Landscape and pedogenesis of an Oxisol-Inceptisol-Ultisol sequence in southeastern Brazil

The topographic sequence of Oxisols, Inceptisols, and Ultisols is frequentl y observed in tropical hilly surfaces in the southeastern region of Brazil. The purpose of this study was to relate pedogenesis to major geomorphic su rfaces (MGS) in the Caetes watershed,located in Paty do Alferes, Rio de Jan eiro State. The landscape is characterized by steep bedrock hills and cliff s of pre-Paleozoic gneiss, granite, and related metamorphic rocks rising ab ove long, nearly Level, accordant ridge crests, convex hills, and narrow fl uvial plains. Intense soil development, with deep weathering and kaolinite formation in the gneiss-granite rock, took place on the ridges and convex h ills. Six pedons were examined using field investigation and laboratory soi l characterization techniques. The degree of pedogenesis on the various geo morphic surfaces supports the landscape evolution theories of Penck and Kin g. A Typic Hapludox, with the greatest degree of pedogenesis, formed on the stable summit position, MGS1. The upper part of the retreating slope, MGS2 , bevels MGS1, and the material eroded from MGS2 moved downslope and formed a surface with lower gradient, MGS3. Dystrochrepts are on shoulder positio ns and shallow Hapludox are on backslope positions of the geomorphic surfac e MGS2, and Kandiudults formed on footslopes, MGS3. Eutrochrepts are on the youngest surface MGS4, a toeslope position.