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| Titel |
A glacial chronology for post Little Ice Age glacier changes based on proglacial geomorphology, tree rings, OSL- and 14C-dating at Mt. Pulongu, southeastern Tibet |
| VerfasserIn |
David Loibl, Philipp Hochreuther, Daniela Hülle, Haifeng Zhu, Frank Lehmkuhl |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092394
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| Publikation (Nr.) |
 EGU/EGU2014-6769.pdf |
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| Zusammenfassung |
| The remote eastern Nyainqêntanglha Range contains numerous temperate monsoonal
glaciers which are highly sensitive to climate change. However, there is still a great lack
of information on late Holocene glacier fluctuations and the factors driving these
changes. We conducted field work at two large debris covered glaciers on the northern
and southern slopes of Mt. Pulongu (~6,300 m a.s.l.). Detailed geomorphological
mapping of the proglacial settings revealed similar patterns of two major and three
minor/recessional glacial advances. At the northern glacier, tree ring dating for
the moraines of the two major advances resulted in minimum ages of ~1670 AD
and ~1745 AD, respectively. These Little Ice Age (LIA) ages are supported by
geochemical measurements on glacial and glacio-fluvial sediments from these settings
showing almost no signs of chemical weathering. Further evidence, including 14C-age
and depositional characteristics of a buried tree, and moraine topography, suggest
that the second advance was stronger but was hampered by a dead ice relict of the
previous advance. At the northern glacier, this obstacle led to an ice tailback and
subsequently to lateral moraine oversteepening and breaching, resulting in a large
lateral glacier lobe. At the southern glacier, the valley is narrower and hence did not
allow the formation of a lateral glacier lobe. However, the proglacial setting, i.e.
pronounced push moraines, suggests a similar sequence of events. Furthermore, both
settings contain two moraine-dammed lakes in similar positions. A combination of
OSL-dating, tree ring based reconstruction of the local climate, and constraints
from the proglacial geomorphological setting enabled the inclusion of the 3 minor
moraine stages into the glacial chronology. This multiproxy-approach resulted in a
well-established morphochronology with multiple direct and indirect dates that
allow the reconstruction of the glacial fluctuations at Mt. Pulongu since the LIA. A
regional remote sensing study revealed that these settings are no special cases, but that
many large glaciers in the eastern Nyainqêntanglha range show similar proglacial
sequences, including several examples of large lateral glacier lobes. We therefore
assume that – despite great heterogeneity in this high-mountain environment – the
emerging patterns were caused by climatic changes that affected the whole region. |
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