Petrochemistry of metapsammitic rocks from the Patom Highland: Reconstruction of the protolith composition

Precambrian psammitic rocks of the Patom Highland as constituents of metasedimentary groups belong to the quartz-polymictic family, which is divided in each group into the following five petrochemical types: (A) highly silicic quartz sandstones, (B) silicic quartz sandstones, (C) alkali silicic quartz sandstones, (D) Fe-Si polymictic sandstones, and (E) Fe-Al-Si polymictic sandstones. The mineralogic-petrographic classification elaborated by Shutov (1967) may be applied to the calculated quantitative mineral and component compositions of metasandstone protoliths. According to this classification, the petrochemical types A–E may be correlated with monomictic (A′), oligomictic (B′), and mesomictic (C′) sandstones, feldspar-quartz graywacke (D′) and graywacke proper (E′), respectively.Quartz-polymictic sandstones make up the direct petrographic (mineralogic-petrographic) series A′-B′-C′-D′-E′ and the almost mirror inverse series E′-D′-C′-B′. The direct series A′-E′ represent the transgressive branches of sedimentary cycles that begin with the crustal redeposited products of chemical weathering, including high-Al schists and monomictic (A′) and oligomictic (B′) quartz sandstones. As the humid climate became arid, the sandstones gave way to the mesomictic sandstones C′ and to the polymictic sandstones D′ and E′ in the middle sections of sedimentary cycles. The polymictic sandstones mark culminations of tectonic activity that led to the formation of high mountains. The inverse series E′-B′ begin from the periods of mountainous topography and characterize regressive branches of sedimentary cycles that mark the decreasing tectonic activity. Polymictic sandstones E′ and D′ are replaced by oligomictic sandstones B′ in these branches. Thus, petrographic or mineralogic-petrographic series reflect the compositional evolution of psammitic rocks between epochs of peneplanation. The termination of these epochs and resumption of orogenic movements are documented by deposition of the Teptorgo-Mama, Kadalikan, and Bodaibo sedimentary groups. The onset of tectonic events fell on the terminal Paleoproterozoic, Early Riphean, and the Middle-Late Riphean. The composition of sedimentary rocks underwent progressive changes during the tectonic evolution of the continental margin of the Siberian Craton and the concomitant variation of paleoclimate.     

Deep seismic studies in the central Karelian Craton

On the basis of analysis and generalization of the extensive seismic information obtained over the last forty years, the modern concept of the deep crustal structure in the central Karelian Craton is developed. The tomographic models are reconstructed, the stratification of the Earth’s crust and geometry of seismic boundaries are refined, and the subsidence of the boundary between the crust and mantle down to a depth of 60 km is noted. The comparison and integrated interpretation of the sections studied by the common depth point (CDP), deep seismic sounding (DSS), and converted-wave methods together with the available geological data shows that the results derived by different seismic methods differ markedly. However, since various methods have revealed the different characteristics of the medium, the entire body of seismic evidence can be used for geological interpretation.     

Anthropogenic transformations of the Arctic ecosystem of Lake Imandra: Tendencies for recovery after long period of pollution

Transformation of an Arctic aquatic ecosystem (a case study of Lake Imandra) under the impact of a mining industrial complex is considered. Water chemical composition and the ecosystem’s structural components (phyto- and zooplankton, zoobenthos, and ichthiofauna) are analyzed for the following periods: the preindustrial background (reference) conditions, industrial development of mineral resources and strong anthropogenic impact, industrial recession and decreased anthropogenic impact, and stabilization. The main regularities of the aquatic ecosystem successions under the conditions of anthropogenic loads and their decrease are established.     

On the 75-day cepheid and the envelope of the period-amplitude diagram in M31

On the basis of 30 observations the period of the new cepheid in M31,P=75.487 is obtained. Ths cepheid has an extremely long period and gives a possibility to determine the period-amplitude envelope toward the long-period region in M31 galaxy. A comparison of the period-amplitude diagrams in various galaxies is made.     

Estimation of cosmological parameters from peculiar velocities of flat EDGE-ON galaxies

We estimate the values of the cosmological parameters using the data about peculiar velocities of 1493 flat edge-on spirals from the RFGC catalogue. The obtained values Ω _m = 0.21_{− 0.09} ^{+ 0.22}, σ₈ = 1.07_{− 0.24} ^{+ 0.28} differ from the WMAP values by approximately 2–3σ, but well agree with modern constraints on these parameters. Due to a strong correlation between these quantities the shape of the 1σ, 2σ and 3σ-boundaries are rather narrow. This gives us the opportunity to use this estimation to verify the corresponding values, obtained by different methods.     

Photoelectric catalogue of globular clusters in the Andromeda Nebula M31 and its companions NGC 147, NGC 185, and NGC 205

The photoelectric catalogue of the globular clusters (including the objects previously considered to be clusters) in the Andromeda Nebula M31 and its companions NGC 147, NGC185, and NGC 205 is presented. The catalogue based on all published data includes 338 objects withUBV, six objects withBV, and one object withV measurements.     

Paleobiology of the Mesoproterozoic-Neoproterozoic transition: the Sukhaya Tunguska Formation, Turukhansk Uplift, Siberia

Silicified carbonates of the latest Mesoproterozoic Sukhaya Tunguska Formation, northwestern Siberia, contain abundant and diverse permineralized microfossils. Peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of Lyngbya and Phormidium. In subtidal to lower intertidal settings, mat-dwelling microbenthos and possible coastal microplankton are abundant. In contrast, densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats; the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. Eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface. Most microbenthic populations are cyanobacterial, although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton. Protists are more securely represented by large (up to 320 micrometers in diameter) but poorly preserved acritarchs in basinal facies. The Sukhaya Tunguska assemblage contains 27 species in 18 genera. By virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions, including substrates, Proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and, thereafter, resist competitive replacement. The resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of Phanerozoic plants and animals.     

Novae in M 31 in 1998

We present data on the six novae in the galaxy M 31 that were discovered by different groups of observers in 1998. Three of these novae were found near the nucleus of M 31, and one was found near the nucleus of M 32.