Late holocene climate and vegetation changes around lake Malye Chany

The paper presents the palynological and sedimentological study of bottom sediments of Lake Malye Chany. Lake Malye Chany is one of the five basins of the largest lake in Western Siberia - Lake Chany. Lake Malye Chany is situated in the forest-steppe zone in southern part of the West Siberia. Two rivers, Chulym and Kargat, flow into the lake. The climate of the area is continental. We used palynological method to reconstruct the late Holocene climate and vegetation around the lake and sedimentological method to reconstruct the history of the lake development. According to the sedimentological data we recognized two distinct stages in lacustrine conditions. At the earliest stage terrigenous material dominated in the sediments, river’s delta penetrated into the center of the lake which implies that lake was very shallow; about 4 ka BP climate around the lake was very dry, sage steppe dominated. Pollen samples from this stage contained large amount of chlamydospores of Glomus and charcoal particles. These non-pollen palynomorphs are indicators of dry climate and high intensively of soil erosion processes. At the second stage after 3 ka BP sediments predominately consisted of organic matter and autogenic minerals, the lake became gradually deeper. According to pollen data the period between 3-2 ka BP was wetter and a bit colder than the previous one; local plant associations were dominated by sedge-grass steppe. After 2 ka BP climate became wetter and colder which resulted in a highest stand of the lake. Pollen samples from that stage showed high concentrations of green algae (Pediastrum boryanum, Botryococcus braunii, Tetraedron minimum). These non-pollen palynomorphs are associated with open water estuaries with oligo- to mesotrophyc conditions. From 2 ka BP onward concentrations of Anabaena akinets increases dramatically. Blue-green alga Anabaena is an indicator of phosphoric eutrophication possibly related to human activity (farming, cattle breading) in the lake region. During the period 2-0 ka BP forest-steppe dominates and lake banks have been gradually covered by macrophyts (pondgrass, typha, reed).

palynology, sedimentology, Holocene, forest-steppe, climate, biomisation