Vegetation response to climate changes in the eastern Arctic during the Middle Gelasian age of the Early Pleistocene.

Palynological analysis of sediments from El'gygytgyn Lake document vegetation changes in the Eastern Arctic from early marine isotope stage (MIS) 74 to late MIS 80 (c.2.1–1.9 MA) and close the last remaining gap in the El'gygytgyn pollen record. Cooler climates were characterized by a mix of Larix forest-tundra, shrub Betula tundra, and herb-dominated communities. During interglaciations, Larix forests with tree Betula and Alnus, and perhaps with a minor component of Picea and tree Pinus , characterized areas that today are tundra. These forests included a rich shrub understory of Betula , Duschekia , Salix , and Pinus pumila. Although MIS 77 has been considered a "super" interglaciation, the data do not indicate that this stage was exceptionally warm. Interstadial conditions are denoted by pollen assemblages that indicate the regional vegetation was dominated by Larix forest -tundra and an absence of Pinus pumila. The palynological results from this Early Pleistocene interval demonstrate the need to: 1) modify the El'gygytgyn age model; 2) reevaluate the relationship of sediment facies to climate change; and 3) reconsider the occurrence and/or definition of "super" interglaciations. • MIS 77 "super" interglaciation is not exceptionally warm. • Larix forest dominated interglacial and interstadial periods during MIS 75-MIS 79. • Larix forest-tundra dominated glacial periods during MIS 75-MIS 79. • MIS 77 and MIS 78 are the warmest and coolest periods during MIS 75-MIS 79. [ABSTRACT FROM AUTHOR]