A sediment core recovered in Lake Lyadhej-To at the northwestern edge of the Ural Mountains reflects the complete Holocene environmental history from ~11,000 cal. yrs BP. Five limnological episodes are identified in the diatom and geochemical records. The initial lake stage, Episode I (~11,000-10,850 cal. yrs BP), was characterized by the absence of biogenic production and a high influx of clastic sediments. Episode II (~10,850-8650 cal. yrs BP) is characterized by ice-free conditions during summer, highest bioproductivity, strong growth of planktic diatoms and anoxic bottom waters. This period represents the Holocene climatic optimum. Deterioration of climatic conditions commenced in Episode III (~8650-7000 cal. yrs BP) as indicated by distinctly lower bioproductivity and longer persistence of winter ice on the lake. During Episode IV (~7000-2500 cal. yrs BP) the diatom and pollen records indicate that temperatures were cool and the growing season was short. Finally, in Episode V (~2500 cal. yrs BP to present) limnological conditions, indicated by increased organic carbon and diatom deposition, initially suggest improved conditions followed by a return to modern conditions beginning ~500 cal. yrs BP. The pollen stratigraphy from Lake Lyadhej-To is consistent with other paleoclimatic records from northern Eurasia, confirming rapid postglacial warming, the presence of dense tree forests during the climatic optimum and finally a gradual southward retreat of the treeline towards its modern location.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene