Last glacial-Holocene geochronology of sediment cores from a high-altitude Tibetan lake based on AMS ¹⁴C dating of plant fossils: Implications for paleoenvironmental reconstructions

We obtained three sediment cores from a high-altitude lake (Lake Pumoyum Co; altitude, ~5020m asl) on the southern Tibetan plateau for reconstruction of environmental changes during the last glacial-Holocene transition. In this study, we established the first reliable chronology for sediment cores from Lake Pumoyum Co, ca. 18.5cal ka BP at the bottom, by ¹⁴C analyses of terrestrial plant residue concentrates (PRC, >125μm) and aquatic plant residues. The calibrated ages of the PRC fraction in the surface sediment were nearly modern (0.1±0.1cal ka BP), and the δ¹³C values (-22‰ to -24‰) were agreed well with those of modern terrestrial C₃ plants. In addition, we estimated ¹⁴C reservoir ages of macrophyte remains from changes in their δ¹³C values. The major climate boundary layers in the cores (transitions to Bølling-Allerød, 14.5±0.5cal ka BP; Younger Dryas, 12.8±0.1cal ka BP; and Preboreal, ~11.6cal ka BP) were confirmed by our new ¹⁴C chronology. The transition to the Bølling-Allerød warm phase from the last glacial (14.5±0.5cal ka BP) coincided with an obvious lithologic boundary (a rapid decrease in the abundance of the macrophyte remains) in the Lake Pumoyum Co sediment cores.