干旱区生态环境知识资源中心

Degradation processes and their association with spatial and lithological discontinuities in argillic horizons of nine profiles in northeastern Chubut province were examined. Twelve test pits were used as stratigraphic controls. The reconstruction of the upper limit of the argillic horizons and its position in relation to the soil surface was performed in different topographical positions. Lateral discontinuities may have been due to the erosion of surface and argillic horizons in the intermound area, or to the development of desert pavements and vesicular layers, which may or may not be buried. The lithological discontinuities that were nor associated with the erosion processes may be caused by (1) profile development on different parent materials, as a result of lateral facial variations, (2) development of different profiles under different conditions of moisture as related to paleomicrorelief. The observed shapes of the argillic horizons associated with water erosion suggest that the surface peds of these horizons had been removed. The distribution of soluble salts in the soil profile from top to bottom, the carbonate at varying depths, and the argillic horizons superimposed on calcic and natric horizons indicate a reforming of polygenic and polycyclic profiles formed under different moisture conditions. Examination of genesis of these soils based on soil dynamics and the development of the geomorphic surface indicate a need for reclassification.