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| 2. |
- Cunningham, L., et al.
(author)
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Amplified bioproductivity during Transition IV (332 000-342 000 yr ago) : evidence from the geochemical record of Lake El'gygytgyn
- 2013
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In: Climate of the Past. - Gottingen, Germany : COPERNICUS GESELLSCHAFT. - 1814-9324 .- 1814-9332. ; 9:2, s. 679-686
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Journal article (peer-reviewed)abstract
- To date, terrestrial archives of long-term climatic change within the Arctic have widely been restricted to ice cores from Greenland and, more recently, sediments from Lake El'gygytgyn in northeast Arctic Russia. Sediments from this lake contain a paleoclimate record of glacial-interglacial cycles during the last three million years. Low-resolution studies at this lake have suggested that changes observed during Transition IV (the transition from marine isotope stage (MIS) 10 to MIS 9) are of greater amplitude than any observed since. In this study, geochemical parameters are used to infer past climatic conditions thus providing the first high-resolution analyses of Transition IV from a terrestrial Arctic setting. These results demonstrate that a significant shift in climate was subsequently followed by a rapid increase in biogenic silica (BSi) production. Following this sharp increase, bioproductivity remained high, but variable, for over a thousand years. This study reveals differences in the timing and magnitude of change within the ratio of silica to titanium (Si/Ti) and BSi records that would not be apparent in lower resolution studies. This has significant implications for the increasingly common use of Si/Ti data as an alternative to traditional BSi measurements.
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| 3. |
- Nowaczyk, N. R., et al.
(author)
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Chronology of Lake El'gygytgyn sediments - a combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses
- 2013
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In: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 9:6, s. 2413-2432
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Journal article (peer-reviewed)abstract
- A 318-metre-long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El'gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chronostratigraphic methods. The 12 km wide lake is sited off-centre in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the earth's magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest geomagnetic Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El'gygytgyn occurred in concert with global climatic cycles. The upper similar to 160m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka(-1), whereas the lower 160m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka(-1). This study also provides orbitally tuned ages for a total of 8 tephras deposited in Lake El'gygytgyn.
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| 4. |
- Scherer, SW, et al.
(author)
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Human chromosome 7: DNA sequence and biology
- 2003
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In: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 300:5620, s. 767-772
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Journal article (peer-reviewed)abstract
- DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.
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| 5. |
- Tarasov, P. E., et al.
(author)
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A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic - new insights into climate-vegetation relationships at the regional scale
- 2013
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In: Climate of the Past. - : Copernicus GmbH. - 1814-9332. ; 9:6, s. 2759-2775
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Journal article (peer-reviewed)abstract
- The recent and fossil pollen data obtained under the frame of the multi-disciplinary international El'gygytgyn Drilling Project represent a unique archive, which allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could be potentially present in this region during the past. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) long phases of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals in the study region within the past million years. During the late Pliocene-early Pleistocene interval (i.e., similar to 3.562-2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation from generally warmer/wetter environments of the earlier (i. e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction indicates that the taxon-rich cool mixed and cool conifer forest biomes are mostly characteristic of the time prior to MIS G16, whereas the tundra biome becomes a prominent feature starting from MIS G6. These results consistently indicate that the study region supported significant tree populations during most of the interval prior to similar to 2.730 Ma. The cold-and drought-tolerant steppe biome first appears in the reconstruction similar to 3.298 Ma during the tundra-dominated MIS M2, whereas the tundra biome initially occurs between similar to 3.379 and similar to 3.378 Ma within MIS MG4. Prior to similar to 2.800 Ma, several other cold stages during this generally warm Pliocene interval were characterized by the tundra biome.
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