Pedoweathering and mineralogical change in cryosols in an ultra-continental climate (Central Yakutia, Russia)

• Published in: Acta Geodynamica et Geomaterialia
• Main Authors: Lessovaia, Sofia N., Goryachkin, Sergey V., Desyatkin, Roman V., Okoneshnikova, Matrena V.
• Format: Article in Journal/Newspaper
• Language: unknown
• Subjects: Geologie. Meteorologie. Klimatologie; jílové minerály; clay minerals; weathering in soil environment; cryosols; loess-like substrate; 7; 551; permafrost; Yakutia
• Online Access: https://kramerius.lib.cas.cz/view/uuid:d2d939fe-e883-4340-aa01-6419b8be42b4; https://doi.org/10.13168/AGG.2013.0047

This study investigates the clay mineralogy of permafrost-affected soils derived from predominantly calcareous loess-like material under the cold ultra-continental climatic conditions of Central Yakutia. These soils are named "Palevye (Pale)" following the Russian Classification, or Cryosols (WRB, 2006). Based on the data obtained, the loess-like substrate of Central Yakutia is enriched by chlorite in comparison with that of the loess-like parent material of European Russia. The clay mineralogy of the fine size fractions (<1μm) of all soil profiles is dominated by a smectitic mineral (most likely random mixed-layer illite-smectite and probably chlorite-smectite where smectite is ≥ 50 %), with subordinate chlorite and illite as well as the products of their transformation with smectite (vermiculite) layers < 50 % in the upper horizons, and finally traces of kaolinite. Pedogenesis has brought about change in the more acidic upper horizons, including a marked reduction in the expandability of the smectitic phase, possibly accounted for by the introduction of non-exchangeable hydroxy-Al into the interlamellar space and / or partial dissolving of smectitic phase, together with a relative reduction in the contents of bothillite and chlorite. Illite has been at least partially transformed to a mixed-layer illite-vermiculite (smectite), whereas chlorite has either been completely decomposed or has transformed to a mixed-layer expandable component. In one profile, the smectitic mineral appears to be absent from the upper horizon, suggesting that it may have been completely decomposed. An alternative explanation is that it has been eluted or translocated down the profile to accumulate in a Bt horizon. The distribution of clay minerals relates to the change of pH values in the profiles (acidic in the upper part, neutral - slightly alkaline in the middle, and alkaline in the basal horizons) possibly determined by seasonal migration of dissolved carbonates. Sofia N. Lessovaia, Sergey V. Goryachkin, Roman V. Desyatkin ...