Nature and Distribution of Frozen Saline Soils on the Russian Arctic Coast

PERMAFROST AND PERIGLACIAL PROCESSES Permafrost Periglac. Process. 13: 83–90 (2002) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ppp.411

Nature and Distribution of Frozen Saline Sediments on the Russian Arctic Coast Anatoli Brouchkov* Research Center for North Eurasia and North Pacific Regions, Hokkaido University, W8 N9, Kita-ku, Sapporo, Hokkaido, 060-0809 Japan

ABSTRACT Frozen saline sediments are widely distributed along the Russian Arctic coast and in other regions.

They have unique properties and are characterized by low bearing capacity. The origin of the salinity is related to seashore processes. The salts within porous solutions are partially taken out upon freezing, and redistributed. Salt moves, together with water, to the freezing front of clay deposits, and, by contrast, away from the freezing front in sand. Salinization is determined by both the conditions at formation, and subsequent processes at cryogenic temperatures. An increase in salinization with depth is observed. This is most likely caused by moving of salts from the upper permafrost layers as the result of the migration of pore water. Salinization in general increases with an increase in ice content. Changes in salinization cause changes of cryogenic structure. An important feature of the saline soils of the Russian Arctic coast is their heterogeneity. Copyright  2002 John Wiley & Sons, Ltd. KEY WORDS:

frozen soils; salinization; permafrost; Russian Arctic coast

INTRODUCTION Frozen saline sediments are widely distributed along the Russian Arctic coast and in other regions, such as Central Siberia. They have special properties, and are characterized by low bearing capacity and occupy a position between frozen and unfrozen soils.

They freeze at lower temperatures and contain more unfrozen water than other frozen materials. Frozen saline sediments are distinguished by their physical characteristics, deformability, and other properties.

This paper examines frozen fine-grained soils, mainly of Pleistocene and Holocene age, that are distributed along the Arctic coast at the surface and which contain soluble salts. Frozen saline sediments are recognized as those containing 0.05% by weight soluble salts compared to a dry soil. * Correspondence to: Dr Anatoli Brouchkov, Research Center for North Eurasia and North Pacific Regions, Hokkaido University, W8 N9, Kita-ku, Sapporo, Hokkaido, 060-0809, Japan.

E-mail: anatoli@nenp.hokudai.ac.jp

Copyright  2002 John Wiley & Sons, Ltd.

Despite the obvious significance of salts for permafrost processes in general (e.g. see Williams and Smith, 1989; Ershov, 1998), the origin of frozen saline soils and their salt distribution needs further study. A problem of past studies was that the grainsize composition and certain basic physical properties are relatively similar to soils without salts. The distribution of frozen saline soils, the salt content, the relationships with unfrozen soils and cryopegs, and their quantitative and qualitative structure are insufficiently investigated. Relevant literature includes that

by Dubicov and Ivanova (1989), who studied the distribution of saline soils in the north of Western Siberia, and Anisimova (1981), Grigor’ev (1987), Neizvestnov (1982) and others who have described conditions of soil salinization. Research described in this paper has been carried out since 1980, in Western Siberia and the Ugor Peninsula. Samples of saline permafrost from over 100 sites along the Arctic coast were examined and freezing experiments were carried out (Brouchkov, 1998).

Received 21 December 2001 Accepted 7 January 2002

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SALINIZATION OF FROZEN SEDIMENTS AND TYPES OF SALINIZATION There are various types of salinization of frozen soils. The salts form during the actual process of sedimentation, through the redistribution of water and salts during the diagenesis of the deposits, and during the variable freezing of deposits of different type. The origin of the salinity is usually presumed to be the sea; marine, glacial-marine, shallow-water and lagoon deposits predominate. During freezing, salts are partially removed, and redistributed. Generally, Salt moves together with water towards the freezing front of clay deposits, and away from the freezing front in sand. There is an insignificant change in chemical composition of porous solutions during freezing. The formation of marine and shallow-water frozen soils that have high salinization is promoted by low negative temperatures, as well as by synchronous accumulation and freezing of marine deposits. It is suggested that salinization is usually synchronous with formation of deposits.

For example, the formation of modern saline frozen soils was observed on the marine foreland near the town of Amderma (Table 1). The saline sandy deposits that were recently below sea level are now freezing at depths up to 3–7 m; salinization increases with an increase in ice content (Figure 1). Beneath the frozen layer, saline underground waters have concentrations up to 50–130 g/l and higher. Frozen clay deposits alternate with unfrozen saline soils

and frozen soils having a higher salinization as one progresses towards a shallow lagoon located behind the foreland (Figure 2).

(a)

Dsal, % 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

W 0.5 1

0.4 0.3

2 freezing front

0.2 0.1

2

4

6

8

10

0 12

Depth, cm (b) 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

W

Dsal, %

5

1

4 3 2

frozen

2 1

unfrozen

0 1

2

3

4

Depth, m Figure 1 Results of freezing of saline soils: (a) water content (1) and salinization (2) of marine silt after experimental freezing; (b) water content (1) and salinization (2) of marine sand, both after freezing on the Amderma foreland.

Table 1 Physical properties of frozen saline soils, Amderma site. (a) Water content, density, porosity and salinity. (b) Grain size. (a) Depth, m

2.5–3.5 4.0–4.5 4.5–5.0 6.1–6.8 4.1–5.0 8.5–9.3 (b) Depth, m

2.5–3.5 4.0–4.5 4.5–5.0 6.1–6.8 4.1–5.0 8.5–9.3

Soil

Water content, W

Sandy silt

0.23 0.30 0.24 0.22 0.24 0.30

Silt Soil

Sandy silt

Silt

Density, g/cm3 wet dry 1.83 1.78 1.80 1.88 1.83 1.67

1.49 1.38 1.45 1.55 1.48 1.29

Density of particles, g/cm3

Porosity, n

Salinization, Dsal , %

2.68

44.4 48.5 45.8 40.7 44.8 52.2

0.2 0.14 0.2 0.16 0.16 0.8

2.70

Grain composition, % Size of particles, mm 2–1.0

1.0–0.5

0.5–0.25

0.25–0.1

0.1–0.05

0.05–0.01

0.01–0.005

<0.005

0.2 0 0.1 0.1 0.1 0.1

0.3 0.1 0.3 0.2 0.1 0.5

8.4 0.3 1.3 0.5 0.6 2.1

21.7 2.1 9.2 5.4 6.3 9.2

41.6 55.2 43.1 58.4 56.3 14.7

19.7 27.7 28.8 20.8 20.3 36.1

3.0 0.8 8.9 5.4 7.2 14.7

5.1 13.8 8.3 9.2 9.1 22.6

Copyright  2002 John Wiley & Sons, Ltd.

Permafrost and Periglac. Process., 13: 83–90 (2002)

Frozen Saline Sediments on the Russian Arctic Coast 85

Water content Salinization, %

The process of formation of frozen saline deposits along the Arctic coast is presented in Figure 3. If the deposits are marine in origin, the pore water is saline and the deposits freeze subaqueously, or after recession of the sea. Fluctuations in sea level, temperature regime, alternations in conditions of sedimentation, and the possibility of freezing from different directions result in a complex distribution of salts in such frozen sediments. If salinization takes place after the formation of deposits, by incursion of the sea, then salinization is secondary, or asynchronous. Frozen saline soils are formed during freezing as the sea regresses.

It is possible to distinguish between autogenetic and allogenetic types of salinization. One example of autogenetic salinization is a marine deposit saturated by sea salts; these occupy large areas of the Arctic coast of Eurasia and North America. Even deposits of terrestrial origin may contain salts from previous sea incursions, or from other sources. For example, the alluvial deposits of the coastal areas of Yamal are saturated with sea salts. If terrestrial deposits are saturated by salts of other origins, this type of salinization is allogenetic. Examples of allogenetic salinization are the lake and slope deposits of Yamal, some eluvium deposits of Chukotka, and

2 1.5 1 0.5 0

2

1 0

2

4

6

8

Depth, m Figure 2 The distribution with depth of water content (1) and salinization (2) within marine deposits in the Amderma lagoon.

Stratigraphy: 0.5–1.0 m organic; 1.0–4.5 m sand; 4.5–8.5 m silt.

Synchronous type Marine deposits; saline pore solution Freezing Continental and marine deposits affected by sea level raise and by sea water saturation

Frozen saline soils

Asynchronous type

Figure 3 The major types of frozen saline soils. If salinization is formed simultaneously with the freezing of deposits, it is termed syncryonous. If there is a difference between time of freezing and salinization, then the type of salinization is termed asyncryonous.

Copyright  2002 John Wiley & Sons, Ltd.

many glacial deposits of Canada that contain sea salts.

Alluvial deposits can also be saturated by salts during their deposition. This is what is observed in the Lena valley and in areas where evaporation is greater then precipitation—this is salinization of a continental type. In the last case, the saline composition is different from sea salts: normally the salts contain calcium instead of sodium and sulphur instead of chloride.

FROZEN SALINE SOILS RUSSIAN ARCTIC COAST

ALONG

THE

In general, frozen saline sediments up to 10–20 m in depth along the Arctic coast of northern Russia contain salts within the limits of 0.05–2%. They belong mainly to the sea type of salinization (Tables 2 and 3). As a rule, the active layer, except for some slope and coastal sites, is not saline because it is normally washed out by ground waters (Brouchkov, 1998).

The alternation of layers having different salinization is typical of marine deposits of shallow-water where sharp changes in sedimentation and freezing occur.

According to Danilov (1974), high salinization distinguishes the Pleistocene-age, mostly clay, deepwater marine deposits of the Pechora lowland and Yamal; any shallow-water marine deposits are less saline. However, data in this paper show that shallowwater marine deposits may have high salinization.

For example, the salinity of Holocene-age lagoon clay deposits at one locality on the Ugor Peninsula are illustrated in Figure 2. Typically, the smaller the grain size, the higher the salinization (Dubicov and Ivanova, 1989). It has been established that the high salt content is characteristic of the autogenetic type of salinization. Alluvial deposits of the allogenetic type are poorly saline downstream of the Haipudir Bay coast. Also, the alluvial and lake deposits of Yamal are considerably less saline than marine ones (Dubicov and Ivanova, 1989).

In sandy shallow-water marine strata, at depths of 10–20 m from the surface, there is a relatively uniform distribution of salinization, or a slight increase with depth. Clayey frozen saline soils are of two types: 1) homogeneous or layered (including inclusions of cooled soils and cryopegs; 2) increasing salinization to depths of 10–15 m. A non-uniform distribution of salinization with depth can be caused by conditions of formation; for example, by the regressive character of geological phases and the freezing of deposits. An increased salinization, as reported by Dubicov and Ivanova (1989), is usually related to a zone of adfreezing of soils with ice.

This is typical for modern lagoon deposits, such as Permafrost and Periglac. Process., 13: 83–90 (2002)

86

A. Brouchkov Table 2

Ion composition of frozen saline soils and waters of the Russian Arctic coast (%).

Area Kara sea Cryopegs Pechora sea coast Amderma Central Yamal Yamal (Harasavei) Yamal (Uribei) Chukotka Shmidt Pevek

HCO3

Cl

SO4

Ca

Mg

Na C K

Total salt content, g/l

5 5.8 3.1 4.6 7.5 0.7 2.2 6.5 0.3 7.5 2.3

42 6.0 61 45 39 48 44 39 34 39 43

2.8 — — — 3.3 0.7 3.2 3.5 15.1 3.9 5.0

1.4 5.0 5.2 2.1 3.2 2.2 0.7 2 5.6 3.9 3.0

3.5–7.5 5.2 5.2 9.5 11.7 6.1 1.6 1.0 5.0 5.9 1.0

40 26 25 38 34 41 47 47 39 40 46

25.9 9.1 57.9 33 0.7 1.3 — 0.76 1 — —

Table 3 Average salinization of frozen soils of the Russian Arctic coast.

Area

Deposits

Sampling site

Salinization, %

European part of Russia

Marine and alluvial deposits

Haipudir Bay Saremboi river Pionerni village Amderma Kolguev island Pechora river

0–0.3 0.1–0.2 0.1 0.1–1.5 0.2–0.8 0.1–0.2

Western Siberia

Marine, lake, slope and alluvial deposits

Bovanenkovo Sharapovi Koshki Northern Yamal Southern Yamal Harasavei Nei-to lake Ob-Pur area Dikson Gidan Suhoi Polui river

0.03–2.1 ¾2.4 0.5–2.0 0.2–0.5 0.2–0.4 0.2–0.6 0.05–0.1 0.5–1.0 0.4–1.2 0.6

Eastern Siberia

Marine deposits

Chukotka Rilpihin lagoon Shmidt Pevek Anadir Lena river Vankina Guba Alazeya river Hallerchenskay tundra Anadir Chukotka

0.2 1.5–3.0 ¾1.0 0.1–0.5 0.2–0.5 0.1 0.4–1.2 0.2–1.0 0.8–2.0 0.3 0.1–0.2

Eluvial, lake and alluvial deposits

the Amderma lagoon (see Table 1, and Figures 1 and 2). These sediments are characterized by a homogeneous or layered distribution in salinization.

Because this is caused by conditions of formation it is termed ‘‘conditional-layered’’, or primary, Copyright  2002 John Wiley & Sons, Ltd.

type. As a rule, these have high salinization. A progressive increase of salinization with depth is observed in sections of ‘‘imposed’’, or secondary, type. This increase is most likely caused by the process of salts being lost from the upper layer Permafrost and Periglac. Process., 13: 83–90 (2002)

Frozen Saline Sediments on the Russian Arctic Coast 87

Copyright  2002 John Wiley & Sons, Ltd.

Salinization, %

(a)

1.4 1.2 1 0.8 0.6 0.4 0.2 0 1-4 M

4-7 M

7-10 M

10-15 M

Depth 1.2

Salinization, %

(b)

1

1

3

0.8 0.6

2

0.4

5

4

0.2 0 1-4 M

4-7 M

7-10 M

10-15 M

Depth

Salinization, %

(c)

0.7 1 0.6 0.5 0.4 0.3 0.2 0.1 0 1-4 M

2

3

4 5

4-7 M

7-10 M

10-15 M

Depth Figure 4 Distribution of salinization with depth: (a) marine Palaeogene deposits of Tazovsky Peninsula; (b) marine and glacial deposits of Northern Yamal (1), Central and Southern Yamal (2), Gidan (3), Tazovsky Peninsula (4), Ob-Pur area (5); (c) marine and coastal deposits of Late Pleistocene (the same legend as for b). Source: Unpublished data supplied by Grigory Dubicov.

Water content, %

of permafrost due to migration of salts and salts moving out in the active layer. There is a seasonal movement of unfrozen water carrying salts in freezing and frozen soils. This process is directed according to a gradient of temperature: upwards in the winter, downwards in the summer. For example, winter water and salt flow is directed towards the active layer whose salts are washed away during the summer. Any summer water and salt flow causes salt accumulation at depth. The process of migration of water and salts under different gradients of temperature is considered in other papers (Brouchkov, 1998, 2000).

The ‘‘conditional-layered’’ type of salinity is characteristic of late Pleistocene and Holocene deposits (e.g. Figure 4). The sediments of older deposits of high marine terraces, where there was sufficient time for the removal of salts, normally belong to the ‘‘imposed’’ or secondary type. Preservation, with significant differentiation in depth, of highly-salinized Palaeogene deposits is explained, apparently, by the large initial content of salts.

Salinization reduced with an increase in ice content (Figure 5) locally. This reduction is connected to the replacement of saline pore water solution by ice during freezing. The reduction in salinization is due to the moving-out of salts due to their migration. Inadequate attention is given to this process in the literature, despite the well-known example of removal of salts from sea ice (e.g. Savel’ev, 1989).

Gradual removal of salts from upper layers of permafrost occurs under natural conditions. The transition from frozen saline to unfrozen soil is gradual in space, there being no well-defined border. However, due to their thermal properties, the temperature regime of saline soils is special.

The connection between the lithologic structure of Pleistocene deposits and their salinization is also evident in the Pechora lowland. The occurrences of more fine-grained and therefore, more saline soils is characteristic of northern coastal areas (Danilov, 1974). An increase in salinization of alluvial deposits is also observed in the down-river direction in Western Yamal (Dubicov and Ivanova, 1989).

Sea incursions play a major role in salinization.

Certain types of marine deposits are formed in this way (Danilov, 1974). Incursions also cause thawing of frozen deposits beneath the sea and the subsequent saturation of pores by salt water. One of largest incursions was immediately post-glacial.

0.6 0.5 0.4 0.3 0.2 0.1 0 0

0.5

1

1.5

Salinization, % Figure 5 Salinization and total water content of frozen marine Pleistocene silts of Yamal Peninsula.

Permafrost and Periglac. Process., 13: 83–90 (2002)

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Marine deposits are fixed at heights of 150 m a.s.l.

(Kanin Peninsula), 120 m a.s.l. (northern Timan), 120 m a.s.l. (Pechora lowland), and at 25–300 m a.s.l. (Pai-Hoi). The frozen deposits inundated by the sea melted and salts penetrated in porous solution (Baulin et al., 1981). Then, the deposits were frozen during a cooling of climate and were probably melted again later. An essential influence in preserving the salinity of frozen soils was the climatic optimum of the Holocene. The area of thawing would have reached 68–69° northern latitude. Thus, frozen deposits would have melted in all territory of Bolshezemelskay tundra and even in the southern part of Ugor Peninsula (Baulin et al., 1981). For Western Siberia, the southern limit of this zone passed, most likely, close to the polar circle. Frozen saline deposits of marine origin are problematic south of this border.

The marine type of salinization is normally characteristic for coastal areas with absolute altitudes up to 150–200 m a.s.l., and north of the border of melted frozen soils during the climatic optimum of the Holocene. Asynchronous salinization is characteristic for the non-marine deposits in this area. Continental salinization is observed in dry areas of modern, mainly, alluvial, lake and slope sedimentation.

A mixed type of salinization is characteristic of the ‘‘land-sea’’ zone of interaction and this is distributed throughout the Arctic coast, where salts of both marine and continental origin participate simultaneously in the salinization of deposits.

Frozen saline soils of both marine synchronous and asynchronous types occur in the European territory of Russia—in Kolguev island, and the Southern island of Novaya Zemlya, Kanin Peninsula, Haipudir Bay coast, and downstream in Pechora river. Soils cooled below 0 ° C and cryopegs are common on the marine terraces and lowlands of the coast of the Barents Sea (Bolvansky, Pahancesky, Haipudir and Pechora bays, and also in the deltas and downstream of the rivers Naruta, Black, Moreu, and Karotaiha).

It is established that, for the Haipudir Bay coast and Saremboi-Yaha valley, salinization of soils is about 0.1% and increases with depth. Frozen saline soils also occur on Ugor Peninsula. For example, according to results obtained by the drilling of more than 100 boreholes, salinization varies between 0.1 and 1.5%, and increases with depth.

The Yamal Peninsula is characterized by frozen soils of the marine synchronous type of salinization.

The asynchronous type is more common in the eastern part of the peninsula and is connected with the distribution of alluvial deposits. Continental alluvial frozen deposits are saline on Yamal Peninsula in the zone of sea influence. The deposits of marine, alluvial, Copyright  2002 John Wiley & Sons, Ltd.

lake, and slope genesis are saline, with average values from 0.03 to 2.1%.

The zone of frozen saline soils neighbouring the Arctic coast gradually narrows to the east in Middle and Eastern Siberia. This is related to high elevations and to the prevalence of soils of continental origin. Deposits of the asynchronous marine type occur in the areas of the Lena and Kolyma rivers. The saline soils are related to marine Pleistocene and Holocene deposits within the limits of the Northern Siberian lowland, along the coasts of Yakutia and the Chukotka Peninsula, on the Anadir lowlands. For example, saline marine deposits (salinization 0.2–0.5%), and saline slope and eluvium deposits have been described from Chukotka (Krivonogova and Kagan, 1973). A large area of continental salinization occurs in the Lena river valley where evaporation exceeds precipitation. Continental salinization is also observed in the intermountain depressions of the Baikal region, and also on the plains and plateaus of Central Asia. Frozen saline soils reach depths of 40–80 m in the large lake depressions of Tibet.

Saline soils, mainly marine in origin, are widely distributed along the Arctic coast of North America.

Continental salinization, by analogy with the Lena valley, probably occurs in the Mackenzie valley, up to the southern permafrost border. However, salinization of soils in the Mackenzie valley as a whole is insignificant (personal communication, E. Hivon).

Frozen saline soils are thought to occupy significant areas on Banks, Somerset, Devon, and Victoria islands, in Coronation and Queen Maude Gulfs, on other high Arctic islands, and also on the northern coast of Greenland. The highest salinization is on Baffin Island and marine synchronous salinization occurs in Hudson Bay on low marine terraces.

STRUCTURE AND COMPOSITION OF FROZEN SALINE SOILS The chemical and mineral composition of frozen saline soil is, as a rule, close to the composition of frozen soils that do not contain salts. As an example, the mineral composition of the sandy and silty fractions of soils on Yamal and Ugor peninsulas is characterized by the prevalence of quartz (67–85%), with some plagioclase. There are also hydro-micas, kaolin, and montmorillonite in the clay fraction. Organic substances are characteristic of saline soils, as they are connected to low temperatures and fast freezing.

Several studies of the chemical composition of porous solutions (e.g. Velli, 1980; Dubicov et al., Permafrost and Periglac. Process., 13: 83–90 (2002)

Frozen Saline Sediments on the Russian Arctic Coast 89

1988; Dubicov and Ivanova, 1989; Aksenov and Brouchkov, 1993; Brouchkov, 1998 and others) show that they differ by the constancy and prevalence of sodium chloride (NaCl). Secondary processes (i.e. an increase in content of sulphur-ion (SO4 ) and other processes) influence the formation of cryogenic structures resulting from pore water solutions (Anisimova, 1981; Dubicov and Ivanova, 1989). Increases in the relative contents of calcium, sulphur, and carbon acid ions occur with subsequent thawing. The prevalence of calcium, sulphur, and carbon acid ions is characteristic of frozen saline soils of Central Yakutia and other areas of continental salinization (Anisimova, 1981).

A fine-grained composition is usually characteristic of frozen saline soils of marine origin. The variable sizes of gulfs and lagoons, their small depth and partial freezing, and alternations in conditions of sedimentation cause fluctuations in composition and structure of sediments. These particularities, together with salinization, lead to low bearing capacities (Table 4).

Salinization and its chemical composition, affects the structure of frozen sediments and its cryogenic structure. The number of subvertical ice lenses increases and their size decreases at high levels of salinization (Khimenkov and Minaev, 1990; Brouchkov, 1998). Also, the size of crystals decreases with an increase in salinization. Field studies show that, as a whole, the cryogenic structure of saline soils differs from non-saline soils. An increased density of soils and a layered cryostructure are characteristic for the asynchronous type of salinization which, as a rule, is normally insignificant and only about 0.05–0.15%.

Frozen soils of the synchronous type are differentiated by weak sorting and low density, increased ice content, and greater salinization. An important feature of the structure of saline soils is their heterogeneity; a combination of frozen (ice inclusions) and

Table 4 Bearing capacity of frozen saline sand under the base of a post foundation.

Salinization Dsal , % 0.05 0.1 0.15 0.2 0.3 0.5

Bearing capacity, kPa (kg/cm2 ), at temperature, ° C 1 2 3 4 90 (0.9) 110 (1.1) 50 (0.5) 90 (0.9) 25 (0.25) 70 (0.7) 15 (0.15) 50 (0.5) 30 (0.30) 15 (0.15)

180 (1.8) 130 (1.3) 110 (1.1) 100 (1.0) 60 (0.6) 20 (0.2)

Copyright  2002 John Wiley & Sons, Ltd.

250 (2.5) 170 (1.7) 140 (1.4) 120 (1.2) 90 (0.9) 30 (0.3)

unfrozen (saline mineral layers) elements simultaneously characterize the cryogenic structure.

CONCLUSION Frozen saline soils are characterized by low bearing capacity, and occupy a position between frozen and unfrozen soils. The several ways of formation of salinization of frozen fine-grained soils, as part of the sedimentary process in the cryolithozone, have been described. Salt, as a rule, moves collectively with water to the freezing front of clay deposits and away from the freezing front in sand. The distribution of salinization is connected to the structure of sediments and is determined by both conditions of sedimentation, and subsequent processes when frozen.

The marine type of salinization is characteristic for most areas of the Russian Arctic coast with altitudes of up to 150–200 m a.s.l. and to the north of the border of thawing of frozen soils during the Holocene climatic optimum. The salts within porous solutions are partially removed and then redistributed during the freezing and thawing process. An increase of salinization with depth is usually observed; this is caused, most likely, by the moving-out of salts from the upper permafrost layer as a result of the process of water and salt migration.

The composition, structure, and properties of frozen saline soils are distinguished by a combination of attributes of frozen and unfrozen fine-grained soils.

Salinization increases with an increase in ice content; changes of salinization cause changes in cryogenic structure. Finally, an important feature of the structure of the saline soils of the Russian Arctic coast is their heterogeneity.

ACKNOWLEDGEMENT I am grateful to Dr Grigory Dubicov for the assistance in the research and to Dr E. Hivon for data on saline permafrost in northern Canada. I also thank Professor Hugh French, Editor-in-Chief, for undertaking substantial editorial modifications.

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