Published by The Institute of Geological Sciences of the National Academy of Sciences of Belarus & The Belarusian Geological Society, Minsk, Republic of Belarus
Abstract: The second paper concerned with formations of the platform cover of Belarus includes a system descrip-tion of sulfate-chloride and magmatic formations and the analysis of the problem of formation-based cartography of the studied region. Sulfate-chloride (halogenic) formations were revealed in deposits of the Hercynian com-plex only, where these are represented by thick strata of Frasnian, Famennian and Lower Permian rock salt in-cluding horizons of potassic salt, anhydrite, limestone, dolomite and marl. The accumulation of Devonian halo-genic formations is related to the main rifting phases in the Pripyat Trough, and the Lower Permian ones are as-sociated with postrifting molassoids. The platform magmatic formations are genetically due to volcanism which evidences were shown in the Middle Riphean, Early Vendian and Late Devonian. Trachyandesite and rhyolite-diabasic formations of the Lower Riphean are spatially confined to plutonic rocks and are independent of the basement structures, Upper-Riphean gabbrodiabasic and basalt-diabasic formations are indicative of dispersion magmatism within the Volyn-Orsha and Krestets paleorifts. Lower-Vendian basaltic, dacite-liparite and gabbro-diabasic formations locate the position of the continental rift, which is buried under accumulative deposits in the East European Craton southwestern margin. Rift Upper Devonian magmatic associations are represented by al-kaline and ultrabasic igneous products of central- and fissure-type volcanos and by rocks genetically related to diatremes. These rocks show promise for diamonds. Magmatic formations of the region reflect the stages of the Earth's crust destruction. Medium-scale structure-formation, formation-paleogeodynamic and formation-paleotectonic maps of the territory of Belarus are advised to be compiled with the suggested formation model and unconventional techniques.
Early paleorift formations of the western and central part of the East European platform. pp. 18--30
Abstract: Early (Riphean) paleorifts are widespread in the western and central parts of the East European platform. These basins are infilled with a cataplatform cover, which involves the Dalslandian and Lower-Baikalian structural complexes. The Dalslandian complex is represented by three formations, which replace one another in vertical direction. These are red-coloured arkosic-gravel-sandy, volcanic-gravel-sandy and red-coloured quartz-sandy formations. The first and second ones formed under rifting regime (Ladoga and Krestsy grabens and Sherovichi de-pression). The latter was probably deposited under conditions of a slowly subsiding vast depression. The fragments of this formation are preserved in the Orsha depression, Moscow graben and Pachelma aulacogen. The Lower-Baikalian complex fills in an extended Volyn-Central Russian depression system and Pachelma aulacogen. The complex is divided into two structural stages. In the Volyn-Central Russian depression system they are represented by two horizontal associations of formations. Every formation was deposited under specific paleogeographical and paleotectonic conditions. However, each structural stage shows common structural features. At the lower stage the clastic material becomes coarser upwards. On the contrary, at the upper stage it becomes thinner in the same direction. In the Pachelma aulacogen the Lower-Baikalian structural complex is divided into two formations which vertically replace one another. There is some similarity in the structure and rock composition of the Lower-Baikalian deposits of the Pachelma aulacogen and Volyn-Centralrussian depression system.
Tectonic correlation of structural complexes of the Russian plate crystalline basement. pp. 31--48
Abstract: Some peculiarities of the geological section, prevailing rock parageneses, their composition, degree of regional metamorphism and dislocation of supracrustal rocks, as well as their ratio to intrusive and ultrametamorphic rocks were used to distinguish several types of structural complexes in the crystalline basement of the Russian plate. Among them there are granulitic, gneissic-amphibolitic, metabasite-gneissic-schist, ferruginous-siliceous-schist and terrigenous-schist complexes, that compose the lower highly folded basement structural stages, and weakly deformed and less metamorphozed or unmetamorphozed volcanic, volcanic-plutonic and molassic ones that form superimposed depressions and extended magmatic belts. The analysis of the spatial distribution of the above structural complexes and correlated formations of the Ukrainian Shield and eastern part of the Baltic Shield showed that one of the most typical features of the basement structure is its roughly symmetric zonality: granulitic and gneiss-amphibolitic complexes are widespread in the eastern and western parts of this territory, whereas metabasite-gneissic-schist complexes and the younger ones are confined to the central (axial) zone - Karelian-Kursk-Krivoy Rog granite-greenstone superbelt. Within this superbelt stratigraphic sequences of the Upper Archean and Lower Proterozoic are known to be quite complete and thick, while their synchronogenic complexes in the eastern and western regions are either absent or distributed sporadically over small areas. It suggests a similarity in the geological evolution of the plate eastern and western parts that had been separated in the early Late Archean by an extended mobile long-lived superbelt. The main difference between the crystalline basement of the plate western and eastern parts consists in strong tectonic and thermal reworking of the plate western part under the influence of tectonic processes in the adjacent mobile (geosynclinal ?) area. This is shown in a number of isotopic ages at 1900-1700 Ma obtained for rocks from structural complexes different in composition and age.
Abstract: The Derbina V section exposes covering deposits in the Eastern Sayan in northwest. The structure of the Derbina V section is discussed. 12 layers were distinguished in this section (including 3(5?) buried soils and pseudomorphs on polygonal ice-wedges). Abundant finds of bones of big mammals of Late-Paleolithic complex, artefacts of the early stages of the Late Paleolithic and dated by 14C-et 29-32 Ka are associated with one of buried soils reworked by solifluction (layer 7 - Derbinian pedosediment). Many terrestrial mollusks of the loessel complex and microteriofauna, remains that arespecific to periglacial landscapes were collected from this pedosediment. The above data allow the layer 7 pedosediment dating to the Konoschelian cooling of Siberia (in according to the scheme by N.V. Kind, 1974). Gastrocopta thelii was found in the layer 11. Together with other mollusks it suggest the Riss-Wurmian age of the layer 11. In that case the layers 10, 9 and 8 can be dated, re-spectively at the Early Wurm, Early and Malokhetian warming of the Middle Wurm; layers 6 and 4 - at two warmings of Novoseli stage, that were separated by a cooling (layer 5); the formation of polygonal ice-wedges is related to the first half of the Late Wurm and the layer 3(2?) - to the second half of the Late Wurm.
Reconstruction of Late Glacial and Holocene palaeoenvironments in the upper Berezina plain (Belarus). pp. 58--66
Abstract: Sediments from the sublittoral zone of the lakes Teklits and Okono were studied using the palynological method. The pollen analysis has shown that the basal layers of the lakes were deposited in the Late Dryas (10,900-10,200 yrs. BP) and Allerod (11,800-10,900 yrs. BP). The stratigraphic division was based on the cor-relation of the above sediment with well-dated neighbouring cores. The vegetation evolution and palaeoclimatic conditions in the Upper-Berezina glaciofluial plain have been reconstructed since the Late Glaciation till nowa-days. Pollen species reflecting the human impact and occurring from ca 4,200 yrs. BP permit a conclusion about the economic activities of ancient tribes in the Neolithic and Early Bronze ages, that was mainly based on "slash-and-burn" agriculture, the cattle breeding being of much smaller importance. Hunting, fishing and gathering were also, in common practice.
Phosphates in Cambrian deposits of southwestern Belarus. pp. 67--73
Abstract: Phosphate mineralization is peculiar to the whole Baltic section of the Lower Cambrian of Belarus, but its distribution is irregular. Rounded and slightly flat phosphate pebbles and nodules are typical for assorted coarse-grained sand-stones of the Rovno and Lontova strata, and also for the levels inside of intraformational breaks. Light-yellow and greenish-yellow subrounded grains associated with glauconite are found throughout the section of the Baltic series except for the quartz strata and thinly laminated clayey strata in the upper part of the Lontova horizon. Euhedral hexagonal crystals of apatite are associated with quartz sandstones in the base of the Vysokoye series, but spherolitic formations - with glauconite-free strata of the Baltic series bottom. The main source of phosphorus was volcanic rocks of the Vendian, that were exposed in the northeastern part of Podlasie-Brest depression and subjected to denudation. This is confirmed by the predominance of mont-morillonite in the clay material of weathered rocks.
Material structure and petrogenesis of granitoids of the Bragin granulite massif (Belarus). pp. 74--80
Abstract: Petrographical and petrogeochemical features of granitoid rocks abundant within the Bragin granulite massif (the crystalline basement of the eastern part of the Pripyat Through) have been discussed in the paper. A detailed study was used to distinguish the Kopan massif of intrusion rocks located in the northeast of the region, and migmatite-granites and granite veins have been described too. The paleogeodynamic conditions of rock formation have been assessed. A peculiar feature of the geological evolution of the granulite-gneissic complex in the studied region is a polyphase operation of the processes of metamorphism and magma generation. A close connection with enclosing metamorphic rocks (aluminous gneisses) is characteristic of the greater portion of migmatite granitoids of the Bragin granulite massif, that is indicative of their anatectic origin. The Gaisin complex of the Ukrainian shield was distinguished as a probable analogue of the magmatic complex of the Kopan massif, when correlations with the Ukrainian shield were carried out.
T.A. Starchik, S.M. Obrovets
The effect of listric tectonics on the paleorelief and sedimentogenesis of the Early-Mid-Famennian basin in the Pripyat trough. pp. 81--88
Abstract: A new interpretation of the evolution of extensive linear zones free of thick enough (hundreds of metres) Famennian sequences is based on the listric nature of step-forming faults in the Pripyat Trough. Across the listric fault zones the sequence changes in completeness, thickness and in the lithofacies of the intersalt Zadonsk-Petrikov and uppersalt Lebedian-Oressa deposits. This suggests that at the active phase of rifting with high general rates of downwarping and sedimentation the frontal parts of steps experienced ascending movements. Submarine tectonic scarps and chains of islands, where sediments did not deposited and/or were washed out had formed in the basin bottom relief. A mechanism of relative upwarping and destruction of the frontal parts of steps was due to a listric character of the step-forming faults in the Pripyat Trough. The crustal block (step) sinking along a concave path resulted in its surface rotation about an axis parallel with the fault strike. The step warped down along the fault downthrown wall with simultaneous upwarping of its frontal part in the uplifted wall. The faulting process was accompanied by stage-by-stage discrete splitting of the frontal part of the step, and a series of intermediate blocks formed in the listric fault zone. The edge of the fault uplifted wall changed and migrated, and, subsequently, the bottom relief and sedimentation conditions in the fault-line zone changed too. A belt of destructed or not deposited sediments in the frontal part of the step increased simultaneously in width.
Yu.V. Kazantsev, T.T. Kazantseva
The main structural features of the southeast of the East European platform. pp. 89--95
Abstract: Abundant thrust-faults of various shape and spatial orientation have been distinguished within the territory of the southeastern part of the East European Platform. Their general distribution pattern has been revealed: arcuate features are characteristic of the central regions and linear features are found within the territory adjacent to the Urals. Tectonics of one type shows its evidences in a zone dominated by the other type tectonics. Such a penetration of structural features is typically for areas found at the junctions of zones showing different structure. An evident discordance between the horizon plans is due to both a widespread occurrence of some thrust dislocations, and several stages of thrusting processes. Such a situation is in agreement with tectonic periods distinguished in the Paleozoic evolution of the Urals and Peri-Urals regions adjacent to the platform, that had a direct impact on the platform evolution regime.
Upper Permian deposits in the Pripyat trough. pp. 96--106
Abstract: A complex of variegated terrigene deposits of the molassic formation of the Pripyat Trough comprising the Dudichy, Vystupovichy, Korenev, Mozyr, Kalinkovichy and Narovlia suites is a continuous series without regional breaks that had been accumulated within a single continental water basin. The Vystupovichy suite wedges out northward due to its lithological replacement by the Dudichy and Korenev sutes, but not washing out before the deposition of the Korenev suite. A local absence of the Dudichy suite from the sequence and of the Korenev suite in the crests of some cryptodiapirs and discordant bedding of the Korenev and Mozyr suites over the more ancient deposits were caused by the absence of sedimentation in a shallow basin within topographic highs, mainly in crests of rapidly growing salt uplifts. The absence of the Dudichy suite deposits in the periphery and discordant bedding of the Korenev suite over the more ancient rocks down to the basement was associated with the expansion of the sedimentary basin area. A regional break at the Permian and Triassic boundary within the East European Platform may be correlated with a large lacuna - regional and angular unconformity in the Dudichy suite bottom. Therefore, it would be reasonable to relate the unfossiliferous Dudichy and Vystupovichy suites, as well as the overlying paleontologically dated Korenev suite, to the Indian stage of the Lower Triassic, and to abandon a differentiation of Upper Permian deposits according to the decision of the Interdepartmental Stratigraphic Conference on the Triassic of the East European Platform (Saratov, 1979). The bottom of Triassic deposits should be traced at the base of the Upper Dudichy subsuite, as the Lower Dudichy subsuite is of Lower Permian age.
Oil geological regions distinguished within the Podlasie-Brest depression from hydrogeological criteria. pp. 107--112
Abstract: The Podlasie-Brest petroliferous basin is situated in Belarus and Poland and is shaped as a sublatitudinal bay. It occurs centroclinally within Belarus and is bounded by the positive structures: Belarusian Anteclise on the north, Lukov-Ratno horst on the south, Polessie saddle on the east. The main oil-promising horizons are associated with Cambrian deposits. They rise towards the depression borders and outcrop the Premesozoic surface at the boundaries of the positive structures. For a long time there were favourable conditions for the fresh infiltration water penetration. At present an area of fresh water occurrence covers the eastern part of the depression (the territory of Belarus and Eastern Poland). A depth of the infiltration water penetration within the depression ranges from 1,000 to 1,200 m. Below this depth in the central part of the structure the mineralized and highly mineralized chloride-calcium water occurs in abundance within Cambrian, Ordovician, Silurian, Permian and Triassic deposits. In the northern and eastern monoclinal slopes of the depression these deposits are found within the fresh water zone. In sites of contact of the pressure water infiltration and elision systems the hydrodynamic barriers have been created that contribute to the formation of commercial petroliferous zones. Under favourable conditions (structural traps, oil reservoirs and cap rocks) oil and gas deposits can be formed there. The oil-promising area is limited at a depth of 2,000 m by the Cambrian deposit surface. West of this depth the probability of oil and gas occurrence is not very high as reservoirs are absent there.
A.V. Matveyev, A.A. Kovalev, L.A. Nechiporenko, N.A. Shishonok, S.I. Kononovich, J.N. Chiberkus
Recent Horizontal movements of the Earth's crust within the Volozhyn and Soligorsk geodynamic testing areas (Belarus). pp. 113--117
Abstract: The results of measurements of horizontal movements of the Earth,s crust are analyzed in the paper. These measurements were carried out within 1996 and 1999 using a system of satellite navigation WILD GPS-SYSTEM 200. Special reference marks confined to various basement blocks separated by faults were constructed for the purposes of monitoring of horizontal movements within the Volozhyn and Soligorsk geodynamic testing areas. These objects were selected for studies as the Volozhyn Graben and Soligorsk centrocline, that the testing areas are confined to, are the most mobile at the recent stage. The left-side displacements along the Korelichi superregional deep fault that crosses the territory of the Volozhyn graben, as well as along the Darasin fault, that is a part of the Central tectonic zone of the Starobin deposit of potassium chloride have been determined as a result of observations carried out with the Leica mathematical software (GPS-SYSTEM 200...,1996). The recorded average annual velocities of horizontal displacements were 0.042 and 0.052 m per year, respectively. These values are close to those obtained in the other regions.
Assessment of tendencies of changes in the purity level of surface waters and groundwaters. pp. 118--124
Abstract: The article presents the technique that enables the changes in the surface water and groundwater purity to be determined. Practical attempts to apply this method (the Wz contamination coefficient) have shown its value in spatial and temporal assessment of the tendencies of changes in the water quality. The coefficients of water contamination (Wz) and water purity (Wzch) are used to analyse the space and time changes of water quality in the rivers Ner and Warta, as well as of groundwater in various regions of Poland. A multigrade scale used to assess a degree of changes of the river water and groundwater purity was essentially improved.
A problem of searching for fluorite deposits in Belarus. pp. 125--130
Abstract: A raw material important for the fluorite production (now imported in Belarus) may be discovered in the territory of the region if direct evidences of a fluorite mineralization are revealed. This problem is risen in the paper, as in view of a new stratiform cryptocristalline type of mineralization there are prospects of finding fluorite deposits in buried graben-like structures. There are some geological and mineralogical preconditions of revealing fluorite of hydrothermal genesis, in particular, at the junction of the Bragin-Loev and Zhlobin Saddles, where subalkaline effusive and sedimentary formations are widespread and long-lived deep tectonic faults are abundant. Under conditions of a thick sedimentary cover geophysical and geochemical studies are supposed to be used for solving the similar task. Illustrations of neutron-activation logging spectrographic and other analyses for fluorine are presented. The most effective techniques in present-day economic conditions are recommended.
Abstract: The phosphorus compounds are extensively involved in colloidal hypergene processes, migrate and are accumulated in different forms and are radioisotope concentrators. They amount (% P< sub >2O< sub >5): 0.05-0.71 mg/l in peat sediments, 0.02-0.85 in plants, 0.005-0.372 mg/l in subsoil water. The phosphate-ferriginous mineralizations are abundant in river valleys with peat floodplain and are represented by vivianite, kerchenite, bosphorite, beraunite and phosphate ochers, which are often of colloidal and subcolloidal composition. The relation between phosphates and technogene and natural radioisotopes is discussed. An experiment study of sorption and desorption of Sr-90 and Cs-137 by newly deposited amorphous calcium and iron phosphates and their minerals - vivianite and apatite has been carried out with an aim to ascertain the role of phosphorus compounds in radioisotope migration. At was shown that all the phosphates investigated have the high Sr-90 absorption capacity (90-95 %). Caesium-137 does not create any phases with calcium phosphate and amorphous iron compounds. Its sorption amount is about 30 % of the initial solution with vivianite only, as the latter shows a high desorption capacity (95-98 %). The strontium phosphates are characterized by a low desorption capacity (about 5 %), which is due to the hydroapatite Sr(H2PO4)2 formation, which is subsequently turned to hardly soluble Sr10(PO4)6(OH)2.
L.N. Ryabova, A.A. Razlutskaya
Reconstruction of ecologic and geochemical conditions in the territory of the Krivino massif in the Holocene second half (Belarussian Dvina region). pp. 137--144
Abstract: Geochemical investigations of the Neolithic and Bronze age site of Osovetz-2 in the Dvina area of Belarus were carried out. The cultural layer includes many bone remains of wild and domestic animals. The peat layer creates a non-agresive medium (humate composition of the organic matter, pH 5.2-6.4), which contributed to a good safety of bones. The chemical composition of forest marten remains from different age layers (one type anatomical set) shows some difference in the bone content of young and adult individuals. The concentrations of P2O5, Al2O3, Ti, Cu are higher with increasing of the ash content of bones of adult marten. An essential difference was revealed in the average content of the bone fossil zone between the upper (3,350 years ago) and lower (4,320 years ago) layers. This is in agreement with the chemical element distribution in soils. Differences in the chemical composition of marten bones were due to paleogeographical evidences, sharp changes in environmental geochemistry. The climate cooling in the Middle-Late Holocene resulted in increased terrigene wash-down of carbonate materials from the drainage system territory, in Ca, P, S, Fe concentration in accumulative landscapes. The C14 dating of carbonate concretions in the border zone of the cultural layer and peat (IGSB-614 28374𫗝 years) was used for these geochemical reconstructions. The data obtained suggest that under sharp paleoclimatic, litho- and pedogeochemical changes in the Holocene the changes of the environmental geochemical situation took place. These resulted in simultaneous changes of the chemical composition of soil horizons and living organisms.
Geochemical pecularities of the soil cover in the river Sozh floodplain. pp. 149--152
CHRONICLE. pp. 153--157
JUBELEES. pp. 158
BEREAVEMENTS. pp. 159--160
IN COMMEMORATION OF A SCIENTIST. pp. 161--168
NEW GEOLOGICAL PUBLICATIONS. pp. 169--169