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| Titel |
Depositional dynamics in the El'gygytgyn Crater margin: implications for the 3.6 Ma old sediment archive |
| VerfasserIn |
G. Schwamborn, G. Fedorov, N. Ostanin, L. Schirrmeister, A. Andreev, The El'gygytgyn Scientific Party |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 6 ; Nr. 8, no. 6 (2012-11-26), S.1897-1911 |
| Datensatznummer |
250005976
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| Publikation (Nr.) |
 copernicus.org/cp-8-1897-2012.pdf |
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| Zusammenfassung |
| The combination of permafrost history and dynamics, lake
level changes and the tectonical framework is considered to play a crucial
role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic.
The purpose of this study is to propose a depositional framework based on
analyses of the core strata from the lake margin and historical
reconstructions from various studies at the site. A sedimentological program
has been conducted using frozen core samples from the 141.5 m long
El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary
permafrost west of the lake that partly fills the El'gygytgyn Crater. The
total core sequence is interpreted as strata building up a progradational
alluvial fan delta. Four macroscopically distinct sedimentary units are
identified. Unit 1 (141.5–117.0 m) is comprised of ice-cemented,
matrix-supported sandy gravel and intercalated sandy layers. Sandy layers
represent sediments which rained out as particles in the deeper part of the
water column under highly energetic conditions. Unit 2 (117.0–24.25 m) is
dominated by ice-cemented, matrix-supported sandy gravel with individual
gravel layers. Most of the Unit 2 diamicton is understood to result from
alluvial wash and subsequent gravitational sliding of coarse-grained (sandy
gravel) material on the basin slope. Unit 3 (24.25–8.5 m) has ice-cemented,
matrix-supported sandy gravel that is interrupted by sand beds. These sandy
beds are associated with flooding events and represent near-shore sandy
shoals. Unit 4 (8.5–0.0 m) is ice-cemented, matrix-supported sandy gravel
with varying ice content, mostly higher than below. It consists of slope
material and creek fill deposits. The uppermost metre is the active layer
(i.e. the top layer of soil with seasonal freeze and thaw) into which modern
soil organic matter has been incorporated. The nature of the progradational
sediment transport taking place from the western and northern crater margins
may be related to the complementary occurrence of frequent turbiditic layers
in the central lake basin, as is known from the lake sediment record. Slope
processes such as gravitational sliding and sheet flooding
occur especially during spring melt and promote
mass wasting into the basin. Tectonics are inferred to have initiated the
fan accumulation in the first place and possibly the off-centre displacement
of the crater lake. |
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