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| Titel |
Variation and possible forcing mechanism of organic carbon isotopic compositions of loess in Northeastern China over the past 1.08 Ma |
| VerfasserIn |
Anqi Lyu, Huayu Lu, Lin Zeng, Shuangwen Yi, Enlou Zhang, Hongyan Zhang |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151482
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| Publikation (Nr.) |
 EGU/EGU2017-16071.pdf |
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| Zusammenfassung |
| As a valid indicator for reconstructing paleovegetation, the stable carbon isotopic
composition of total organic matter (δ13C) in aeolian deposits has been widely used,
especially on the Chinese Loess Plateau (central China), the area of typical loess sediments.
By comparison, little is known about the long-term variations and influencing factors of the
loess δ13C in Northeastern China, which is also an important part of the Eurasian loess belt.
On the basis of previous study, here we present magnetic susceptibility, grain size and δ13C
data of a new high-resolution loess-paleosol profile, the Sanbahuo profile (SBH) in the
Chifeng region in Northeastern China since the early Pleistocene (∼ 1.08 Ma). The
results demonstrate that the values of the three indicators show generally similar
variations on glacial-interglacial cycles, with positive δ13C values occurring in
paleosol layers and negative values in loess layers. By estimating C3/C4 relative
abundance, we get a rough threshold of δ13C value as the discriminator of pure
C3and mixed C3/C4 plants. The forcing mechanisms of the two types of vegetation
compositions are different. When the δ13C values are more positive than the threshold,
mainly during interglacial periods, temperature in the region was high enough for
the growth of C4plants. Both precipitation brought by enhanced Asian summer
monsoon and temperature favored a higher relative abundance of C4 plants. Although
according to modern investigation, the δ13C values of C3 plants are more negative
corresponding to greater precipitation and temperature, the effects were not enough to offset
the positive variations on the δ13C values by the increasing relative abundance of
C4 plants. On the other hand, during glacial periods due to low temperature, the
contribution from C4 plants to the loess could be neglected. Then the δ13C values
in this region recorded mainly the response of δ13C of predominant C3 plants to
climatic factors, both temperature and precipitation. The forcing mechanism in
this region is different from that on the Chinese Loess Plateau. The relationship
between climatic factors and loess deposits in Northeastern China requires further
study.
This work was supported by the Global Change Program of Ministry of Science and
Technology of China (grant No. 2016YFA0600503) and the National Natural Science
Foundation of China (Grant Nos. 41371203 and 41472138). |
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