Micromorphology of Pedogenic Carbonate Features in Soils of Kohgilouye, Southwestern Iran

The micromorphology of pedogenic carbonate features in calcareous soils of arid and semiarid regions of Kohgilouye Province, Southwestern Iran, has been studied to determine their genesis and distribution in different climatic regions. Eight representative pedons (from a total number of ۲۴ pedons) were studied in aridic-ustic (minimum rainfall), ustic and xeric (maximum rainfall) soil moisture regimes. Micromorphological studies indicated that the frequency of secondary calcite as pedogenic nodules, coating or infilling in voids or channels increase from aridic-ustic to xeric soil moisture regimes. The presence of pedogenic calcite coating superimposed on clay coatings in pedons of more humid regions probably suggests a complex history of carbonate leaching, deposition of secondary calcite and clay illuviation. Pendants of calcite were observed in soils with coarser texture in aridic-ustic region as a common pedofeature. Pedogenic nodules in more developed soils of xeric regions were harder containing denser and more contiguous micritic calcite. Degree of impregnation of calcite nodules with Fe/Mn oxides as well as calcite depletion pedofeatures increase in areas with higher rainfall. Needle shaped calcite and cytomorphic calcite were observed in the near surface horizons of the regions with higher rainfall and denser vegetation growth of ustic and xeric soil moisture regimes.

Keywords:

Micromorphology , Arid zone , Calcite , soil , Southwestern Iran