Dnieper Glaciation Research Articles

Mechanisms of influence of forest ecosystems on the aggregate composition and water stability of soil aggregates in the semi-arid area of southeast Ukraine

Modern processes of climate change are accompanied by a number of negative factors, which include aridization, desertification, soil degradation and erosion. The research was were carried out on the territory that is the southern border of the distribution of the late glacial phase of the Dnieper glaciation (Middle Pleistocene, 100–230 thousand years ago). The influence of forest ecosystems on the aggregate composition and water stability of soil aggregates, the features of which determine the protection of soils from erosion and other degradation processes in semiarid conditions, was assessed. It has been established that luvic chernozems of forest ecosystems are characterized by an increased content of aggregates of fractions 2–3, 1–2 and 0.5–1.0 mm, as well as water-stable aggregates of fractions > 5, 0.5–1.0 and 0.25–0.5 mm in the 0–20 cm layer compared to ordinary chernozems of steppe ecosystems. The content of soil organic matter is a determining factor on which the aggregate composition and content of water-stable aggregates in luvic chernozems of forest ecosystems depends. The existence of close direct relationships has been established between the content of soil organic matter and the content of aggregates of the 0.5–1.0 mm fraction, as well as between the content of soil organic matter and the content of water-stable aggregates of fractions 3–5, 2–3 and 1–2 mm in chernozems of steppe and forest ecosystems. The existence of close direct relationships between the sand content and the content of water-stable aggregates of fractions 3–5 and 2–3 mm was revealed. The established increase in the content of soil organic matter and sand in luvic chernozems of forest ecosystems compared to ordinary chernozems of steppe ecosystems is the reason for the improvement in the aggregate composition and the increase in the content of water-stable aggregates. This is a key aspect of increasing the resistance of soils in forest ecosystems to various negative factors, such as desertification, degradation, wind and water soil erosion.

CONDITIONS OF KAME FORMATION NEAR VILLAGE OF MASHIV (VOLHYNIAN POLISSIA)

Kames located in the Volhynian Polissya remain the most widespread and the least studied type of relict glacial landform. The article is focused on the specific conditions of kames creation within the peripheral parts of the Volhynian Polissya glacial bed elevation and their significant role in the formation of fissure net in the zones of deadened ice compression inherited from the stages of their inactivity. These compression zones were predetermined by the general planned configuration of the glacial bed landform climaxes. The presented reservoir is located to the north of the village of Mashiv and belongs to a complex of similar glacial accumulations crowed at the culmination of pre-glacial relief and placed at a considerable distance from the marginal formations of the maximum stage of the Dnieper glaciation. The morphological and geological structure of the form is analyzed to explain the conditions of its formation. It is revealed that its structure is dominated by fine-grained sediments; textural and structural features of them allow distinguishing two lithofacial complexes. The basis of the form is loamy sandy and sandy lake-ice deposits covered by a complex of fine-medium-grained sandy fluvioglacial sediments. The morphology of the form, its correlation with the elements of buried pre-glacial relief and the textural peculiarities of the described section deposits, allow to state that the accumulation of the material occurred within a semi-flowing or stagnant during certain periods basin filled with sediments of a small convey water-glacial outcasts; they were accumulated by activity of low energy melt water flows within the peripheral part of the ice glade. The glade was formed on the fracture zone line of the inactive (dead) ice, laid above the glacial bed landform climaxes. The textural and structural features of the form give reason to identify it as kame. Key words: Volhynian Polissia, deglaciation, kames, sedimentation, lithofacies analysis, glaciolacustrine and glaciofluvial sediments.

Micromorphological peculiarities of the Pleistocene soils in the Middle Pobuzhzhya (Ukraine) and their significance for paleogeographic reconstructions

The basic micromorphological features of fossil Pleistocene soils of the Middle Pobuzhzhya region are revealed. The early Neopleistocene (Shyrokyne, Martonosha, Lubny) and Middle Pleistocene Zavadivka soils are characterized by bright brownish, reddish and brownish colors of plasma, compact composing structural separations in the form of cleave blocks with densely packed nodular formations of ferruginous matter, cracksman ship of the mass, a significantamount of ferruginous, manganese and carbonate new formations. In the soils of the early optimum of the Kaydaky stage, signs of the eluvial-illuvial processes were observed (impoverished on the thin clays and humus fields with the «washed» grains of the mineral skeleton, the destroyed microaggregates in the eluvial and the impregnation of the plasma by calomorphic clays in the form of streaks, films, streams in the illuvial horizons). In the Pryluky soils there is a well-expressed microagregation of the mass, a branched net of twisted pores, humus coagulation in the humus and humus transition horizons, various forms of carbonate new formations as the impregnation and plasma cementation by microcrystalline calcite, presence of isolated crystals of crypto-, micro- and small crystalline calcite. The specific individual features of the Vytachiv soils are cleave block microstructure, the presence of the nodular concentric organo-iron-clay formations, and microorsteins. Dofinivka soils are characterized by a loose microstructure, fuzzy rounded microaggregates, a developed system of twisted pores, and enrichment of mass on carbonates. In order to clarify the genetic types of fossil Pleistocene soils of the Middle Pobuzhzhya, identification of the signs of elementary soil formation processes was carried out on the basis of micromorphological analysis data. The significance of the results of micromorphological researches for paleogeographical reconstruction is outlined. It has been established that certain groups of soil formation processes are characteristic for fossil soils of separate paleogeographical stages. In the soils formed up to the Dnieper glaciation (Shyrokyne, Martonosha, Lubny and Zavadivka), signs of processes of claying, rubbification, ferralization, cleaving were displayed, but weakly expressed humus formation, thoughcarbonization were diagnosed. In the soils formed after the maximum glaciation (Kaydaky, Pryluky, Vytachiv, Dofinivka), signs of the such processes as humus formation, podzolization, lessive, leaching, damp-meadow soil formation on floodplain, migration of carbonates, etc., are established. It is processes which are predominating in the modern soils of the territory of Ukraine. Assertaintment of elementary soil-forming processes, diagnosed in multi-annual fossil soils, have made it possible to identify their genetic types and as a result, to reconstruct the soil cover in separate stages of the Neopleistocene, to establish regional patterns of evolutional stadial changes and the natural environment in the Pleistocene on the territory of the Middle Pobuzhzhya.

New data on the age of the glaciation in the New Siberian Islands (Russian Eastern Arctic)

To estimate the age of the glaciation in the New Siberian Islands, fossils of small mammals from the Sana-Balagan site (Faddeevsky Island, Russian Eastern Arctic) have been studied. The evolutionary degree of this fauna, which indicates the age of the sediments underlying the glacial deposits, suggests that the glaciation of the New Siberian Islands began no earlier than 190–210 thousand years ago. The new biochronological data in combination with 230Th/234U dates show that the geological event in question was synchronous with the Moscow glaciation or the Moscow stage of the Dnieper glaciation (the Vychegda glaciation, the final stage of the Saalian, the final stage of the Riss, the end of the MIS 6, 180–140 thousand years ago).

DEVELOPMENTAL CHARACTER OF NATURE IN THE MIDDLE NEOPLEISTOCENE OF UKRAINE

The landscape-climatic conditions of Ukraine in the Middle Neopleistocene (400-120 ths. y.) were characterized by the contrast changes of cold and warm epochs. These events are distinctly shown in the structure of loess-soil formation. In the territory of Ukraine for this period of time there have been established the traces of one glaciation that took place after the Chigirin (Zavadovka) interglacial. The last warm epoch at the end of the Middle Neopleistocene was marked by forming of Kaidaki (Korshevsk) paleosol and, later, by Tyasmin loess horizon. In the glacial zone they correspond to the Pripyat stadial deposits of the Dnieper glaciation and loess-like loams with two paleosols.

Features of the soil cover of the Vetluga-Unzhensk interfluvial area (Northeast of the Kostroma oblast)

This paper reveals the features of the soil cover of the territory of the Vetluga-Unzhensk interfluvial area, which is adjacent to the northern part of Uvaly, where contrasting combinations of alpha-humic and organo-accumulative soils are widespread. This is due to abruption of the clayey rocks of the Triassic age on the background of fluvioglacial sand sediments of the Dnieper glaciation, which is due to the complicated history of the formation of the relief of the characterized territory.

Paleoenvironmental history of the Middle Dnieper Area from the Dnieper to Weichselian Glaciation: A case study of the Maksymivka loess profile

The paper presents the results of interdisciplinary studies on environmental characteristics of the Middle and Upper Pleistocene (MIS 8-2) of central Ukraine based on an example of the new research site at Maksymivka. The tested profile is situated on the left bank of the Dnieper River on the western edge of the Dnieper Plain. It is a representative section of the cliff of the east lakeshore of the Kremenchuk Reservoir, located in the border zone both in longitudinal and latitudinal terms. It is located in the southern part of the Dnieper terraced plateau on the border of two varieties of forest-steppes with an admixture of meadow steppes, defined as left-bank-Dnieper and Dniester-Dnieper. To the south of the site extends a typical steppe zone. The transient position of the research site is a good point to start to trace the history of the volatility of the vegetation cover and the shift of the landscape-vegetation boundaries according to the climatic fluctuations. To reconstruct environmental changes in the analysed time interval the litho-, pedo- and palaeobotanical methods were used. To determine the chronology of changes a number of parallel datings of the loess-paleosol sequence were conducted: TL (Gdańsk, Kyiv, Lublin), OSL (Gliwce).The profile is comprised of glacial and loess parts. The bottom section is built of glacigenic sediments of the marginal zone of the Dnieper Glaciation. The overlying loess-soil sequence of the last two glacial–interglacial cycles underwent detailed analyses. This section is composed of multiple soil levels, whose participation in the entire thickness of the layer dominates over primary loess. The studies have confirmed that they are lower stratigraphic rank soils of the Vytachiv (vt) unit (=MIS 3), and two complex higher rank units: Pryluky (pl; MIS 5) and Kaydaky (kd; MIS 7). For the distinguished litho- and pedostratigraphic units, paleoenvironmental characteristics were developed. The stratigraphic rank of these units was confirmed by dating. The results of the TL and OSL dating of the samples show good agreement between the laboratories, particularly in relation to the last cycle. However, the OSL dates for the penultimate cycle are significantly underestimated in relation to the TL dates, which in turn relate well to the global time framework. The reasons of the OSL dates underestimation might be connected with the post-sedimentation pedogenic changes.

Water regime of upland oak forests of the south Russian forest steppe

In the southern forest steppe, the upland oak forests on loamy dark grey soils, which have the automorphic mode of water supply, usually endure droughts during the second half of the vegetative season due to the creation and use by biogeocenoses of some moisture reserves into soil and groundwater (GW), which are accessible to deep layers of root systems of trees. Two shallow sandy horizons interlaying moraine loams of the Dnieper glaciation at altitudes of 120 and 143 m above sea level serve as collectors and transporters of GW, the table of which is 10-15 m lower than the surface of the watershed plateaus and terraces. By autumn, trees desiccate subsoil horizons to the capillary fringe of GW. In early spring, the moisture of dried horizons is restored. The reserves of GW permit the upland oak forests to preserve rather high values of predawn leaf water potential such as Ψ PD ≥ −0.8 MPa despite the decrease in water potential of soil at a depth of 0-2 m of the soil layer to a value of Ψ S ≈ −2.4 MPa.

Четвертинні відклади льодовикового комплексу Волинського Полісся як джерело корисних копалин

Material composition of Quaternary sediments in the Volhyn Polissia studied enough. The same applies to the accumulation of deposits of glacial complex. Data of mineralogy of glacial and fluvioglacial sediments and their petrographic composition of coarse fragment component was considered. The possibility of using of the material for search of non-traditional mineral deposits in Volhyn Polissya was noted. Key words: Volhyn Polissia, Dnieper glaciation, building materials, diamond, pyrope, amber, phosphate sandstone, native gold.

Upper Pleistocene loess–palaeosol and vegetational successions in the Middle Dnieper Area, Ukraine

The loess–palaeolsol successions of the Middle Dnieper Area provide high-resolution records of the Last Interglacial–Glacial cycle. In the paper, the palaeoenvironmental information is based on the results of pedostratigraphic and pollen studies. The Last Interglacial is recorded by pollen succession of the Mikulino (Eemian) type in the Kaydaky pedocomplex, overlying the deposits of the Dnieper Glaciation. The soils of the Pryluky pedocomplex are correlated with the Early Glacial interstadials, and the Tyasmyn loess and the silt beds of the Pryluky unit are compared with the stadials of the Early Glacial. Two main loesses of the Pleniglacial are separated by the Middle Pleniglacial Vytachiv pedocomplex. It includes three interstadials (boreal soils) and two stadials (silt beds formed in subperiglacial environments). The Bug loess corresponds to the first half of the Late Pleniglacial. It documents frequent oscillations in humidity at the beginning of the interval and strong stable loess input during the second half of the Bug time. The Dofinivka pedocomplex of subarctic soils separates the Bug and Prychernomorsk loesses. The last one corresponds to the end of the Late Pleniglacial (the last strong loess input) and to the Late Glacial stadials and interstadials.

Evolution of the fluvial system of the Prypiat, Desna and Dnieper during the Late Middle - Late Pleistocene [ Evolution des systèmes fluviatiles des rivières Prypiat, Desna et Dniepr au cours du Pléistocène moyen récent et du Pléistocène supérieur.

A hypothesis that envisages Late Pleistocene braided rivers with enlarged meanders, unlike the present rivers of the European plains, anses from a tentative model for the development of the Prypiat-Dnieper-Desna alluvial plain in the late Middle - Late Pleistocene. This plain (local relief - 30-60 m) consists of a staircase of six river terraces and corresponding alluvial suites that have been forming since the Dnieper (Saale) Glaciation. Each terrace occupies a definite altitudinal step in this staircase and has a unique position within the plain as well as characteristic relief features related to terrace boundary shapes, longitudinal and cross profiles, primary fluvial and superimposed aeohan, cryogenic and erosional landforms. The alluvial suites have a cut-and-fill framework and noticeable differences in faciès composition expressed by sedimentary structures and other hthological features. Data inferred from the relief and from geological structures indicate complex fluvial system development with six main stages of varying duration and significance. These comprised one accumulative phase and five erosion-accumulation cycles, associated with weak pulsating tectonic uplift, expressed as 7-20 m of incision. The direct influence of the decay of the Dnieper ice sheet, alternations of glacial -interglacial runoff and stream load, significant fluctuations of precipitation, displacement of vegetation zones as well as permafrost thaw, all caused changes in the fluvial erosion-sedimentation regime. Glacially-fed suspended load streams, sandy meandering and braided streams, as well as sandy bedload braided and low sinuosity streams succeeded each other following the Dnieper Glaciation. These changes were accompanied by remarkable transformations of the river network general westward displacement, downstream displacement during the latest stages, abandonment of tributaries and inner fan formation. Proof of the existence of discontinuous permafrost or deep seasonal frost penetration has been obtained for the first time in the Late Pleistocene fluvial deposits of the area. Relying on the evidence of cryogenic and aeohan activity, the final phases of accumulation of the 1st Terrace Suite presumably correlate with the maximum of the Last Glaciation and the formation of the Peripheral Terrace Suite with permafrost degradation at the end of the Late Pleistocene.

Quaternary stratigraphy and optical dating of loess from the east European Plain (Russia)

Optical dating of silt-sized potassium feldspar grains was found to be suitable for dating the formation of key loess units at two sites on the central east European Plain. Loess bracketing the Bryansk palaeosol yielded optical ages in agreement with the well-dated radiocarbon chronology when corrected for anomalous fading. Optical ages from loess bracketing a significant pedogenic unit below the Bryansk palaeosol support our lithostratigraphic interpretation that it is the Mezin palaeosol complex, and its formation during the Last Interglaciation, Oxygen Isotope Stage (OIS) 5. Optical ages from a stratigraphically older loess unit directly underlying a significant (∼10 m thick) till unit, in conjunction with its regional stratigraphic context, suggest that the loess, and the till were deposited during the Dnieper Glaciation, which probably occurred during OIS 6.

Loess-paleosol formation on the Russian plain

The East European loess province is the largest one not only in the Northern Hemisphere, but also on the Earth. The chronostratigraphic scheme for this province was worked out on the basis of data obtained by different research methods. Accumulation of loess like deposits began at the end of the Pliocene in the post-Akchagilian time. Deposition of silt material and loess formation began in the second half of the Eopleistocene. During this period up to the Holocene (about 1 Ma), 6 interglacial soil complexes can be identified. According to paleomagnetic data the Brunhes-Matuyama boundary occurs within the Don Loess, which corresponds to maximum (Don) glaciation of Eastern Europe. The composition of the loess-paleosol complex of the Middle Pleistocene is much more complicated; there are 3 interglacial soil horizons overlain by the Middle Pleistocene moraine of the Dnieper glaciation. A well-developed interstadial soil horizon (Bryansk Soil) can be distinguished within the Late Pleistocene formation (32-26 ka BP). The structure of the loess-paleosol complex varies over different regions of the East European loess province. These differences can be shown on a new type of map: that of loess-paleosol chronocomplexes.