Paleopedogenisis in the Middle Pleistocene Loess-Paleosol sequences in the Southern Tajikistan: Insights to the paleoclimate changes

Quaternary loess- paleosols sequences in the southern Tajikistan carry detailed paleoenvironment records of Central Asia. Micromorphological studies of loess and paleosols provide accurate information of the past pedogenic processes which are suitable for paleoenvironmental reconstruction. The micromorphological index of soil development (MISECA) demonstrated a good correlation between the degree of soil development and pedogenic features. The objective of this study was to investigate the micromorphological properties of Khonako II section to reconstruct paleoinvironmental changes of southern Tajikistan. The physical and chemical properties (e.g. soil organic carbon, calcium carbonate equivalent and soil pH), which are sensitive to environment and climate changes, are reliable to determine the paleoenvironmental changes. Four represenrative pedocomplexes (PC۵, PC۶, PC۷ and PC۸) which separated by loess units (L۵, L۶, L۷, L۸) were selected to study pedogenic processes and paleoenvironmental interpretation.Increasing precipitation and available soil moisture was the main reason for calcium carbonate depletion and pH decreasing in pedocomplexes in comparison to the loess units. The most developed and preserved clay coatings were found PC۵ due to the higher soil moisture and lower shrink-swell properties. The accumulation and depletion of carbonates in the soil can be attributed to leaching intensity. Calcite depletion pedofeature is mostly observed in PC۵ which had been affected by humid periods. Based on MISECA values, pedogenic development of the soils was in order of PC۵> PC۶> PC۷=PC۸. The appearance of numerous redoximorphic features in PC۷ and PC۸ in comparison to the other pedocomplexes demonstrates periodical saturation due to higher precipitation. This study was supported by of INSF (Iran National Science Foundation Project № ۹۹۰۰۶۷۵۸) and NordForsk (THOCA project № ۹۶۹۲۶).

کلیدواژه ها:

Loess section ، Paleopedology ، Micromorphologhy ، Climate change