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Julie Brigham-Grette Lyn M. Gualtieri Olga Yu. Glushkova Thomas D. Hamilton David Mostoller Anatoly Kotov 《Quaternary Research》2003,59(3):386-398
The Pekulney Mountains and adjacent Tanyurer River valley are key regions for examining the nature of glaciation across much of northeast Russia. Twelve new cosmogenic isotope ages and 14 new radiocarbon ages in concert with morphometric analyses and terrace stratigraphy constrain the timing of glaciation in this region of central Chukotka. The Sartan Glaciation (Last Glacial Maximum) was limited in extent in the Pekulney Mountains and dates to 20,000 yr ago. Cosmogenic isotope ages > 30,000 yr as well as non-finite radiocarbon ages imply an estimated age no younger than the Zyryan Glaciation (early Wisconsinan) for large sets of moraines found in the central Tanyurer Valley. Slope angles on these loess-mantled ridges are less than a few degrees and crest widths are an order of magnitude greater than those found on the younger Sartan moraines. The most extensive moraines in the lower Tanyurer Valley are most subdued implying an even older, probable middle Pleistocene age. This research provides direct field evidence against Grosswald’s Beringian ice-sheet hypothesis. 相似文献
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Julie Brigham-Grette Martin Melles Pavel Minyuk Scientific Party 《Journal of Paleolimnology》2007,37(1):1-16
Sediment piston cores from Lake El’gygytgyn (67°N, 172°E), a 3.6 million year old meteorite impact crater in northeastern
Siberia, have been analyzed to extract a multi-proxy millennial-scale climate record extending to nearly 250 ka, with distinct
fluctuations in sedimentological, physical, biochemical, and paleoecological parameters. Five major themes emerge from this
research. First the pilot cores and seismic data show that El’gygytygn Crater Lake contains what is expected to be the longest,
most continuous terrestrial record of past climate change in the entire Arctic back to the time of impact. Second, processes
operating in the El’gygytygn basin lead to changes in the limnogeology and the biogeochemistry that reflect robust changes
in the regional climate and paleoecology over a large part of the western Arctic. Third, the magnetic susceptibility and other
proxies record numerous rapid change events. The recovered lake sediment contains both the best-resolved record of the last
interglacial and the longest terrestrial record of millennial scale climate change in the Arctic, yielding a high fidelity
multi-proxy record extending nearly 150,000 years beyond what has been obtained from the Greenland Ice Sheet. Fourth, the
potential for evaluating teleconnections under different mean climate states is high. Despite the heterogeneous nature of
recent Arctic climate change, millennial scale climate events in the North Atlantic/Greenland region are recorded in the most
distal regions of the Arctic under variable boundary conditions. Finally, deep drilling of the complete depositional record
in Lake El’gygytgyn will offer new insights and, perhaps, surprises into the late Cenozoic evolution of Arctic climate.
This is the first in a series of eleven papers published in
this special issue dedicated to initial studies of El'gygytgyn
Crater Lake and its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest
editors of this special issue. 相似文献
3.
I. V. Tibilov 《Russian Journal of Pacific Geology》2008,2(1):72-86
The autochonous nature of the Late Mesozoic minor intrusions of Chukotka has been shown. They were formed under the subsurface conditions of the ancient relief. The structural-geological and microscopic features of the minor intrusions point to solid state origin. 相似文献
4.
P. S. Minyuk J. Brigham-Grette M. Melles V. Ya. Borkhodoev O. Yu. Glushkova 《Journal of Paleolimnology》2007,37(1):123-133
The inorganic geochemistry of sediments from El’gygytgyn Lake shift in phase with interpreted paleoclimatic fluctuations seen
in the record over the past 250 ka. Warm periods, when the lake was seasonally ice free and fully mixed, are characterized
by increased concentrations of SiO2, CaO, Na2O, K2O, and Rb, by decreased contents of TiO2, Fe2O3, Al2O3, and MgO, and by a lower chemical index of alteration (CIA). Increased levels of SiO2 reflect increases in limnic productivity whereas many of the other elements and the CIA likely reflect increased hydrological
activity coincident with an increase in coarser sand and silt content and a decrease in clay mineral content. For cold/cooler
periods when perennial lake ice cover lead to a stratifed water column and anoxic bottom waters, the opposite is generally
observed suggesting a decrease in hydrological activity and an increase in post-depositional chemical alteration.
Peaks in P2O3 and MnO, coincident with an increased abundance of vivianite, suggest possible linkages to the paleoproductivity of local
fish fauna regardless of climate change across the region surrounding Lake El’gygytgyn. Strontium is high in concentration
during warmer intervals and may also be linked to paleoproductivity. Enrichment of the post-Eemian portion of the sediment
record in niobium, and yttrium appears independent of glacial–interglacial change; rather it may reflect a gradual shift in
the geomorphology of the catchment, particularly the hydrology of large alluvial fans along the western side of the lake.
In contrast to some lake records, changes in Zr concentration over time suggests only a weak, if any, increase in eolian sediment
supply during colder periods.
This is the first in a series of eleven papers published in this special issue dedicated to initial studies of El'gygytgyn Crater Lake and
its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue. 相似文献
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S. V. Efremov 《Russian Journal of Pacific Geology》2009,3(1):80-90
Basite magmatism preceding the intrusion of large volumes of felsic magmas takes place only during powerful tectonic rearrangements, which span both the continental crust and lithospheric mantle. The study of this magmatism makes it possible to solve many genetic problems and obtain important geological information on the sources and processes that are responsible for granitoid magmatism. This paper reports the results of the geochemical study of potassic and ultrapotassic magmatic rocks that predate the intrusion of the granitoid complex and belong to it. In terms of geochemistry, the studied magmatic rocks of Chukotka correspond to the derivatives of potassic and ultrapotassic magmas, which allows us to use the models of formation of ultrapotassic magmas for interpreting the genetic features of tin-bearing granites, in particular, for explaining the anomalous contents of incompatible elements in these rocks. Using modern genetic models in combination with geological, geophysical, and geochemical data, it is established that the source of this specialization was the lithospheric mantle domain. The domain was formed within a convergent geologic boundary owing to the metasomatic reworking of the mantle wedge by fluids that were released during dehydration of the oceanic lithosphere. Based on the obtained results, a new model was proposed for the formation of tin-bearing granitoids in the collisional orogens. This model is underlain by the concept of a particular lithospheric source, which acquired its geochemical and metallogenic signatures during intense tectonic transformation that involved the lithospheric mantle. These signatures were inherited by magmas formed during melting within this domain. 相似文献
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