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| Titel |
Monsoon-driven vegetation dynamics on the NE Tibetan Plateau during the Mid-Pleistocene Transition as evidenced in Qaidam Basin lake sediments |
| VerfasserIn |
Andreas Koutsodendris, Jörg Pross, Dirk Sachse, Christian Herb, Erwin Appel, Xiaomin Fang |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074232
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| Zusammenfassung |
| The Mid-Pleistocene Transition (MPT; ~1.2-0.7 Ma BP) marks the shift from the 41-ka to
the 100-ka ice-volume cycles during the Quaternary. Information on the character and
expression of the MPT in Central Asia is as of yet very limited, with its influence on the
Asian monsoon dynamics remaining largely unexplored. To better understand the
development of the Asian monsoon system across the MPT, we here investigate the
vegetation signature (at centennial to millennial timescales) using a continuous palaeolake
sediment core from the western Qaidam Basin (NE Tibetan Plateau). In light of the
strategic position of the Qaidam Basin between the monsoon-westerlies-Siberian High
climate systems and the sensitive response of desert plants to moisture shifts, this
study provides a unique, continuous record of short-term climate change during the
MPT in Central Asia. Vegetation is dominated by steppe and desert plants, with
Artemisia and Chenopodiaceae accounting for ~60 % of total pollen grains in each
sample. The Artemisia/Chenopodiaceae (A/C) ratio was used as a measure of relative
moisture availability in arid regions, allowing identification of distinct dry/wet phases
that correlate with glacial/interglacial cycles during the MPT. These phases show
coeval shifts in sedimentological parameters and biomarker distributions (including
n-alkane average chain length, CaCO3, C/N ratio, and magnetic susceptibility),
suggesting that moisture availability was the primary driver of processes in the
aquatic and surrounding terrestrial environments. The A/C ratio provides evidence
for increasing moisture availability during the younger intervals of the MPT in
the Qaidam Basin (i.e. MIS 17-21). We interpret this trend to be related to orbital
forcing, which is marked by relatively low eccentricity, obliquity and precession
during that time. This orbital configuration implies a weak seasonality and low ice
accumulation in high latitudes, which enhanced the summer monsoon and suppressed
influence of the winter monsoon over the Tibetan Plateau. To test this scenario, ongoing
analysis of leaf wax n-alkane δD values aim to provide information on the sources of
moisture influencing the Qaidam Basin and their potential shifts during the MPT. |
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