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Geomorphologic structure of salty lakes region (The Ambarnaya Inlet, Varanger fjord, south-western part of the Barents Sea)

Lazareva E.I., Bobkov A.A.

Saint-Petersburg State University, Department of Geography and Geoecology, Saint-Petersburg, Russia

selena11.91@mail.ru

Investigation is based on materials of complex expedition taken place in August, 2011. Two salty lakes Linyalampi and Sisyayarvi belonging to the Inlet of Ambarnaya located on the Murmansk shore of Kola Peninsula, washing by the Barents Sea waters, became objects of these notes. The Inlet of Ambarnaya is located to the east of the Pechenga Inlet and separated from it by the peninsula which northeast point the Romanov's Cape is. Its continuation are partially isolated two basins mentioned above, oriented in north-south direction which are separated from parent inlet by two underwater rapids in width, depending on height of a tide, of 20-30 m and extent up to 50 m.

Morphometric parameters of both basins taken from topographic map of scale of 1:50 000: the Lake of Linyalampi, the area 394 200 м2, perimeter (extent of coastal line) makes 3 040 m, the maximum sizes 900х750 m in cross; the Lake of Sisyayarvi, the area 629 900 м2, perimeter of 4 200 m, the maximum cross sizes 650х1700 m.

On a configuration of coastal line, a surrounding and bottom relief the Inlet of Ambarnaya and both lakes should be carried to an inlet of fjard type.

The researched area is notable for complicated roughness of its relief that has affected on configuration of coastline. The locations of fjords and fjards are determined by tectonic structure.

Four main directions of morpho-tectonic lineaments have formed basins of the Ambarnaya Inlet and lakes. NNE longitudinal fault has formed the basin of Sisyayarvi lake. Lineament of NNW trend is well-marked on aerospace images and maps on eastern shortened section of the inlet shore. In the south this lineament is marked as clough, then it changes direction on WSW and further on SSW trend. Probably the clough shows the boundary between the Archean granitoids and Archean gneisses. ENE lineament is situated to the west from the Ambarnaya Inlet and also forms a underwater rapid between inlet and Linyalampi lake. There was an intrusion of mafic rocks here that formed this underwater rapid. The lineament of WNW direction is a boundary between granitoids of Archean.

The researched area is situated on the Baltic shield. Here rockmass of Murmansk granite has contact with gneisses in the clough and with microcline granites in the north. The assemblage of gneisses of early Archean had formed folded structures that were intruded by oligoklaz granites. The assemblage of quaquaversal microcline granites is dated late Archean. There was a propagation of quartz’s lodes and knots on rock’s fissures. Later, probably in Proterozoic, mafic rocks ortoamphibolite penetrated in faults.

The evolution of the relief took place in longstanding period of stable elevation and wide distribution of crystalline rocks. Tectonic processes (formation of faults, intrusions, vertical block movements) and processes of denudation have been proceeding together. During the Pleisticene and the Quaternary periods the relief was revived by glaciers. Directions of fluctuations of glaciers were usually in phase with morphostructures and it made the relief more contrastive. The result is low-mountain (max altitude in the researched area is 292 m) and rough relief.

The main forms of the relief are: astructural-denudation table land and slopes. The table has undulate surface and it is situated on several altitude levels. There is abundance of erratic boulders of different sizes (on average one and a half meters in diameter), lakes of a different configurations and glacial scour on the table surface.

Affluence of grabens, faults explain numerous very steep slopes (slope bevel more than 35 о) and vertical cliffs. These slopes are usually covered on a half by screes. There are also steep slopes (35 о -15 о), average steep slopes (15 о -8 о) and gentle (<8 о) slopes in this area.

The coastline of salty lakes is an alternation of beaches and cliffs. Cliffs are situated close by water and their average altitude is 80 m. Beach sediments consist of three fractures: sand, gravel, pebbles. Wideness of beaches ranges from 1 till 10 m. There are a few small tidal marshes in the researched area. They have been formed to the south from Sisyayarvi lake, where depths of lake grow gradually.

Fluvio-glacial and glacial sediments are almost absent. There are several flat-topped hills consisted of fluvio-glacial sediments; they are situated opposite rivers on the coast and on the underwater rapid between inlet and lake. There is a fragment of moraine on the underwater rapid between lakes. Its configuration can be described as amphitheater with saddle, altitude is 5 m. The moraine’s consistence is unscreened ratchels of a different size (gravel, pebbles) with sandy joining material.

Samples of bottom sediments for granulomertic analysis were taken on different depths and in tidal marshes of Sisyayarvi lake. The samples were from morphologic diverse parts of lake bed, on depths from 10 till 22 m. In a most of samples gravel and small pebbles are prevail over other fractures. But on tidal marshes subsoils are close-grained. Particles of shells and lithothamnium are noticed everywhere. The red king crab was marked on the depths 13-21 m, on gentle and steep slopes.

Geomorphologic map and granulometric analysis are of great importance for applied hidrobiological and ecological investigations. Particularly, the red king crab (Paralithodes Camtschaticus) is an important component of a bottom biocenosis prefers rocky, pebbly or muddy subsoils with plenty of fodder organisms. It is considered in forecasting of fishery areas of crabs.

Dates of the geomorphologic investigations have been mapped; results of the granulometric analysis are presented in a table.

References:

1. Antropov, P.Y. (1958) Geology of the USSR, Gosgeoltehizdat, Moscow, 710 pp

2. Pavlov, V.Y. (2003) The biography of the red king crab (Paralithodes Camtschaticus), Moscow, 110 pp

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