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| Titel |
Pliocene to Pleistocene climate and environmental history of Lake El'gygytgyn, Far East Russian Arctic, based on high-resolution inorganic geochemistry data |
| VerfasserIn |
V. Wennrich, P. S. Minyuk, V. Borkhodoev, A. Francke, B. Ritter, N. R. Nowaczyk, M. A. Sauerbrey, J. Brigham-Grette, M. Melles |
| 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 ; 10, no. 4 ; Nr. 10, no. 4 (2014-07-23), S.1381-1399 |
| Datensatznummer |
250117018
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| Publikation (Nr.) |
 copernicus.org/cp-10-1381-2014.pdf |
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| Zusammenfassung |
The 3.6 Ma sediment record of Lake El'gygytgyn/NE Russia, Far East Russian
Arctic, represents the longest continuous climate archive of the terrestrial
Arctic. Its elemental composition as determined by X-ray fluorescence
scanning exhibits significant changes since the mid-Pliocene caused by
climate-driven variations in primary production, postdepositional diagenetic
processes, and lake circulation as well as weathering processes in its
catchment.
During the mid- to late Pliocene, warmer and wetter climatic conditions are
reflected by elevated Si / Ti ratios, indicating enhanced diatom production
in the lake. Prior to 3.3 Ma, this signal is overprinted by intensified
detrital input from the catchment, visible in maxima of clastic-related
proxies, such as K. In addition, calcite formation in the early lake history
points to enhanced Ca flux into the lake caused by intensified weathering in
the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the
development of permafrost in the region triggered by cooling in the
mid-Pliocene.
After ca. 3.0 Ma the elemental data suggest a gradual transition to
Pleistocene-style glacial–interglacial cyclicity. In the early Pleistocene,
the cyclicity was first dominated by variations on the 41 kyr obliquity band
but experienced a change to a 100 kyr eccentricity dominance during the
middle Pleistocene transition (MPT) at ca. 1.2–0.6 Ma. This clearly
demonstrates the sensitivity of the Lake El'gygytgyn record to orbital
forcing.
A successive decrease of the baseline levels of the redox-sensitive Mn / Fe
ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall
change in the bottom-water oxygenation due to an intensified occurrence of
pervasive glacial episodes in the early Pleistocene. The coincidence with
major changes in the North Pacific and Bering Sea paleoceanography at ca. 1.8
Ma implies that the change in lake hydrology was caused by a regional cooling
in the North Pacific and the western Beringian landmass and/or changes in the
continentality. Further increases in total organic carbon and total nitrogen
content after ca. 1.6 Ma are attributed to reduced organic matter decay in
the sediment during prolonged anoxic periods. This points to more extensive
periods of perennial ice coverage, and thus, to a progressive shifts towards
more intense peak glacial periods.
In the course of the Pleistocene glacial–interglacial sequence eight
so-called "super-interglacials" occur. Their exceptionally warm conditions
are reflected by extreme Si / Ti peaks accompanied by lows in Ti, K, and
Fe, thus indicating extraordinary high lake productivity. |
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