New data on the history of the development of the southeastern part of the Baltic Sea from the Late Glacial to the present. Seas of Russia - Baltic Sea

Deeply cut into the land, the Baltic Sea has a very complex outline of the coast and forms large bays: Bothnian, Finnish and Riga. This sea has land borders almost everywhere, and only from the Danish Straits (Great and Small Belt, Sound, Farman Belt) is it separated by conditional lines passing between certain points on their coasts. Due to the peculiar regime, the Danish Straits do not belong to the Baltic Sea. They associate him with North Sea and across it to the Atlantic Ocean. The depths above the rapids separating the Baltic Sea from the straits are small: above the Darser threshold - 18 m, above the Drogden threshold - 7 m. The cross-sectional area in these places is 0.225 and 0.08 km 2, respectively. The Baltic Sea is weakly connected with the North Sea and has limited water exchange with it, and even more so with the Atlantic Ocean.

It belongs to the type of inland seas. Its area is 419 thousand km 2, volume - 21.5 thousand km 3, average depth - 51 m, maximum depth - 470 m.

Bottom relief

The bottom relief of the Baltic Sea is uneven. The sea lies entirely within the shelf. The bottom of its basin is indented by underwater depressions, separated by hills and socles of islands. In the western part of the sea there are shallow Arkon (53 m) and Bornholm (105 m) depressions, separated by about. Bornholm. IN central regions In the sea, quite extensive spaces are occupied by the Gotland (up to 250 m) and Gdansk (up to 116 m) basins. North of about. Gotland lies the Landsort Depression, where the greatest depth of the Baltic Sea is recorded. This depression forms a narrow trench with depths of more than 400 m, which stretches from the northeast to the southwest, and then to the south. Between this trough and the Norrköping depression located to the south, an underwater hill stretches with depths of about 112 m. Further south, the depths again increase slightly. On the border of the central regions with the Gulf of Finland, the depth is about 100 m, with the Bothnian - about 50 m, and with the Riga - 25-30 m. The bottom relief of these bays is very complex.

Bottom relief and currents of the Baltic Sea

Climate

The climate of the Baltic Sea is of maritime temperate latitudes with features of continentality. The peculiar configuration of the sea and a significant length from north to south and from west to east create differences in climatic conditions in different areas seas.

The Icelandic low, as well as the Siberian and Azores anticyclones, most significantly affect the weather. The nature of their interaction determines the seasonal features of the weather. In autumn and especially in winter, the Icelandic Low and the Siberian High interact intensively, which intensifies cyclonic activity over the sea. In this regard, in autumn and winter, deep cyclones often pass, which bring with them cloudy weather with strong southwestern and western winds.

In the coldest months - January and February - the average air temperature in the central part of the sea is -3° in the north and -5-8° in the east. With rare and short-term intrusions of cold Arctic air associated with the strengthening of the Polar High, the air temperature over the sea drops to -30° and even to -35°.

In the spring-summer season, the Siberian High collapses, and the Baltic Sea is affected by the Icelandic Low, the Azores and, to some extent, the Polar High. The sea itself is located in a zone of low pressure, along which cyclones are less deep than in winter, from Atlantic Ocean. In this regard, in spring the winds are very unstable in direction and low in speed. Northerly winds are responsible for the usually cold spring in the Baltic Sea.

In summer, predominantly western, northwestern and southwestern weak to moderate winds blow. They are associated with the cool and humid summer weather characteristic of the sea. The average monthly temperature of the warmest month - July - is 14-15° in the Gulf of Bothnia and 16-18° in other areas of the sea. Hot weather is rare. It is caused by short-term inflows of warm Mediterranean air.

Hydrology

About 250 rivers flow into the Baltic Sea. The largest amount of water is brought per year by the Neva - an average of 83.5 km 3, the Vistula - 30 km 3, the Neman - 21 km 3, the Daugava - about 20 km 3. The runoff is unevenly distributed across the regions. So, in the Gulf of Bothnia it is 181 km 3 /year, in Finland - 110, in Riga - 37, in the central part of the Baltic - 112 km 3 /year.

Geographical position, shallow water, complex bottom topography, limited water exchange with the North Sea, significant river runoff, and climate features have a decisive influence on hydrological conditions.

The Baltic Sea is characterized by some features of the eastern subtype of the subarctic structure. However, in the shallow Baltic Sea, it is represented mainly by surface and partially intermediate waters, significantly transformed under the influence of local conditions (limited water exchange, river runoff, etc.). The water masses that make up the structure of the waters of the Baltic Sea are not identical in their characteristics in different areas and change with the seasons. This is one of the distinguishing features of the Baltic Sea.

Water temperature and salinity

In most areas of the Baltic Sea, surface and deep water masses are distinguished, between which lies a transitional layer.

Surface water (0-20 m, in some places 0-90 m) with a temperature of 0 to 20°C, a salinity of approximately 7-8‰ is formed in the sea itself as a result of its interaction with the atmosphere (precipitation, evaporation) and with the waters of the continental runoff. This water has winter and summer modifications. In the warm season, a cold intermediate layer is developed in it, the formation of which is associated with a significant summer heating of the sea surface.

The temperature of deep water (50-60 m - bottom, 100 m - bottom) - from 1 to 15 °, salinity - 10-18.5‰. Its formation is associated with the entry of deep waters into the sea through the Danish straits and with mixing processes.

The transitional layer (20-60 m, 90-100 m) has a temperature of 2-6°C, salinity of 8-10‰, and is formed mainly by mixing surface and deep waters.

In some areas of the sea, the structure of the waters has its own characteristics. For example, in the Arkon region, there is no cold intermediate layer in summer, which is explained by the relatively shallow depth of this part of the sea and the influence of horizontal advection. The Bornholm region is characterized by a warm layer (7-11°) observed in winter and summer. It is formed by warm waters coming here from the slightly warmer Arkona basin.

In winter, the water temperature is somewhat lower near the coast than in the open parts of the sea, while it is slightly higher near the western coast than near the eastern one. So, average monthly temperature water in February near Ventspils is 0.7 °, at the same latitude in the open sea - about 2 °, and near the western coast - 1 °.

Water temperature and salinity at the surface of the Baltic Sea in summer

Summer temperature surface water is not the same in different regions of the sea.

The decrease in temperature at western coasts, in the central and southern regions is explained by the predominance of westerly winds that drive the surface layers of water away from the western shores. Colder underlying waters rise to the surface. In addition, a cold current from the Gulf of Bothnia passes along the Swedish coast to the south.

Clearly pronounced seasonal changes in water temperature cover only the upper 50-60 m; deeper, the temperature changes very little. In the cold season, it remains approximately the same from the surface to the horizons of 50-60 m, and deeper it drops somewhat to the bottom.

Water temperature (°C) on a longitudinal section in the Baltic Sea

In the warm season, the increase in water temperature as a result of mixing extends to horizons of 20–30 m. From there, it abruptly decreases to horizons of 50–60 m and then again rises somewhat towards the bottom. The cold intermediate layer persists in summer, when the surface layer warms up and the thermocline is more pronounced than in spring.

Limited water exchange with the North Sea and significant river runoff result in low salinity. On the sea surface, it decreases from west to east, which is associated with the predominant flow of river waters into eastern part Baltics. In the northern and central regions of the basin, salinity somewhat decreases from east to west, since in cyclonic circulation, saline waters are transported from south to northeast along the eastern coast of the sea further than along the western one. A decrease in surface salinity can also be traced from south to north, as well as in bays.

In the autumn-winter season, the salinity of the upper layers slightly increases due to a decrease in river runoff and salinization during ice formation. In spring and summer, salinity on the surface decreases by 0.2-0.5‰ compared to the cold half-year. This is explained by the desalination effect of continental runoff and the spring melting of ice. Almost throughout the sea, a significant increase in salinity from the surface to the bottom is noticeable.

For example, in the Bornholm Basin, salinity at the surface is 7‰ and about 20‰ at the bottom. The change in salinity with depth is basically the same throughout the sea, with the exception of the Gulf of Bothnia. In the southwestern and partly central regions of the sea, it gradually and slightly increases from the surface to horizons of 30-50 m, below, between 60-80 m, there is a sharp layer of a jump (halocline), deeper than which the salinity again slightly increases towards the bottom. In the central and northeastern parts, salinity increases very slowly from the surface to 70–80 m horizons; deeper, at 80–100 m horizons, there is a halo wedge, and then salinity slightly increases to the bottom. In the Gulf of Bothnia, salinity increases from the surface to the bottom by only 1-2‰.

In autumn-winter time, the flow of North Sea waters into the Baltic Sea increases, and in summer-autumn it somewhat decreases, which leads to an increase or decrease in the salinity of deep waters, respectively.

In addition to seasonal fluctuations in salinity, the Baltic Sea, unlike many seas oceans characterized by significant interannual changes.

Observations of salinity in the Baltic Sea from the beginning of this century until recent years show that it tends to increase, against which short-term fluctuations appear. Changes in salinity in the basins of the sea are determined by the inflow of water through the Danish Straits, which in turn depends on hydrometeorological processes. These include, in particular, the variability of large-scale atmospheric circulation. The long-term weakening of cyclonic activity and the long-term development of anticyclonic conditions over Europe lead to a decrease in precipitation and, as a consequence, to a decrease in river runoff. Changes in salinity in the Baltic Sea are also associated with fluctuations in the values ​​of continental runoff. With a large river runoff, the level of the Baltic Sea slightly rises and the sewage flow from it intensifies, which in the shallow zone of the Danish Straits (the smallest depth here is 18 m) limits the access of salt water from the Kattegat to the Baltic. With a decrease in river flow, saline waters more freely penetrate into the sea. In this regard, fluctuations in the inflow of saline waters into the Baltic are in good agreement with changes in the water content of the rivers of the Baltic basin. IN last years an increase in salinity is noted not only in the bottom layers of the basins, but also in the upper horizons. At present, the salinity of the upper layer (20-40 m) has increased by 0.5‰ compared to the average long-term value.

Salinity (‰) on a longitudinal section in the Baltic Sea

Salinity variability in the Baltic Sea is one of the most important factors regulating many physical, chemical and biological processes. Due to the low salinity of the surface waters of the sea, their density is also low and decreases from south to north, varying slightly from season to season. Density increases with depth. In the areas of distribution of saline Kattegat waters, especially in basins at the horizons of 50-70 m, a constant layer of a density jump (pycnocline) is created. Above it, in the surface horizons (20-30 m), a seasonal layer of large vertical density gradients is formed, due to a sharp change in water temperature at these horizons.

Water circulation and currents

In the Gulf of Bothnia and in the shallow area adjacent to it, a density jump is observed only in the upper (20-30 m) layer, where it is formed in spring due to freshening by river runoff, and in summer due to heating of the surface layer of the sea. A permanent lower layer of the density jump is not formed in these parts of the sea, since deep saline waters do not penetrate here and year-round stratification of waters does not exist here.

Water circulation in the Baltic Sea

The vertical distribution of oceanological characteristics in the Baltic Sea shows that in the southern and central regions the sea is divided by a density jump layer into upper (0-70 m) and lower (from 70 m to the bottom) layers. In late summer - early autumn, when weak winds prevail over the sea, wind mixing extends to horizons of 10-15 m in the northern part of the sea and to horizons of 5-10 m in the central and southern parts and serves as the main factor in the formation of the upper homogeneous layer. During autumn and winter, with an increase in wind speeds over the sea, mixing penetrates to horizons of 20–30 m in the central and southern regions, and up to 10–15 m in the east, since relatively weak winds blow here. As autumn cooling intensifies (October - November), the intensity of convective mixing increases. During these months, in the central and southern regions of the sea, in the Arkon, Gotland and Bornholm depressions, it covers a layer from the surface up to about 50-60 m. ) and is limited by the density jump layer. In the northern part of the sea, in the Gulf of Bothnia and in the west of the Gulf of Finland, where autumn cooling is more significant than in other areas, convection penetrates to horizons of 60-70 m.

The renewal of deep waters, the sea occurs mainly due to the inflow of the Kattegat waters. With their active inflow, the deep and bottom layers of the Baltic Sea are well ventilated, and with small amounts of salt water flowing into the sea at great depths, stagnation occurs in the depressions up to the formation of hydrogen sulfide.

The strongest wind waves are observed in autumn and winter in open, deep areas of the sea with prolonged and strong southwestern winds. Stormy 7-8-point winds develop waves up to 5-6 m high and 50-70 m long. Gulf of Finland strong winds of these directions form waves with a height of 3-4 m. In the Gulf of Bothnia, storm waves reach a height of 4-5 m. The largest waves occur in November. In winter, with stronger winds, the formation of high and long waves is prevented by ice.

As in other seas of the northern hemisphere, the surface circulation of the Baltic Sea has a general cyclonic character. Surface currents are formed in the northern part of the sea as a result of the confluence of waters emerging from the Gulf of Bothnia and the Gulf of Finland. The general flow is directed along the Scandinavian coast to the southwest. Going around on both sides about. Bornholm, he is heading through the Danish Straits to the North Sea. At south coast the current is directed to the east. Near the Gulf of Gdansk, it turns north and moves along the eastern coast to about. Khnum. Here it branches into three streams. One of them goes through the Irben Strait to the Gulf of Riga, where, together with the waters of the Daugava, it creates a circular current directed counterclockwise. Another stream enters the Gulf of Finland and along its southern coast extends almost to the mouth of the Neva, then turns to the northwest and, moving along the northern coast, leaves the bay together with river waters. The third flow goes to the north and through the straits of the Aland skerries penetrates into the Gulf of Bothnia. Here, along the Finnish coast, the current rises to the north, goes around the northern coast of the bay and descends to the south along the coast of Sweden. In the central part of the bay, there is a closed circular counterclockwise current.

The speed of the permanent currents of the Baltic Sea is very low and is approximately 3-4 cm/s. Sometimes it increases to 10-15 cm/s. The current pattern is very unstable and is often disturbed by the wind.

The prevailing wind currents in the sea are especially intense in autumn and winter, and during strong storms their speed can reach 100-150 cm/s.

Deep circulation in the Baltic Sea is determined by the flow of water through the Danish straits. The inlet current in them usually passes to horizons of 10-15 m. Then this water, being denser, descends into the underlying layers and is slowly transported by the deep current, first to the east and then to the north. With strong westerly winds, water from the Kattegat flows into the Baltic Sea almost along the entire cross section of the straits. East winds, on the contrary, increase the outlet current, which extends to the horizons of 20 m, and the inlet current remains only near the bottom.

Due to the high degree of isolation from the World Ocean, the tides in the Baltic Sea are almost invisible. Fluctuations in the level of the tidal character in individual points do not exceed 10-20 cm. The average sea level experiences secular, long-term, inter-annual and intra-annual fluctuations. They can be associated with a change in the volume of water in the sea as a whole and then have the same value for any point in the sea. The secular level fluctuations (except for changes in the volume of water in the sea) reflect the vertical movements of the shores. These movements are most noticeable in the north of the Gulf of Bothnia, where the rate of land rise reaches 0.90-0.95 cm/year, while in the south the rise is replaced by the sinking of the coast at a rate of 0.05-0.15 cm/year.

In the seasonal course of the Baltic Sea level, two minima and two maxima are clearly expressed. The lowest level is observed in spring. With the arrival of spring flood waters, it gradually rises, reaching a maximum in August or September. After that, the level goes down. The secondary autumn low is coming. With the development of intense cyclonic activity, westerly winds drive water through the straits into the sea, the level rises again and reaches a secondary, but less pronounced maximum in winter. The height difference between the summer maximum and the spring minimum is 22-28 cm. It is greater in the bays and less in the open sea.

Surge fluctuations in the level occur quite quickly and reach significant values. In open areas of the sea, they are approximately 0.5 m, and at the tops of bays and bays they are 1-1.5 and even 2 m. -26 h. Level changes associated with seiches do not exceed 20-30 cm in the open part of the sea and reach 1.5 m in the Neva Bay. Complex seiche level fluctuations are one of the characteristic features of the Baltic Sea regime.

The catastrophic St. Petersburg floods are connected with sea level fluctuations. They occur when the level rise is due to the simultaneous action of several factors. Cyclones that cross the Baltic Sea from the southwest to the northeast cause winds that drive water from the western regions of the sea and drive it into the northeastern part of the Gulf of Finland, where the sea level rises. Passing cyclones also cause seiche fluctuations in the level, at which the level rises in the Aland region. From here, a free seiche wave, driven by western winds, enters the Gulf of Finland and, together with the surge of water, causes a significant increase (up to 1-2 m and even 3-4 m) in the level at its top. This prevents the flow of the Neva water into the Gulf of Finland. The water level in the Neva is rapidly rising, which leads to floods, including catastrophic ones.

ice coverage

The Baltic Sea is covered with ice in some areas. The earliest (around the beginning of November) ice forms in the northeastern part of the Gulf of Bothnia, in small bays and off the coast. Then the shallow areas of the Gulf of Finland begin to freeze. The maximum development of the ice cover reaches in early March. By this time, motionless ice occupies the northern part of the Gulf of Bothnia, the region of the Aland skerries and the eastern part of the Gulf of Finland. Floating ice occurs in the open areas of the northeastern part of the sea.

The spread of motionless and floating ice in the Baltic Sea depends on the severity of the winter. Moreover, in mild winters, ice, having appeared, may completely disappear, and then appear again. IN harsh winters the thickness of immobile ice reaches 1 m, and floating ice - 40-60 cm.

Melting begins in late March - early April. The release of the sea from ice goes from the southwest to the northeast.

Only in severe winters in the north of the Gulf of Bothnia, ice can be found in June. However, the sea is cleared of ice every year.

Economic importance

In the significantly freshened waters of the bays of the Baltic Sea, freshwater fish species live: crucian carp, bream, chub, pike, etc. There are also fish that, in fresh waters spend only part of their lives, the rest of the time they live in the salty waters of the sea. These are now rare Baltic whitefish, typical inhabitants of the cold and clean lakes of Karelia and Siberia.

A particularly valuable fish is the Baltic salmon (salmon), which forms an isolated herd here. The main habitats of salmon are the rivers of the Gulf of Bothnia, the Gulf of Finland and the Gulf of Riga. She spends the first two or three years of her life mainly in the southern part of the Baltic Sea, and then goes to spawn in the rivers.

Purely marine fish species are common in the central regions of the Baltic, where salinity is relatively high, although some of them also enter fairly fresh bays. For example, herring lives in the Gulf of Finland and Riga. More saltwater fish - Baltic cod - do not enter the fresh and warm bays. Eel is a unique species.

In fishing, the main place is occupied by herring, sprat, cod, river flounder, smelt, perch and various types of freshwater fish.

A 12.38 m long core sample was sampled in the Gdansk depression on the cruise of the R/V Poseidon within the framework of the Russian-German GISEB project. The complex of studies included isotope determination of age by 14 C and 210 Pb, palynological, phase X-ray diffraction, granulometric and X-ray fluorescence analyses. New detailed data have been obtained on climate change and the development of the Gdansk Basin from the Belling to the subatlantic. The sedimentation rates are calculated from 0.37 to 1.62 mm/year. To establish the main variations in salinity pool waters, caused by paleogeographic changes in the late Pleistocene - Holocene, the concentrations of bromine in sediments were determined. It was shown that the formation of the Yoldia Sea within the Gdansk basin was not accompanied by an increase in water salinity. Based on the data obtained on changes in the paleosalinity of waters and an increase in near-bottom hydrodynamic activity, several transgressive-regressive cycles of the Littorin time have been recorded.

Keywords: paleogeography, paleo-Baltic, isotope dating, geochemistry of bottom sediments.

Since the degradation of the last glaciation about 14,000 years ago, the water area of ​​the modern Baltic Sea has gone through several stages of development, representing either a closed freshwater lake system or a marine system connected to the ocean. The existence of these stages was the result of climate change, staged degradation of the last glaciation, eustatic rise in the level of the World Ocean, glacioisostatic uplift of the Baltic Shield, neotectonic movements, and other factors. Global warming and the current rise in the level of the World Ocean, apparently, marked the beginning of a new phase in the development of the Baltic Sea. Predicting changes in the geological environment at this new stage is possible only on the basis of a paleogeographic analysis of the development of the basin. One of the optimal objects for such studies is the sediments of the Baltic Sea depressions, since they are characterized by almost continuous sedimentation and the formation of "complete" sections.

The Gdansk depression is a large basin of the South-Eastern Baltic, separated from the rest of the sea by the Gotland-Gdansk threshold and elongated in a submeridional direction (Fig. 1). The paleogeographical conclusions made on the basis of the study of the sections of the deposits of the Gdansk depression in the 1970-1980s are most fully presented in the works of the JSC IO RAS [ Blazhchishin, 1998; Geology…, 2002]. In the southern part of the basin, a number of soil cores up to 15 m long were studied. Litho- and chemostratigraphy were used to determine the relative age of the deposits. The paleosalinity of the waters of the Gdansk depression was studied by the method of "equivalent boron" [ Blazhchishin, 1982]. Later, in the Department of Marine Geology of the Polish Geological Institute, columns were studied, the stratigraphic subdivision of which was based on the data of spore-pollen analysis and radiocarbon dating [ Zachowicz, 1995; Zachowicz et al., 2008].

Research methodology and factual material. The ground core at station POS 303700 with a length of 1238 cm was selected on the cruise of the Poseidon research vessel (Germany) as part of the Russian-German GISEB project "GIS for modeling the spatial and temporal distribution of precipitation depending on environmental changes in the Baltic Sea". The station is located in the southeastern part of the Gdansk depression (54°49.34 N, 19°11.1 E, sea depth 105.4 m) (Fig. 1). Sampling was carried out using a direct-flow gravity soil tube 15 m long with plastic liners. A multicorer sampler was used to sample near-surface bottom sediments.

Geological description The section was carried out at VSEGEI when extracting cores from liner pipes. Samples for palynological analysis and geochemical studies were taken along the section with a step of 8 cm, for other types of analyzes - from characteristic lithostratigraphic layers.

Geochemical methods 140 samples were studied. The samples were dried to an air-dry state and abraded. Determination of Br , As , Pb , Zn , Cu , Ni , Fe , Mn , Cr was carried out on X-ray scanning crystal-diffraction spectrometer SPEKTROSKAN-005 in the Department of Regional Geoecology and Marine Geology of VSEGEI.

Palynological analysis was also carried out in the department of regional geoecology and marine geology of VSEGEI. 140 samples were studied with a weighed sample of 25 g of wet sediment. Primary processing was carried out according to the method of V.P. Grichuk [ Grichuk and Zaklinskaya, 1948 ]. The samples were viewed on a JENAVAL microscope at a magnification of 500 times. At a high concentration of spores and pollen, at least 500 grains of pollen from Quaternary woody plants were counted; at the same time, herbaceous pollen, spores, and redeposited forms were counted. At low concentrations, palynomorphs were counted in the entire sample.

The concentration of spores and pollen in the sediment was determined by the formula

C = an/0,02bm,

Where C- the amount of pollen in 1 g sample; A- the volume of the suspension in milliliters; n- the number of counted grains; b- the number of drops viewed during the analysis; 0.02 - the volume of one drop in 1 ml; m- rock sample in grams.

When constructing the spore-pollen diagram, the TILIA and TILIAGRAPH programs were used [ Grimm, 1990]. The percentage of taxa was calculated from the total number of Quaternary palynomorphs. When interpreting the data, the paleoecological method was used with the identification of palynocomplexes reflecting cold and warm intervals. The results obtained were compared with sections of the Upper Quaternary deposits of the Baltic Sea and adjacent land [ Kleimenova et al., 1979; Malyasova and Spiridonova, 1983; Stelle et al., 1976; Yakubovskaya et al., 1983; Geology…, 2002; Nilsson, 1964; Zachowicz, 1995; Zachowicz et al., 2008].

Isotopic dating deposits was carried out at the Center for Isotope Research of VSEGEI for 14 C (7 samples) and 210 Pb using a Quantulus 1220 liquid scintillation alpha-beta spectrometer. In radiocarbon dating, for the transition to age in calendar years using the Calib 5.0 program (calib .qub .ac .uk /calib ), calibration was carried out using the Marine 04 curve [ Hughen et al., 2004]. To determine 210 Pb, samples were taken from intervals of 0-5, 5-10, 15-20, 90-95 and 174-178 cm. The last two samples were analyzed to determine the background equilibrium 210 Pb.

Granulometric analysis produced in the laboratory of geoecology of JSC IO RAS. To remove organic matter, the sample was treated with hydrogen peroxide. The content of fractions from 0.3 to 50 µm was determined on a laser particle analyzer "Analysette 22 Compact". The particles were dispersed using sodium tripolyphosphate and suspension treatment in an ultrasonic bath "Laborette 17". Sieve analysis (wet sieving) was carried out on a vibrating screen "Analysette 3" (sieves with meshes of 250, 100, 50 microns). The results of laser and sieve analyzes were combined using computer program Analyzette 22 32Bit Program .

Composition of clay minerals (< 0,001 мм) определялся для 11 проб в Центральной аналитической лаборатории ВСЕГЕИ с помощью рентгеновского дифрактометра ДРОН-6.

Method for determining the salinity of water by bromine. To determine the salinity of the pore waters of bottom sediments, an element of the halogen group, bromine, was used for the first time. The ratio Cl/Br = 293 for the interstitial waters of the surface sediments of the World Ocean is practically the same and does not differ from the normal one in oceanic water. For the Baltic Sea, the Cl/Br ratio in surface sediments is 230 [ Shishkina, 1969]. By calculation, the Cl content can be obtained from the sediment section. In many works, in particular V.A. Snezhinsky [ 1951 ], an empirical formula is given for converting the chlorine content to the total salinity of ocean waters: S ‰ = 0.03 + 1.805Cl ‰. For the Baltic Sea, the coefficients included in this formula have been refined: S ‰ = 0.115 + 1.80655Cl ‰ [ Lyakhin, 1994]. The use of this formula is possible provided that the coefficients did not fundamentally change during the studied geological time, which is applicable for marine sedimentation conditions. For freshwater systems, this is not entirely correct. The probable error of the formula for the sediments of basins with low salinity was estimated experimentally. For this purpose, the concentration of Br in modern sediments of the Russian part was determined. Curonian Lagoon, where the water salinity does not exceed 1‰. The calculated salinity turned out to be comparable with the data on the salinity of the waters of this part of the bay [ Fisheries…, 2008 ]. The proposed technique can also be used for relatively freshwater conditions.

When calculating the mineralization of paleobasin waters by Br, it was taken into account that its concentrations in bottom sediments are determined not only by water salinity. The sources of the sedimentary material that forms the deposits of the studied section are diverse in composition; therefore, the use of clarke contents of Br to account for its initial content in the deposits is hardly applicable. It is more justified to use the Br concentration in the sediments of a long-lived freshwater basin as a background one, located in geological and geomorphological and geomorphological conditions similar to those of the Baltic Sea. natural conditions. For this, Lake Ladoga was chosen, the background concentration of Br for aleuropelitic sediments of which is 0.00046%, which is close to its clarke for medium (0.00045%) and sedimentary (0.0006%) rocks. By subtracting the background value of Br from the contents obtained during the analysis of samples, it can be assumed that the remaining Br is due to a change in the salinity of the waters of the sea basin. All calculated salinity values ​​are corrected for the background Br concentration.

Research results. When summarizing the lithological description of the data of granulometric, spore-pollen and radiocarbon analyzes, a stratigraphic subdivision of the core was performed.

Lithostratigraphy. The primary description of the section of bottom sediments, taking into account the previously identified lithocomplexes in the Gdansk depression [ Blazhchishin, 1998] made it possible to distinguish four main lithostratigraphic horizons by characteristic external material features, correlated with the stages of development of the Baltic Sea.

In the lower part of the section (11.35-12.38 m), the deposits are represented by compacted gray clays with inclusions of microlenses of clay-aleurite composition and individual silt-sandy grains. This horizon was apparently formed at the stage of development of the Baltic Glacial Lake (BLL). The glacier was already at a considerable distance from the Gdansk basin, as evidenced by the absence of band-type layering.

Higher in the section (8.35-11.35 m), the deposits are represented by light gray rather monotonous silty clays with inclusions of microlenses and thin layers enriched in silty and sandy material. The maximum enrichment with silty sandy material, according to the granulometric analysis, was noted in the interval of 9.35-11.35 m (Fig. 2). In the middle part of the member (horizon 10.07-10.08 m) there is a layer of silty sand. A similar pack 40 cm thick was previously described as a drainage tape at the base of the AK-2682 core [ Blazhchishin, 1998]. Its origin was presumably associated with the drainage (descent) of the BLO at the beginning of the allered. According to modern concepts, the descent of the BLO manifested itself in the South-East Baltic twice: at the end of the Allered and at the end of the Younger Dryas [ Uscinowicz, 2003]. At the interval of 7.93-8.35 m, a transitional layer was identified.

For the overlying horizon (6.44-7.93 m), the deposits of which are represented by gray, sometimes almost black silty clays (clays), a characteristic feature is the presence of amorphous sulfide nodules (hydrotroilite). The dimensions of the constrictions usually do not exceed one millimeter. Their distribution along the section is uneven, sometimes chaotic, often they are concentrated in the form of lenticular layers with a thickness of 2 to 20 mm. The presence of hydrotroilite concretions in a section usually serves as a diagnostic feature characteristic of the deposits of Lake Ancylus and the Yoldian Sea. At the interval of 6.15-6.44 m, a transitional layer was identified, represented by olive-gray silty clays with rare lenticular stripes 1-5 mm wide of dark color and black microconcretions.

In the upper part of the section from the mark of 6.15 m to the near-surface layer, the deposits are represented by olive-gray silt-clay silts. Sediments are characterized by rhythmic banding (layering), in places they are porous, gas-saturated, and contain remains of shells. There is a smell of hydrogen sulfide. Sediments here accumulated in the late Holocene under conditions of the Littorina and postlitorina marine basins.

The inertness of the change in sedimentation processes under the conditions of conservatism of the environment of the deep-water basins of the Baltic Sea probably explains some “lag” in the change in external lithological features of deposits in the section from the actual change in paleogeographic conditions. Analytical studies made it possible to clarify the position of the boundaries between the horizons formed at various stages of the development of the Baltic.

radioisotope dating. Sediment samples taken from a depth of more than 650 cm are characterized by a low content of carbonaceous matter (less than 1 wt %). The datings made for deposits above this mark can be considered the most reliable (Table 1). The average rate of sediment accumulation in the Late Pleistocene - Holocene, calculated from the dating results, is 0.84 mm/year, varying from 0.37 to 1.62 mm/year. In column 2EL 96, located 7.5 km to the north, [ Zachowicz et al., 2008] sediment accumulation rates, also according to the results of radiocarbon dating, are in the range of 0.5-0.7 mm/year. The current rate of sedimentation, according to the determination of 210 Pb for the surface layer of sediments, is 4 ± 2 mm/year (Table 2), which is associated with the deconsolidation of surface sediments compared to the underlying horizons.

Palynological analysis and biostratigraphy. The spore-pollen spectrum of a surface sample (0-5 cm) is characterized by the predominance of pollen from woody plants (93% of the total composition of certain forms), among which the most pollen Pinus sylvestris Linnaeus (61%), pollen count Betula sect. Albae Regel is 19, Alnus sp. - 7, Picea abies(Linnaeus)H. Karst - 4%, pollen of the genera Salix, Corylus, Tilia, Ulmus, Fagus, Quercus occurs in single specimens. The herbaceous group (5% of the total composition) is dominated by Poaceae, Chenopodiaceae, Artemisia sp. Among the spores (2% of the total composition), Polypodiaceae dominate. The main introduction of spores and pollen into the study area comes from two physiographic zones - mixed (coniferous-deciduous) and broad-leaved forests.

An analysis of the distribution of Quaternary spores and pollen made it possible to identify ten palynological zones in the section, comparable with the Blitt-Sernander climatic periods (Fig. 3, Table 3). The absolute age of the boundaries between the periods was taken according to J. Mangerud [ Mangerud et al., 1974]. At the boundary between the 5th and 6th palynozones, the concentration of Quaternary spores and pollen sharply increases from 23-51 to 218-1080 grains/g. In addition to Quaternary palynomorphs, redeposited Late Cretaceous-Paleogene and Neogene pollen of the genera Gleichenia, Taxodium, Ilex, Rhus and the Normapolles group, as well as conifers and angiosperms, have been found. Their maximum content is noted in the lower parts of the section (up to 13%). Starting from the 6th palynozone and up the section, redeposited palynomorphs occur singly and not in all samples.

Palynozone 1 reflects periglacial-tundra and tundra vegetation with a predominance of tree and shrub species of birch, wormwood, heather and grasses. The climate at that time was cold and dry. The vegetation of the Belling warming (13,000–12,000 years 14 BP) and the Middle Dryas cooling (12,000–11,800 14 BP) in the near-glacial regions is displayed in similar spore-pollen complexes.

Palynozone 2 testifies to the warming and the change of periglacial-tundra plant formations to tundra, and further south to forest-tundra cenoses. The cooling of the Younger Dryas (palynozone 3) again led to the appearance of periglacial-tundra vegetation. The pine pollen found in this palynozone is smaller and often poorly preserved, which indicates the distant introduction of this pollen. In the preboreal period, warming occurred, which led to the gradual development of forest landscapes (palynozones 4 and 5). Further warming in the boreal (palynozone 6) caused widespread pine forests. The climatic optimum of the Holocene was recorded by spore-pollen spectra in the first half of the Atlantic period (palynozone 7). The palynocomplex of that time testifies to the maximum development of broad-leaved forests with a significant admixture of oak, elm, linden and hazel, which occupied a larger area than at present, the border of their range was shifted to the north. In the second half of the Atlantic period (palynozone 8), due to an increase in the dryness of the climate, the area of ​​broad-leaved forests decreased, while that of pine forests increased. The most favorable climatic conditions during the formation of palynozones 7 and 8 are also evidenced by the maximum concentration of spores and pollen. In the Subboreal period (palynozone 9), the area of ​​distribution of broad-leaved forests decreased. Nevertheless, judging by the greater content of oak and linden pollen than in the surface sample, it was warmer than at present. In the Subatlantic period (palynozone 10), a cooling occurred, as evidenced by a decrease in the amount of pollen from broad-leaved trees.

Bromine concentration and salinity. The Br distribution graph clearly shows a high degree of differentiation of the Br content along the section (Fig. 4). Based on the premise that the vast majority of Br in sediments is due to its presence in pore waters, a possible relationship between its concentrations in samples and the content of clay minerals with a significant sorption capacity was nevertheless determined. According to X-ray diffraction analysis, more than 45% of the clay fraction of the deposits is represented by illite, evenly distributed over the section. Smectite (0-4%) and chlorite (15-20%) have a similar distribution along the section. The greatest inhomogeneity of distribution along the section is characteristic of kaolinite (Fig. 4). Correlation analysis showed that there is no significant relationship between the content of Br and clay minerals. Organic matter is also capable of accumulating Br. In the upper part of the studied section (0-80 cm), the content of organic carbon (Corg) reaches 1-3%, and it is natural that Br accumulates in this case. Below, the content of Corg varies from 0.02 to 0.22%, and, as shown by the correlation analysis, it does not have a noticeable effect on the accumulation of Br, i.e. The determining parameter of Br accumulation is the salinity of the reservoir during sedimentation, and not the sorption capacity of bottom sediments.

The distribution of bromine along the vertical section and the corresponding change in the calculated salinity of bottom sediments (Fig. 5), taking into account the data on absolute age, make it possible to identify several time intervals due to paleogeographic changes during the development of the Baltic Sea basin.

In the lower part of the section (belling), there is a slight tendency to increase the concentration of Br and the calculated salinity. However, in general, in the deposits accumulated before the end of the Early Preboreal, i.e. during the existence of the Baltic Glacial Lake (BLO) and up to the initial stage of Lake Ancylus, the distribution of Br concentration has a uniform character, the calculated salinity remains insignificant and practically does not change, amounting to about 2‰. The invariability of the Br concentration in the sediments comparable in age with the time of the existence of the Yoldian Sea in relation to the deposits of the BLO and the initial phase of Lake Antsyl makes it possible to state that the Yoldian stage of the development of the Baltic was practically not manifested in the Gdansk Basin. This is confirmed by the data obtained from the results of diatom analysis of soil cores that the salinity of the waters of the Yoldia Sea within the Gdansk depression was insignificant [ Blazhchishin et al., 1974; Kessel et al., 1973 ]. Only at the boundary between the Early and Middle Preboreal, which approximately corresponds to an age of 9200 years (14 C BP), was an increase in salinity up to 4‰ (Fig. 5). The duration of this period of increased salinity is a little over 200 years.

In the second half of the Ancyle stage, starting from the boundary between the Late Preboreal and Boreal, up to the level of 549 cm, a gradual increase in the Br concentration to 0.0015% and salinity to 4‰ is noted. The latter indicates a gradual expansion of communication with the ocean, which coincides with the data of A.I. Blazhchishin [ 1998 ] that in the late phase of development, Lake Antsylovoe was brackish.

From the mark of 549 cm, approximately corresponding to the age of 7700 years 14 C BP, there is an abrupt increase in the salinity of sediments from 2 to 9‰. There is a radical change from freshwater lacustrine conditions to marine brackish water conditions. In the work "Geology of the Baltic Sea" [ 1976 ] provides evidence that about 8,000 years ago, due to the eustatic rise in the ocean level, the waters of the North Sea began to flow intensively through the Danish straits into the Baltic. The date of this event, according to various authors, ranges from 8,000 to 8,500 calendar years BP [ Berglund, 1964; Bitinas & Damusyte, 2004]. Given that the process of saline ocean water inflow is extended in time and space, this date is consistent with our results, which determine the beginning of the maritime period, or the first Littorina transgression, according to a sharp increase in salinity, approximately 7,700 years 14 C BP. Some authors distinguish this period as the Sea of ​​Mastogloy [ Eronen, 1983]. The completion of this phase, obviously, falls on the mark of 509 cm (about 7340 years 14 C BP), above which the salinity change gradient takes on a sign-changing character, and in general salinity stabilizes. This age can be considered the beginning of the development of the Littorina Sea itself. In the work of Sh. Usinovich [ Uscinowicz, 2003] the date of the beginning of the Littorina phase is 7500 years 14 C BP.

The Littorina Sea itself is characterized by four peaks of salinity maxima, probably due to periods of maximum water exchange with the ocean, i.e. sea ​​transgressions. Three peaks fall on the Atlantic period. Two peaks located at 461-462 cm (approximately 6,700 years 14 C BP, 0.0033% Br, salinity 12‰) and 403-404 cm (approximately 6,475 years 14 C BP, 0.0029% Br, salinity 10‰), fall on AT1-2. The most significant peak with a maximum in the range of 259-268 cm (5080 years 14 C BP) with a Br concentration of 0.0046% and a salinity of up to 17‰, reached during the postglacial climatic optimum, falls on AT2. The last, fourth peak of maximum salinity of 16‰, located at around 217 cm, belongs to the early Subboreal (about 4640 years 14 C BP).

The assumption about the relationship between the salinity maxima of the Littorina Sea and the processes of transgression is consistent with the data of other researchers who identify several transgressive-regressive cycles, although the number of these cycles varies among different authors. In Sweden, different authors identify traces of four to six transgressions [ Berglund, 1964], in Lithuania three [ Bitinas & Damusyte, 2004]. On the shores of Germany Lampe & Janke, 2004] found traces of four transgressions of the Litorinian time. The first of these took place at the beginning, the second in the middle, and the third at the end of the Atlantean period. The fourth transgression is attributed to the Subboreal time.

The final stage in the development of the Littorina Sea is marked by a noticeable drop in its salinity. This is primarily due to the tectonic uplift of the earth's crust in the region of the Danish Straits, which led to a decrease in the inflow of salt water [ Blazhchishin, 1998]. This process was accompanied by eustatic regression of the Littorina Sea. The age boundary between the Littorina and post-Litorina stages, according to various sources, is in the range from 4500 to 4000 years 14 C BP. This agrees well with our results, which show that starting from the mark of 217 cm, there is an intense and significant drop in the Br concentration with a local minimum of salinity of 12‰ in the region of the mark of 177–178 cm, corresponding to an age of about 4200 years 14 C BP. Higher up the section, the content of bromine in the sediment and its salinity are relatively stable. Since that time, the Baltic has practically taken on a modern look.

Mathematical data processing. The purpose of statistical processing of data on the distribution of chemical elements in the section, carried out using factor analysis by the method of principal components, was an attempt to clarify the associative relationships between elements in the process of sedimentogenesis at various stages of the development of the Baltic. Samples were considered that characterize the distribution of data over the intervals of the section associated with two main stages - essentially freshwater and marine.

For marine conditions, analysis of the distribution of factor loads allows us to distinguish two associations of elements (Fig. 6, a). The first association is represented by Zn, Ni, Cu, Co, the second - by Fe 2 O 3 , MnO, As, Cr. Br, like Pb, is not included in any of the identified associations and is an antagonist with respect to other elements. The antagonism of Br indicates that it is little associated with the initial terrigenous material of bottom sediments and is not involved in the processes of authigenic mineral formation, while its accumulation in sediments has a superimposed character and depends primarily on the mineralization of near-bottom and interstitial waters.

The results of factorial analysis of data on a sample characterizing lacustrine, essentially freshwater conditions showed that Br does not exhibit antagonistic properties with respect to other elements. For example, under the conditions of the freshwater ancylic stage, it is included in a large group of elements that have a significant relationship with the first factor (Fig. 6b). Consequently, under freshwater conditions, the content of Br in sediments is determined not by water mineralization, but mainly by its occurrence in terrigenous and authigenic minerals.

currents. Deep circulation in the Baltic Sea is determined by the North Sea waters, which in the bottom layer slowly flow from depression to depression. In the deep layers, the average transport speed is only a few centimeters per second. At the same time, with large inflows of North Sea waters (“major inflows” events) and their overflows through the thresholds between the basins, fast (jet) currents can arise that prevent sedimentation and are capable of eroding the bottom surface [ Sivkov and Sviridov, 1994 ]. In the process of sedimentation in a moving medium, sedimentary particles are separated according to hydraulic fineness. For the conditions under consideration, the granulometric fraction is 10–20 µm [ McCave, 1985] is most sensitive to fluctuations in the average velocity of the bottom current. It is obvious that the estimation of the velocity of paleocurrents from the particle size distribution of sediments is possible only if the conditions for the supply of sedimentary material are uniform. The relative conservatism of the sedimentation conditions in the Gdansk depression makes it possible to trace changes in the activity of near-bottom currents in the Late Holocene. Since the sampling point of core POS 303700-7 is located near the saddle of the Gdansk-Gotland threshold, through which water exchanges with the western basins of the Baltic (Fig. 1), it can be assumed that sedimentation here is subject to the influence of North Sea waters, and the great depth of the sea excludes the influence of wind currents.

Based on the change in the parameters of the particle size distribution of the sediments, four periods of intensification of near-bottom currents were identified (Fig. 7). The first falls on the final stage of the ancylic stage, during which many researchers note the transgression of a brackish water body with an increase in salinity by 2‰. The second interval practically coincides with the Mastogloy phase. It represents a transition from lacustrine to marine conditions with an avalanche-like increase in salinity up to 9‰. The third period can be identified with the phase of activation of the Littorina transgression in the second half of the Atlantic time and the increase in salinity up to 12‰. The fourth period is timed to coincide with the completion of the Littorina stage, the regression of the sea, and the transition to the post-Litorina stage. In this case, an increase in hydrodynamic activity corresponds to a decrease in salinity from 16 to 13‰, which indicates a possible change in the regime of inflows of saline North Sea waters, which no longer directly reached the Gdansk depression. Less saline waters, displaced by inflows from the western basins of the Baltic, got here in the form of bottom currents.

conclusions

1. Palynological analysis made it possible to identify 10 palynozones in the section, comparable with the climatic periods of Blitt-Sernander and reflecting the stages of development of the region's paleoclimate over the past 13,000 years. In combination with isotopic dating data, this made it possible to refine the position of lithostratigraphic boundaries and calculate sedimentation rates varying from 0.37 to 1.62 mm/year.

2. It was shown for the first time that the element of the halogen group Br can serve as an indicator of the paleosalinity of the pore waters of bottom sediments and, accordingly, the paleosalinity of the basin.

3. From the time of the existence of the Baltic Glacial Lake to the final stages of the development of Lake Antsyl, the distribution of bromine concentration has a uniform character with a calculated salinity of about 2‰, which confirms that the Gdansk Basin is freshwater in the Yoldian stage.

4. The initial stage of development of the Littorina Sea (Mastogloya Sea) - the transition from relatively freshwater lacustrine to marine conditions - is characterized by a sharp increase in bromine concentration and estimated salinity up to 9‰.

5. The Littorina Sea itself is characterized by four peaks of salinity maxima associated with marine transgressions. The maximum salinity values ​​(up to 17‰) occur in the second half of the Atlantic period.

6. An analysis of the grain size distribution of Holocene sediments made it possible to identify four intervals along the section, when sediments accumulated under conditions of relatively increased near-bottom hydrodynamic activity associated with the manifestation of transgressive-regressive phases of the development of the Baltic, established by sharp changes in the salinity gradient.

The studies were carried out under state contract No. K-41.25.04.05.004. Part of the analytical processing was supported by the Russian Foundation for Basic Research (grant RFBR-BONUS 08-05-92420). The authors are deeply grateful to E.V. Valiguras, K.A. Gruzdov, D.V. Dorokhov, E.V. Zykina and V.F. Sapega, who took part in the analytical work, as well as Ya. Kharfu and E.M. Emelyanov - organizers of the GISEB project.

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New data on the development history of the Southeast Baltic Sea from late glacial age to present

A.G. Grigoriev, V.A. Zhamoida, M.A. Spiridonov, A. Yu. Sharapova, V.V. Sivkov

Core-section 12.38 m long was sampled in the Gdansk Basin within the cruise of r/v "Poseidon" in the frame of Russian-German Project GISEB. Down-core analysis of the sediment core includes 14 C and 210 Pb dating, X-ray diffraction, pollen, grain-size and geochemical analysis. A high-resolution record of climate and environment in the Gdansk Deep from the B e lling to Subatlantic has been established. The fluctuations of the rate of sedimentation during Late Pleistocene - Holocene from 0.37 to 1.62 mm/yr have been specified. The main trends of relative salinity variations of the water during the Late Pleistocene - Holocene have been determined using analysis of bromine concentrations in the sediments. Formation of the Yoldia Sea did not follow to salinity increasing within the Gdansk Basin. Several stages of Litorina transgression-regression cycles were fixed, as well as episodes of increasing of near-bottom current activity in Gdansk Basin.

keywords:paleogegraphy, paleo-Baltic, 14 C and 210 Pb dating, geocheistry of sedimentation

Edition: Nauka, Moscow, 2009, 379 pages, ISBN: 978-5-02-025361-2

Language(s) Russian

In the composition of the igneous provinces of the northeastern part of the Baltic Shield, manifestations of dike magmatism occupy a significant place both in terms of the volume of intruded melts and in terms of their occurrence. As a rule, kid swarms mark large stages of activation of plume-lithospheric processes that occurred either during the restructuring of the basement of Fennoscandia or in adjacent territories. In the latter case, dikes associated with distant tectonic events are very rare, but their role in assessing the scale and nature of tectonomagmatic processes is significant. In the Kola region, the study of dike magmatism was carried out locally and was associated with the study of the intrusive activity of certain stages of the evolution of the Baltic Shield or with the study of the magmatism of a particular structure. Despite the significant progress in intrusive petrology, the problems of dike magmatism can without exaggeration be classified as the most difficult to solve. Let us name at least three reasons complicating the study of dikes.

First, the spatial disunity of the scattered huge area small bodies and swarms leads to the fact that geologists are forced to organize high-cost field studies large territories, carrying out large-scale mapping of dike development regions remote from each other and, as a result, obtaining data on only a few geological objects. More often, the study of dike magmatism is carried out along the way, in the course of the study of other intrusive bodies. In this case, data is collected over many field seasons. It is in this way that factual material was collected for the present work, which summarizes the results of the authors for more than thirty years of research on the dikes of the region.

Secondly, in order to correlate dike swarms and elucidate the nature of relationships between subvolcanic and plutonic manifestations of magmatism, it is necessary to determine the age of each dike, or at least an individual swarm. Unfortunately, large-scale isotope studies are unlikely to be possible in the foreseeable future. Given the above, we tried to make the maximum number of determinations of the absolute age of laika rocks using Rb-Sr, U-Pb, 40Ar/39Ar and Sm-Nd methods. Already the first dates obtained made it possible for the first time to identify manifestations of the Grenville stage of tectonomagmatic activation on the territory of the Kola region, as well as to outline the area of ​​development of Paleozoic dolerite dikes.

Thirdly, since a dike is an independent intrusive body, the question of the need to determine the chemical composition of each dike and to estimate the contents of trace elements in its rock is of particular relevance. The task is complicated by the presence of zoning in dikes, the presence of xenogenic material in them, and the manifestation of processes of contamination by the material of host rocks.

Thus, a systematic study of dike magmatism required much greater expenditures both for the organization of field work and for analytical studies. In this paper, for the first time, we tried to summarize all the currently available factual data on laik magmatism, accumulated by the authors in the course of more than 30 years of studying the Precambrian (Zh.A. Felotov - Zh.A.F.) and Paleozoic (A.A. Arzamastsev - A.A.A., L.V. Arzamastseva) dikes. The work also uses primary materials collected by the authors in the course of joint work with industrial geological organizations.

Material on the dikes of the Khibiny massif was collected by one of the authors (A.A.A.) in the course of a joint project of the Geological Institute of the KSC RAS ​​and the Khibinogorsk GRP of the Murmansk GRE PGO "Sevzapgeologiya" (V.A. Kaverina) (1986-1988).

The material on manifestations of kimberlite magmatism was obtained (A.A.A.) in the course of joint work of the Geological Institute of the KSC RAS ​​and the Central Kola State Geological Survey (M.M. Kalinkin, I.V. Polyakov) (1991-1993).

The material on the framing dikes of the Ivanovo volcano-plutonic complex was obtained during joint studies of the Geological Institute of the KSC RAS ​​(A.A.A.) and the experimental-methodological batch of the Kola complex geological survey of ultra-deep drilling PGO "Nedra" (M.S. Rusanov, V.I. Khmelinsky) (1985-1989).

Material on the composition and distribution of dikes in the area of ​​the northern framing of the Keiv and Kolmozero-Voronya structures was obtained in the course of joint research by the Geological Institute of the KSC RAS ​​(Zh.A.F.) and the Central Kola State Geological Survey (A.P. Lipov) (1979-1981) .

The material on dikes of the East Murmansk coast was collected in the course of joint work of the Geological Institute of the KSC RAS ​​(Zh.A.F.) and the mineralogical party of the Central Kola State Geological Survey (S.S. Karavaev) (1988-1991).

The distribution of dikes in the rest of the area of ​​the Kola region was estimated according to the reports of the geological survey crews of the Central Kola Geological Survey. The collections of thin sections of dike rocks collected by production organizations were studied by us in the museum of Murmangeolkom in Apatity. In addition, the collection of thin sections of dike rocks of Academician A.A. Polkanov, kept at the Department of Petrography of the Geological Faculty of St. Petersburg University, was examined.

Most of the analytical work was carried out in the laboratories of the Geological Institute of the KSC RAS ​​(Ya.A. Pakhomovskii, L.I. Koval). Precision studies of the composition of minerals (LA-ICP-MS) and rocks (1CP-MS) were carried out jointly with professors Fernando Bea and Pilar Montero (University of Granada, Spain). Isotopic and geochronological studies were carried out jointly with B.V. Belyatsky (Institute of Geology and Geochronology of the Precambrian RAS) and A.V. Travin (Analytical Center of the Joint Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the Russian Academy of Sciences). Part of the isotope determinations of Proterozoic dikes was made by Yu.V. Amelin (Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences). Great help in preparing the manuscript for publication was provided by S.E. Tsarev and T. Smarchuk. The authors express their deep gratitude to all the above colleagues.

The work was carried out within the framework of the priority programs of the ONZ RAS 6 and 8, and was also financed by the Russian Foundation for Basic Research (grants 09-05-00224a

NAVIGATIONAL GEOGRAPHICAL OUTLINE

General information. This charter contains a description of the Gulf of Finland and Riga, as well as the eastern and southern coasts of the Baltic Sea, from Cape Ovishi (57°34" N, 21°43" E) to Cape Rozeve (54°50" N, 5 18°20" E ).

The boundary of the Gulf of Finland in the west is considered to be a line connecting the western tip of the Hanko Peninsula - Cape Hankoniemi (59°48 "N, 22°54" E) with Cape Pysaspea (59°14" N, 23°31" E) and passing through the island Osmussaar. Throughout the northern coast of the Gulf of Finland is bordered by skerries. While in this area, you should take into account the peculiarities of swimming in skerries.

Shores.The Gulf of Finland. The northern coast of the Gulf of Finland is composed of hard crystalline rocks (granites and gneisses) covered with a thin layer of soil. It is low, strongly broken, very picturesque, although somewhat monotonous, and almost entirely overgrown with coniferous forest. This coast is characterized by an abundance of moraines and hills, alternating with lakes and swamps; everywhere there are many rocks and boulders.

This coast is heavily indented with bays and bays. All of them are shallow or cluttered with hazards and for the most part only 5 are accessible to small craft. Most large bay northern shore is the Vyborg Bay.

Almost the entire length of the northern coast of the Gulf of Finland is bordered by skerries, which are many small islands, rocks and banks, stretching from the coastline 10 by 10 - 20 miles. The islands located on the edge of the skerries are usually devoid of vegetation, and those that lie in the depths of the skerries are wooded. All these islands are similar to each other.

On the northern coast of the Gulf of Finland, the most significant is the Kyminjoki River, which flows into the bay near the city of Kotka.

Islands and straits. Several islands are located in the eastern part of the Gulf of Finland between meridians 26°40" and 28°25" east. duty. The most significant of them are the islands: Seskar, Powerful, Big Tyuters and Gogland. All islands are bordered by reefs and banks.

Near the northern shore of the Gulf of Finland there are many rocky islands that form the so-called Finnish skerries, stretching from the eastern approaches to Vyborg Bay to the peninsula of Hanko. All the islands in the skerries are made of mostly red granite. Some of them are low, flat and devoid of vegetation, others covered with a thin layer of soil, wooded. The islands are bordered by rocky shoals; there are many dangers between the islands. In the skerries of the northern coast of the Gulf of Finland there are convenient internal communications, sheltered from winds and waves, but navigation here is possible only along the fairways. Finnish skerries are crossed by several longitudinal fairways running along the coast, and many transverse fairways, which serve either to enter the skerries or to approach anchorages, raids and harbors located deep in the skerries.

There are no islands off the eastern coast of the sea.

Depths, bottom relief and soil. The Gulf of Finland is shallow. Its bottom is dotted with banks of various sizes. Particularly uneven bottom relief near the northern shore of the bay in the area of ​​Finnish skerries.

The depths in the Gulf of Finland increase in the direction from east to west, from the Tolbukhin lighthouse to Seskar Island they are 20–40 m, further to Maly Island 40–50 m, and between the islands Moshchny and Gogland increase to 70 m. Between the island of Gogland and the entrance to the Gulf of Finland depth is 60-80 m, and only in some small depressions near the islands of Prangli and Osmussar they exceed 100 m. The greatest depth in the Gulf of Finland 121 m is 1 mile NE from Prangli Island. Between the islands of Powerful and Gotland, depths of more than 60 m are located in the middle of the bay, and from the island of Gotland to the entrance to the bay, they are closer to its southern coast.

To the west of the islands of Hiiumaa and Saaremma, the bottom topography is more even than in the Gulf of Finland; banks and reefs are concentrated here in the coastal strip, and mainly to the west of the island of Saaremma.

In the middle part of the Gulf of Finland, the soil is silt; along the northern shore of the bay, sand, silt or stone are most often found. In the bays of the northern coast, the soil is predominantly clay.

Off the coast of the islands of Hiiumaa and Saaremma, the soil is predominantly stone, slab and sand. With distance from the coast, the soil becomes silty.

Terrestrial magnetism. The magnetic study of the area is satisfactory. The magnetic declination for the 1980 epoch in the described part of the Baltic Sea is eastern; it varies from 6.8° in the northeast of the region to 0° in the southwest. The isogon direction is close to meridional. The average annual change in magnetic declination increases from -0.02° (in the northeast of the region) to +0.03° (in the southwest of the region).

Characteristic of the Baltic Sea is the presence a large number anomalous regions, as well as individual anomalous points, 5 in which the declination varies from 7° W to 16° E.

The greatest deviation of the compass needle to the east is observed in winter at about 9-10 o'clock, and to the west in winter and summer at about 14-15 o'clock local time.

During very strong magnetic storms, the amplitude of diurnal variations in magnetic declination can reach 3° in the south of the region and 7° in the north.

The value of the horizontal component of the magnetic field strength increases from 150 mOe in the north of the region to 179 mOe in the south. The direction of the isodynamics is latitudinal. The magnetic inclination decreases from 73° N 15 in the north to 68.8° N in the south of the region being described. The direction of the isoclines is close to the latitudinal one.

Navigation aids. The described area, especially the Gulf of Finland, is saturated with coastal and floating aids to navigation. All navigational hazards located in the vicinity of the usual routes of ships are protected by milestones, illuminated buoys and buoys, and in many cases also by sectors of illuminated signs and beacons. Fairways leading to ports and harbors, and skerry fairways are fenced off with luminous signs and signs, luminous buoys and buoys, as well as milestones. Navigation in the open parts of the Gulf of Finland and along the eastern coast of the Baltic Sea is provided by lighthouses and luminous signs, the visibility ranges of which overlap.

Most of the coastal aids to navigation are in operation throughout the year. The floating navigational fence in the Gulf of Finland is usually removed for the winter.

The reliability of the location of buoys and milestones, as well as the strict constancy of the characteristics of the lights, cannot be fully relied upon.

Areas with a special regime of navigation. In the Baltic Sea, the Gulf of Finland, Vyborg and Riga, there are former mine-hazardous areas open to all ships. Vessel navigation in former mine-hazardous areas is recommended to be carried out within the established fairways, plotted on maps and announced in the Summary Description of the Navigation Regime in the Baltic Sea, the Gulf of Finland and the Gulf of Riga in Lake Ladoga.

When sailing in former mine-hazardous areas, the navigation regime announced in the summary description for each area should be strictly observed. Anchoring of vessels in former mine-hazardous areas is permitted only in designated areas. Fishing with bottom fishing gear in former mine-hazardous areas is permitted only subject to strict compliance with the requirements of the Instructions to Masters of Vessels on Mine Safety Rules when Swimming and Fishing.

In addition to the areas listed above, in the Baltic Sea, the Gulf of Finland and the Gulf of Riga there are areas prohibited for navigation, and areas prohibited (or temporarily dangerous) for anchoring and fishing with bottom fishing gear. There are also ship training areas, training mine ranges and explosives dump areas.

All the areas mentioned above are mapped; the boundaries of the regions and an indication of the peculiarities of navigation in them are given in the Summary description of the navigation regime in the Baltic Sea, the Gulf of Finland and the Gulf of Riga and in Lake Ladoga.

Vessel traffic separation systems. Vessel separation systems have been installed in certain areas of the Baltic Sea to reduce the risk of collision in areas of heavy navigation.

These traffic separation systems are intended for use by ships during the day and at night in all weather conditions in ice-free waters or in light ice conditions where no special maneuvering or ice assistance is required.

The use of traffic separation systems must be carried out in accordance with COLREGs-72.

Pilot service. In the described area there is a developed network of pilot stations. In some harbors where there are no pilot stations, the duties of pilots are performed by harbor captains or local fishermen who know the conditions of navigation well.

The pilot is called according to the International Code of Signals. Detailed information about pilots and pilotage is given in the rules of navigation and in the appropriate places in the navigation description.

HYDROMETEOROLOGICAL OUTLINE

Hydrometeorological conditions for navigation of ships in the eastern part of the Baltic Sea, in the Gulf of Finland are generally favorable, although there are a number of factors that make navigation difficult.

One such factor is storms, which are usually accompanied by heavy seas. Storms are most likely in winter.

Difficulties for swimming are created by fogs, in which visibility is sharply reduced. Fogs are most often observed from December to March - April (off the coast from September to May). Visibility also deteriorates significantly during precipitation, which in the open sea is confined mainly to the autumn-winter period of the year. A significant threat to the safety of navigation of ships, especially small ones, is created by icing of ships, which is observed in the Gulf of Finland from November to April, and in the eastern part of the sea from December to March.

In winter, sailing conditions are also complicated by ice. The ice cover reaches its greatest development in the Gulf of Finland.

METEOROLOGICAL CHARACTERISTICS. In the area described, the climate is maritime in temperate latitudes; it is characterized by small annual fluctuations in air temperature, significant humidity and high cloudiness, and frequent precipitation. It should be noted that the climate of the Gulf of Finland is more severe than the climate in the areas high seas, which is due to the influence of the continent, into which the Gulf of Finland deeply protrudes.

The winter is rather mild, with a predominance of cloudy weather and frequent precipitation. Very coldy are rare and usually short-lived. In winter, winds from S, SW and W prevail, often reaching storm strength.

Temperature and humidity. February is the coldest month of the year. At this time, the average monthly air temperature ranges from -1 to -8° in the area of ​​the Gulf of Finland and from +1 to -3° in the area of ​​the eastern part of the sea. The air temperature on some days of very severe winters can drop to -36, -42° in the area of ​​the bays and to -23, -34° in the area of ​​the eastern part of the sea. During exceptional thaws, it rises, respectively, to 6° and to 10-12°.

winds. Winds from SW, S and W prevail in most of the region in February. In addition, winds from SE are quite frequent at this time.

The average wind speed in February is 5-8 m/s, and the wind speed in the eastern part of the sea and bays is slightly higher than on the coast.

Calms are rare, their frequency from September to March is 1-3% per month.

The frequency of storms in the eastern part of the sea and in the bays from September to March is 5-15%.

fogs. In the eastern part of the sea, the frequency of fogs in February is 6-9% (in some places 12%). In the Gulf of Finland, their frequency varies from 3 to 6% during the year.

Often fogs are observed on the islands of the Gulf of Finland, where the average annual number of days with them reaches 65-125.

Visibility. In February, the frequency of visibility is less than 1 mile (10-20%). The repeatability of visibility over 5 miles reaches 30-60%.

Cloudiness and precipitation. Cloudiness is high and subject to significant fluctuations throughout the year. Over the eastern part of the sea and the bays, the highest frequency of cloudy sky conditions falls on the period from October to March and amounts to 60--80%; the frequency of a clear sky during this period does not exceed 10-20%.

Most precipitation in the eastern part of the sea and bays falls on the period from October to February, when their frequency is 15--30%.

HYDROLOGICAL CHARACTERISTICS. The hydrological regime of the Gulf of Finland and the eastern part of the Baltic Sea is characterized by well-developed wind currents, low steep waves, low salinity and low density of the surface water layer and more saline and denser waters at depths.

One of the most distinctive features of the level regime of the Baltic Sea is the seiches.

Fixed ice is observed in the Gulf of Finland and along the eastern coast of the sea.

Level fluctuations. In February, tidal level fluctuations are small. The surge, seiche and seasonal fluctuations are of greater importance.

The magnitude of level fluctuations in the described area can sometimes reach very large values.

currents. The current regime is determined by the water exchange of the Gulf of Finland and Riga with the Baltic Sea, and in the southern part of the region with the North Sea. The flow of water from land has a significant effect on the currents.

Rice. 1.

Permanent surface currents in the Baltic Sea are formed from the confluence of two currents, one of which emerges from the Gulf of Finland and the other from the Gulf of Bothnia. Although constant currents are weak and do not significantly affect the drift of ships on the high seas, however, near capes, in straits and narrows, as well as near underwater hazards, where the speed of currents, as a rule, increases, it is not recommended to neglect them.

In the Gulf of Finland, there is a more or less stable constant current directed to the west. This current is due to the flow of the waters of the Neva River.

The speed of constant currents varies on average from 0.2 to 0.5 knots, in some places it increases to 0.7-0.9 knots.

Under the influence of winds, temporary wind currents arise, the second ones often exceed the permanent ones in speed and follow in the open parts of the area in the direction of the wind, deviating from it by about 30 ° to the right. As the wind increases, the deflection angle decreases and in strong winds it does not exceed 10°. Near the shores, the deviation angles can vary considerably.

Excitement. In the Gulf of Finland and the eastern part of the sea, strong waves are most often observed in February, when the frequency of wave heights of 2–6 m reaches 34–39%; in the west of the Gulf of Finland and in the sea, although rare, wave heights of more than 10 m can also be encountered. 45%.

ICE MODE. A significant part of the Gulf of Finland from the port of Leningrad to Moschny Island, as well as skerries from the port of Vyborg to the Khanko Peninsula and the eastern part of the sea are covered with immovable ice. In the open areas of the bays, drifting ice is usually observed, which in severe winters occurs throughout the entire water area of ​​the Gulf of Finland.

In February, still ice in moderate winters can spread to Gotland Island, and drifting ice to Keri Island.

It should be borne in mind that the nature of the development of ice processes and the thickness of ice from year to year are subject to very significant fluctuations depending on the severity of winter.

In very severe winters, the largest ice thickness is also observed in the port of Kotka and reaches 80 cm.

Icing of ships. A significant threat to the safety of navigation of ships, especially small ones, in the Baltic Sea is posed by icing of ships, which is observed in the Gulf of Finland from November to April, and in the eastern part of the sea from December to March.

Icing of ships occurs at negative air temperatures and strong winds, which cause the development of waves, and, as a result, splashing of the ship with outboard water. Icing can also be observed when supercooled precipitation falls, when the ship is in supercooled fog, and when the sea soars.

Navigational and geographical outline of the passage by the Baltic Sea

In the eastern parts of the Baltic Sea there are areas dangerous from mines, prohibited for anchoring, prohibited for navigation, etc., the boundaries of which are swayed on the maps. Information about these areas is given in the Summary description of the regime of navigation in the Baltic Sea.

Shores. The eastern and southern shores of the Baltic Sea from Cape Ovishi to Cape Rozeve are predominantly low and sandy. Here the plain rises to the sea, in places cultivated for crops, and in places covered with forest or shrubs. Throughout these coasts are bordered by wide sandy or pebble beaches. Behind the beaches, a chain of dunes stretches parallel to the coastline, overgrown with a rare coniferous forest or tall grass. This part of the coast is slightly indented.

The southern coast of the Baltic Sea is predominantly low and sandy. Here the plain rises to the sea, in places cultivated for crops, and in places covered with forest or shrubs. Throughout the coast is bordered by wide sandy or pebble beaches; behind the beaches, dunes covered with sparse coniferous forest or tall grass stretch parallel to the coastline. In many places, the southern coast is cut by rivers, in which the Odra River is the most significant. Ports and harbors are located at the mouths of rivers.

The eastern part of the southern coast of the Baltic Sea is slightly indented. Extensive bays protrude into the western part of the southern coast of the Baltic Sea: Mecklenburg, Keeler-Verde and Flensburger-Verde. The northern coast of the southern part of the Baltic Sea from Cape Torhamnsudde to the port of Ohus (55°56" N, 54°09" E) is elevated, wooded and bordered by many islands, rocks and banks forming skerries. From the port of Ochus to Cape Falsterbuudde, this coast is not much different in character from the southern coast of the Baltic Sea. It is also low, sandy, forested in places and slightly indented.

Straits and islands. Of the straits in the area described, the following are of the most important navigational importance: the Hamrarne Strait or Bornholmsgat, which separates the island of Bornholm from the northern coast of the southern part of the sea; the Fehmarn-Belt Strait, located between the islands of Lolakn and Fehmarn, and the strait, known as the Cadet-Rennen Passage, leading to the Mecklenburg Bay from the northeast. The strait of Hamrarne is wide, deep-water and almost clear of dangers, the other two straits are narrower and shallower, there are more dangers here. All three straits are available for large ships. Of lesser navigational importance are the narrow and shallow straits of Stralsunder-Farwasser and Fehmarn-Sund, which separate the islands of Rügen and Fehmarn from the mainland, respectively.

There are few islands in the southern part of the Baltic Sea. In the middle of the southern part of the sea is the large island of Bornholm, the surface of which is a high plateau covered with forests and fields. The coast of the island of Bornholm for the most part broken and deep. 14 miles east of the northern tip of Bornholm are the Christianse Islands.

Off the southern coast of the southern part of the sea lie two large islands: Rügen and Fehmarn. West Side the islands of Rügen are low-lying, and the eastern one is elevated; the forest on the island grows mainly near its shores. The island of Fehmarn is covered with low hills, there is almost no forest on it. Near the northern coast of the southern part of the sea, between Cape Torhamnsudde and the port of Ohus, there are many low, rocky islands and islets that form skerries.

Depths, bottom relief and soil. The shores of the southern part of the Baltic Sea are bordered by shallows with depths of less than 20 m, and in places up to 40 miles wide. The most subdued area between the port of Ohus and Cape Falyeterbuudde; the 20 m isobath passes here mainly 4-10 miles from the coastline. Seaward isobaths of 20 m, the depth varies from 30-40 m in the western part of the region to 50-90 m in its eastern part. The dangers in the area described are concentrated mainly near the coast on a shallow with depths of less than 20 m. Seaward of the 20 m isobath, the most dangerous are the extensive Rönne Banke shallow, protruding from the southern coast of Bornholm Island, north of the port of Davide Banke, lying in the Hamrarne Strait. The soil in the southern part of the Baltic Sea is more seaward than the 20 m isobath, mostly clay and silt; near the coast, the soil is mainly sand, and in some places there is stone, silt, shell and gravel.

Navigation aids. The shores of the southern part of the Baltic Sea are well equipped with visual aids to navigation, providing safe approach to the coast, navigation through the main straits, passages and fairways and approach to ports, harbors and anchorages. Many hazards are protected by luminous and non-illuminated buoys and milestones. In conditions of reduced visibility, navigation safety is ensured by the GPS system, and various means of fog sound alarms. Most of the coastal and floating aids to navigation are in operation throughout the year. The reliability of the location of buoys and milestones, as well as the strict constancy of the characteristics of the lights, cannot be fully relied upon.

Ports and anchorages. Southern coast of the Baltic Sea from the cape. Rozeve to the island of Rügen is characterized by low indentation, so there are almost no bays and bays in which ships could take refuge from winds and waves. The ports of Ustka, Darłowo, Kołobrzeg, Swinoujście and Szczecin are located near this part of the coast. The western part of the southern coast of the Baltic Sea is quite indented; here are the vast Mecklenburg, Keeler Förde, Eckernförder Bucht and Flenoburger Förde bays, sheltered from the winds and waves. The ports of Sassnitz, Stralsund, Rostock, Warnemüde, Wismar, Lübeck, Travemünde, Kiel and Flensburg are located in this area.

There are several ports and many harbors along the northern coast of the southern part of the Baltic Sea. The most important are the ports of Karlskrona, Ystad and Trelleborg. In addition, there are many anchor and loading places in the skerries. Loading places are, as a rule, one or more anchorages where ships are loaded from the water; some loading bays have small berths.

Repair capabilities and supply. Repair of the hull and ship mechanisms is carried out in almost all major ports. In the same ports, it is possible to replenish fuel, water and food supplies.

Rescue Service. There is a network of rescue stations in the southern part of the Baltic Sea; there are rescue boats in major ports. The location of rescue stations and their equipment is given in the navigation description.

Hydrometeorological essay of the Baltic Sea.

The climate of the described region is characterized by high humidity and cloudiness, significant development of fogs in the cold (November - March) period of the year, frequent precipitation, fairly evenly distributed throughout the year, prevailing westerly winds and relatively small fluctuations in air temperature throughout the year. The prevailing are south-western and western winds, often reaching the strength of a storm. Spring is cold and long. Precipitation is less frequent than in winter, and storm activity is significantly reduced towards the end of the season. The frequency of clear skies increases, and the frequency of fogs decreases.

Summer is moderately warm, hot weather is rare and does not last long. Fogs are observed much less frequently than in winter and autumn. The frequency of cloudy skies decreases, but the amount of precipitation falling in the form of showers increases noticeably. The climate of the described area is formed under the influence of the general circulation of the atmosphere, which determines the transfer of warm and humid air masses from the Atlantic Ocean. In addition, the North Atlantic Current has a significant impact on the climate, bringing large masses of warm water to the shores of the northwestern part of Europe, part of which enters the Baltic Sea through the Kattegat, Greater and Lesser Belts and the Sound.

The described area is characterized by six types of weather: northeast, southeast, southwest, northwest, light windy clear and unstable overcast.

Temperature and humidity. The coldest months of the year are January and February, the average monthly temperature of which varies from -2° to 4°, and is higher in the open sea than on the coast. The lowest temperature during these months ranges from -20° to -30°, and the highest from 10° to 15°.

The warmest months of the year are July and August. Their average monthly temperature is 15°-17° everywhere. The highest air temperature during these months ranges from 30° to 36°, and the lowest from 2° to 6°.

The annual temperature amplitude in the conditions of the described climate is 17°--19°.

The daily amplitude of air temperature increases from winter to summer and amounts to 3°--5° and 8°--10°, respectively. Relative humidity is quite high throughout the year. The largest 80--90% is observed from October to March, and the smallest 70--80% from April to June.

Daily fluctuations in relative humidity in winter are 3-8%, and in summer 10-20%.

winds. The wind regime in the described area is determined mainly by the nature of the atmospheric circulation. On the coast, local conditions have a significant influence on wind speed and direction. Most of the year winds from SW and W prevail everywhere, the total frequency of which is 35--50%. Only in April and May the frequency of these winds decreases to 20-30%. In addition, in the summer months, winds from NW are often observed with a frequency of 15 - 25%. The average monthly wind speed on the coast in the period from October to April is 3–6 m/s, and from May to September it decreases to 2–5 m/s. In the open sea, the average monthly wind speed increases to 8 m/s and 4-6 m/s, respectively.

Calms in the described area are rarely observed, their frequency during the year is 2--7. The average annual number of days with a storm in most of the region is 16-28. Only in some places it decreases to 4-7. Storms are observed in all seasons of the year, but they are most frequent in the period from October to April, when the average monthly number of days with a storm is 2–4, and in the period from May to September it does not exceed 1. In the areas of the port of Karlshamn and the city of Ustka, storms do not happen annually. The highest wind speed during storms often reaches 25 m/sec, in exceptional cases 34-36 m/sec. The duration of storms, as a rule, does not exceed one day. Storms lasting up to two days or more are observed from September-October to March on average from 3 to 5 times during this period. Squalls accompanied by thunderstorms are quite frequent in summer. In the warm season, breezes are observed. The sea breeze occurs before noon, in the afternoon it reaches a speed of 3-6 m / s and subsides before sunset. The coastal breeze is weaker than the sea breeze, but extends up to 8 miles, that is, twice as far as the sea breeze.

fogs. In the open sea, the frequency of fogs varies from 3-6% in the warm period of the year to 6-9% in the cold.

On the coast, the average annual number of days with fog is 25-50, in some places 65. Fogs are most often observed from September-October to March, when the average number of days with them is 3-6 per month, and in some places 7-10 per month. month. Fogs are observed least often in June-August, on average not exceeding once a month. In April and May, the average number of days with fog ranges from 2 to 5 per month.

Visibility of 5 miles or more most of the year is predominant. Its highest frequency of 60-85% is observed from April - May to September, and from October to March its frequency decreases to 30-50%. In the warm period of the year, the frequency of visibility of less than 1 mile does not exceed 1–5% everywhere.

radar observability. Throughout the year, the coastal strip to the east of the port of Swinoujscie is dominated by radar observability, the frequency of which is 40–50%, and the frequency of increased radar observability is 20–30%. In spring, the conditions of radar observability improve, the frequency of reduced observability decreases and the frequency of ultra-long radar observability increases. In summer, along with the prevailing normal radar observability, increased radar observability increases.

Cloudiness and precipitation. Cloud cover is high throughout the year. Its largest average monthly number of 7-8 points falls in the period from November to February, in the remaining months it is about 6 points. Overcast weather prevails throughout the region throughout the year. Thus, the average annual number of cloudy days ranges from 120 to 160, while the average annual number of clear days does not exceed 30-60. Cloudy weather on the coast is most often observed from October to March. At this time, the average monthly number of cloudy days ranges from 12 to 20, while clear days do not exceed 1-3. In the rest of the year, the average monthly number of cloudy days decreases to 5-11, while clear days increase to 3-8. The summer months are characterized by cumulus clouds, the autumn and winter months by stratocumulus and nimbostratus.

The region has moderate rainfall. Their average annual amount varies everywhere from 560 to 800 mm. The maximum precipitation during the year occurs in July and August: in these months, the average monthly precipitation reaches 70--90 mm. The minimum precipitation is observed from February to May, when their average monthly amount does not exceed 30-50mm. In the remaining months, it ranges from 40 to 70 mm; only in some areas in some months the amount of precipitation increases to 75--90 mm. The maximum amount of precipitation per day in summer in some places reaches 90 mm, in other seasons it ranges from 25 to 60 mm.

Summer is characterized by heavy rainfall. Heavy rainfall most often lasts from 6 to 12 hours, but sometimes for several days in a row with short breaks. Heavy rainfall lasts no more than 1-3 hours.

currents. The current regime in the described area is determined by water exchange with the North Sea and land runoff, which determine the system of constant surface currents, wind activity, which causes drift currents, as well as the configuration of the coasts and the bottom topography, which affect the speed and direction of the total currents. A constant surface current is formed in the northern part of the Baltic Sea from the confluence of two currents, one of which emerges from the Gulf of Finland, and the other from the Gulf of Bothnia. after the connection, the general flow, clinging to the Swedish coast, is directed to SW, rounding the island of Gotland on both sides, and then, turning first to W, and then again to SW, goes to the southern part of the sea. Bypassing the island of Bornholm, this current flows through the straits into the North Sea. Along the southern coast of the sea, east of the island of Rügen, the current goes to E, and then, approximately at the eastern border of the area described, it divides into two branches; one of them passes through the Gulf of Gdansk, turns N and heads along the east coast of the sea, and the other turns NW and W, where it merges with the general flow along the Swedish coast towards SW. To the east of the island of Bornholm, the water cycle is counterclockwise throughout the year. The permanent currents are very weak and subject to significant changes depending on the season and mainly or the prevailing winds. Under the influence of the winds, they can change their speed and direction. Although constant currents do not have a significant effect on the drift of ships in the open sea, however, it is not recommended to neglect such currents near capes protruding into the sea, in straits and narrow places, and also near underwater hazards, where the speed of currents, as a rule, increases. The speed of constant currents averages 0.1-0.2 knots and only in some cases increases to 0.7-0.9 knots. Drift currents generated by wind have the most significant impact on shipping. At sea, drift currents generally follow the direction of the wind. When the direction of the wind changes, the direction of the current also changes relatively quickly; as a result, the regime of drift currents is characterized by its instability, which must be borne in mind when sailing. The observed drift currents are often determined not local winds, but by the previous wind or stronger wind blowing in neighboring areas. Thus, strong winds from NW or W over the North Sea drive significant masses of water into the Baltic Sea through the straits and cause 5 east current in the southern part of the sea; when these winds weaken, the mass of water rushes back. In straits and closed bays, the drift current, as a rule, does not agree with the direction of the wind and may even have the opposite direction. The speed of the drift current is determined by the strength of the wind that caused it O and can reach 2-4 knots or more. In the Pomeranian Bay, the speed of coastal currents reaches 3 knots, and in the strait between the island of Rügen and the mainland, with strong winds from the north, it reaches 4-5 knots. Tidal currents in the described area are not essential for navigation. In the open sea, the speed of tidal currents does not exceed 0.1 knots. Excitement. The small size of the sea, especially the bays, as well as the relatively shallow depths, prevent the development of strong waves. From March to October, a wave of magnitude 1-6 prevails, the frequency of which at this time reaches 60--80%; Quite often there is excitement IV-V points, the frequency of which during the year ranges from 20 to 40%;

Excitement of VI points and more occurs mainly in September-February; when its frequency reaches 10-15% from March to August, the intensity of such a wave weakens everywhere, and its frequency does not exceed 3-8%. Waves come mainly from SW and W (30 - 60%), but in the warm season, in addition, waves from NW are also noted. The height of the waves in the open part of the region sometimes reaches 7-8 m, and in the bays 4-5 m.

Temperature, salinity, density of water. The highest average monthly water temperature on the surface (15°-18°) is observed from July to September, and it is higher near the southern coast (Pomorskaya Bay) than in the open sea. In October, the water temperature drops noticeably, and in November-December it does not exceed 4°-8°. The salinity in the open sea varies little during the year and is about 7°/oo. Near the coasts in spring and summer, due to the melting of ice and the inflow of water from land, the salinity of the surface layer is the lowest in the year and is 10-11 ° / oo.