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| Titel |
Small-scale variability of Holocene alas evolution in Central Yakutia inferred from thermokarst basin deposites |
| VerfasserIn |
Johannes Schmidt, Mathias Ulrich, Alexander N. Fedorov, Christine Siegert, Peter Efremov, Birgit Schneider, Christoph Zielhofer |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109148
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| Publikation (Nr.) |
 EGU/EGU2015-9028.pdf |
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| Zusammenfassung |
| The degradation of ice-rich permafrost is a major environmental change at high latitudes and
results in the expression of thermokarst basins. These geomorphological patterns, called
alases, are widespread in Central Yakutia, Eastern Siberia. However, alas sizes and
characteristics are varying widely and seem to change due to different cryolithological
conditions. Even though the evolutionary history of Holocene thermokarst development is not
sufficiently clear, it is presumed that it was a dominantly climate driven process. How and
when the Central Yakutian alases were formed or how they have evolved through the
Holocene is still subject of contemporary research.
The overall aim of this study was to reconstruct Holocene permafrost degradation
processes, their influencing factors and environmental impacts in Central Yakutia.
Therefore, in total 14 sediment cores were drilled down to 3-4 m depth and sampled
in summer 2013 from two differing thermokarst key sites in Central Yakutia. A
multi-proxy approach was applied to analyze the following characteristics with
focus on 6 cores: water/ice-content, grain size distribution, mass-specific magnetic
susceptibility, TOC and TN contents, CaCO3, element composition (XRF) and
stable carbon isotopes. Additionally, organic material and bulk sediment for selected
samples were dated with the AMS method to determine 14C ages for thermokarst
deposits.
Due to the results of the elementary composition different lake phases could be identified.
Furthermore, end-member analyses on grain-size distributions could be used to clarify the
provenance and transport process of the sediments. The results of the 14C dating
confirm an extensive deposition of reworked Pleistocene sediments in peripheral basin
zones during thermokarst lake growth, while the basin centers are characterized by
autochthonous subsidence of Pleistocene sediments. A synopsis of all analyzed
proxies in consideration of the geomorphological location of the cores, however,
reveal a small-scale variability of sediment origin in each Central Yakutian alas. |
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