Soils on Red-Colored Calcareous Substrate from Lena-Angara Plateau: Factor Limits of Clay Differentiation

The study objects are represented by the soils on red-colored carbonate substrate located in the southern part of the Lena-Angara plateau. The areas of such substrates are widespread in Eastern Siberia. Pedogenesis has led to Luvisols formation with different level of profile differentiation affected by the altitude areas. All soils are loamy and characterized by the high proportions of the total and dithionite extractable iron. Clay mineralogy of the clay size fraction of the studied soils has illustrated the spatial variation of the mineralogy of the red colored substrate. The latter is characterized by illite – chlorite association of the pure clay minerals within predominance of the dioctahedral minerals (mica and sometimes di-chlorite). Formation of the differentiated profile – Сalcaric Albic Rhodic Luvisol occurs in the most humid environment realized at altitudes more than 1000 m. The specificity of such soils is: vertical homogeneity of parent substrate; weak color differentiation within reddish tint in the upper part; distinct differentiation of the clay size fraction, and a reduced thickness of illuvial horizon due to close occurrence of the hard carbonate substrate. The signs of clay illuviation are less pronounced in the soils from the levels lower than 1000 m that led to Сalcaric Chromic Luvisol and Calcaric Rhodic Luvisol formation.