Vladimir B. Spektor, Yaroslav I. Torgovkin, Alena A. Shestakova, Valentin V. Spektor, Lena D. Ivanova, Boris M. Kozmin

1. Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk 677010, Russia

2. Diamond and Precious Metal Geology Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk 677980, Russia

Engineering Geological Map of the Sakha (Yakutia) Republic?

Vladimir B. Spektor1?, Yaroslav I. Torgovkin1, Alena A. Shestakova1, Valentin V. Spektor1, Lena D. Ivanova1, Boris M. Kozmin2

1. Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk 677010, Russia

2. Diamond and Precious Metal Geology Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk 677980, Russia

The Engineering Geological Map of the Sakha (Yakutia) Republic covers about 3 million kilometers which is one-fifth of the territory of Russia. The map displays ground and geocryological conditions and active faults. Seismic intensity, schemes of zoning by factors of engineering geological conditions, and the general scheme of engineering geological zoning of the Sakha (Yakutia) Republic or the SR(Y), are shown on the inset maps. The map is required to provide information for planning, construction and exploitation of engineering structures in the SR(Y). A distinguishing feature of the map is the indication of almost blanket distribution of the frozen ground class. Types of the frozen ground class are separated by lithology, while ground varieties are separated by temperature. Fresh and ultra-fresh suprapermafrost water is predominant within the territory. The compiled map indicates parts of the Arctic-Asian and Baikalo-Stanovoi planetary seismic belts that make engineering geological conditions more complicated.

engineering geological map; ground types; frozen ground; exogenous processes; Sakha (Yakutia) Republic

1 Introduction

The Engineering geological map of the Sakha (Yakutia) Republic (SR(Y)), scale 1:1,500,000, is needed for planning, construction, and exploitation of engineering structures in the SR(Y) and adjacent regions. Scientific purposes of the map include systemizing data according to distribution features of various natural factors and their interactions, as well as predicting environmental changes under construction and exploitation of engineering objects.

The map shows ground and geocryological conditions (Figure 1). Inset maps show seismic intensity, schemes of zoning along various factors of engineering geological conditions, and a general scheme of engineering geological zoning of the SR(Y) territory. The proposed map may be considered as a continuation of work on compiling the Modern Engineering Geological Map of Russia started in 2008 under the supervision of V. S. Krupoderov and V. T. Trofimov.

An electronic variant of the map is compiled in the format "ArcGIS 10 version 10.1". The cartographic information on the electronic map montage was grouped according to the map legend into the following units: (a) engineering geological groups, ground types, and geocryological factors; (b) hydrogeological factors; (c) active faults; (d) topography; (e) hydrographic network. Small-scale (1:15,000,000) inset maps of zoning ofengineering geological conditions were compiled. Each region is defined in terms of general features of geological structure, tectonic aspects, neotectonics, exogenous processes in operation, aggressiveness of suprapermafrost water, prevailing complex of ground types and varieties. Particular small-scale zoning schemes of suprapermafrost water, cryolithozone structure, and seismic intensity were compiled.

2 Materials and methods

The data used for the map production were derived from the materials of meso-scale geological survey, as well as from the following summaries performed on the basis of the same materials: Geological map of the Yakutian ASSR, scale 1:1,500,000 (1978); Geological map of the Sakha (Yakutia) Republic, scale 1:1,500,000 (2006); monograph Geology of Yakutian ASSR (1981); Geocryological map of the USSR, scale 1:2,500,000 (1997); sheets of Geological map of the Sakha (Yakutia) Republic, scale 1:500,000, published in different years; manuscripts from the holdings of the Geological Committee on Geology and Subsoil Use of the Sakha (Yakutia) Republic and Melnikov Permafrost Institute SB RAS.

The main cartographic featureof the present map isa ground factorof engineering geological conditions which is indicated by color. The more stable ground varieties and their combinations are shown on the map by toned down and light shades while the most unstable ones are shown by toned up and heavy shades.

Under conditions in which permafrost occurs everywhere, thegroundis a constituent of a single cryogenic geosystem. A cryogenic geosystem (Khimenkov, 2013) designates a geological formation (in our case, a ground body or a complex of ground bodies) along with assemblage of ice inclusions (cryogenic texture). Let us consider in particular a ground constituent. The term "ground" is understood as "any subsurface rocks, soils, sediments and anthropogenic geological formations considered asmulti-component dynamic systemsinvestigated in relation to planning, accomplishing or completing engineering human activity" (Trofimov, 2000). The complexity of the ground is also stressed by V. T. Trofimov in his later works. "In a general case, the ground is a mineral and mineral-organic, organo-mineral, multicomponent, multiphase system including solid, liquid, and gaseous components..." (Trofimovet al., 2011). In our case, for the continuous permafrost zone, a ground component is a basis of a cryogenic geosystem which consists of two sub-systems: lithogenous and cryogenic ones. According to Khimenkov (2013), "a lithogenous basis is a system-forming factor which, via determinate variations of material composition, identifies characteristics of cryogenesis processes and ultimately, spatial distribution and morphology of ice elements. The choice of lithogenous [ground] constituent as a base structural element permits separating boundaries of cryogenic [frozen ground] geosystems of different hierarchy levels". From this system position V. T. Trofimov considers syncryogenic and epicryogenic rocks as ground. The map shows cryogenic geosystems of low hierarchy levels. These are ground "mono-rock" bodies or their combinations, integrated according to matching physical properties and, primarily, rock strength parameters controlled by various ground temperatures, among other factors.

Most of the area concerned belongs to continuous permafrost zone (Figure 2). Nevertheless, in the scopes of the prescribed approach, the cryogenic factor does not have an independent significance in assessment of physical properties of the ground. As concluded above (Melnikovet al., 2010; Khimenkov, 2013) this factor forms a cryogenic sub-system of the single cryogenic geosystem. "[A] cryogenic sub-system represents ice inclusions or consists entirely of ice" (Khimenkov, 2013). This definition does not include a temperature indicator. Such an indicator is of great significance for our map because it influences the ground strength parameters. The frozen dispersive ground characterized by temperatures above ?5 °C is termedplastic-frozen ground. The ground characterized by lower temperatures is termedhard-frozen ground.

Numeration is used for designating thecryogenic constituent(temperature and iciness). The latter allows separating frozen ground varieties. Finally, the ground variety is shown on the map in fractional form. The numerator denotes the ground type and corresponds to the number of a sign in the Legend section "Ground Conditions". The denominator characterizes the ground variety and corresponds to the number of a sign in the Legend section "Geocryological Factors".

The hydrogeological factor is portrayed on the map by speckle. Within the area, the most abundant hydrogeological factor is the suprapermafrost gravitational water of cryolithozone (Figure 2), which is subdivided into three subtypes: suprapermafrost perched water, water of the seasonal thaw layer, and suprapermafrost ground water (Shepelev, 2011).

Exogenous and endogenous processes as well as seismic intensity are shown on the inset maps. Modern active faults are shown on the map by red lines. The map legend consists of three sections. Each section addresses the most important factors of engineering geological conditions: ground and geocryological constituents, and hydrogeological factors. Individual symbols are used for indication of the distribution areas of ground types and varieties which are expressed in the map scale and have thickness of 10 m or more.

Figure 1 Fragment of the Engineering Geological Map of the Sakha (Yakutia) Republic with the legend

Map Legend. Ground (lithogenous) constituents (Figure 1) occupy the first section of the legend. Frozen ground in engineering geology is subdivided into the same taxons as thaw ground. In comparison with traditionally separated groups of rocky, half-rock, and dispersive ground, the groups of combination of rocky and half-rock ground as well as half-rock and dispersive ground were separated.

The "two-layer" structure wherein the upper part represents dispersive ground from 3 to 10 m thick while the lower part represents other classes and groups of ground is also separated into an individual group. In total, the legend includes 124 types and varieties of ground which can influence engineering geological properties.

The cryogenic constituent is provided in the second section of the legend (Figure 1).

Hydrogeological factor. Depth and aggressiveness of suprapermafrost water are the most significant factors for an assessment of engineering geological conditions. Aggressiveness of suprapermafrost water is subdivided into the following types: sulphate, general acid, non-aggressive water and water with various degrees of aggressiveness. Non-aggressive suprapermafrost water is distributed in most of the area. The depth of this water is less than 3 m (Figure 3).

Seismic intensity. About 1.5 million square kilometers of Yakutia territory belongs to earthquake zone that is 30% of the whole seismically active zone of Russia. Earthquakes with intensities of 6 to 9 on scale MSK-64, are known to take place here and may occur in future. Earthquake areas are located south and south-east of the Siberian platform and Verkhoyano-Chukot orogen, mostly at boundaries of the large lithosphere plates.

Figure 2 Cryolithozone zoning of the Sakha (Yakutia) Republic.

The territory of Yakutia is crossed by two seismic belts: Arctic-Asian (AASB) and Baikalo-Stanovoi (BSSB) (Figure 4).

The AASB includes the Gakkel Ridge in the Arctic Ocean. Southward, it crosses the Laptev Sea shelf, and extends south-east through the mouth of the Lena River, Yana Gulf, and Cherskogo Ridge System to the Sea of Okhotsk and Kamchatka where it joins the seismic belts of the Pacific Ocean. A series of seismic events ranging from 6 to 10 in epicenter is known within the AASB. The most damaging of them were registered in the northern Verkhoyansk Range close to Bulun and Kyusyur villages in 1927–1928. One of the largest events was the magnitude 9 Artykski earthquake in 1971. Its epicenter was restricted to the zone of influence of Tchai-Yureinski fault bounding the Upper-Nera depression from north-east. The earthquake perceptibility area was about 1 million square kilometers within the SR(Y), Magadan Region, and Khabarovsk Territory. A magnitude 8 event occurred in November 2011 within the Ulakhan Range, in the zone of the same-named fault. A magnitude 8–9 Abyi earthquake occurred in March 2013 on northeast-facing slopes of the Moma Range in the zone of Ilin-Tas and Myatis faults. Its macro-effects were registered over 500,000 square kilometers away.

Figure 3 Suprapermafrost water distribution in Yakutia.

Figure 4 Seismic intensity of Eastern Siberia. M: magnitude of earthquake; H: depth of seismic focus

The BSSB represents a stripe of earthquake epicenters stretching eastward of the Baikal Lake. It crosses the Middle Olekma River in Southern Yakutia and is traced by mountain chains of the Stanovoi Range to the Sea of Okhotsk. The strongest magnitude 9–10 events were registered along the Middle Olekma River. These were the Olekminsk and Nyukzha earthquakes in 1958 and Tas-Yuriakh earthquake in 1967.

3 Discussion and conclusions

The Engineering Geological Map of the SR(Y) produced by the principles concluded above permits description of engineering geological conditions for the area, which is rather heterogeneous by its geological structure and natural conditions. Zoning of the SR(Y) area was undertaken according to properties of engineering geological conditions taking into account regional factors under the principles stated by Trofimov and Krasilova (2007). The largest regional units indicated on the map areareas.The areas belong to large tectonic structures (platform, orogen, young platform,etc.) where the same-type relief (mountains, plain, plain-lowland or other) is prevailing. Units of subordinate rank areregions. Their main feature is a predominant distribution of ground referred to a class or group, or their stable combinations.

The following engineering geological areas are separated within the SR(Y) territory: I. Plains and Plateau of Central Siberia; II. Verkhoyansk-Kolyma Mountainous Area; III. Area of Primorsky Lowlands and Shelf; IV. Okhotsk-Chukotka Area; V. Aldan-Stanovoi Area (Figure 5).

I. Engineering Geological Area of Plains and Plateau of Central Siberia

The area belongs to one large tectonic structure––the Siberian Platform. It is characterized by active positive neotectonics movements likely controlled by inheriting tectonic movements, and somewhat isostatic rebound as well as proximity to the planetary tectonic seismic belts. The area is bounded by the Baikalo-Stanovoi mountain belt from the south and by the Verkhoyansk-Chukot belt from the east. Due to inheriting tectonic movements during the Mesozoic and Cenozoic eras, one of the main features of the platform is that the more ancient (Precambrian) rocks are restricted to the positive morphostructures while the younger rocks are restricted to negative ones. The summaries of regions separated within the area are listed as follows:

I.1 Anabar Regionis located at the northwestern part of the area within the large structure of the Siberian Platform–– Anabar Massif (Mokshantsev, 1975; Geology of the Yakutian ASSR, 1981). It is characterized by predominant distribution of cryotic Archaean rocky ground: gneiss, crystalline schist, quartzite, and, rarer, calciphyre and marble. One of the main features of the region is the deepest permafrost thickness (about 1,500 m) in Siberia. The region is referred to as the Anabar Upland. The summit plain is located at elevations of 400–500 m a.s.l.. In addition, the maximum elevation points reach 700 m. Non-aggressive suprapermafrost water to a depth of 3 m is widespread here, and active exogenous processes result in formation of talus, slumps, slides, stone rivers, frost cracking, solifluction, and deep erosion.

I.2 Olenek Regionbelongs tectonically to Anabar Anteclise (Mokshantsev, 1975). This region is characterized by a predominant distribution of cryotic Cambrian rocky carbonate ground. Cryotic Riphean and Vendian rocky terrigenous-carbonate ground is less abundant. Scarce isolated fields within the region are composed of cryotic effusive-terrigenous and terrigenous half-rock ground of Permian, Triassic, and very rare Carbonic periods. The region occupies the eastern part of the Central Siberian Plateau, and the summit plain is located at elevations 200–400 m smoothly rising northward. Active exogenous processes represent (in descending order) talus formation, stone rivers, solifluction, karst in carbonate ground, frost cracking, and swamping. Non-aggressive suprapermafrost water to a depth of 3 m is widespread in the region.

I.3 Lena-Vilyui Regionis restricted to the upper part of Vilyui Syneclise and Angara-Vilyui Fore Deep (Mokshantsev, 1975; Geology of the Yakutian ASSR, 1981). Hard-frozen ground is of predominant distribution here. It represents the combination of Middle Jurassic terrigenous dispersive and half-rock ground composed (in descending order) of sandstone, sand, conglomerate, gravel, clay, siltstone, mudstone, and coal. Carbonaceous ground of the Paleozoic carbonate basement often crops out at low elevations. Outcrops of frozen soluble ground are known south-west of Suntar Bend in the basin of Kempendei River (Kempendei dislocations). They represent rock salt and gypsum (Devonian Kygyltus and Namdyr suites). The relief is referred to the transition zone between the Central Yakutian Plain and Central Siberian Plateau. The summit plain is located at elevations 200–400 m. Exogenous processes are moderate, representing talus formation, slides, solifluction, stone rivers, frost cracking, side and bottom thermal erosion. Non-aggressive suprapermafrost water to a depth of 3 m is widespread in the region. Aggressive sulphate water to a depth of 3 m is widespread in the Kempendei dislocations zone as well as in the basins of the Middle Bolshaya and Malaya Botuobiya rivers.

I.4 Tungus Regionis located within the Tungus Syneclise. Hard-frozen Permian and Triassic half-rock and rocky volcanogenic-terrigenous ground as well as cryotic rocky magmatogene (basalt and diabase) ground are predominant here. Frozen Lower Paleozoic carbonaceous and terrigenous-carbonaceous rocky ground occurs at low elevations in river valleys. The region is referred to the Central Siberian Plateau. The summit plain is located at elevations 300–500 m and the terrain is characterized by high roughness and relatively high elevation changes. Predominant active exogenous processes include talus formation, stone rivers, rock falls, frost cracking, and bottom erosion. Not-aggressive suprapermafrost water to a depth of 3 m is widespread in the region.

I.5 Central Yakutian Regiontectonically corresponds to the central part of the Vilyui Syneclise. Plastic- and hard-frozen ice-rich dispersive ground (silts and loams) of Quaternary ice complex, cryotic dispersive quicksand ground of sand dunes (local name tukulans), hard- and plastic-frozen icy sand ground infilling wide river valleys are of predominant distribution. Hard-frozen rudaceous ground of glacial genesis is widespread in the Verkhoyansk Range foreland. Plastic-frozen ground of the dispersive and half-rock combination represented by sand, silt, clay, sandstone, siltstone and coal is widespread on the periphery of Vilyui Syneclise and in single patches among dispersive ground. These combinations are referred to as the Cretaceous strata. The "two-layer" sections wherein the upper part to the depth of 10 m is composed of plastic-frozen icy dispersive ground while the lower part represents both plastic-frozen and hard-frozen dispersive or half-rock ground are also distributed here. The whole territory belongs to the Central Yakutian Plain. It is characterized by a low position of the summit plain (100–200 m). The most active exogenous processes are thermokarst, swamping, aeolian transition of sand (tukulan formation), solifluction, side erosion, and thermal suffosion on tukulans. Non-aggressive suprapermafrost water to a depth of 3 m is widespread in the region.

I.6 The Upper-Lena Regionis referred to the Pre-Baikal Fore Deep. Frozen and thawed rocky ground types and varieties with low ice content represented by carbonaceous and terrigenous-carbonaceous ground enclosing strata of soluble rocks (gypsum) are distributed here. Intermediate discontinuous permafrost and sites of frequent alternation of thawed and perennially frozen ground are typical for the region. The region in geomorphological relation belongs to the Prelensko Plateau. The summit plain is located at elevations 400–600 m, while the topography is characterized by a high roughness. Active exogenous processes represent talus formation, stone rivers, slides, carbonaceous karst, erosion, and thermal erosion. Sulphate aggressive water to a depth of 3 m, and occasionally to 10 m, is widespread within the region.

I.7 Lena-Aldan Regionis referred to the Aldan Anteclise. Cryotic Lower Cambrian carbonaceous and terrigenous-carbonaceous rocky ground is predominant here. Discontinuous permafrost is widespread. Small massifs of carbonaceous ground are in a thawed state. Rocky magmatic ground represented by alkaline granite and syenite is known south of the region. The region in geomorphological relation belongs to the central part of the Prelensko Plateau. The summit plain gently rises from elevations of 500 m to 700–800 m. Furthermore, the southern part has island topography. The highest elevations up to 1,000–1,500 m are re-stricted to island mountains. Exposures of rocky magmatic ground of alkali composition are widespread here. Active exogenous processes represent formation of talus, stone rivers, slides, karst, solifluction, and frost cracking. Non-aggressive suprapermafrost water to a depth of 3 m is predominant. Sulphate aggressive water occurs locally in the southern part of the region.

I.8 Amga Regionbelongs to the eastern part of the Aldan Anteclise. A combination of dispersive plastic-frozen ground with low ice content and cryotic half-rock ground is predominant. The region is referred to as the eastern Prelensko Plateau. The summit plain is located at elevations 300–470 m. Active exogenous processes represent formation of talus, slides, solifluction, slot-like valleys, carbonaceous karst niches, and blind creeks. Non-aggressive suprapermafrost water to a depth of 3 m is widespread here.

I.9 Anabar-Olenek Regionis restricted to the north-western Siberian Platform. It belongs in tectonic relation to the Lena-Anabar Mesosoic Fore Deep. Quaternary icy dispersive hard-frozen silts and combinations of Mesozoic hard-frozen dispersive and cryotic half-rock ground are widespread here. The region belongs to the eastern North-Siberian Lowland. The summit plain is downwarping to its central part where elevations fall to 30–40 m. The most active exogenous processes are slides, formation of solifluction terraces, talus, thermokarst, and thermal erosion. Non-aggressive suprapermafrost water to a depth of 3 m is widespread in the region.

Figure 5 Scheme of engineering geological zoning of the Sakha (Yakutia) Republic.

II. Verkhoyansk-Kolyma Mountainous Area

The area covers a considerable part of the Verkhoyansk-Kolyma Fold System, including anticlinoria and synclinoria between the Siberian Platform and Kolyma Massif (Mokshantsev, 1975). Four engineering geological regions are separated within the area. Three of these regions are the Verkhoyansk Region, Cherkski-Moma Region, and Yana Region located westward, eastward, and in the center, correspondingly. The fourth region, the Sette-Daban Region, is separated south-west of the area. Even as an extension of the adjacent Verkhoyansk Region, the Sette Daban Region differs markedly from it by the carbonaceous composition of the ground.

II.1 Verkhoyansk Regioncorresponds to the belt of anticlinoria which is located at the boundary between the Siberian Platform and Verkhoyansk-Kolyma area of Mesozoic folding. Dislocated cryotic Upper Paleozoic and Mesozoic half-rock terrigenous ground (sandstone, siltstone, and mudstone) of the Verkhoyansk complex is widespread within the region. Cryotic rocky carbonaceous and terrigenous-carbonaceous ground (Precambrian rocks) as well as rocky magmatic ground (Mesozoic granites) are occasionally encountered. The region covers low-mountain structures of the Pronchischev and Tchekanoski Ranges as well as the mid-mountain Verkhoyansk Range with elevations to 2,300 m. Active faulting, rockfalls, talus, stone rivers, slides, thermal erosion, and frost cracking are widespread. Suprapermafrost water to a depth of 3 m has a total acid aggressiveness (pH <6).

II.2 Yana Regionis located between the uplands of the Verkhoyansk and Cherski Ranges. Cryotic Triassic and Jurassic terrigenous half-rock ground (sandstone, siltstone, and mudstone) is predominant here. Cryotic Lower-Middle Paleozoic carbonaceous and terrigenous-carbonaceous ground as well as cryotic Mesozoic magmatic ground (granitoid) rarely occur in horst-anticlinoria. Depressions filled with frozen Cenozoic dispersive ground (sand, silt, gravel) are widespread. The highest uplands are the Kular Range (maximum elevations to 1,300 m), Yana Highland (1,770 m), Elga Highland (1,700 m), and Oimyakon Highland (2,000 m). The topography and occurrence of the Cenozoic sedimentary facies point to the intensive positive tectonic movements with increasing amplitude from north to south. Some data permit the hypothesis of considerable horizontal displacements (Nenneli depression in the Polousnyi Range). Active exogenous processes represent the formation of talus, slides, stone rivers, and, rarer, rock falls, thermal erosion, and frost cracking. Thermokarst develops on ice complexes which occur in depressions. Suprapermafrost water to a depth of 3 m has a total acid aggressiveness.

II.3 Cherski-Moma Regionencompasses the area of anticlinoria. It represents the most complex and active part of the Verkhoyansk-Kolyma Mountain Fold System, up until now. Several Mesozoic tectonic structures are separated within the Cherski Range. These, from west to east, are the In’yali-Debin Synclinorium, Tas-Khayakhtakh Horst Anticlinorium, Moma Horst Anticlinorium, and Uyandina-Yasach Volcanogenic Belt. Various, predominantly Mesozoic and Paleozoic, rocky terrigenous, carbonaceous, magmatic, and volcanogenic soils are widespread here. The territory of the modern Moma depression and Moma Range is referred to as the Mesozoic Moma-Zyryanka Downwarping (Mokshantsev, 1975). Cryotic Late Jurassic and Cretaceous half-rock terrigenous ground representing sandstone, siltstone, mudstone, gravelstone, conglomerate, and, rarely, coal, is widespread within the Moma-Zyryanka Depression (including the Moma Range). Frozen Quaternary rudaceous ground of glacial and slope genesis, and, in a lesser extent, alluvial sands and gravel, occur in the Moma Depression. The territory is referred to the zone of very active modern differentiated vertical and horizontal (?) movements and high seismic intensity. The highest elevations (3,147 m) on the Russian North-East are known within the Cherski Range. Exogenous processes (rock falls, talus, stone rivers, icings, karst, and thermal erosion), among which the slope ones are predominant, are very active. Suprapermafrost water of total acid aggressiveness is shallow.

II.4 Sette-Daban Regioncorresponds to the samenamed anticlinorium. Frozen Riphean, Vendian, Cambrian, Ordovician, and Silurian carbonaceous and terrigenous-carbonaceous ground is widespread. The topography of the Range has a block structure. The highest (up to 2,400 m) mountain massifs are located in north. Active, predominantly positive, modern movements are typical. Active exogenous processes (talus formation, rock falls, stone rivers, karst, and erosion) are typical for the mountainous sites of the region. Suprapermafrost water of total acid aggressiveness is shallow.

III. Area of Primorsky Lowlands and Shelf

Most of the area in tectonic relation represents a young (Quaternary) downwarping at the modern passive continental margin. Mesozoic tectonic basement of the territory is covered by Cenozoic sediments. It is exposed at separate uplands of the Primorsky Lowland and New Siberian Islands. Three engineering geological regions are separated here by structure and spatial distribution.

III.1 Yana-Kolyma Regionencompasses the whole Primorskaya Lowland, Lena River Delta, and lowland in vicinity of Mamontov Klyk Peninsula. The Mesozoic basement of this territory is referred to two fold systems. These are the Verkhoynsk-Kolyma (western) and Novosibirsk-Chukot (eastern) systems. The boundary between the systems is drawn along theSvyatoi Nos-Oloi Volcanogenic Belt. The latter stretches from the Lower Kolyma River (the Omolon River mouth) to the cape Svyatoi Nos at the shore of the Dmitri Laptev Strait. Hard-frozen Quaternary dispersive ice-rich ground of ice complexes is predominant in the region. Ice complexes of the arctic type are widespread on shores of the Laptev and East Siberian Seas. They are composed of 60%–80% or more of wedge ice. Ice wedges can be as deep as several dozen meters. Ice complexes of the continental type occur in southern Lowland and on the Laptev Sea shore. They can contain up to 60% of segregation and wedge ice. Hard-frozen silty and peaty ground filling the dried lake depressions known as alases is widespread. The same ground occurs at the bottom of multiple thermokarst lakes. Hard-frozen Quaternary sandy ground is less extensive. Its occurrence is restricted mainly to the Lena River Delta. Cryotic Palaeogene and Neogene sandy coal-bearing ground is very locally distributed. Additionally, the outcrops of the Pre-Cenozoic basement are of very local distribution as well. They represent cryotic half-rock volcanogenic, terrigenous ground, and intrusive granites. The Lowland summit plain with average elevations to 100 m is practically horizontal. Small island uplands (340–540 m) stretch from the cape Svyatoi Nos to the shore of the Sellyakh Gulf. Modern upward movements being partially compensated by the sea level rise are typical for the region. Active exogenous processes are thermal abrasion, slides, thermokarst, frost cracking, and swamping. Suprapermafrost water is non-aggressive.

III.2 Novosibirsk Regionoccupies New Siberian Islands. The tectonic basement belongs to the Mesozoic Novosibirsk-Chukot Fold System. Hard-frozen dispersive ground of ice complexes is of predominant distribution within the islands. Cryotic Early and Middle Paleozoic carbonaceous and terrigenous-carbonaceous rocky and half-rock ground is widespread on the Kotelny Island. Hard-frozen sandy marine ground is widespread on the Bunge Land eastward of the Kotelny Island. Furthermore, small fields of cryotic Palaeogene and Neogene dispersive sandy and loamy ground are known on the New Siberia Island. Exposures of cryotic terrigenous half-rock and rocky intrusive (granites) ground is known to be found on the Bolshoi Lyakhovski Island. The islands have a low topography with elevations of several dozen meters a.s.l.. Maximum elevations (293 m) are found on the Bolshoi Lyakhovski Island. Low roughness of terrain is typical for the Islands which may be indicative of small amplitude modern positive movements. The sea level rise likely occurs rapidly. It provides high rates of thermal abrasion of the shores. Prevailing active exogenous processes are thermal abrasion, slides, thermokarst, frost cracking, swamping. Suprapermafrost water is non-aggressive.

III.3 Kolyma Regionin tectonic relation represents a modern intramontane depression. Hard-frozen dispersive icy ground of ice complexes as well as hard-frozen organo-mineral ground of bottom sediments in alases are widespread. Cryotic Palaeogene and Neogene terrigenous sandy ground is of limited extent, and hard-frozen Quaternary rudaceous slope ground is rarely encountered. Pre-Cenozoic formations are predominantly located in the Alazeya High Plateau. Among them, cryotic Mesozoic half-rock and rocky volcanogenic ground, Middle Paleozoic half-rock crystalline schist, and Jurassic half-rock volcanogenic-terrigenous ground are widespread. Most (eastern) territory belongs to the Kolyma Lowland. Its summit plain is located at low elevations to 50 m. Small island massifs rise above the summit plain to elevations of 250 m. Active exogenous processes in this part of the region are thermokarst, swamping, and flooding. The western part of the region belongs to the Alazeya High Plateau. The summit plain here rises to 800–900 m. Upward tectonic movements accompanied by talus formation, slides and deep erosion prevail here. Suprapermafrost water is non-aggressive.

IV. Okhotsk-Chukotka Area

This area covers small territories along the eastern boundary of the SR(Y). They are associated with relatively wide distribution of Late Mesozoic volcanogenic formations. The area is subdivided into several spatially discrete regions within the SR(Y).

IV.1 Suntar Regionis located in the southern Suntar-Khayata Range. It represents a part of the Verkhoyansk-Kolyma Fold System (Suntar-Labynkyr upland; Mokshantsev, 1975) which was volcanic at the end of Mesozoic Period. Cryotic Upper Paleozoic and Early Mesozoic half-rock terrigenous (siltstone, mudstone, sandstone) as well as half-rock volcanogenic and volcanogenic-sedimentary ground is widespread here. The region is referred to as the highest (to 2,800 m) part of the Suntar-Khayata Range which was involved in block uplift movements during the Quaternary. Exogenous processes include rock falls, talus formation, slides, stone rivers, bottom erosion. Suprapermafrost water is of total acid aggressiveness.

IV.2 Yukagir Regioncorresponds in tectonic relation to the Pre-Kolyma horst-anticlinorium of the Verkhoyansk-Kolyma Fold System affected by volcanism at the end of Mesozoic Period. Cryotic Pre-Cambrian rocky metamorphic and volcanogenic, Paleozoic rocky carbonaceous and terrigenous-carbonaceous, Upper Paleozoic and Mesozoic rocky and half-rock tuffaceous and terrigenous, and Cretaceous half-rock volcanogenic ground is widespread here. Hard-frozen rudaceous ground is predominant in intramontane depressions. The summit plain within the Yukagir High Plateau is located at elevations of 300–1,100 m. Active exogenous processes are the formation of talus, stone rivers, slides and bottom ero-sion in uplands, and swamping and side erosion in depressions. Water aggressiveness is of total acidity.

IV.3 Anyui-Omolon Regioncovers the Oloi Volcanogenic Depression. Cryotic Devonian half-rock volcanogenic, Mesozoic and Upper Paleozoic half-rock tuffa-terrigenous, Cretaceous rocky intrusive and volcanogenic ground is widespread here. Hard-frozen fine-grained ground of ice complexes is distributed in small depressions. Frozen Triassic half-rock terrigenous, Jurassic half-rock volcanogenic, Cretaceous rocky intrusive and half-rock volcanogenic ground occurs on the right bank of the Kolyma River estuary. The summits are located at elevations to 1,000 m. Active exogenous processes represent the formation of talus, slides, stone rivers, solifluction, frost cracking, and bottom erosion. Suprapermafrost water is non-aggressive.

V. Aldan-Stanovoi Area

The area represents one region which is referred to as the Aldan Shield of the Siberian Platform. Its southernmost part, referred to as the Stanovoi Range, as well as the Aldan Mountains, represent a young orogen likely activated in Late Cenozoic. Cryotic and thawed Archaean crystalline metamorphogenic ground (crystalline schist, gneiss, plagiogneiss, quartzite and, rarer, calciphyre, marble, and subgabbro) and intrusive (granite and alkaline granite) ground are widespread within the shield. Cryotic Proterozoic rocky terrigenous ground as well as thawed and cryotic Vendian and Cambrian rocky carbonaceous ground are less extensive. Frozen with low ice content, cryotic, and thawed terrigenous ground of mixed classes (half-rock and dispersive) represented by sandstone, sand, siltstone, mudstone, coal, silt, and conglomerate is distributed in depressions. The distribution of frozen dispersive clastic ground of alluvial and glacial origin is less significant. A block structure is predominant in topography. Linear block structures occur locally. Altitude movements of the summit plain at the block boundaries comprise 1,000 m or more. The elevations of the summit plain restricted to uplifted blocks are about 1,700 m, while on the descending side they comprise 700–800 m or less. Activation of various slope processes representing rock falls, talus, slides, stone rivers, solifluction is typical for the area. Erosion processes, and specifically bottom erosion, are also rather active. Suprapermafrost water of total acid aggressiveness to a depth of 3 m is widespread on the majority of territory, especially on north and on the Stanovoi Range. Mesozoic depressions are restricted to zones of shallow (to 3 m) non-aggressive suprapermafrost water and, for the areas of thaw ground, to non-aggressive ground water to a depth 3–10 m.

The analysis of data presented on the Map permits assessment of engineering geological conditions of cryolithozone in the Russian North-East. The territory of the SR(Y) is characterized by the distribution of multiple types of frozen ground varied in composition and stability. The dispersive ice-rich ground of ice complexes is the least stable when subjected to both anthropogenic influence and climate changes. Low-temperature (less than ?5 °C) hard-frozen ground varieties occupy most of the Primorsky Lowland. Even under such conditions, however, these ground varieties are very sensitive to external influence. High thermal abrasion rates (dozen meters per year) are observed in coastal cliffs of the Arctic Seas. Erosion rates of river banks composed of ice complexes also can be very high, reaching dozens of meters per year. Thermokarst rates of ice complexes are high even when mean annual air temperatures are about ?15 °C to ?20 °C. Disturbances of ice complex ground cover by land transport result in swamping and subsequent development of thermokarst. High-temperature varieties of ice complexes are widespread in the Central Yakutian Region. Here, they are to a greater extent influenced by natural and anthropogenic factors leading to more thermokarst failures. Engineering constructions which use this ground as foundations without thermal regime regulations have very low stability. The ground widespread on the other territories of the SR(Y) has higher stability. It may be used as an engineering structure foundation when proper conditions of thermal regime regulation are satisfied.

Acknowledgments:

The map is compiled under support of the State Contract #1135 of the Sakha (Yakutia) Republic.

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: Spektor VB, Torgovkin YI, Shestakova AA,et al., 2014. Engineering Geological Map of the Sakha (Yakutia) Republic, Scale 1:1,500,000. Sciences in Cold and Arid Regions, 6(5): 0484-0493.

10.3724/SP.J.1226.2014.00484.

April 18, 2014 Accepted: June 14, 2014

*Correspondence to: DSc. Vladimir B. Spektor, Chief research scientist of the Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences. Merzlotnaya 36, Yakutsk 677010, Russia. Tel: 7-4112-390846; E-mail: vspektor@mail.ru