Provenance analysis for Middle Eocene sediments in the West Kamchatka sedimentary basin (Tigil area)     

A. I. Khisamutdinova  A. V. Solov’ev  D. V. Rozhkova 《Lithology and Mineral Resources》2016,51(4):310-332

The paper presents the results of reconstruction of Middle Eocene provenances for the West Kamchatka sedimentary basin (WKSB) corresponding to the Tigil area. It has been established that the early (Eocene) evolution stage of WKSB was marked by the deposition of terrigenous sediments in intermontane depressions followed by the accumulation of shallow-marine sediments after transgression. In terms of the composition, sandstones of the Middle Eocene Snatol Formation correspond to graywackes. With respect to the geochemistry of sandstones, their provenances were confined to an active continental margin and island arc. The mineral composition of the heavy fraction suggests an alternating dominance of felsic and mafic rocks in the provenances. Dating of the clastic zircon from sandstones of the Snatol Formation by the LA-ICP-MS method revealed a wide variation range of their age. The most significant peak is close to the age of calc-alkaline magmatism in the Okhotsk–Chukotka volcanic belt. This fact provides insight into the Eocene paleogeography: the major rock provenances were located in the Okhotsk–Chukotka volcanic belt and the eastern Achaivayam–Valagin island arc. Local sources of clastic material were represented by the Utkholok and Kinkil volcanic belts.  相似文献   

Isotopic compositions of C,O, Sr,and S and problem of ages of the Katera and Uakit Groups,western Transbaikal region     

B. G. Pokrovsky  M. I. Bujakaite 《Lithology and Mineral Resources》2016,51(4):262-282

The age of the Katera Group, which occupies a large area in the western North Muya Range and occurs 100–150 km east of the Uakit Group, is a debatable issue. Based on geological correlations with reference sections of the Baikal Group and Patom Complex, the Katera and Uakit groups were previously considered nearly coeval units and assigned to Late Precambrian (Khomentovskii and Postnikov, 2002; Salop, 1964). This was supported partly by the Sm–Nd model datings (Rytsk et al., 2007, 2009, 2011). Finds of the Paleozoic flora substantiated the revision of age of the Uakit Group and its assignment to the Late Devonian–Early Carboniferous (Gordienko et al., 2010; Minina, 2003, 2012, 2014). We have established that Sr and C isotopic compositions in carbonates of these groups differ drastically, as suggested by their different ages. Sediments of the Nyandoni Formation (Katera Group), which contains carbonates characterized by minimum values of ⁸⁷Sr/⁸⁶Sr = 0.7056 and maximum values of δ¹³C = 4.9‰, were accumulated in the first half of Late Riphean (800–850 Ma ago), whereas the overlying Barguzin Formation (⁸⁷Sr/⁸⁶Sr_min = 0.70715, δ¹³C_max= 10.5‰) was deposited at the end of Late Riphean (700–750 Ma). Judging from the isotope data, the Nerunda Formation (Uakit Group), which contains carbonates with characteristics matching the most rigorous criteria of fitness for the chemostratigraphic correlation (Sr content up to 4390 μg/g, Mn/Sr < 0.1, δ¹⁸O = 23.0 ± 1.8‰), was deposited at the end of Vendian ~550–540 Ma ago). The sequence includes thick typical carbonate horizons with very contrast carbon isotopic compositions: the lower unit has anomalous high δ¹³C values (5.8 ± 1.0‰); the upper unit, by anomalous low δ¹³C values (–5.2 ± 0.5‰]). Their Sr isotopic composition is relatively homogeneous (⁸⁷Sr/⁸⁶Sr = 0.7084 ± 0.0001) that is typical of the Late Vendian ocean. The S isotopic composition of pyrites from the Nyandoni Formation (Katera Group) (δ³⁴S = 14.1 ± 6.8‰) and pyrites from the Mukhtunny Formation (Uakit Group) (δ³⁴S = 0.7 ± 1.4‰) does not contradict the C and Sr isotopic stratigraphic data.  相似文献   

The Latnenskoe refractory clay deposit (Central Russia)     

N. S. Bortnikov  A. D. Savko  V. M. Novikov  N. M. Boeva  S. V. Soboleva  E. A. Zhegallo  D. I. Dmitriev  A. V. Krainov  A. P. Zhukhlistov  E. B. Bushueva 《Lithology and Mineral Resources》2016,51(6):425-438

This paper reports the results of our recent studies and generalizes previously known data on the geology, mineralogy, geochemistry, and genesis of the Russia’s largest Latnenskoe refractory clay deposit. It is shown that conditions of its localization were defined by regional and local factors. The regional factors controlled the distribution of the clay raw material in the region, while the local factors were responsible for the genesis and composition of refractory clays of the Latnenskoe deposit. Our studies showed that the formation of refractory clays is not only related to terrigenous but also to authigenic processes of sedimentation. The terrigenous component of clays was formed by the erosion of kaolin weathering crusts of the Voronezh anteclise crystalline basement and Paleozoic sedimentary hydromica–kaolinite rocks. Authigenic processes were significantly contributed by organic matter, which determined the environmental pH and Eh parameters. It is established that the mineral matter of clays of the deposit is represented by three morphological modifications (crystalline, amorphous, and biomorphic), which were formed subsequently and (or) simultaneously and could be transformed into each other. Application of a complex of modern precision methods allowed us to reveal a previously unknown biomorphic modification of kaolinite, the major rock-forming mineral, as well as mixed-layer kaolinite-smectite in the clays. It is shown that the distribution of major and trace elements and the sulfur isotope composition in different technological types of clay depend mainly on the facies conditions of their formation. Technological properties of clay raw material are considered.  相似文献   

Some general relations of the development of complex molecular objects at early stages of biosphere formation as a consequence of the physical properties of condensed medium     

V. I. Baranov  L. A. Gribov  V. A. Dement’ev  I. V. Mikhailov 《Geochemistry International》2016,54(11):1011-1018

We analyzed the character of molecular transformations under conditions of condensed media, in which intermolecular interactions always occur. It was shown that, instead of discrete transfer of external energy into the molecule, the energy characteristics of the condensed medium (appearance of zones) could result in gradual accumulation of internal energy in reaction centers owing to sequential thermal collisions with particles of the medium initiating the chemical reaction. This does not require high temperatures. The established physical properties related to the energy characteristics of condensed media could play an important role in molecular transformations and, consequently, formation of complex molecular objects at early stages of biosphere formation.  相似文献   

Contained density currents with high volume of release   总被引：1，自引：0，他引：1       下载免费PDF全文

Quentin Theiler  Mário J. Franca 《Sedimentology》2016,63(6):1820-1842

Contained density currents with high volume of release reflect against the boundaries of the reception environment commonly leading to oscillatory flow. These flows exist in sediment clarifiers, compromising their operations, and deposited signatures of contained turbidity currents are found as part of the infill of sedimentary basins; for operation of the former and interpretation of the latter it is essential to understand the dynamic processes of these flows. Six lock‐exchange experiments with different initial densities were made in a horizontal flume, where the volume of the saline mixture in the lock was equivalent to the volume of the ambient fluid. A further two tests, with a repeated initial density, were made: one with high volume of release and very long duration; and another with low volume of release. Firstly, the movement of the current is discussed, including the oscillations within the experimental tank involving the density current and an upper layer counter‐current. It is shown that the cyclic behaviour is self‐similar with the reduced gravity of the initial density in the lock. Secondly, entrainment and water mixing processes are characterized. The time evolution of mixing is characterized qualitatively by analysing the background potential energy of the density distributions to show that mixing occurs even in the earlier stages of the current, and mainly within the first cycle of the oscillation. Quantified analysis reveals that, in currents with high volume of release, entrainment discharge is one order of magnitude higher, mainly due to the larger interface between the ambient fluid and the current. A model for the evolution of the mixing process is proposed for density currents with high volume of release. Finally, the dynamics of the head of the current is analysed. The entrainment in the head, when compared to the entrainment in the remainder body of the flows, is less important for the configuration with a larger lock.  相似文献   

The phosphate-containing interlayers of the Bazhenov Formation as potential reservoirs     

A. G. Kalmykov  E. A. Manuilova  G. A. Kalmykov  V. S. Belokhin  N. I. Korobova  O. M. Makarova  E. V. Kozlova  R. A. Khamidullin  V. A. Shishkov  A. G. Ivanova 《Moscow University Geology Bulletin》2016,71(6):429-435

The possible reservoir type of the Bazhenov Formation relative to the intervals enriched in phosphates (apatite varieties) is described in this work. The phosphate rocks are characterized by a highly developed pore space; their porosity can reach up to 14%. Along with this, these rocks have explicit geochemical characteristics of oil-reservoir rocks in comparison with other rock samples in the well. As an example, the productivity index and oil-saturation index for phosphates are twice as high as the background values. The composition of such rocks can slightly vary: fluorine can be observed in phosphate minerals, while the rock is always enriched in organic matter (>8 wt %).  相似文献   

Fracturing in the high-carbon formation of the northern flank of the South-Tatar arch     

R. S. Sautkin  R. A. Khamidullin  N. I. Korobova 《Moscow University Geology Bulletin》2016,71(2):205-211

The problem of studying the Domanik deposits and their reservoir potential is among the most important ones. The discovery of hydrocarbon deposits in similar rocks at various depths, the considerable variability of reservoir properties, and ambiguity in establishing the values of the effective thickness set the task for researchers to estimate them more reliably. The high-carbon kerogenic-carbonate-siliceous stratum that is characterized by the development of differently-oriented systems of fractures is of outstanding interest.  相似文献   

The upper Bajocian of the Crimean Mountains: Paleogeography and sedimentation conditions from palynological data     

J. I. Rostovceva  A. N. Stafeev  T. V. Sukhanova  I. V. Latysheva  V. L. Kosorukov 《Moscow University Geology Bulletin》2016,71(4):281-289

Based on the spore-pollen data, the mineral composition of clay rocks, analyzed structures and facies, and a general paleogeographic analysis, the sedimentation conditions and landscapes of islands located during the Late Bajocian in the region of the present-day the Crimean Mountains have been reconstructed. It is shown that the sublatitudinally elongated insular land zone had a width of 30 km, the heights of the islands were no more than 1 km, with steep mudflow-affected northern slopes and with an extensive river system on the southern slopes.  相似文献   

Types of engineering-geological structures of Russia     

T. I. Averkina  V. T. Trofimov 《Moscow University Geology Bulletin》2016,71(6):373-384

Engineering-geological (geotechnical) structures are distinguished based on a combination of regional and zonal geological factors. Classifications of engineering-geological structures of the Earth and Russia are presented. The main engineering-geological characteristics and spatial distribution patterns of continental subaerial, continental subaquatic, and transitional predominantly subaquatic and oceanic predominantly subaquatic engineering- geological mega- and macrostructures distinguished in Russia are described.  相似文献   

Climate change and human impact in a sensitive ecosystem: the Holocene environment of the Northwest Icelandic highland margin   总被引：1，自引：0，他引：1       下载免费PDF全文

Sigrún D. Eddudóttir  Egill Erlendsson  Leone Tinganelli  Guðrún Gísladóttir 《Boreas: An International Journal of Quaternary Research》2016,45(4):715-728

Complex interactions of climate and volcanic activity have shaped the environment of Iceland during the Holocene. Palaeoecological records from Iceland offer a unique look at a Holocene environment that was uninhabited by humans and free of mammal herbivores until about AD 870. We present a new reconstruction of Holocene vegetation and landscape dynamics from a small lake, Barðalækjartjörn, located near the highland margin in Northwest Iceland. A multi‐proxy approach was used to reconstruct vegetation based on pollen and plant macrofossil analysis and landscape stability based on lithological proxies. The record covers the period c. 10 300–200 cal. a BP. For the first two millennia aeolian processes probably played a part in vegetation development. This period is characterized by high input of minerogenic material into the lake and a vegetation assemblage in which plants tolerant of aeolian deposition are prominent. Betula pubescens woodland reached a maximum between c. 7400 and 6500 cal. a BP. Betula nana‐dominated dwarf shrub heath replaced woodland after c. 4000 cal. a BP, following the onset of Neoglaciation. Land use following human settlement caused an environmental shift at the highland margin. Betula pubescens probably disappeared from the vicinity of the lake soon thereafter. Large‐scale soil erosion began at c. 1000 cal. a BP in the wake of human activities, such as introduction of grazing livestock and woodcutting. This study offers an important long‐term perspective of the development of the highland ecosystem under both wholly natural and human‐influenced conditions.  相似文献