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GEOLOGY
The nature reserve’s territory is situated at the border between two megablocks: Kola and White Sea megablocks.

The deep fault between them goes northwest along Bossojavrre-Porojarvi line. The systems of secondary and tertiary faults segment big structures and have northeast, northern and northwest directions.

The main part of the nature reserve is situated on the southern part of the Pechenga Depression and the northern part of the Lapland Granulite Belt.
GEOLOGY
The nature reserve’s territory is situated at the border between two megablocks: Kola and White Sea megablocks.

The deep fault between them goes northwest along Bossojavrre-Porojarvi line. The systems of secondary and tertiary faults segment big structures and have northeast, northern and northwest directions.

The main part of the nature reserve is situated on the southern part of the Pechenga Depression and the northern part of the Lapland Granulite Belt.
See a high-resolution map
Minerals

The 20 km long southern part of the nature reserve and the northern part near the Menikka Island is formed by:

  • ultra-high pressure metamorphic pyroxene diorite,
  • plagiogranites,
  • mica gneiss of Lopian cycle.

In the southern part of the nature reserve they belong to the Runnijoki-Allarechka block, in the northern part they belong to the Porojarvi block of the White Sea megablock.

The area from Jordanfoss to Lake Kaskamajarvi is formed by the Saami-Lopian metamorphic amphibolite and gneiss complex:

  • биотит-амфиболовые и биотитовые гнейсы,
  • амфиболиты,
  • пироксен-плагиоклазовые кристаллосланцы.

The 3 km wide area to the south is formed of:
  • gneiss,
  • amphiboles,
  • schist of complex composition limited by faults.

The central part of the nature reserve at Kalkupja Mountain and Lake Kaskamajarvi is represented by Lower-Proterozoic minerals of so called Kaskama complex:

  • the northern and the eastern parts of Kalkupja Mountain are formed with the minerals of the first phase of the Karelian Craton: metamorphic gabbro, pyroxenite, anorthosite and amphibolite;
  • the basement of the highest peak of the mountain, its southern slopes and hilly surrounding are formed with the minerals of the second phase of the Karelian Craton: metamorphic diorite, granodiorite, plagiogranite and orthogneiss.

    The Pechenga synclinorium has complex composition and is represented in the nature reserve by the Pechenga depression and the Porojarvi block.

    Their distinctive feature is a paralleled line-shape occurrence from west to east. These blocks consist of two stages:

    • the first one is represented by the minerals of the Archeozoic age;
    • the second stage is on the first one and represented by the minerals of the Lower-Proterozoic age.
    There are volcanosedimentary and volcanic formations on the Archeozoic minerals of the Pechenga synclinorium.
    Minerals formation
    The geological history of the Pasvik river valley is characterized by alternating periods of magmatic activity and dormancy.
    As a result of intense magmatic processes, intrusions were introduced along numerous faults.

    The dormant period was marked by the formation of terrigenous rocks: carbonaceous clays and sands of various grades, carbonaceous dolomites. Later, this series sank to great depths and underwent intense metamorphism. At the same time, volcanic sedimentary rocks were transformed into carbonaceous shales, amphibolites, quartzites, tuffs, etc.

    In the northern part of the reserve, in the area of the Glukhoi Dam, near the line of a deep fault on the rocks of the Archean age, there are shale amphibolites of the Proterozoic. Presumably, they arose due to the strong metamorphism of effusive rocks.
    Minerals formation
    The geological history of the Pasvik river valley is characterized by alternating periods of magmatic activity and dormancy.
    As a result of intense magmatic processes, intrusions were introduced along numerous faults.

    The dormant period was marked by the formation of terrigenous rocks: carbonaceous clays and sands of various grades, carbonaceous dolomites. Later, this series sank to great depths and underwent intense metamorphism. At the same time, volcanic sedimentary rocks were transformed into carbonaceous shales, amphibolites, quartzites, tuffs, etc.

    In the northern part of the reserve, in the area of the Glukhoi Dam, near the line of a deep fault on the rocks of the Archean age, there are shale amphibolites of the Proterozoic. Presumably, they arose due to the strong metamorphism of effusive rocks.

    The composition of amphibolites varies greatly:

    • the lower layers are enriched in magnetite and are characterized by dark green and black colors;
    • the upper strata contain biotite-quartz and magnetite-siliceous schists.
    Shale amphibolites occur at the base of volcanogenic rocks of the North Pechenga basin and the Poroyarva monocline of the Pechenga synclinorium. Their formation took place in the Lower Proterozoic in several phases. The thickness of the rocks does not exceed 3000 meters.

    The Poroyarva Group is represented by strongly metamorphosed andesidacites, their tuffs, tuffaceous sandstones, conglomerates, siltstones, basalts, phyllites, carbonaceous and mica schists. In some places, shales come to the surface. Coal shale is characterized by a black color, significant lightness due to fine porosity and highly staining ability.


      Ridges and massifs near the source of the Menikkajoki River, including the vicinity of Mount Purrivaara in the north of the Pasvik Nature Reserve and in the vicinity, are formed by diabase and porphyritic greenstone rocks, porphyritoids. In this part of the region, the rocks are severely destroyed, fragmented. Greenstone rocks in the field are easily distinguished by their greenish-blue color and shale texture.


      To the south of the stratum of greenstone rocks from the Glukha Dam to Mount Kalkupya, the rocks of the Tal’inskaya stratum are located in a narrow strip: these are rhythmically layered chlorite-biotite and two-mica gneissic schists. They lie at the base of the Taglia-tunturi and extend westward to the Pasvik river. Tal’inskaya folded structure is limited by fault faults.

      Differences can be traced in the structure of tectonic structures and resistance to denudation of the rocks composing them, which are reflected in the relief:

      • The most resistant to destruction metamorphosed granites, granodiorites, amphibolites form large massifs and an outlier upland — Mount Kalkupya.
      • Plain areas are formed by the least stable and evenly decaying gneiss complexes.
      • The massifs of the northern part of the reserve are characterized by active denudation of greenstone rocks that emerge on the surface, which is supported by the presence of talus and the gristly-gravelly nature of the soil.

      Differences can be traced in the structure of tectonic structures and resistance to denudation of the rocks composing them, which are reflected in the relief:


      • The most resistant to destruction metamorphosed granites, granodiorites, amphibolites form large massifs and an outlier upland — Mount Kalkupya.
      • Plain areas are formed by the least stable and evenly decaying gneiss complexes.
      • The massifs of the northern part of the reserve are characterized by active denudation of greenstone rocks that emerge on the surface, which is supported by the presence of talus and the gristly-gravelly nature of the soil.
      GEOMORPHOLOGICAL CONDITIONS AND GLACIAL DEPOSITS
      The relief of the Pasvik Reserve is denudation-tectonic, low-mountainous, with an average height of about 50 m above sea level. It is the result of the dissection and glacial treatment of the ancient peneplain plain.
      • Most of the territory is a ridge-ridged plain with developed glacial-accumulative relief forms.

      • Moraine sand and boulder ridges and hills alternate with depressions occupied by small lakes and swamps. The height of the ridges ranges from 10 to 50 m.

      • In the central and northern parts, there are remnant hills (island mountains), the highest is Mount Kalkupya: 357 meters above sea level.

      • The minimum height in the reserve is the Pasvik river edge in the Salmijärvi region: 21 meters above sea level.
      Major landforms of Pasvik Nature Reserve
      Geological and geomorphological forms
      as natural phenomenon
      • Medallion stains (frost cracks) on the top of Mount Kalkupya (and Korablekk — outside the territory of the reserve)
      Category: typical for this natural area, but occupying a small area.

      Characteristic: areas with heaving of the soil, outlined by a roller, with squeezed-out fragments of bedrock, cracks in the soil and overgrown with algae, liverworts and mosses.

      • Stony placers
      Category: typical for the natural zone, not very common in the river valley, the only place in the reserve.

      Description: western and north-western slopes of Mount Kalkupya with thick colluvial deposits (removal of material from the steep upper parts of the mountain slopes).
      Geological and geomorphological forms
      as natural phenomenon
      • Medallion stains (frost cracks) on the top of Mount Kalkupya (and Korablekk — outside the territory of the reserve)
      Category: typical for this natural area, but occupying a small area.

      Characteristic: areas with heaving of the soil, outlined by a roller, with squeezed-out fragments of bedrock, cracks in the soil and overgrown with algae, liverworts and mosses.

      • Stony placers
      Category: typical for the natural zone, not very common in the river valley, the only place in the reserve.

      Description: western and north-western slopes of Mount Kalkupya with thick colluvial deposits (removal of material from the steep upper parts of the mountain slopes).
      GLACIAL PROCESSES
      The formation of the relief was significantly influenced by the last glaciation. Traces of the activity of the Scandinavian ice sheet are developed here everywhere. In the Pasvik river basin, the direction of the glacier was predominantly northeastern, which is confirmed by the orientation of moraine ridges and drumlins, sheep’s foreheads, and the direction of glacial hatching.

      The exaration activity of the glacier manifested itself in the smoothing and grinding of the surfaces of the remnants, deepening and widening of lake basins.

      The Mount Kalkupja is an example

      • has 4 peaks separated by tectonic troughs that have undergone glacial gouging;
      • saddles of various shapes, troughs and troughs also have a northeastern direction and separate the mountain peaks;
      • numerous scars cut through the surfaces of the rocky ridges on the summits;
      • there is a coarse-grained moraine, some boulders of which are sometimes grouped into formations of the seids type;
      • the slopes of the mountain are covered with a cover of moraine of various thickness: on the strongly sloping southeastern and southern slopes, the moraine is concentrated in vast boulder groups, on very steep and steep northwestern slopes it is absent.
      The main monolithic moraine is the most common type of Quaternary deposits. The texture of the moraine is complex and is represented by unsorted greenish-gray or yellowish-gray sandy loam with boulders, boulders, rubble, pebbles, gravel. Large boulders make up 5−10% of the total composition, they are not rounded or poorly rounded. The thickness of the deposits on the uplands is 0.5−3 meters (thin and discontinuous cover), in the depressions — from 3−5 to 7−10 meters.

      The accumulative activity of the glacier manifested itself in the formation of ridges and small hills, in an almost ubiquitous distribution of boulder-blocky material on the surface.

      At the mouth of the Laukkajoki River

      • periglacial deposits of fan cones were noted — up to 5 meters in height, elongated;
      • they are composed of gravel-pebble, coarse and medium-grained sands, cross-bedded and diagonally bedded;
      • forms form plateau-like and trail-like cone-shaped bodies 50×250 meters in size, the excess of which over the surrounding surface is 5−7 meters;
      • they are formed on the main moraine when thin material is washed out by melt water outside the ice sheet.
      Ridges and hills are characterized by northern, northeastern, rarely northwestern and western orientations. Areas of accumulative moraine plains are found throughout the reserve. They represent an alternation of slightly wavy surfaces, in places strongly boggy and lakeside.
      FORMER SEA GULF
      The Pasvik river valley has undergone several marine transgressions in the late and post-glacial periods, therefore the territory bears traces of marine abrasion and accumulation. The valley in the late and post-glacial times was a sea bay or fjord. The sea bay reached almost to the present territory of the village of Rayakoski.
      Transgression boondary
      • Expedition S. Biske, 1949: 90−100 meters above sea level.
      • Within the boundaries of the reserve: 75−80 meters above sea level.
      The transgression boundary should be attributed to the folas and tapes periods, since the soil profiles laid slightly above this mark:

      • have significantly less power,
      • show typical moraine boulders at the base of the profile,
      • the soil horizons have a coarse-grained sandy texture and are non-layered.
      The accumulative relief
      in the northern part of the reserve is represented by a flat, in places slightly sloping sea plain in the surroundings of the Menikkajoki River.
      • The absolute height of the plain is 30−36 meters.
      • Relative excess — 8−10 meters.
      • The plain is very swampy.
      • In the central part there are small lakes.
      • On the surface of the bogs, there are microforms in the form of mounds of permafrost bulging several meters high.
      • Expedition S. F. Biske (1949) established here the presence of a frozen horizon at depths of 0.7−1.5 meters. The marine sediments here are represented by gray-green and bluish-green clays and heavy loams (less often sandy loams), also exposed along the shores of Lake Salmijärvi up to the strait connecting it with Lake Kuetsjärvi.
      • The thickness of marine sediments reaches 5−7 meters.
      The accumulative relief
      in the northern part of the reserve is represented by a flat, in places slightly sloping sea plain in the surroundings of the Menikkajoki River.
      • The absolute height of the plain is 30−36 meters.
      • Relative excess — 8−10 meters.
      • The plain is very swampy.
      • In the central part there are small lakes.
      • On the surface of the bogs, there are microforms in the form of mounds of permafrost bulging several meters high.

      • Expedition S. F. Biske (1949) established here the presence of a frozen horizon at depths of 0.7−1.5 meters. The marine sediments here are represented by gray-green and bluish-green clays and heavy loams (less often sandy loams), also exposed along the shores of Lake Salmijärvi up to the strait connecting it with Lake Kuetsjärvi.
      • The thickness of marine sediments reaches 5−7 meters.

      RIVER PROCESSES
      Alluvial deposits are distributed fragmentarily, in narrow strips along the banks of the Pasvik river. Channel alluvium, represented by fine- and medium-grained cross-bedded sands, was formed near waterfalls, in the place of which hydroelectric power plants were built, and is also common in the bed of Lake Kheyuhenjärvi in the southern part of the protected water area.
      In some places, alluvial oxbow deposits with a thickness of 1−3 meters are found. Lacustrine-alluvial deposits are just as rare, the formation of which is associated with the functioning of flowing lake basins with a calm hydrodynamic regime. These are fine and medium-grained sands and sandy loams horizontally and cross-bedded, 2−2.5 meters thick, near the river banks.

      Biogenic deposits are the most rare, as mainly peat is underlain by moraine. In the central part of the sea plain near the mouth of the Menikkajoki River, on the plains south of the Kalkupya and Kaskama mountains, peat deposits reach 1.5 meters or more.
      Eluvial-deluvial and deluvial-colluvial deposits are noted on the slopes of Mount Kalkupya, in places — in the northern part of the reserve on Mount Purrivaara. The cover of these Quaternary deposits alternates here with outcrops of granite-gneisses.

      Eluvial deposits are the parent rock for the soils of the tundra belt. Deluvium, represented by fine earth and rubble-boulder material, is concentrated on the sloping slopes and at the foot of the hill. Colluvial sediments are clasts of bedrock in the form of scree on the steep and very steep northwestern slopes of Mount Kalkupya in tectonic troughs.
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