FORMS OF IRON COMPOUNDS IN DRY STEPPE SOILS ON ANCIENT WEATHERING CRUSTS

Features of iron compounds in dry steppe soils on ancient weathering c rusts (northern Kazakhstan) are investigated by a complex of methods: morphological, chemical, X-ray diffractometric, NGRS, and magnetic mea surements. In soil underlain by brown-red montmorillonite heavy clay, free iron compounds are represented primarily by hematite, which contr ibutes to the aggregation of material and prevents the profile differe ntiation. In soils with a profile differentiated by the eluvial-illuvi al type underlain by kaolinite heavy clays, among free iron forms prev ail finely dispersed compounds (with particles < 9-10 nm in diameter), hematite, and sometimes goethite. Iron compound forms in soil profile s are inherited from ancient rocks, they do not undergo changes in mod ern dry steppe conditions, and they and have an impact on the soil pro perties and processes. Iron compounds in soils underlain by ancient we athering crusts are one of the diagnostic indicators in solving the cl assification problem of these soils.