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Soil‐landscape Relationships in the Occidental Plateau of São Paulo State, Brazil: II. Soil Morphology, Genesis, and Classification
Author(s) -
Lepsch I. F.,
Buol S. W.,
Daniels R. B.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100010031x
Subject(s) - geology , ultisol , calcareous , clay minerals , mollisol , soil water , geochemistry , inceptisol , soil morphology , plateau (mathematics) , saprolite , gleysol , entisol , weathering , soil science , soil classification , paleontology , mathematical analysis , mathematics
Nine profiles representing the major soils in the Occidental Plateau of São Paulo State, Brazil, were characterized after detailed geomorphic and soil mapping were completed on a 70.8 km 2 area. The stable upland geomorphic surface had Oxisols, surrounded by younger erosional surfaces with Ultisols, Alfisols, and Inceptisols. Mollisols formed where the erosional surfaces exposed calcareous sandstone. The argillic horizons of the Ultisols and Alfisols in these positions apparently have formed in material that would qualify as an oxic horizon before it was exposed. Laterally moving water at these sloping sites is believed to initiate free Fe removal and lessivage. Lateral water movement at the contact between the surficial deposits of oxic composition and the underlying calcareous sandstones appears to supply the bases for the Alfisols developed in the oxic material. Kaolinite dominates the clay mineralogy of the soils formed in unconsolidated deposits, but attapulgite and smectite are present in the calcareous sandstone. In the soils shallow to calcareous sandstone the attapulgite apparently has weathered to smectite within a few centimeters of the rock.