A 94–10ka pollen record of vegetation change in Qaidam Basin, northeastern Tibetan Plateau

Abstract

Drill core (ISL1A) was obtained from the Qarhan Salt Lake in central eastern Qaidam Basin, northeastern Tibetan Plateau (NE TP). Fossil pollen and the lithology of the core sediment were analyzed in conjunction with AMS C-14 and Th-230 dating. The results indicated that Artemisia and Chenopodiaceae dominated the steppe/desert steppe vegetation developed around the lake between 94 and 51.2 ka, corresponding with the organic-rich silty clay deposited in the core sediments. Pediastrum continuously appeared in the core sediments between 94 and 51.2 ka, indicating freshwater to oligohaline conditions of the paleo-Qarhan Lake during the late marine isotope stage (MIS) 5, MIS 4, and early MIS 3. During the 51.2 to 32.5 ka period, Ephedra dominated shrub-desert vegetation expanded in the basin, while, Pediastrum disappeared in the core sediments. The core sediments consisted of interbedded layers of halite silt and clay-rich halite between 51.2 and 32.5 ka, signifying a shift toward drier hydrologic conditions. Thus, the paleo-Qarhan Lake experienced periods of desiccation and shallow water levels. Artemisia and Chenopodiaceae dominated steppe/desert steppe vegetation appeared again from 32.5 to 253 ka, with clay-rich sediments in the core, thereby suggesting an increase of runoff from the lake under relatively wetter climatic conditions. Since 253 ka, however, pollen concentrations declined, corresponding with the amount of halite deposited in the core sediment and, suggesting a cold, dry climatic condition during MIS2. Our findings have important implications for understanding complex regional vegetation and climatic responses to large-scale forcings in the Qaidam Basin. (C) 2015 Elsevier B.V. All rights reserved.