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Schlagwörter:
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Zusammenfassung:
Improved knowledge of deglaciation processes during the termination of the Last Glacial Maximum on the Tibetan Plateau can provide important
information for understanding deglaciations in
climate-sensitive high-altitude ecosystems. Little,
however, is known about this time interval because
most lacustrine sediment records from the Tibetan
Plateau are younger than 19,000 years. This study
focused on a lake sediment record from Nam Co,
south-central Tibetan Plateau, covering the interval
from *23.7 to 20.9 cal ka BP. We analysed the
distribution and compound-specific hydrogen isotope composition (dD) of sedimentary n-alkanes, as well as the bulk sediment TOC, TN, d13Corg and d15N
composition, to infer lake system development. Pronounced
changes in environmental conditions
between *21.6 and 21.1 cal ka BP, as well as
between 23.1 and 22.5 cal ka BP (Greenland Interstadial
2), were inferred from increased aquatic nalkane
amounts and decreased dDn-C23 values within
these time intervals, respectively. Freshwater inputs,
which most likely resulted from enhanced glacier
melting, caused these changes. Our results suggest that
mountain glacier retreat on the Tibetan Plateau started
earlier than previously assumed. The required energy
for thawing was probably provided by temperature changes caused by reorganization of atmospheric circulation, which has also been recorded in Greenland ice records.
