Barun-Alan 1 is a multilayer archeological site located in 80–90 m above the valley of Alan River. This is one of few sites in Transbaikalia situated on mountain slopes with cultural layers that were not entirely destroyed. In that context, we can retrace the sequence of Stone Age archeological culture development. Results of investigating paleosoils, spore-and-pollen and paleontological remains from lithological layers of Barun-Alan-1 allowed to reconstruct general and local characteristics of paleoenvironment dynamic in Alan river valley during long-term period and correlate them with the data of archeological materials research. Presented article focuses on new data concerning climatic changes and paleoenvironment of Western Transbaikalia population in Paleolithic time reconstructed on the base of stratigraphical and palynological data from Barun-Alan 1 archeological site. Excavations of this site were started in 2004 and were continued until 2015. Site’s profile revealed a set of lithological layers containing asynchronically archeological materials – from Middle Paleolithic until Early Iron Age. Results of the investigations show that archeological cultures of Barun-Alan 1 site occurred and developed in rather cold climate of the Late Pleistocene time. The lower layers containing stone industry with the combination of levallois technique and subprismatic knapping were deposited in terms of steppe with the patches of forests on the ridges in the period of the end of MIS 4 – beginning MIS 3. According to spore-and-pollen analysis, this time is characterized by almost open unforested landscapes. It can be proposed that the environment was similar to contemporary – a wide valley of the mountain stream and grassy slopes of mountains with forb-grass steppes. The main difference from the present time consists in colder then present-day climatic conditions. The combination of open forests included larch-tree, fir and cedar. Levallois and subprismatic industry of lower layers was replaced by bifacial culture whose creators lived in cold climate of MIS 2 under conditions characterized by expansion of mesoxerophytic species from both dry and wet habitat. Upper layers show forests expansion in Holocene in connection with the changing of climate. These layers are related with the evidences of the ritual-cult activity of the population in Bronze and Early Iron Ages.

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