Permafrost

presence may be debated since there is limited unfrozen water in the soils/sediments to feed ice
growth. Unlike in the Arctic where contraction cracks infill with water and from ice-wedge
polygons, virtually all contraction cracks are in-filled with local and wind blown sand/silt,
thereby forming sand-wedges. Ice-wedges have been noted, however, at a few coastal locations.
Also, massive ice-lenses may have formed at one location near a seasonal flowing river. The
flowing water would provide a source for both heat, which would increase the amount of
unfrozen water in the soil, and water to fuel the growth of syngenetic ice.
Examples of each type of ground ice will be presented together with ice chemistry,
including stable isotopes, and physical characteristics. These characteristics are useful for
understanding the mechanism of formation and for parameterizing our models of sublimation
and ice condensation. Generalization of ice source may be made based on these data; however,
these do not always suffice to distinguish between the potential ice sources. We present our
most recent findings about the origin, nature and chronology of the subsurface ice, and consider
the implications for the distribution and stability of ground ice on Mars.
Key words: Permafrost, ground ice, dry valleys, antarctica
Quaternary Sediments of Kara Sea Coast and
Their Cryogenic Structure
R. Shirokov 1 , I. Streletskaya 2
(1.Earth Cryosphere Institute SB RAS, 30/6 Vavilov str. Moscow, 119991, Russia; 2.Lomonosov Moscow State
University, Physical Faculty, Leninskie Gory, Moscow, 119992, Russia)
Abstract: The Eastern coast of the Galf of Yenisey and the western coast of the Yamal
peninsula are the key sites for studying Quaternary sediments of Russian Arctic. There, coastal
cliffs contain most representative sedimentary strata: continental sands and sandy loams with
syngenetical and epigenetical ice wedges underlined by clayey marine saline sediments with
massive ground ice. The volumetric ice content of the coastal sediments varies from 30% to
80%, which is one of the major factors of thermal erosion. The widest distribution of massive
ground ice is linked to the lowland areas of several Pleistocene marine transgressions.
Sediments, inclosing ground ice are often have ice wedges of various ages indicating a change
of sedimentary and thermal regimes after the ground ice of marine lowlands was formed.
During the last four years detailed investigations of the sedimentary strata have being
conducted. Field and laboratory work included chemical, isotope, mineralogical, granulometric
analysis as well as absolute dating of sediments. It was found that the relict lithological and
thermal processes occurred on the marine shelf are presently reflected in the modern coastal
lowlands. As a result, relict Pleistocene marine shelf, which constitutes present-day coastal
plains, can be considered as the analogy with modern shelf. We have developed a new
offshore/onshore classification of permafrost. This study can lead to the developing of several
criteria for age gradation of modern shelf. Continuation of this work is important for
understanding temporal evolution of costal landscapes of Russian Arctic and for
paleoreconstructions.
Key words: Ground ice, ice wedges, thermal erosion, Quaternary sediments
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