Palaeobotanical evidence for warm summers in the East Siberian Arctic during the last cold stage.

Abstract

Plant macrofossils from the Mamontovy Khayata permafrost sequence on the Bykovsky Peninsula reflect climate and plant biodiversity in west Beringia during the last cold stage. 14C dates suggest sediment accumulation between about 60,000 and 7500 14C yr B.P. The plant remains prove that during the last cold-stage arctic species coexisted with aquatic, littoral, meadow and steppe taxa. The reconstructed vegetation composition is similar to modern vegetation mosaics in central and northeast Yakutian relict steppe areas. Thus, productive meadow and steppe communities played an important role in the Siberian Arctic vegetation during the late Pleistocene and could have served as food resource for large populations of herbivores. The floristic composition reflects an extremely continental, arid climate with winters colder and summers distinctly warmer than at present. Holocene macrofossil assemblages indicate a successive paludification possibly connected with marine transgression, increased oceanic influence and atmospheric humidity. Although some steppe taxa were still present in the early Holocene, they disappeared completely before ~2900 14C yr B.P.