MORPHOLOGICAL STRUCTURE AND NEOTECTONICS OF THE COASTAL ZONE OF THE MURMANSK EAST SEA-SHORE (WATERSHED ZONE OF THE VORONIA AND RYN DA RIVERS)

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Maksim V. MITIAEV Marina V. GIERASIMOWA Murmansk Marine Biological Institute of Russian Academy of Science 18 30 10, Murmansk Vladimirskaia 17, RUSSIA W>prawy Geograficzne na Spitsbergen UMCS, Lublin.

1 Maksim V. MITIAEV Marina V. GIERASIMOWA Murmansk Marine Biological Institute of Russian Academy of Science , Murmansk Vladimirskaia 17, RUSSIA W>prawy Geograficzne na Spitsbergen UMCS, Lublin MORPHOLOGICAL STRUCTURE AND NEOTECTONICS OF THE COASTAL ZONE OF THE MURMANSK EAST SEA-SHORE (WATERSHED ZONE OF THE VORONIA AND RYN DA RIVERS) The structural relief connected with the ground tectonics can be seen within the watershed zone at 300 m a.s.l. and at the relative height up to 200 meters. The watershed zones are formed as wavy peneplaned surfaces which are cracked and moved along the tectonic faults and remodelled due to glacial exaration and accumulation. The slopes are straight, most often steep and thick coluvial chips are found at the foot. Ground moraine sediments, which build terrace like surfaces are found in the depressions and at the slope foot. The relief depression forms are mainly found along the tectonic zones, due to the destructive activity of the glacier. They possess a stepped structure. Many lakes are found in this area (Fig. 1). In the coastal area within fiords and creeks a few levels of raised marine terraces and berms are found. A regressive cycle of sediments (from the bottom to the top): clay-gravel-boulders occur in some of them. Geomorphology of the region is characterized by duality, "young" and "old" forms of relief are combined in it. These are watersheds created as a result of long cycles of denudation and exaration along with a large number of lake basins (the lacustrine coefficient - 0.3) and steep, often stepped slopes and swift streams which have not reached the profile equilibrium yet. The estuary part of the Voronia River, about 18 km long, is most probably the raised fiord. Steep and often upright slopes, not transformed by the exaration activity of the last glacier, were formed in the last 8 thousand years. They point to a high neotectonic activity revealed in the uneven rise of the earth crust blocks, segmentation of top surfaces and formation of the river system referring to the old any young tectonics. While analyzing absolute heights of the watersheds and their relative heights of the local erosion sites (Figs. 2, 3) we came to the conclusion that the coastal zone is more intensely raised due to neotectonic movements and more strongly eroded compared with the region inside. Therefore lowering of watershed 79

2 absolute heights and greater segmentation of the relief from the region inside towards the coastal zone are observed at present. Taking into account overheights in this region the north-west and south-east blocks can be distinguished (Fig. 3). The borderline between them runs from Malyi Viashchin. Promontory across the upper Alyonka, middle Lust to the settlement Tumannyi. In each block a central zone of watershed minimal rise over the local erosion sites and a suburban one of the higher relative heights can be distinguished. Therefore the western and south-western borderline of the north-west block is interesting. At present it seems to be an inner part of the block but possesses such overheights as a contemporary coastal zone. If the lower part of the Voronia River had been a coastal zone not long ago, then origin of relative heights in SE parts, analogous to those in the coastal zone is note quite clear. Assuming more intense rise of neotectonic coastal zone makes it necessary to distinguish several levels of peneplanation and thus several periods of peneplanation. Morphological structure of the region is determined by tectonic dislocation usually described as tectonic dislocation of order II. Structures of order II developed in all main directions (Fig. 4). N-S and NW-SE structures are most widely spread. Tectonic structures of order II seem to be the elements of higher tectonic structures which are termed as tectonic zones of order I. The are three main tectonic zones of order I: 1. The largest tectonic zone separates the Barent Sea from Kola Peninsula. Individual tectonic structures of order II occupy about 8 km from the shore. This zone stretches NW and SE. 2. The second in size tectonic zone of order I developed in NW direction. It joins the first zone on the coast between the estuaries of the Voronia - Alyonka Rivers at an angle In the central part of the zone it is about 12 km. It stretches several tens kilometers in the SE direction. 3. The third tectonic zone of order I of the N-N W direction joins I i II tectonic zones on the flatness between Jarnyshnya Bay and Parchniha Bay. It joins the first zone at an angle of about 90 and the second It central part is about 15 km wide and stretches many tens kilometres in the SE direction. Based on the above facts there can be distinguished a plane of jointed connection (Jarnyshnya Bay - Krowianoye Lake - Paukowoye Lake - Parchniha Bay) of three main tectonic zones of order 1. It is clearly seen in the coastal zone between Jarnyshnya and Parchniha Bays. A joint of neotectonic deposit structure of intense upright movements was created. As mentioned above the morphological structure of the studied area is determined by the tectonic structures of order II. They divide the region into tectonic blocks. They have the shape of polygons, often directed according to the tectonic structures of order II. They are also divided into smaller blocks. A full hierarchy of tectonic blocks from micro blocks to macroblocks of order I can be distinguished. The tectonic blocks separated by tectonic structures of order II 80

3 belong to one hierarchic level. Each tectonic block possesses its own amplitude of vertical movements. The differences in amplitudes between the blocks can be small or they can even reach a few or several tens meters. Tectonic structures of order II are probably linearly elongated tectonic blocks of smaller amplitude of raising movements. At present they have a form of depressions in which most lake basins are found. The lake basins are situated on different levels which point to uneven raising of some structure parts. The forms were probably created not long ago and the process of their development is still carried on. These are the structures of long time development which transformed by the glacier in the last glaciation period. The evidence of it are overdeepening of lake basins and moraine sediments along the depression edges. In the post-glaciation period faster rising up of watershed zones led to the development of steep slopes which were not transformed by glacial exaration. A new coluvial material was formed at the foot of the slopes. Making out tectonic movements in order to render the relief formed as a result of the lact glaciation seems to be an important problem. It should be remembered that vertical movements of different amplitudes (may be of different directions) could cause rising of surfaces of different ages to the same height and vice versa - the one age surfaces could rise up to different heights. Thus, the first marine terraces in Shielpino Bay and Dalnye Zelentsy Bay are about 80 m a.s.l. but they have different geological structures. A lot of marine fauna occurs in the terrace sediments in Shielpino Bay but it does not occur in Zelentsy Bay. However, a level of pumice occurs in the top part of the covers. That testifies to formation of marine deposits building a terrace in various centuries. A high terrace of the Voronia River is a delta built of fluvioglacial sediments raised to 60 m a.s.l. while the ridge remains on the coast do not occur higher than 45 m. The above facts point to the problem of uneven raising of the region which requires further investigations. 81

4 Fig. 1 Location sketch: 1 - lake valleys and rivers joining Ihem; 2 - watersheds; 3 - larger localities

5 oo Ul Fig. 2 Zones of maximal watershed rising up; 1 - isolines of maximal watershed rising up (cut every 25 m, from 100 to 355 m)

6 Fig. 3 Diagram of watershed overheights over local erosion sites. 1 -isolines of watershed overheights over local erosion sites; 2 - north-west block; 3 - south-east block; 4 - borderlines between blocks

7 oo Fig. 4. Tectonic diagram: 1 -first tectonic zone of order I; 2 - second tectonic zone of order 1; 3 - third tectonic zone of order I; 4 - tectonic structures of order II

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