Permafrost

Permafrost Distribution and Thickness in Mesozoic Basins of the Aldan
Shield
M.N. Zheleznyak and F.V. Mitin
(Permafrost Institute SB RAS, Yakutsk, Russia)
Abstract: A series of Mesozoic basins occur in the junction zone of the Aldan shield and the
Stanovoy fold system situated in north-eastern Eurasia, of which the largest are the Chulman,
Tokarikan-Konerkit, Guvilgra, Ytymdzha, Upper Gynym and Toko basins. Southern Yakutia is
one of the major industrial areas in Yakutia which has a rich variety of minerals. Most mineral
resources occur within or below permafrost. Exploration and development of mineral deposits
require a knowledge of permafrost and groundwater conditions for the construction of
engineering structures, utilities and mines.
Because of little geothermal research in the area, a very general characterization of the
permafrost conditions is available in the literature. Mapping and description of the permafrost
in the Mesozoic basins rest on information obtained for the Chulman basin. Recent observations
indicate that this is not true.
The climate in the Mesozoic basins is characterized by a strong temperature inversion and
the west-east decreasing trend in mean annual air temperature, from –9.5°С in the Chulman
basin to –11.4°С in the Toko basin. Permafrost in the basins is discontinuous and varies in
thickness from a few meters to 250 m. The geothermal heat flux is from 45-47 (the Chulman,
Tokarikan and Guvilgra basins) to 65 mW/m 2 (the Toko basin).
The temperature field and permafrost in the Mesozoic basins within the Stanovoy foreland
develop under the combined effect of air temperature inversion, meridional climate variation
and increased geothermal heat flux relative to the surrounding geological structures. Low mean
annual air temperatures in combination with high precipitation result in a great diversity of
ground temperature conditions, while variations in the geothermal heat flow determine
permafrost thickness in these structures. Permafrost has been found to be discontinuous with a
thickness of 190 m only in the Chulman basin. In the basins located to the east, permafrost is
continuous and ranges 120 to 240 m in thickness (Tokarikan, Guvilgra, Toko and others).
Important features of permafrost in the basins are the presence of open taliks (extensive or
localized) and the decrease in thickness at the contacts with ancient crystalline massif. They are
related to fracture tectonics of these zones and to groundwater dynamics.
Mountain permafrost in Japan: reviews and perspectives
Mamoru Ishikawa
(Institute of Observational Research for Global Change, JAMSTEC, Yokosuka, Japan)
Abstract:In 1970’s Japanese mountain permafrost was found at volcanic high mountain ranges,
Mt. Fuji and Daisetsu Mountains. Thereafter the lower limit of permafrost distribution was
evaluated by annual air temperature monitoring and mapping the permafrost-related landforms.
Intensive geophysical prospecting and ground temperature monitoring conducted at numerous
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