Vegetation Response to Climate Change during the Middle Calabrian in Arctic Chukotka

A palynological record obtained from El'gygytgyn Lake sediments, which spans the 1.244-1.304 million years (Ma) interval of the Calabrian Stage, shows repeated changes in the plant communities of Arctic Chukotka. These variations in the vegetation further suggest a dominance of interstadial and interglacial climates. Eight pollen zones were distinguished within this interval. According to the working age model for the composite El'gygytgyn core, these pollen zones correspond to marine oxygen isotope stages (MIS) 40, 39, and 38. The upper boundary of MIS 38 coincides with magnetic event the Cobb Mountain (1.240 Ma), which is one of the main chronological landmarks used in creating the core's chronology. The features of modern pollen-spore spectra obtained from the water-sediment interface within the lake aided in reconstructing both the local and regional paleovegetation. The consistent presence of Larix pollen throughout the 1.244-1.304 Ma interval indicates that even under the severest climatic conditions Larix forest-tundra persisted on the Anadyr Plateau and near El'gygytgyn Lake. This pattern differs sharply from that seen in the Middle and Late Pleistocene when herb-dominated tundra characterized the glacial intervals in the Arctic. The spore-pollen spectra further show that the warmest climatic conditions occurred during MIS 39. The data from the 1.244-1.304 Ma interval represent the last step in completing the Quaternary vegetation history from this unique site in Arctic Siberia.