干旱区生态环境知识资源中心

The Ust-Oda section exposes the structure of a 25-m terrace of the Kitoy River. The eroded surface of the Jurassic sandstones is overlain by the heterogeneous (primarily aeolian-alluvial) Upper Pleistocene-Holocene deposits that include buried soils. The Quaternary part of the section exhibits five main strati graphic subdivisions, ranging from isotopic stage MIS 5 to MIS 1.

Reconstructed vegetation composition, of the Unit 1 formation age; is typical for Late Quaternary interglacial periods and suggests moderately cool and moderately humid climate. Unit 2 sediments yielded small mammal remains of taiga, steppe, tundra and hydrophilic species, characterizing the fauna as ecologically mixed or disharmonic, typical of cold Pleistocene epochs in Eurasia. For example, Lagurus lagurus and Dicrostottyx sp. are animal species whose current habitats do not cross and are substantially distant from each other. Microtheriofauna species composition and structure imply Unit 2 formation under the conditions of cold and arid climate, together with C-14 dating of the overlying strata suggesting its MIS 4 age. Unit 3 sediments contain spore-pollen spectra typical for MIS 3 interstadial of the Pribaikalye area. MIS 3 climate substantially differed from the modern one. Average January temperatures might have been 15 degrees C lower than the modern ones and the mean July temperatures, 2-3 degrees C lower. Mean annual precipitation value could be lower than the modern one by 100 mm/yr. The analysis of the small mammal species ecological requirements suggests domination of tundra-steppe landscapes in the area during the formation of the Unit 3. Theriofauna of the Unit 5 allows reconstruction of paleoecological conditions close to modern ones in humidity and temperature. (C) 2016 Elsevier Ltd. All rights reserved.