Alla C. Vasil'chuk

Radiocarbon ages of mammoths in northern Eurasia : Implications for population development and late quaternary environment

Many mammoth remains have been radiocarbon-dated. We present here more than 360 14 C dates on bones, tusks, molars and soft tissues of mammoths and discuss some issues connected with the evolution of mammoths and their environment: the problem of the last mammoth; mammoth taphonomy; the plant remains and stable isotope records accompanying mammoth fossils; paleoclimate during the time of the mammoths and dating of host sediments. The temporal distribution of the 16 C dates of fossils from the northern Eurasian territory is even for the entire period from 40 to 10 ka BP.

First direct dating of Late Pleistocene ice-wedges by AMS

We present the first direct dating by 14 C-accelerator mass spectrometry of three Late Pleistocene syngenetic icewedges 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 icewedges 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. fl 2000 Elsevier Science B.V. All rights reserved.

Radiocarbon Dating of δ18O-δD Plots in Late Pleistocene Ice-Wedges of the Duvanny Yar (Lower Kolyma River, Northern Yakutia)

The Duvanny Yar cross-section located in the Lower Kolyma River valley of Northern Yakutia (69 degrees N, 158 degrees E, height above the Kolyma River level 55 m), has been studied and dated in detail by radiocarbon. The sequence mainly consists of sandy loam sediments with large syngenetic ice wedges. Their width at the top is 1-3.5 m. Allochthonous organic material occurs in high content, concentrating as 0.5-0.7 m lenses. Shrub fragments, twigs, and mammoth bones are accumulated in peaty layers. Through interpolation based on a series of (super 14) C dates, dating of the host sediments provides an approximate age for the ice wedges. The (super 14) C dates of various types of organic material are sometimes very close, but not all in agreement. Therefore, the dates do not accurately show the age of the delta (super 18) O and delta D plots. A new approach is developed to a (super 14) C dating strategy of syncryogenic sediments with high admixture of allochthonous organic material. The main purpose of this study is to consider detection of inversions or disturbances in the syngenetic permafrost sediment at the Duvanny Yar cross-section by (super 14) C date series. Direct accelerator mass spectrometry (AMS) dating of the ice confirmed the relatively young age of ice wedges.

14C and 18O in Siberian syngenetic ice-wedge complexes

We discuss the possibility of dating ice wedges by the radiocarbon method. We show as an example the Seyaha, Kular and Zelyony Mys ice wedge complexes, and investigated various organic materials from permafrost sediments. We show that the reliability of dating (super 18) O variations from ice wedges can be evaluated by comparison of different organic materials from host sediments in the ice wedge cross sections.

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.

The 14C age of palsas in Northern Eurasia

We discuss results of 14C dating peat of palsa of different regions of Northern Eurasia. We apply these dates to determine the age of active palsa growth during different periods of the Holocene in permafrost zone.