New insights on Late Quaternary Asian palaeomonsoon variability and the timing of the Last Glacial Maximum in southwestern China

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Description/Abstract

Aw6.35 m core (06SD) was retrieved from Lake Shudu, Yunnan Province, China. The sediments spanning
the period w22.6e10.5 kcal. yr BP (6.35e1.44 m) were analysed using a combination of variables
including pollen, charcoal, particle size, magnetic susceptibility and loss-on-ignition. The resulting
palaeorecord provides a high-resolution reconstruction of Late Pleistocene to Early Holocene climatic
and environmental changes in southwestern China. Our findings indicate that from c. 22.6 to 17.7 kcal. yr
BP, vegetation assemblages were primarily aligned to sparse xerophytic grassland/tundra or cold-tolerant
boreal Pinus forest, indicating that climatic conditions in southwestern China were cold and dry.
However, from c. 17.7 to 17.4 kcal. yr BP, the Lake Shudu record is punctuated by marked environmental
changes. These include the establishment of denser vegetation cover, a marked expansion of boreal Pinus
forest and enhanced hydrological activity in the catchment over centennial timescales, perhaps suggesting
that stepwise variations in the Asian Monsoon were triggering fundamental environmental
changes over sub-millennial timescales. Thereafter, the pollen record captures a period of environmental
instability reflected in fluctuations across all of the variables, which persists until c. 17.1 kcal. yr BP. After
c. 17.1 kcal. yr BP, the expansion of steppe vegetation cover and coldecool mixed forest consisting of
mesophilous vegetation such as Tsuga and Picea, thermophilous trees including Ulmus and deciduous
Quercus inferred from the Lake Shudu pollen record point to the establishment of warmer, wetter and
perhaps more seasonal conditions associated with a strengthening Asian Summer Monsoon during the
shift from Pleistocene to Holocene climatic conditions.