Resumo

ZAPPINO, Rodolfo Oscar; CANTU, Mario Pablo  e  BECKER, Analía. Genesis and evolution of a soil climosequence of the Tucuman plain. Cienc. suelo [online]. 2019, vol.37, n.1, pp.113-132. ISSN 1850-2067.

The genesis and evolution of a soil transect was studied from the western Humid Region to the eastern Semi-Arid Region in the Tucuman's plain. The method of alteration balances, micromorphological techniques and chemical analysis, in total soil and in volcanic glass, was used. It has been found that in the paleosols and recent soils of the Humid Region, there is a continuous and progressive loss of matter from the base to the top of the soils, associated with neoformation of clay and loss of bases, iron and aluminum. The micromorphological study also suggests, a variable sedimentation rate with pedogenesis. These characteristics define a subtractive-redistributive pedogenesis in the paleosols, and an additive-redistributive pedogenesis in the current soils of this region, in which the clay iluviation is the predominant pedogenetic process. In the Semi-Arid Region the alteration balance indicates neoformation of clay, despite the scarce mineral alteration, along with an accumulation of soluble salts, iron and aluminum, which would originate in the alteration of the volcanic glass as indicated by the microprobe analysis. In this region, the pedogenesis is additive-conservative and the predominant pedogenetic process the calcification or isohumism. The analysis clearly shows that the differences in the neoformation of clays can be attributed, both in paleosols and recent soils, to the rainfall gradient that is registered in the Tucuman plain, from the Western Humid Region to the Eastern Semi-Arid Region.

Palavras-chave : Genesis and evolution of soils; alteration balance; micromorphology; Tucuman's province.