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Titel |
The diversity of permafrost-affected soils in the Lena River Delta and its hinterland |
VerfasserIn |
Sebastian Zubrzycki, Lars Kutzbach, Irina Yakshina, Eva-Maria Pfeiffer |
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 |
250080960
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Zusammenfassung |
The North-Siberian Lena River Delta is the largest Arctic delta and an important interface
between the Arctic Ocean in the North and the large Siberian land masses in the South. This
delta consists not only of Holocene deltaic sediment deposits as a river terrace and the
modern active floodplains but also of remnants of the former Pleistocene mainland including
large islands of ice-complex sediments and the Arga-Muora-Sise Island, which is composed
of pure sand sediments of still debated origin. The highly diverse landscape structure of
the Lena River Delta is reflected by a great variety of permafrost-affected soils
(gelisols). This study aims at describing this great gelisol diversity and at analysing the
dominant soil-forming processes in this comparatively scarcely studied soil region. The
soil development in the investigated continuous permafrost region is limited by
the short thawing period of around three months (June to September) and takes
place in the shallow (< 1 m) seasonally thawed active layer. The geological parent
material plays an important role for the development of soils in the Lena River
Delta region. The distribution of the various soil types closely follows the pattern
of the geomorphic units characterised by differing sedimentation conditions. The
properties and genesis of the soils on the Holocene river terrace and the modern
floodplains are strongly affected by the enormous amounts of fluvial sediments
(about 12 x 106 tons per year) brought by the Lena River into its delta. The fluvial
sedimentation together with the also pronounced aeolian sedimentation results in a fast
vertical growth of soils. The upward rise of the soil surface leads to an upward
movement of the permafrost table resulting in fast incorporation of soil material formed
in the supra-permafrost zone into the permafrost. Due to the morphodynamics of
ice-wedge polygons and resulting formation of patterned ground with elevated
rims and depressed and water-saturated centres, the Holocene river terrace of the
delta is in its main extent covered by a soil complex of Glacic Aquiturbels and
Typic Historthels. The active floodplain levels are dominated by sandy or gleyic
subgroups of the Orthel suborder as e.g. Psammentic Aquorthels or Typic Psammorthels.
The surfaces of the Arga-Muora-Sise Island are frequently reshaped by aeolian
sedimentation and erosion. The soils on these scarcely vegetated landscapes are
dominated by cryoturbated and sand-rich soil subgroups with high moisture contents,
e.g., various Psammoturbels and Aquiturbels. The modern soils covering the older
Pleistocene ice-complex plains are influenced by wide ice-wedge net structures
and consist of a soil complex of Glacic Aquiturbels and Ruptic Historthels. The
widespread thermokarst depressions within the ice-complex are covered by Ruptic
Histoturbels and Ruptic Historthels, whereas the slopes are dominated by various
Aquiturbels and Fluvaquentic Historthels. For the largely unexplored Lena River
Delta’s hinterland it can be assumed that the active genesis of the soils lasts longer
than in the active delta regions due to a much lower sedimentation and more stable
surface conditions. In these regions widespread cryoturbated and peat-rich soil
groups like Histoturbels and Historthels as well as Fibristels are found. An increased
understanding of spatial variability and genesis of permafrost-affected soils is essential for
meaningful predictions of climate change consequences in Arctic permafrost regions. |
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