pedons co vering a range of parent materials and field morphology were selected in the study area. Their characterization included field morphology, p hysico-chemical routine analyses, clay mineralogy, heavy minerals in t he fine sand and micromorphology. The data obtained indicate that most soils in the study area are formed from layered materials, a situatio n which is not always obvious from routine field observations. Several lines of evidence have been used to assess lithological discontinuiti es in order to separate recent sediments from paleosols. It is conclud ed that the main process of soil formation at present is faunal mixing of organic and mineral material to form well structured fine granular upper horizons. Much of the variation among the soils can be related to the geomorphological history of the region.