Permafrost, Phillips, Springman & Arenson (eds)
© 2003 Swets & Zeitlinger, Lisse, ISBN 90 5809 582 7
Relict permafrost in the central part of Western Siberia
G.V. Ananjeva (Malkova), E.S. Melnikov & O.E. Ponomareva
Earth Cryosphere Institute, Siberian Division, Russian Academy of Sciences: Russia, Moscow
ABSTRACT: Relict permafrost has been encountered during the investigation of numerous oil and gas fields
in the central part of Western Siberia at depths ranging from 100–150 m (top of permafrost) to 250–400 m (base)
below ground surface. We present results of ongoing geological and hydrogeological research and provide additional
information on the geocryological conditions prevalent in this territory. The new data have modified our scientific views on the character of relict permafrost in the central part of Western Siberia. Computer maps depicting
the extent of relict permafrost and the accompanying database are available based on GIS – technology.
A map of Western Siberian permafrost thickness and
structure (scale 1:2 500 000; V. Baulin editor) accompanied by explanations and borehole catalogues was
issued in 1985 as a result of this research (Baulin &
Dubikov 1982).
Furthermore, geologists and geographers from
Moscow State University under the supervision of V.
Trofimov were engaged in the exploration of permafrost occurrences in Western Siberia in 1970–1985
(Trofimov 1977).
We collected all separate data sources in which the
relict permafrost in the central part of Western Siberia
are mentioned, and have augmented this with new data
on permafrost occurrences derived from geological
surveys of oil- and gas-fields and prospective drilling
for potable water, which were carried out in last decades
(1980–2000).
1 INTRODUCTION
The cryolithozone in the central part of Western Siberia
is characterized by the presence of relict permafrost at
depth. The relict permafrost was formed as a result of
severe climatic conditions in the Pleistocene. Huge
soils masses froze which were both on land and under
the shallow sea at that time. With subsequent Holocene
climate warming the permafrost soils thawed from the
ground surface, but persisted at depth as relics.
Relict permafrost bodies are found in Western
Siberia between 60° N and 64° N at depths between
100 and 300 m, sometimes to 400 m below the surface.
The area of relict permafrost coincides with the territory of the main oil- and gas-fields in Western
Siberia. The development of this territory during the
last 40 years was accompanied by extensive drilling
and the application of a variety of geophysical methods.
The available borehole data and survey results enabled
us to work out an approximate representation of the
distribution of relict permafrost.
3 METHODOLOGY
The processing of our data is based on GIS-technology.
We created a computer database, including all archival
and literature data on the depth of permafrost top and
base using the results of drilling boreholes and of
interpretation of geophysical surveys. The GIS-database used PARADOX software.
It contains the results of testing 1100 geological and
hydro-geological, 120 –3000 m deep boreholes. More
than 900 boreholes show evidence of relict permafrost.
For each borehole, the coordinates, elevation and depth
of drilling were entered into the database. The depth
of the top and base of the relict permafrost and the
permafrost thickness were stored. All data were placed
in *.db or *.dbf formatted tables.
The map of relict permafrost distribution was created with GEOGRAPH software on the basis of these
data. A Gauss-Kruger projection with 72° axial meridian was used (GeoGraph 1996).
Finally, all maps were transferred to ARCINFO format by means of so-called exchange gen-files.
2 DATA SOURCES
Most research on permafrost occurrence in the West
Siberian lowland was carried out by V. Baulin’s scientific group (E. Belopuchova, L. Shmelev, G. Dubikov,
A. Chekhovskiy etc.), and also by V. Solov’ev and G.
Ginsburg. These researchers were the first to bring
attention to the occurrence of deep permafrost horizons so far south in Western Siberia. They described
the methods of discovering deep frozen horizons,
made the first conclusions on the deposition laws of
the relict permafrost, and developed a hypothesis for
its origin.
Their research is based on analysis of data from several hundred boreholes and vertical electrical sounding
(VES) profiles. They compiled summary catalogues
of prospecting boreholes which detected permafrost
in Western Siberia (Baulin 1985).
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Figure 1. The relict permafrost map of the central part of Western Siberia: 1 – the isograms of permafrost base (m, with
reference to sea level); 2 – the same for permafrost roof; 3 – the probable southern boundary of the cryolitozone; 4 – the open
taliks. I-I – section line Noyabrsk-Surgut.
The position of the top of the permafrost and the
base are plotted on the maps as isolines (with the special
graphic software GEOFIT). This GEOFIT-software
allowed us to automatically draw the isolines of depth
of the top of the relict permafrost and its base, with
reference to sea level, using borehole coordinates. We
chose an isoline interval of 50 m. The depth with
reference to sea level is displayed on the map. If the
depth of the top of the permafrost and base relative to
the surface had been used then the picture would have
depended very much on relief.
Isolines of the top of the permafrost and base depth
(relative to sea level) show the wavy character of the
relict permafrost. They define the upward and downward anomalies and allow an estimation of the permafrost thickness at any point (Fig. 1).
Unfortunately, the borehole distribution in the
research area is not uniform. Most data are available
from developed oil- and gas-fields, river valleys and
vicinities of large settlements. Thus the reliability of the
plotted isolines depends on these factors, and sometimes the isolines are approximate.
The relics are found at depths of 80–400 m below
surface.
The depth of the top of the relict permafrost depends
upon exogenous factors such as the age of the geomorphologic expression and hydro-geological, hydrological and landscape conditions of the site.
The depth of the relict permafrost base also
depends on these factors and in addition on endogenous factors: depth to bedrock, neo-tectonic processes, the geothermal gradient etc. (Geocryology
USSR 1989)
The greatest depth and the thickest relict permafrost
are found under the oldest and highest geomorphologic terrains (marine, glacial and lacustrinealluvial high plains with elevations of 100–150 m
above sea level). Shallower and thinner relict permafrost is prevalent at sites with young and low geomorphologic terrain (lacustrine-alluvial and alluvial
low plains and floodplains with elevations of 10–30 m
above sea level).
The depth of the relict permafrost base ranges
from 300 m below sea level (on the left bank of the
Ob River, near Khanty-Mansiysk city) up to 0 m in the
west of the area (near Igrim city).
The top of the relict permafrost in one spot is
about 180 m (below sea level) near Kogalym city.
Usually it is 50 to 100 m below sea level and only
in the western part of the area does it rise above sea
level (up to 50 m).
4 RESULTS AND DISCUSSION
The data obtained during the last two decades have
significantly enlarged the information on relict permafrost and improved our knowledge of this subject.
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Figure 2. Permafrost relic along the section Noyabrsk-Surgut. 1 – overburden: sands, sandyloam and loam; 2 – Oligocene:
interleaving sands, clay and argillites; 3 – Eocene: clay; 4 – contemporary permafrost; 5 – relict permafrost.
geocryological features, but this territory is tectonically non-uniform. At the same time, the highest elevation of permafrost is found at the southern city of
Megion. Here the permafrost is found from 0 to 50 m
(relative to sea level).
The cross-section shown in Fig. 2 represents the
character of discontinuous permafrost in the central
part of Western Siberia. As can be seen on the crosssection between Noyabrsk, Kogalym, and Surgut, the
thickness of relict permafrost decreases gradually
from north to south.
Besides the wide-spread relict permafrost horizon,
some frozen masses can be found 100–150 m below
surface. They are relics of another cold climate of the
Pleistocene epoch (Zemtsov 1972). Isolated masses of
modern (Holocene) permafrost can be found to the
north of Kogalym city. They are just subsurface and
their thickness is 20–50 m. Peat bog or thick coniferous wood landscapes are on the surface.
Usually open taliks underlay the rivers. Taliks are
also formed under favorable geological and hydrogeological conditions. Deep ground water is transmitted through them.
Relict permafrost can even be found in areas with
numerous lakes. For example, there is permafrost in
the lakes district near the Samotlor-oilfield at depths
from 60–100 m (top of permafrost) to 140–200 m (bottom). The permafrost thickness here is 70–105 m. We
The data show that the maximum thickness of the
relict permafrost is 345 m. This thickness is from a
borehole on the right bank of the Vakh River’s mouth,
near Nizhnevartovsk city. The most common thickness
ranges from 100 to 200 m.
The thickness of the relict permafrost depends
mostly on the geothermal gradient. For example, the
geothermal gradient varies near Nizhnevartovsk city
from 2.5 to 3.5°C/100 m (Mizerov 1988). In the southwestern part of the West Siberian cryolithozone
(located within neo-tectonic zones) the observed
increased geothermal gradient is more than 4°C/100 m.
Here, the depth of the base of the relict permafrost
decreases and a reduction of permafrost thickness
ranging to a complete pinching-out is observed.
It is worth paying attention to the relict permafrost
in the western area: the permafrost depth is at about
100 m below surface, while the top of the permafrost
is found at depths between 0 and 50 m (relative to sea
level). Neo-tectonic domes or ledges of platform
mantle are found in these sites and geothermal gradients are up to 4.8°C/100 m.
Rather variable depths of the permafrost top and base
positions are found along the east-west section of the Ob
River (from Surguts to Nizhnevartovsk). The permafrost
situation in this territory is very difficult to interpret.
There are significant quantities of data allowing detailed consideration of all geological and
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are displayed as isolines. It displays the general characteristics of the relict permafrost spreading in the
central part of Western Siberia and allows the estimation of the thickness of the permafrost at any point.
Relict permafrost locations correspond mainly
to natural climatic zones. Local differences in the
permafrost thickness are controlled by neotectonics,
geomorphological, geological and hydro-geological
features. The thickness of the relict permafrost depends
largely on the geothermal gradient.
Our information on relict permafrost differs significantly from data published in available literature:
discovered relict permafrost from 190 to 230 m directly
under Lake Pultankhor (about 2 km diameter) located
to the north of Surgut city.
The heating influence of large, deep water reservoirs
was unable to form an open talik under the lake. It
appears that favorable neo-tectonic and geo-thermal
conditions in this area promote permafrost preservation
even under large lakes.
As shown on earlier published maps (Baulin &
Dubikov 1982, Trofimov 1977) extensive open
hydrogenous taliks are found on the floodplains of
large rivers (Ob, N. Sosva, Konda, Vakh). Nevertheless,
our surveys show that isolated relict permafrost bodies
occur along the floodplain of the Ob River between
Nizhnevartovsk city and Beresovo city. This was determine by exploratory water well drilling. Numerous
such boreholes are located in various places on the
floodplain of the Ob River. It therefore appears that
the open taliks in the relict permafrost body do not
occur all across the wide floodplains of the large rivers,
but are restricted to considerably smaller areas. They
form narrow strips only under river-channels and low
floodplains of the Ob and Irtysh and their tributaries.
Such taliks are shown in Fig. 1 with a symbol.
The isoline map of relict permafrost distribution,
drawn using modern data, has allowed us to adjust the
southern border of the cryolithozone in the central
part of Western Siberia. It should be drawn much farther to the south than is shown on earlier published
geocryological maps. It is obvious that separate thin
horizons of relict permafrost can be found far south of
the east-west section of the Ob River and even to the
south of the 60th parallel.
•
•
•
The southern boundary of relict permafrost should be
moved to the south significantly, possibly to 60°N.
We have changed the configuration of the open
taliks under the Ob valley. The taliks can be found
only as narrow strips under the river channels of the
Ob, Irtysh and their tributaries, instead of under the
full width of the floodplain.
The heating influence of large and deep water reservoirs was unable to form open taliks under lakes. It
appears that favorable neo-tectonic and geo-thermal
conditions in this area promote permafrost preservation even under large lakes.
ACKNOWLEDGEMENTS
This research was supported by the Russian
Foundation for Basic Research, grants 01-05-64256,
02-05-64331.
REFERENCES
5 CONCLUSIONS
Baulin, V. & Dubikov, G. 1982. Map of zoning of Western
Siberian plain on power and structure of a permafrost
(scale 1:2500000). M. PNIIS. (in Russian).
Baulin, V. 1985. Permafrost of oil-and-gas-fields areas
USSR. M. Nedra. 176 pp. (in Russian).
GeoGraph for Windows: User manual. Version 1.5. 1996.
M. IG PAS. (in Russian).
Geocryology USSR. Western Siberia. 1989. Under E
Ershov edition. M. Nedra, 454 pp. (in Russian).
Relief of West Siberian lowland. 1988. Under A. Mizerov
edition. Novosibirsk. Nedra. 192 pp. (in Russian).
Trofimov, V. 1977. Laws of spatial variability engineeringgeological of conditions of the West-Siberian plate. M.
MSU. 272 pp. (in Russian).
Zemtsov, A. 1972. About a connate permafrost in Western
Siberia. Proceeding of All-Union scientific meeting on
geocryology. M. MSU. 262–264. (in Russian).
There are many gas- and oil-fields in the central part
of Western Siberia. In the last decades, by means of
borehole drilling and geophysical research carried out
in this region, a widespread horizon of relict permafrost has been found at depths from 100–150 m up
to 300–400 m below surface.
Modern geological and hydro-geological research
conducted in the region give additional data on the
geocryological features of the territory.
We have processed all modern data and information
on the relict permafrost, using GIS-technology and
specially made electronic database of the boreholes.
The map of relict frozen ground was created using
these data. The top and the base of relict permafrost
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