The calcification of soils and the effects of topography on this process were studied in semi-arid regions of Kermanshah. From a toposequence, based on the previous soil surveys of the region, five profiles were selected, and field studies and laboratory analyses were carried out on soils. Alluvial - colluvial fans, piedmont alluvial plains, and old plateaux were three main physiographies on the selected toposequence. Soil moisture and temperature regimes were Xeric and Thermic, respectively. The results indicate that redistribution of carbonates and soil formation processes may be categorized in four specific stages to be described in the text. Accumulation of calcium carbonates in soil profiles showed two basic forms: one in sandy layers of fine - textured soil profiles under the influence of abrupt textural changes and lower permeability, and the second in subsurface horizons of soils with calcareous parent material. The morphological evidences showed that in addition to translocation from upper horizons of carbonates by solution and suspension, physical movements to subsurface layers of fine calcareous materials have also affected the formation of calcic horizons. In other words, CaCO3 may have moved as fine particles through soil cracks and subsequently accumulated in the lower horizons. Soil mineralogy showed considerable amounts of illite, Chlorite, smectite and palygorskite clay minerals. Some pedogenic transformations of illite and chlorite may have caused formation of smectite and palygorskite.

Keywords: Toposequence, Calcification, Pedogenic, Clay minerals

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