Title: PEDOWEATHERING AND MINERALOGICAL CHANGE IN CRYOSOLS AN ULTRA-CONTINENTAL CLIMATE (CENTRAL YAKUTIA, RUSSIA) |
Authors: Lessovaia Sofia N., Goryachkin Sergey V., Desyatkin Roman V. and Okoneshnikova Matrena V. |
DOI: 10.13168/AGG.2013.0047 |
Journal: Acta Geodynamica et Geomaterialia, Vol. 10, No. 4 (172), Prague 2013 |
Full Text: PDF file (1.1 MB) |
Keywords: clay minerals, weathering in soil environment, cryosols, loess-like substrate |
Abstract: 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 both illite
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. |