Desarrollo de un nuevo modelo geoedafológico sobre la génesis, propiedades y taxonomía de los vertisoles y suelos vérticos de la región pampeana argentina

Abstract

The Rolling Pampa is one of the subregions of the great pampas plain and the most important on agricultural production. The parent materials of the soils are Quaternary loessic sediments, and both their origin and composition are still a controversial subject. To the east of the subregion, the Vertic Argiudolls are dominant, while in the rest of the area the Typic Argiudolls are the characteristic zonal soils. According to some authors, the vertic properties of these Argiudolls are due to the pedogenic neoformation of smectites. On the contrary, according to others, smectitic clays would be inherited from their parent material. On the other hand, since the Typic Argiudolls also show high expansibility, certain physical properties used in the Taxonomy are not useful for discriminating between the two subgroups of Argiudolls in this area. In the Rolling Pampa two superficial sedimentary levels have been distinguished. The lower one is a smectitic loessic sediment, covered by a relatively thick illitic loessic deposit. New studies undertaken in large pit have revealed the existence of diapiric structures in the lower sediment, which remained hidden up to the present. Therefore, it can now be considered that Vertisols were also dominant soils her, later buried by the thick loess. In the humid periods, the summit of convex slopes would have been partly eroded, leaving the underlying smectitic material closer to the surface. Consequently, current Mollisols on top of the landscape developed vertic properties due to the mixing of materials and depending on the greater or lesser proximity to the paleosurface. Therefore, these pampean Vertisols and vertic Mollisols can be considered polygenetic and related by different degrees of a same process.