Литосфера, 2001, No.1 14
/ Издания академии / Научные журналы
Литосфера, 2001, No.1(14)
Номер 1(14), 2001
СОДЕРЖАНИЕ
ОБЩИЕ ПРОБЛЕМЫ
G.V. Zinovenko
Geodynamics and structural features in the East European Platform Southwest. pp. 5--12
Abstract: Complicated geodynamics at the southwestern border of the East European Craton was due to tectonic processes that occurred within geosynclines, as well as within rift structures immediately adjacent to the old platform or some distance away from its limits. Zones of pericratonal subsidences, syneclises, faults of various extent, horsts and grabens, monoclines, etc. have been distinguished in a series of geodynamic structures formed at different stages of the platform tectonic evolution.
Some specific structures as troughs of rift genesis, zones of pericratonal subsidences had formed at the Baikalian and Caledonian stages under the infuence of geosynclines adjacent to the old platform. These structures had been developed under the effect of complex compressive and tensile stress fields that sometimes were of obviously wave nature. Tectonic processes that operated in Hercynian geosynclines of Western Europe somewhat distant from the old platform limits caused intense faulting, formation of horsts and grabens and the new larger structures such as the Lvov-Ljublin and Pripyat Troughs. The stress fields changed repeatedly during the Hercynian stage, the field vectors changed their orientations.
At the Cimmerian-Alpine stage the monoclines inclined toward the rift structures had formed within the old platform under the effect of tectonic movements, which the origin and evolution of rift structures in the Mesozoic (Danish-Polish Trough) and Cenozoic (the area of the Gulf of Bothnia) are associated with. Thick strata of terrigenous and carbonate rocks not dislocated by disjunctions had been accumulated within the monoclines under the general tension and downwarping conditions.
V.A. Kuznetsov
Self-purification of the river valley landscapes from the radioactive contamination. pp. 13--21
Abstract: The processes and factors contributing to the selfpurification of river valley landscapes from radioactive pollution associated with the radioactive decay, second dispersion haloes, geochemical differentiation, matter redistributions in biota, soil and vegetation covers, with geochemical barriers and some resulting technogenic measures are characterized.
Three degrees of the landscape relative selfpurification -- high, moderate and poor ones have been distinguished and used to describe the conditions in river-beds, floodplains and oxbow-lakes. Within a river-bed the selfpurification is determined by the hydrodynamic regime of the stream and sedimentation; in a floodplain it is dependent on the flood, facies and geomorphological conditions; in oxbow-lakes moderate or poor selfpurification is dominant due to the accumulative properties of the basins. The principles of geochemical zoning and mapping of floodplains are discussed.
ГЕОЛОГИЯ
L. Lindner, Ya. Yelovicheva
Correlation scheme of glacial and interglacial units in the Pleistocene of Poland and Belarus. pp. 22--31
Abstract: Geologic and palaeobotanic data from the region of Poland and Belarus allow us to determine 9 (10?) main glaciations and 8 (9?) interglacials separating them in the Pleistocene of these countries. The glaciations include, from the oldest: Narevian (only in Poland), Nidanian = Narevian in Belarus, Sanian 1 = Servetskian, Sanian 2 = Berezinian, Brok = Glacial - 4 in Belarus, Liviecian = Glacial - 5, Odranian = Dnieperian, Wartanian = Sozhian, (Torunian? - only in Poland) and Vistulian = Poozerian. Among the interglacials, from the oldest the following have been distinguished: Podlasian = Augustovian? (only in Poland), Malopolanian = Korchevian, Ferdynandovian = Byelovezhian, Mrongovian = Ishkolidian, Mazovian = Alexandrian, Zbojnian = Smolenskian, Lubavian = Shklovian, (Krastudian? - only in Poland) and Eemian = Muravian. A tentative scheme correlating them with global climate coolings and warmings, registered in deep water sediments of the Atlantic Ocean as 18O stages is presented.
R.A. Zinova
The Solenovskaya horizon described by G.I.Goretsky and its age analogues. pp. 32--38
Abstract: The Solenovskaya horizon was first distinguished by G.I.Goretsky in 1948 within the NorthernYergeni region in the south of the East European Platform and named after the settlement of Solenovskaya Stanitsa (Goretsky, 1982). This horizon is also named "ostracode bed". It occurs in the top of the Lower-Oligocene (Rupelian) part of thick deposits of the Maikop series. By now the Solenovskaya horizon has been adequately studied by various paleontological methods (Zaporozhets, 1998) and is used by investigators of Cenozoic deposits as a reliable reference level, in particular, for correlation purposes. Deposits of the Solenovskaya horizon are easily identified within vast territories from France, Belgium, Germany, Switzerland, Bulgaria and Hungary on the west to Kopetdag, Ustug, Mangyshlak and the Aral Sea region on the east (Veselov, Sheremeta, 1964). Such long-distant correlations are possible because of a very peculiar endemic brackish-water fauna of mollusks of Ergenica cimlanica contained in the Solenovskaya horizon. This species was first revealed by B.P. Zhizhchenko (1953) on the Don in the region of the Tsimliansky settlement and described as a new genus and a new species.
Age analogues of the Solenovskaya horizon are known in Belarus (Stradubka suite), Ukraine (Zmiyev beds), Kazakhstan (Zhanaarka suite), West Siberia (Novaya Mikhailovka suite). Deposits of the Solenovskaya horizon age identified in remote regions of Eurasia make possible distant correlations and connections that were of great inportance in G.I.Goretsky's opinion.
K.I. Davydik, T.V. Yakubovskaya, T.P. Zakharenko
Correlation of geological and biotic events in the light of new data on the stratigraphy of the Oligocene and Miocene of Belarus. pp. 38--46
Abstract: A correlation between the geological and biotic events on the one hand and the natural-historical boundaries, as well as the crises of ecosystems on the other hand, at the end of the Palaeogene and Neogene within the Belarus territory is considered in the paper. Therewith the new ideas of the following issues have been used: age of the Eocene - Oligocene boundary (33.7 million years) and of deposits located in the bottom of the Kharkov Series (37 -- 38 million years); widespread occurrence of the Kharkov Series within the Belarus territory in comparison with that of the Kiev Suite; the Miocene but not Pliocene age of the considerable part of the Belitskaya Series in the Ponemanie area.
It was revealed that the natural-historical boundaries between the Eocene and Oligocene, as well as between the Miocene and Pliocene coincide with such geological events as the climate cooling, the World Ocean level lowering, orogenic phases in the Alpine belt and others. These events entailed the threshold states and rearrangement of ecosystems. The natural-historical boundaries are recorded in geological sections as erosional unconformities and lithological changes. A correspondence between the natural-historical and stratigraphic boundaries proves the validity of stratigraphic divisions.
N.V. Veretennikov, V.P. Korzun, A.G. Laptsevich, N.D. Mikhailov
Petrology of diatremes from the Zhlobin field (Belarus). pp. 46--55
Abstract: Round or oval-shaped magnetic anomalies detected in the Rogachev-Zhlobin region are due to volcanic-magmatic formations infilling the upper (crater) parts of the explosion pipes (diatremes) that outcropped in Early-Late Frasnian (Rechitsa) time. These formations are composed of volcanoclastic alkali-ultrabasic rocks which lithoclasts contain all three families of this rock series: alkali picrites, ultrabasic foidites and melilitites. Among them in various diatremes there were melanephelinites, olivine and leucitic-olivine ones included; olivine and nepheline- and melilite-olivine melaleucitites; olivine and leucitic-olivine melilitites; feldspathoid and melilite-pyroxene picrites, as well as transition rocks from feldspathoid picrites to olivine melaleucitites.
A.A.Makhnach, G.D.Streltsova, L.F.Gulis, V.I.Gulakova, V.V.Gulis
Composition and texture peculiarities of Upper Devonian dolomite rocks from the Pripyat trough and Orsha depression. pp. 56--59
Abstract: The analysis of texture, mineralogical and chemical composition of Upper Devonian dolomite rocks from the Pripyat Trough and Orsha Depression has revealed several peculiarities associated with the changes of dolomite aggregates during dolomitization and neomorphism. The size, boundary shape and zoning of dolomite crystals, the way of substitution and degree of substrate preservation are the most informative parameters among the texture features. The peculiarities of the dolomite rock mineral composition that are of importance for the classification of dolomites comprise relics and neogenic calcite and evaporite minerals occurred in matrix, allochems and voids, as well as the distribution of terrigenous admixture and empty pores and caves. The most informative chemical indicators of the genesis of dolomite are the CaCO3, Mn and Fe contents that affect parameters of the dolomite crystal lattice and the Ba, B and Sr concentrations caused by the salinity of the dolomite formation environment.
E.A. Vysotsky, N.S. Petrova
Geological models and interpretation of environments of the potassium-bearing horizon thinning within the Pripyat trough. pp. 60--65
Abstract: Some problems associated with the reconstruction of environments in which potassium deposits had been accumulated in the Late Devonian within the Pripyat Trough have been discussed. Extensive geological data have been summarised and used as the basis of the type descriptive-graphical models which represent characteristic features of the potassium-bearing horizon thinning and facies replacement in the Trough marginal zones and at the intrabasin uplifts.
The whole range of the observable thinning and facies replacements of potassium-bearing horizons is described by four basic models (I-IV).
A type of the potassium-bearing horizon facies replacement predominanty by potassic salt containing halopelite interlayers and sylvinite impregnations (model I) is among the most widespread ones in the Pripyat Trough. The model II represents the potassium-bearing horizon and enclosing rock salt member thinning in a direction of contrasted paleouplift or the shore line of potassium-accumulating subbasins. A type of the sylvinite and carnallite horizon replacement by halopelites (model III) is rather widespread. The models I-III represent the thinning and facies replacement environments resulting from the integrated influence of the primary sedimentation agents: tectonic, paleogeographical, paleogeomorphological, climatic, etc. The model IV describes the transformation of potassium-bearing horizons to hematite interlayers represented by dye-stuff of potassic or potassium-magnesium salts. The transformation of potassium deposits to stratified hematite analogues is a rather characteristic phenomenon of the region under study.
The modelling of the environments of thinning and facies replacement of potassium-bearing horizons of redrock association carried out advances the following problems to be solved by investigators: to specify and justify geochemically the processes that caused the replacement of potassium deposits in intrabasin uplifts; to assess the specific contribution of clastic material to the potassium accumulation.
N.N. Levykh, A.S. Makhnach
The origin of alteration of Vendian basalts in Belarus. pp. 65--72
Abstract: The origin of alterations of Vendian basalts from the Podlasie-Brest Depression (Belarus) has been discussed on the basis of petrographical, mineralogical and geochemical studies.
It has been revealed that the basalt polygenetic alterations involved the process of hydrothermal metasomatism, as well as weathering processes.
Mineral indicators of hydrothermal metasomatism are quartz, montmorillonite, dolomite, iddingsite, bowlingite, serpentine, palagonite and zeolite. The formation of these minerals was accompanied by an intake of silicon, potassium and, sometimes, by the calcium, magnesium and sodium supply.
The weathering crust consists of a zone of the original rock transformation and the kaolinite and montmorillonite zone. The crust is revealed by an upward increase of the rock alteration degree, the rock impregnation with the ferrous compounds, the development of montmorillonite after palagonite and dark-colored components, the formation of kaolinite which substitutes plagioclase and montmorillonite. Active removal of sodium, potassium, magnesium and silicon is a characteristic process of the weathering crust formation.
Geochemical studies of the basalt by the absolute mass approach with regard to lithological factors have permitted the reliable determination of the lower boundary of the weathering crust.
L.N. Taran
Distribution of the Okolovo unit in the crytalline basement of Belarus. pp. 72--81
Abstract: The Okolovo series distinguished within the Central Belarusian belt (CB) has been considered to be Archaean in age and composes the linear structure. Recently obtained petrological and geochronological data suggest the need of reappraisal of the distribution and lithological composition of the Okolovo series.
Tectonicly, the CB extends for more than 600 km along the Fennoscandia-Sarmatia suture zone that is the fundamental lithospheric boundary in the western part of the East European Craton. The major Minsk fault subdivides the belt into two lithologically different parts. The northwestern part of the belt including the ca 2.0 Ga Okolovo arc-related volcanic-sedimentary series is dominated by metavolcanics and minor metasediments with numerous ca 1.9-Ga TTG intrusions. The southeastern sub-terrane is composed mainly of paragneisses and migmatites, and minor metavolcanics intruded by 1.8 Ga sub-alkaline granites and quartz syenites.
The Okolovo metavolcanics are mostly basalts and basaltic andesites with the lower alkali contents for andesitic compositions as compared to metavolcanics of the southeastern CB. Mafic metavolcanics have volcanic arc affinities, but the southeastern metavolcanics show, the more calc-alkaline compositions. Felsic igneous rocks of active continental margin settings were presumable sources of sediments from the southeastern part of the Central Belarusian belt, while the mafic material was probably responsible for the formation of the Okolovo sediments proper.
The ca 2.0-Ga Okolovo volcanics underwent initial metamorphism under high amphibolite-facies conditions during progressing southeastward subduction. Peak metamorphic conditions at ca 1.90 Ga were associated with the emplacement of 1.9 Ga TTG intrusions. Tectonothermal reworking lasted until ca 1.7 Ga. In contrast, sediments of the southeastern sub-terrane deposited roughly at the same time as the Okolovo metavolcanics, experienced moderate-T and low-P initial metamorphism during fast burial to depths of ca 25 km, where they resided until having been entrained up by the 1.95 Ga high-T granites. Subsequent isobaric cooling of both granites and metapelites occurred at shallow depths of 12-14 km.
Contrasting styles of the tectonothermal evolution and geochemical rock particularities within the CB allow us to conclude that metamorphic rocks comprising the southeastern part of the CB could be considered as an independent stratigraphic unit (Dumichi unit).
A.A. Arkhipova, I.V. Naidenkov
Early Precambrian granitoids of Belarus: geodynamic position and metallogenic trends. Paper 1. Granitoids of the Belarusian-Baltic granulitic belt. pp. 82--91
Abstract: The crystalline basement of western Belarus with its major structural units Belarusian-Baltic granulite belt (BBGB) in the west and Smolevichi-Drogichin suture zone (SDSZ) in the central part is formed by granitoid complexes of various age and composition. The study of their mineralogic-petrological and petrochemical peculiarities and their correlation with the standard geochemical types of granitoids formed under different depth and tectonic conditions permitted an assessement of the geodynamic setting at various stages of the regional continental crust evolution.
Some groups of granitoids may be differentiated according to their formation time and relevance to specific geodynamic conditions.
At the early stage, when the primary basite crust deoxidation occurred (presumably in the Early Archean), charnockites of the enderbite-charnockite complex had formed under the granulite-facies conditions, then crustal (with a portion of the I-component) collision anatectic granitoids of the Golenovo complex and, finally, postcollision mantle-crust granitoids of the Osmolovo complex geochemically similar to the latite series granitoids developed within the present BBGB territory. Their formation completed the evolution of the granulite-basite layer of the Earth's crust in the region.
In the Late Archean-Early Proterozoic the granitisation processes developed under the amphibolite-facies conditions were universally evident in all regional structures and resulted in fusion of anatectic granites of the Polonka complex in the collision environment that correspond geochemically to ultrametamorphic granites. These processes completed the development of the granite- metamorphic layer of the Earth's crust in the region.
Postcollision mantle-crust granitoids (showing geochemical features of the andesite series) from a complex of intrusive charnockitoids with an isochronous age of 1.8 Ga are locally widespread in the BBGB.
Under the stable platform conditions, the most recent (1.5 Ga) anorogenic or intraplate mantle-crust granitoids of the latite series formed due to tectonic-magmatic activation within the BBGB territory at the intersection with the Mazur-Mogilev zone of tectonic-magmatic activation.
V.S. Konischev
The internal structure of the Chernin Famennian salt ridge in the Pripyat trough. pp. 92--99
Abstract: The Chernin famennian salt ridge is situated in the northen part of the Pripyat Trough and is superimposed on a monocline in intersalt deposits in the middle part of the Rechitcha-Shatilky step. The Chernin salt ridge formed as a result of salt flow in the halite subformation of the Famennian salt formation. It stretches from west to east reaching 60 km in length and 4--8 km in width. An amplitude of the salt ridge is 800--3.000 m. The salt ridge consists of two series of anticlines and domes. The nothern one includes Holopenechy and Ozemlja anticlines, Moiseev dome, North-Chernin anticline and Molchan dome. The southern series includes the Malun anticline, Moiseev dome, Chernin and Kormian anticlines. The halite subformation thickness increases from 20-30 m on the nothern slope and 400 m on the southern slope of the salt ridge to 1000--1500 m and more at the crests of salt anticlines and domes of the salt ridge. All anticlines and domes are diapiroids. Their salt massifs do not pierce suprasalt deposits. The halite subformation consists of seven members. Every member includes sulphate-carbonate and salt strata. Halokinesis is evident in salt strata in four lower members of the halite subformation and its intensity depends on the thickness of salt strata: the average thickness of the first, lower salt stratum is 151 m and varies from 42 to 581 m; the average thickness of the second salt stratum is 66 m and varies from 23 to 222 m; the average thickness of the third salt stratum is 78 m and varies from 21 to 436 m; the average thickness of the fourth salt stratum is 231 m and varies from 37 to 446 m. Salt lenses were created in salt strata, as a result of halokinesis, they superimposed over one another and formed salt massifs. The average thickness of the fifth, sixth and seventh salt strata are 45.6 m (10--173 m), 37.7 m (9--103 m) and 68 m (34--201 m), respectively, and they do not show visible signs of halokinesis: their thickness has no obvious connections with salt massifs. In the
depth range from 2000 to 3000 m halokinesis is evident when a thickness of salt strata exceeds 60--70 m. The thickness of three upper salt strata is small for halokinesis, besides these occur in a very rigid framework of sulphate-carbonate strata: their average thickness is 7 m (3--25m), 20.4 m (5--42 m) and 18 m (8--40 m), respectively, which exceeds those of sulphate-carbonate strata in four lower members: 1.5 m (1--3 m), 4.1 m (2--20 m) and 10.8 m (1--32 m). Some salt strata (the third, fourth and seventh ones) include allochthonous blocks of the halite subformation, as a rule with the fifth, sixth and seventh members. Two kinds of halokinesis evidences have been distingushed in the Chernin salt ridge: laminar salt flow in salt strata and detachment of salt formation blocks and their movement with salt.
V.F. Nalivaiko
Neotectonic stresses within eastern Belarus. pp. 100--106
Abstract: The problem of reconstruction of neotectonic stresses is considered using the structural-geomorphological method applied to Bykhov key site. The comprehensive geological and geomorphological studies and computer processing of topographic lineament analysis data have been performed. Maps of the topographic lineament density have beeen compiled and used for further geodynamic reconstructions. It has been determined that the stress conditions within the site was distinguished by the prevalence of sublateral compression and submeridional extension at the neotectonic stage of evolution. Such a geodynamic situation caused the development of active disjunctive structures in the strike-slip stress field. The peculiarities of the territory geomorphology and geological structure confirm the strike-slip stress conditions of the studied area.
An analysis of two different active fault maps was performed in order to check the accuracy of the results obtained. The similar geodynamic conditions determined from the analysis of two maps suggest the correctness of conclusions. The results obtained show the general horizontal direction of neotectonic movements, and need to be corrected for the vertical component of neotectonic processes, which must be taken into account.
V.N. Luksha
Hydraulic correlation of aquifers within the limits of water in-takes of the town of Gomel estimated with helium measuring method. pp. 107--111
Abstract: Helium measuring tests have been carried out within four water intakes of the town of Gomel. For each water intake the average helium contents have been determined in exploited aquifers. A comparison characteristic of the degree of groundwater protection of the Gomel water intakes has been given. It is suggested that the helium positive anomaly detected within the "Korenevski" water intake overlies a fault zone. An isohelium map of Paleogene and Albian-Cenomanian aquifers have been compiled for the "Korenevsky" water intake. A close connection of the helium fields in different seasons has been assessed within each water intake. The helium concentration change was studied during a year in the Albian-Cenomanian aquifer of the "Southwestern" water intake. The helium measuring tests of groundwater in the Gomel area were used to reveal an exponential relationship between the helium content and a depth of testing.
Yu.M. Obukhovsky
The landscape indication in Belarus and its contribution to studying the lithosphere. pp. 112--119
Abstract: The landscape indication is an applied science, which was developed at the junction of geography, geology, biology. As an independent field of knowledge it was formed in the middle sixties. Indication and landscape investigations in Belarus were preceded by regional geological, structural-geomorphological and geobotanical works performed by Belarusian scientists, as well as by experts from other countries.
Nowadays various aspects of indication are being worked out at different institutes of the National Academy of Sciences of Belarus, higher educational institutions, industrial institutes and rarely in production organizations. Such independent fields of studies, as tectonic, litho- and hydroindication, indication of soils and exogenic processes may be differentiated in the landscape indication. The landscape indication forms the methodological basis for remote sensing and is widely used for a complex assessment of ecological conditions of the environment, its monitoring and protection.
The indication studies curried out in Belarus are presented in several monographs, however the factual data available have not yet been pooled together to form a manual.
ГЕОФИЗИКА
A. Sas-Uhrinovsky, S. Mrochek, G.I. Karatayev, Yu.V. Belov, O.I. Karagodina
Reflection of the recent depth tectonophysical processes in the dynamics of the gravity and magnetic fields in Belarus. Article 1. Structure of the monitoring geophysical network and time variations of the gravity field. pp. 120--130
Abstract: To study the recent dynamics of the tectonosphere of Belarus a network of geodynamic geophysical reference sites including gravimetric and magnetic testing areas which lines cross all large tectonic units of the region, and a regional network for studying components of secular variation of the geomagnetic field were created. The sites are located both immediately on crustal blocks, described by relative stability, and in zones of deep faults distinguished by intensive palaeo- and recent geodynamics. Gravimetric observations in the testing area are carried out once in a year, and magnetic observation in testing areas and sites of secular changes of the magnetic field -- once in two years.
Variations in the time of gravity acceleration are studied withing the Belarusian gravimetric test area built along the line Lida-Rossoni-Borisov-Kalinkovichi-Lida with a break along Lida-Minsk-Borisov (33 sites, spaced 30--50 km apart).
The research of secular changes of the modulus of the total magnetic displacement vector, its inclination and declination are carried out at the Pleschenitsi observatory and at 14 sites evenly distributed over the territory of Belarus. Anomalies of the secular changes are studied at the Belarusian geodynamic magnetic testing ground which strikes along the line Lida-Polotsk-Lepel-Senno-Yelsk-Lelchitsi-Slutsk-Lida with a break along Vileyka-Pleschenitsi-Bobr. The ground includes 37 basic magnetic sites that are 20--40 km spaced with 5--12 km spaced additional points between them. A total of 163 magnetic points are located within the testing ground.
The repeated gravity observations provided the following information about the recent dynamics of the gravity field in the territory of Belarus. In gravimetric points located in fault zones the most significant variations (as high as 0.4 mGal) of the gravity field are observed. A curve of the regional field variations (except for the disturbing influence of the fault zones) changes slightly in increments. However, the accumulated variations of the regional field relative to nodal gravimetric points (g.p.) Lida, Rossoni, Usha show quite significant values determined with high reliability. This testifies to the modification of the density regime of large depth masses between these points. So, the variations field is reduced by -0.1 mGal in a northward direction from the g.p.Lida located on the stable Vilnius block of the Earth's crust of the type A towards the Polotsk-Kurzem deep fault zone. In our opinion, it is due to processes of the subcrustal material deconsolidation in the Polotsk-Kurzem deep fault zone that were earlier recorded in the data of complex interpretation of the gravity field anomalies and in seismological data obtained by the method of exchange waves from earthquakes. Further northwards this field increases to the Rossoni point up to + 0.1 mGal. Within a fragment of the profile g.p. Rossoni -- g.p. Usha crossing the Central-Belarusian junction zone between Fennoscandian and Sarmatian segments represented by the Lepel and Minsk blocks of the Earth's crust of the types C and CD, respectively, the variations field practically remains unchanged at about + 0.1 mGal testifying to the material consolidation.
Within a fragment of the profile g.p. Usha -- g.p. Kalinkovichi, in particular, south of the g.p. Bobruysk, near the Pripyat palaeorift the regional variation field essentially decreases to a value of -0.3 mGal. The similar picture is observed within a transition from the Vilnius block (g.p.Lida) to the Pripyat palaeorift (g.p.Starobin), but less pronounced. There is no doubt that this is due to processes of the material deconsolidation in the bottom of the Earth's crust and upper mantle of the Pripyat palaeorift, low velocity zones have been determined by seismic sounding.
Important data on the gravity field variations were also obtained within a fragment of the profile g.p. Porozovo-Kamenets, crossing a depth mantle fault and separating the Brest and Vilnius blocks of various types: the Vilnius block is characterized by a stable Earth's crust, and the Brest block forms a part of the Pripyat palaeorift and Pripyat-Brest activation zone, where recent tectonophysical processes occur.
ГЕОХИМИЯ
V.A. Kuznetsov, V.A. Generalova
Geochemical importance of humic acids for the radioactive strontium and caesium migration in river valleys. pp. 131--136
Abstract: The distribution of radioisotopes in the organic matter which is contained in oxbow-lake amphisapropel, meadow peat, humic clay and sandy loam, turf, as well as in limonite of the river Sozh floodplain has been studied. The organic matter is represented by decalcinate, fulvoacid and humic acid and the insoluble residue. Recent experimental and nature investigations carried out in the last years (the authors, studies included), have shown, that the Sr-90 migration activity is associated with formation of complex compounds of fulvoacid, and a relatively low migration capacity of Cs-137 with the compounds of humic acids. The analyses of floodplain sediment series for the distribution of these radioisotopes throughout the organic matter groups have shown that radiostrontium was tending to combine with organic and radiocaesium -- with mineral and organic-mineral components of the sediments. The role of humic acids, as geochemical barriers, as well as a possibility of using the peat and buried soil exposures in a floodplain as radiomonitoring objects have been discussed.
N.N. Petukhova, S.N. Veremchuk
Geochemical characteristics of floodplain soils in the Zapadnaya Dvina basin. pp. 137--144
Abstract: The Zapadnaya Dvina drainage basin occupies the northern part of Belarus and shows the natural environment much different than that of the other territory. The river valley is situated in the Valdai glaciation area. Sediments of the floodplain facies are composed of fine-grained humus sands, sandy loams and clay sands. The geochemical peculiarities of Holocene soils are due to lake-glacial sediments, that contain rather high concentrations of the main chemical elements, excepting Si, and trace elements. In these soils the amounts of MgO, Ti are 1.7 times, Be -- 1.6, Al2O3, Co -- 1.5, K2O -- 1.4, Cu -- 1.3, V and Pb -- in 1.2 times their clarke values in the soils of Belarus; SiO2, Fe2O3, Na2O, Ni, Cr, Zr, Ba, Y, Yb are within their clarke limits; and CaO -- below the clarke values. The floodplain Holocene soil is as a rule of small thickness and does not show distinct buried humus horizons. Some geochemical zones may be distinguished in the soil sequence. So, the higher values of SiO2 : Al2O3 and the highest value of K2O:Na2O in the strata (lithology being homogenous) suggest active pedogenic processes, that proceed under warm and humid climate conditions with luxuriant vegetation. In this soil horizon the CaO, Na2O and P2O5 contents much increase, the Mn content and the total sum of trace elements are the highest. This is a distinct evidence of soils of the Atlantic period.
КРАТКИЕ СООБЩЕНИЯ
M. Komarovsky, O. Komarovskaya
Representative glacial valleys of Belarus. pp. 145--148
A.I. Trusov
Lateral distribution of the different type crystalline schists in the central part of the Belarus-Baltic granulitic beltRepresentative glacial valleys of Belarus. pp. 149--151
A.S. Glaz
Distribution of natural and technogenic radioisotopes in the Sozh river floodplain deposit (Vetka-Loev region). pp. 151--154
V.A. Vakhrushev
Enigmatic mechanical crystals. pp. 154--155
ОБЗОРЫ. p. 156
ХРОНИКА. pp. 157--163
ЮБИЛЕИ. pp. 164--165
ПОТЕРИ НАУКИ. pp. 166--167
НОВИНКИ ГЕОЛОГИЧЕСКОЙ ЛИТЕРАТУРЫ. pp. 168--169
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