185610,  Россия, Республика Карелия, г.Петрозаводск, ул.Пушкинская 11, ИГ КарНЦ РАН

Научные On-Line проекты Института Геологии:

   Main principles of geosite selection in Karelia, NW RUSSIA:

   Ylo J. Systra

The paper from : ProGEO '97 in Estonia Proceedings. The Second General Assembly of the European Assiociation for the Geological Heritage.Scientific Conference. Tallinn-Lahemaa National Park, Estonia. June 2-4, 1997. ISBN 9985-815-20-3 , Geological Survey of Estonia, 1998.

Abstract
    The Early Precambrian sedimentary - volcanic and igneous rocks of Karelia are covered only by thin Quaternary cover. The first Karelian Geological Heritage List includes over 425 Precambrian  and about  400 Quaternary monuments. Part of well-preserved geosites could be proposed into European Geosite List and some unique geosites into UNESCO World Natural Heritage List.

Introduction
    The Republic of Karelia is located on the south-eastern edge of the Fennoscandian Shield (Sokolov, 1987). Though the bedrocks mainly belong to the Archean, Karelia is the only place in Europe where Early Precambrian sedimentary rocks, volcanites and igneous rocks are represented in so wide diversity, so open for investigations and so well studied. It gives a rare possibility to reconstruct the major sedimentary, volcanic, igneous, tectonic and metamorphic events in time interval from more than 3.5 Ga
to 340 million years ago. Numerous types Precambrian and  a few Paleozoic geosites are selected.
    During the Quaternary glaciations Karelian territory was located in the transition zone between the hilly crystalline Fennoscandian Shield and the flat sedimentary Russian Plain. Therefore Karelia is the only place in Europe are highly developed morainic landscapes, ice-dividing uplands and marginal landforms, more common for the central part of the shield and Finland, and also outwash,glaciolacustrine and marine plains; which are more typical for Russian Plain.

Quaternary cover
    The Karelian Quaternary deposits were formed during the four latest stages of the Quaternary glaciations  and represent the time interval of about 36 000 years: the oldest dated organic material from sequencce near the Petrozavodsk showed age 46 700 +/-1100 years and the last ice in the NW Karelia melted 9 500 years ago, which marked the beginning of formation of  bottom sediments in Lake Paanajarvi (Fig.1).

Karelian Quaternary Geosite List
    More than 420 listed geosites represent the main types of Quaternary monuments. The list includes several till planes, drumlins, eskers, glaciofluvial deltas, kames, glaciolacustrine planes, single big boulders, boulder fields and"roads", glacially eroded large bedrock outcrops, occurence of the earthquakes(Photo 21) and  seismic dislocations. The majority of these, about 325 sites are located within the protected territories of the region (3 strict reserves, 2 national parks, 3 landscape reserves) and  in the 18  geological reserves, planned to be established in the nearest future.
    In the western part of  Karelian  Republic different end moraines and interlobate moraines, eskers and deltas are very common.
They belong to the Rugozero and Kalevala stages which are of the same age as Salpausselka I and II in Finland. Most Karelian Quaternary geosites are located along these ridges(Fig.1). Another place with numerous geosites is on the northwestern shore of the Lake Onega near Chelmuzhi village where end moraines, eskers, kames and deltas of the Neva stage form a  beautiful ridge.
To east and southeast, near the White Sea, lakes Ladoga and Onega, large territories are covered with glaciolacustrine planes with varved clay and continental sand dunes, not typical for such northern territories.


Fig. 1. The Karelian Quaternary Heritage Map. The structure of the Late Valdaian ice cover by V.A. lljin, A.D. Lukashov and I.M. Ekman (unpublished data).
Legend: I - boundaries of the glaciation stages (Lg-Luga Stage, ca.14 200-13 200 years B.P.; Nv -Neva Stage, ca.12 500-11 900 B.P.; Rg - Rugozero Stage = Salpausselka I, ca. 11 800-11 300 B.P.; Kl-Kalevala stage = Salpausselka II, ca. 10 500-10 200 B.P.); 2 - main ice-dividing zones; 3 - large bedrock uplands; 4 - interlobate accumulative elevations; 5 -ice movement direction.
The Quaternary monuments: 6 — till plains; 7— ice-dividing uplands; 8 — glaciofluvial landforms; 9 — denudational-tectonic forms of relief; 10— marine and lake plains; 11 — sequences of Quaternary deposits; 12 — palaeoseismic dislocations; 13 — other monuments.
14-16 - nowadays existing (14) and planned (15) natural and special geological territories. The numbers (16) show: I - Paanajarvi National Park (NP); 2 - Vodloero NP; 3 - Kostomus Strict Reserve (SR); 4 - Kivach SR; 5 - Nizhnesvir SR; 6 - Soroka Landscape Reserve (LR); 7 - Tolvojarvi LR; 8 - Iso-lijarvi LR; 9 - Kenozero NP; 10 - Kalevala NP; II - Tulozero (Tuulijarvi) Protected Territory (PT); 12 - Koitajoki PT; 13 - Ladoga Skerries PT; 14 - Tungozero Geological Reserve (GR); 15 -Ohtanjarvi GR; 16 - Haikola GR; 17- Shongozero GR; 18 - Jushkozero GR; 19 - Ledmozero GR; 20 -Hirvas GR; 21 - Tikshozero GR; 22 - Motka GR; 23 - Vottovaara GR; 24 - Putkozero GR; 25 -Lendery (Lentiira) GR.  


Precambrian bedrocks
    The Karelian bedrock (Sokolov,1987) is represented mainly by the Early Archean granite gneiss and gneissose diorite basement with remnants of sedimentary-volcanic sequences, the Late Archean sedimentary-volcanic greenstone belts and different intrusive complexes, the Early Proterozoic sedimentary and volcanic cover; numerous dykes and intrusions. The Late Proterozoic volcanic-sedimentary rocks are known only in Lake Ladoga and White Sea aulacogens and as diamont-bearing lamproite dykes in the Achean basement of the Karelian Craton and sortavalite dykes in the Early Proterozoic rocks in the Ladoga zone. The Vendian-Palaeozoic sedimentary rocks cover the crystalline basement along the eastern border of the Shield in the southeastern part of Karelia(Fig.2 ). In the eastern part of the Vodlozero Uplift the oldest rocks in Europe are located : basalts and komatiites
( 3.4 Ga) and granites (over 3.5 Ga). Although the Archean rocks are widely developed on the Kola peninsula, in Eastern Finland and Northern Sweden, the wide diversity in the rock types, compositions and structural forms observed in Karelia is unique. It was considered while compiling the first comperatively complite Karelian Precambrian Heritage List.
    Geologically the Republic of Karelia can be subdivided into three major NW- trending structural units, with the Karelian Craton in the centre, bordering with  the Belomorian and Svecofennian fold belts to NE and SW respectively (Systra,1991).. The Karelian Craton was the most stable core of the eastern part of the Fennoscandian Shield during the whole long Precambrian history. Its metamorphosed and strongly folded Archean basement is overlain by the Early Proterozoic sedimentary-volcanic cover, deformed  into open synclines during the 1.9-1.8 Ga Svecofennian Orogeny. Migmatites, Archean supracrustal rocks and Archean, Proterozoic and Palaeozoic intrusions and dykes represent the uplifted Belomorian fold belt. The Svecofennian folded belt is dropped down comperatively the craton. In this region the Archean basement crops only in the cores of mantled granite gneiss domes, while the belt comprises predominantly flyschoidal sediments, more than 3-4 km thick (Fig.2).

Fig.2.  The Karelian Precamhricm Heritage Map.
Bedrock: 1 - Early Archean (AR1); 2 - Late Archean (AR2); 3 - Early Proterozoic (Ptz); Late Proterozoic (Riphean) (R). Large massifs: 5 - granites; 6 - rapakivi granites; 7 - mafic-ultramafic rocks. Boundaries: 8 - with thrusting; 9 - between main tectonic units (terrains) of the eastern Fennoscandian Shield; 10 - Vendian-Paleozoic platform cover.
Precamhrian and Phanerozoic monuments: 11 - intrusive rocks (a-R, b-Ptz, c-AR2, d-ARI); 12 — type sections (a-R, b-Ptz., C-AR2): 13 -typical mineral associations (a-Ptz., b-AR2, c-AR1); 14 -volcanic sections (a-R, h-Ptz, C-AR2, d-AR1); IS - volcanic centres (a-R, b-Ptz, C-AR2); 16 -finds of organic remains (a-Palaeozoic, b-Ptz); 17- tectonic objects (a-Palaeozoic, b-Ptz); 18 - geologically important boundaries; 19-old mines. 20-protected and future protected territories (see also Fig. 1): 1 -Paanajarvi NP; 2 - Vodlozero NP; 3 - Kostomus SR; 4 - Kivach SR; 5 - Nizhnesvir SR; 6 - Soroka LR; 7 - Tolvojarvi LR; 8 - Iso-lijarvi LR; 9 - Kenozero NP; 10 - Kalevala NP; II - Tulozero (Tuulijarvi) PT; 12 - Koitajoki PT; 13 - Ladoga Skerries PT: 14 - Vaskijarvi GR: 15 - Vorochistoye GR; 16 - Kyvikanda GR: 17 -Skohnevo GR; 18 - Gridino GR; 19 - Pongoma GR; 20 - Hirvas GR; 21 - Hisovaara GR.  


The Karelian Precambrian Heritage List
    The Karelian Precambrian Heritage List contains more than 425 monuments. Most of them, 334 geosites are located in the eight presently existing protected territories, in the four new natural areas planned to be protected and on the eight  territories with numerous geosites which are the most suitable  for creating the special-proposed  Early Precambrian geological reserves. Five of them (Vorochistoye, Kyvikanda, Skobnevo, Gridino ang Pongoma) represent different parts of the Belomorian folded(collision) zone, which have passed a long (more than 1.2 Ga) evolution in depth of Earth's crust and show strong multiple folding, metamorphism and migmatization, different intrusive complexes and interior structure of  the deep fracture zones, often accompanied by the intrusions of granites, mafic and ultramafic rocks. The Vaskijarvi locality is a single place where it is possible to see  contact between the Late Archean sandstones, komatiites and other sedimentary-volcanic rocks without any migmatization and the Early Archean strongly migmatized gneisses, amphibolites and migmatites.
    The Hisovaara syncline is a typical Late Archean structure with komatiites, basalts, andesitic basalts and acid volcanites, quartzites, sandstones with well-preserved ripple-marks, superposed metamorphic and metasomatic mineralization. Multiple-storeyed building of the Early Precambrian can be demonstrated in the reserve near the Hirvas village. Here are also well-preserved  the Late Archean (3.0 Ga)  and  the Early Proterozoic (2.4, 2.2 Ga) volcanic centres, ripple-marks(Photo 22), primary textures (Photo 23), the oldest stromatolite buildings and so on.
    From 91 single geosites 4 belong to the Early Archean, 17.- to the Late Archean, 6 - to the border between the Early and Late Archean, 58 - to the Early Proterozoic, 1 - to the Early and Late Proterozoic border, 5 - to the Riphean. There are also 3 Paleozoic monuments.




Photo 21. Rock falls at the foot of the bedrock scarp, caused by postglacial earthquakes, Paanajarvi National Park..



Photo 22. Ancient Jatulian (2.2 Ga)sea shore. Hirvas village.



Photo 23.Rhytmically bedded Kalevian (2.0 Ga) flyschoidal sediments cut by younger Svecofennian (1.9 Ga) granitic veins Lake Ladoga. Impiniemi Cape.



Photo 24. Small Svecofennian thrust zone in Early Proterozoic Sumian (2.4 Ga) andesitic basalts. Kumsa River near Karhumaki town.


    The main problem of the geosite selection was to include as widely as possible geological objects of interest and scientifical importance from the whole geological time, to put into list the whole diversity of rock compositions, their mutual relationships,  structural forms, folds and faults (Photo 24), deep fractures, e.t.c. The list includes unique and typical objects. Most of listed geosites are located along the main roads and only very few important monuments need special transport, 10-15 km walking or seiling on small boats to visit them.
    The Karelian Precambrian Heritage List embraces typical sedimentary-volcanic sequences (more than 15 geosites), well-preserved primary textures, finds of remains of organic material, representatives of the Archean and Proterozoic magmatic complexes (more than 20 igneous  and 15 volcanic complexes), well-preserved volcanic  centres (more than 10), various types
of metasomatic and metamorphic mineralization ( more than 30), folds of different type, age and generation (more than 12 generations and 20 types), dyke swarms (more than 15), places with intersecting of the several magmatic rocks ( more than 40), contacts between sequences of sedimentary-volcanic rock with each-other and  intrusive complexes (more than 50), contacts with unconfirmities and planes of weathering (more than 50), etc.The younger Proterozoic rock are preserved better than the Archean rocks, consequently the number of listed Proterozoic monuments is also larger.  At the same time, it must be noted that the Archean monuments are, as a rule, more complete and of complex significance: the folding is usually accompanied by metamorphic re-crystallization, faulting, intrusion of mafic and granitic massifs, dykes and veins, e.t.c. The Riphean rocks  occupy the limited territory and therefore there are only a few monuments of this age.
    On the map the Precambrian geosites occur unevenly ( Fig.2) : most of them are located in North Karelia, near lakes Ladoga and Onega, alond the borders of  the Karelia Craton.  The territories of  the  better bedrock exposition provide more Precambrian geosites, while the Quaternary geosites occur mainly along the marginal ridges with thick cover of sands, gravels and clays.

European and World Heritage List geosites in Karelia
    To the European Geosite list could be included typical well-studied Early Archean strongly folded gneisses, amphibolites and migmatites of Belomorian Mobile Belt  with numerous magmatic bodies and pegmatite veins; well-preserved large and minor isoclinal and conical folds, thrust and shear zones near Pongoma and Gridino villages, at lakes Vorochistoye and Kyvikanda. All these sites show the Earth crust evolution and its changing in the deep sections. The most complete Early Proterozoic sequence may be listed in the Paanajarvi National Park.
    Also, some well-formed fluvioglacial systems, such as Olanga-Tsipringa deltas in the north and Lentiira-Motka eskers system near the Finnish border at Lake Tuulijarvi may be offered into the European Geosite List.
     The potential geosite submitted for the World Natural Heritage List is the neighbourhood of Hirvas village where five Early
Precambrian sedimentary-volcanic complexes lying with unconformity, well-preserved volcanic centres and primary textures are located. International geological excursions to the territory have been arranged for more than 100 years already.
       Another potential world geosite is the famous Kivakka layered peridotite-gabbro-norite intrusion in the Paanajarvi National Park.

References :
    Sokolov V.A.(ed.) 1987. Geology of Karelia. Nauka, Leningrad, 230 pp.(in Russian).
    Systra Y.J. 1991. The tectonics of Karelian region. Nauka (in Russian).


 GeoWEb ©1998-2003

Геоинформационный центр ИГ КарНЦ РАН