The aim of the work was to perform paleotemperature reconstructions for the Late Pleistocene and Holocene of Kotelny Island according to oxygen isotope analysis of syngenetic ice wedges. Variations ...of δ
18
O in the Late Pleistocene ice wedges formed on Kotelny Island are significant, exceeding 8‰ (from –30‰ to –22.9‰), while they are insignificant at –1.5‰ (from –23.1‰ to –21.6‰) for those in the Holocene. Reconstructions showed that the mean January temperature in the Late Pleistocene changed over 8 to 13°C. The mean annual temperature of frozen soils was about –19 or –20°C in the Late Pleistocene, and about –13 to –15°C in the Holocene, while the current temperature is about –14°C.
•We have synthesized previous and current study of Holocene massive ice and have provided comprehensive discussion of their origin.•Three types of massive ice are identified: (1) brown vertical ...layered ice; (2) white transparent, horizontal layered ice; and (3) brown, non-laminated ice.•14C, δ2H and δ18C as tools to assess the massive ice origin.•The chemical and isotope composition and pollen indicate that the three types of massive bodies have different origin.
Massive ground ice of Holocene age occurs in multiple boreholes near the Sabettayakha River mouth, on the coast of the Gulf of Ob (Ob Bay), Yamal Peninsula, northwest Siberia. The multistage massive-ice bodies are up to 5.7m thick and occur in Holocene sediments of modern floodplain and the first terrace of the coastal lagoon. Massive-ice bodies and cryopegs occur at three to four depths. According to stable isotope analyses, the multistage massive ice bodies formed syngenetically during the freezing of water-saturated sediment, under intensive cryogenic fractionation. Very negative values of δ2H (up to –199.7 ‰) and δ18O (up to –26.48 ‰) for the massive ice are unique not only for Holocene ground ice of Yamal Peninsula, but also for Late Pleistocene ice of northwest Siberia. The ratio of the chloride and sulfate anions, pollen spectra and presence of algae in three different types of massive ice near the Sabettayakha River mouth suggest that (1) vertically layered brown ice formed during freezing of water-saturated sands of the Ob Gulf; (2) brown non-laminated ice formed as a result of freezing of sublake talik water; and (3) white ultra-fresh ice also formed from lake and river water.
High-resolution records of the stable isotopic (δ18O and δD) composition of ice within two closed system (hydrostatic) pingos indicate a complex history of ice formation by segregation and injection ...and pingo growth. Physical properties and internal structure of continuous ice cores in the center of the Weather Pingo near Prudhoe Bay, Alaska, and the Pestsovoye Pingo, in northwestern Siberia, were described and then sub-sampled for analysis of the isotopic composition. Changes in the isotopic signature and physical properties of ice with depth reveal distinct patterns in both pingos indicative of ice growth as permafrost aggraded into the drained lake basin. In the initial stages following active layer deepening and initial freeze back, in-situ water migrating toward the freezing front froze at a relatively rapid rate as revealed by a complex isotopic record and small ice crystal size in the cores of Weather Pingo. Once the water supply became limited, freezing under equilibrium conditions resulted in an isotopic composition consistent with Rayleigh-type fractionation and δ18O and δD values that become more negative with depth. The data for the Pestsovoye Pingo reveal similar trends related to the initial stages of water migration and freezing, followed by isotopic fractionation under equilibrium conditions as unfrozen water available in the talik beneath the pingo became limited. Most of the ice in both pingos (~50%) formed during this final stage of permafrost aggradation. Thus temporal variability in water migration and freezing rate at the base of each pingo created a complex isotopic stratigraphy and ice growth history.
•We examine δ18O and δD records within two typical closed-system pingos•Comparison of co-isotope trends for Weather and Pestsovoye Pingos show isotopic similarity•Isotope values suggest that most of the ice grew under equilibrium freezing conditions•Both pingos formed after permafrost had aggraded into the drained lake basin sediments
•Syngenetic sediments contain allochthonous organic deposit that originated at a distance from its present position.•The ice wedges are considered as key subjects for 14C dating of yedoma.•The ...re-deposition of organic material discussed in terms of cyclic syngenetic sedimentation of yedoma.•Difference between ages of the fractions from the ice wedges consist of about 9–5 kyr.•The principle of the choice of the youngest 14C age from the set and from the layer is proposed for yedoma.
The ice wedges are considered as key subjects for 14C aging of yedoma, as there are no any exchange processes between the environment and the ice wedges. Syngenetic sediments contain allochthonous organic admixtures which originated at a distance from its present position. The main problem of radiocarbon dating within permafrost is the uncertain reliability of the 14C ages. To establish the age of ice wedge formation the strategy for the most authentic radiocarbon age selection for syngenetic sediments is considered on the base of a model of yedoma accumulation and distribution of reversal material by flood and aeolian transport. The re-working of organic material discussed in terms of cyclic syngenetic sedimentation of yedoma.
The advantages and the complications of 14C dating of organic inclusions from ice wedges by the accelerator mass spectrometry (AMS) are discussed applying to the search of true age organic material, which is simultaneous to ice-wedge formation. Radiocarbon ages of different organic materials from the same samples are compared, it is demonstrated that the difference between ages of the fractions from the ice wedges consists of about 9 kyr in Seyaha ice-wedge complex in Yamal Peninsula and about 5 kyr in Bison yedoma, Kolyma River valley. The principle of the choice of the youngest 14C age from the set and from the layer is proposed for yedoma.
The conditions of formation of massive ice near the South Tambey gas-condensate field in northern Yamal Peninsula are studied. It is shown that massive ice bodies up to 4.5 m thick occur in the ...Holocene deposits of the high laida and the first terrace. Therefore, they cannot be the remains of glaciers; they are ground ice formations. All three types of massive ice have quite various isotopic compositions: the values of delta D range from-107 to-199.7, and delta super(18)O from-15.7 to-26.48ppt. Such a significant differentiation in isotopic composition is a result of cryogenic fractionation in a freezing water-saturated sediment. The most negative isotope values are even lower in this Holocene massive ice than in the Late Pleistocene ice-wedge ice of Yamal Peninsula.
The conditions of formation of massive ice near the South Tambey gas-condensate field in northern Yamal Peninsula are studied. It is shown that massive ice bodies up to 4.5 m thick occur in the ...Holocene deposits of the high laida and the first terrace. Therefore, they cannot be the remains of glaciers; they are ground ice formations. All three types of massive ice have quite various isotopic compositions: the values of δD range from-107 to-199.7, and δ18O from-15.7 to-26.48per thousand. Such a significant differentiation in isotopic composition is a result of cryogenic fractionation in a freezing water-saturated sediment. The most negative isotope values are even lower in this Holocene massive ice than in the Late Pleistocene ice-wedge ice of Yamal Peninsula.
We present the first direct dating by
14C-accelerator mass spectrometry of three Late Pleistocene syngenetic ice-wedges from the Seyaha cross-section. They are representative of permafrost with ...multistage ice-wedges from the North of Western Siberia. The most important result is the clear vertical age stratification of the ice, i.e. the old ice is located beneath the young. This shows that a timescale can be assigned to these ice-wedges penetrating down into the permafrost. The age of the ice shows a depth of not more than 3–5 m for frost cracking; water penetrated into the ice-wedges at that depth. The lower part of the ice-wedges from the Seyaha cross-section has been dated between 21 000 and 14 000 BP.
The AMS dating of pollen from syngenetic ice–wedge ice Vasil'chuk, Alla C; Kim, Jong-Chan; Vasil'chuk, Yurij K
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
August 2004, 2004-08-00, Letnik:
223-224
Journal Article
Recenzirano
The features of pollen occurrence in ice–wedge ice such as: size of pollen of tundra plants, incoming pollen into frost cracks together with melt water, dust and partially from host sediment and also ...clay envelopes around pollen grains caused the pretreatment methods of ice–wedge ice samples. Good preservation of thin-wall pollen grains of Salix and Liliaceae after pretreatment evidenced appropriate pretreatment procedure. There is evident correlation between pollen dates and re-deposited pollen and spores content. However an interpretation of 14C dating of pollen concentrate is required independent time scale such as annual laminas or the AMS dates of macro or microfossils.
PDF
