First direct dating of Late Pleistocene ice-wedges by AMS

We present the first direct dating by C-14-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. (C) 2000 Elsevier Science B.V. All rights reserved

Early Holocene climate signals from stable isotope composition of ice wedges in the Chara Basin, northern Transbaikalia, Russia

Stable isotope composition of syngenetic and epigenetic ice wedges, radiocarbon age, and pollen spectra of the surrounding deposits were studied during long term investigations at the “Belyi Klyuch” site on the first (6–8 m height) terrace of the Chara River (720 m.a.s.l.) in northern Transbaikalia to assess climatic conditions during ice-wedge formation. It was revealed that Holocene ice wedges had been formed from 10 to 7.5 ka 14C BP. The isotope composition (δ18О, δ2H) of relict ice wedges is the lightest and amounts −23‰ and −185‰, correspondingly. The isotopic compositions of ice lenses from sandy loam above ice wedges are −15.7‰ and −133‰; of small ice wedge in peat and sand are −15.3‰ and −117.9‰, accordingly. Interpretation of the ice wedge isotope composition has yielded that mean winter temperatures during cold stages of Holocene optimum were lower than today, during warm stages they were close to modern ones. During the coldest stages of Holocene optimum the total annual freezing index varied from −5100 to −5700 °C degree days, i.e. 300–600 °C degree days colder than during extremely severe modern winters. The total annual thawing index varied from 1300 to 1800 °C degree days, which was slightly higher than modern ones

AMS-dating of Late Pleistocene and Holocene syngenetic ice-wedges

We discuss the C-14 dating (both conventional and AMS) of Siberian permafrost sediments and ice-wedge ice. Direct dating of Late Pleistocene and Holocene syngenetic ice-wedges was done on organic material included in the ice. The time of ice formation (in C-14 years) is 21,000-14,000 BP for Seyaha, and 7100 BP for Shchuch'ya. The AMS dates show that the ice-wedges stratification is normal, i.e., the older ice is located below the younger. The C-14 dates yield for the first time a timescale (in C-14 years) for paleoclimatic indicators (oxygen and hydrogen isotope ratios from the ice). (C) 2000 Elsevier Science B.V. All rights reserved

AMS-dating of Late Pleistocene and Holocene syngenetic ice-wedges

We discuss the 14C dating (both conventional and AMS) of Siberian permafrost sediments and ice-wedge ice. Direct dating of Late Pleistocene and Holocene syngenetic ice-wedges was done on organic material included in the ice. The time of ice formation (in 14C years) is 21,000-14,000 BP for Seyaha, and 7100 BP for Shchuch'ya. The AMS dates show that the ice-wedges stratification is normal, i.e., the older ice is located below the younger. The 14C dates yield for the first time a timescale (in 14C years) for paleoclimatic indicators (oxygen and hydrogen isotope ratios from the ice).

First direct dating of Late Pleistocene ice-wedges by AMS

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 21000 and 14000 BP.

OXYGEN STABLE ISOTOPE VARIATION IN LATE HOLOCENE ICE WEDGES IN YAMAL PENINSULA AND SVALBARD

The stable oxygen isotope composition of Late Holocene syngenetic ice wedges from the Erkutayakha River valley in the Yamal Peninsula and from the Adventdalen valley in Svalbard was studied. It was demonstrated that the studied ice wedges located 2000 km apart were formed during the last 2-3.5 ka and continue to grow at present. Variations of δ18O values of the ice of both ice wedges do not exceed 2-3.5‰. Based on the oxygen isotope variations is has been calculated that mean winter air temperatures did not change by more than 3oC during the Late Holocene