Cryptophyta Flagellates of Meromictic Lakes Shira and Shunet(Khakassia,Russia):Mechanisms of Vertical Distribution and Trophic Role

正1 Introduction Many of the stratified lakes are characterized by the presence of large populations of cryptomonads in their chemocline zones(Reynolds,1992;Gervais et al,2003;Pedro's-Alio'et al.,1995).These populations are adapted to low light intensity and high sulfide concentration;they have a mixotrophic ability and form the so-called"deep chlorophyll maxima"(Gervais,1998;Marsha"and Laybourn-Parry,2002).A similar Cryptomonas sp.     

The Berelekh Mammoth “Graveyard”: New Chronological and Stratigraphical Data from the 2009 Field Season

To clarify unanswered questions of site formation, geology and the archaeology of the Berelekh geoarchaeological complex, a special survey was undertaken in 2009 of the area surrounding the site. Several geological units have been revealed. By establishing the spatial and temporal relationship of these deposits—as well as their age—we have reconstructed the formation history of the Berelekh bone bed. The mammoth bone deposit belongs to a paleochannel. Radiocarbon dating of mammoth remains at Berelekh demonstrates rapid accumulation during the Bølling warming. Human involvement in its formation is, at best, questionable, since there is no real overlap between the radiocarbon dates associated with past human activity, and those of the mammoth bone bed. This study confirms that humans used mammoth bone remains after the bone bed was deposited. Culturally, the Berelekh “site” does not have any relationship to the so‐called “Dyuktai culture.” Instead, the Berelekh archaeological finds (side notched stone pendants) show certain similarities to non‐microblade terminal Pleistocene assemblages found from Yenisei to Kamchatka. Additionally, the Berelekh complex presents a clear analogy with lithics found in Eastern Beringia. Teardrop‐shaped incomplete bifaces found in the assemblage are comparable to the Chindadn points of Alaska. The nature of this “Chindadn connection” is intriguing but it is the only visible cultural link between Western and Eastern Beringia.     

Au–Ag–Te Mineralization of the Low‐Sulfidation Epithermal Aginskoe Deposit,Central Kamchatka,Russia

Mineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the Aginskoe and Surprise, in the Late Miocene Aginskoe Au–Ag–Te deposit in central Kamchatka, Russia. The veins consist of quartz–adularia–calcite gangue, which are hosted by Late Miocene andesitic and basaltic rocks of the Alnei Formation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in Fe‐hydroxides and accumulates on the decomposed primary Au‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 Ma. Mineralization of the deposit is divided into barren massive quartz (stage I), Au–Ag–Te mineralization occurring in quartz‐adularia‐clays banded ore (Stage II), intensive brecciation (Stage III), post‐ore coarse amethyst (Stage IV), carbonate (Stage V), and supergene stages (Stage VI). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, Te and S fugacities are estimated as Stage II tellurides precipitated at the log f Te₂ values ?9 and at log fS₂ ?13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300°C. Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the Aginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system.     

Ore‐forming Ages and Sulfur Isotope Study of Hydrothermal Deposits in Kamchatka,Russia

In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ³⁴S_CDT of sulfides are ?2.8‰ for the Ametistovoe deposit in Central Koryak, ?1.8‰ to +2.0‰ (av. ?0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and ?0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ³⁴S_CDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of ³²S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition.     

The IAU 2009 system of astronomical constants: the report of the IAU working group on numerical standards for Fundamental Astronomy

In the 2006?C2009 triennium, the International Astronomical Union (IAU) Working Group on Numerical Standards for Fundamental Astronomy determined a list of Current Best Estimates (CBEs). The IAU 2009 Resolution B2 adopted these CBEs as the IAU (2009) System of Astronomical Constants. Additional work continues to define the process of updating the CBEs and creating a standard electronic document.     

Optimal low-thrust transfers between libration point orbits

Over the past three decades, ballistic and impulsive trajectories between libration point orbits (LPOs) in the Sun–Earth–Moon system have been investigated to a large extent. It is known that coupling invariant manifolds of LPOs of two different circular restricted three-body problems (i.e., the Sun–Earth and the Earth–Moon systems) can lead to significant mass savings in specific transfers, such as from a low Earth orbit to the Moon’s vicinity. Previous investigations on this issue mainly considered the use of impulsive maneuvers along the trajectory. Here we investigate the dynamical effects of replacing impulsive ΔV’s with low-thrust trajectory arcs to connect LPOs using invariant manifold dynamics. Our investigation shows that the use of low-thrust propulsion in a particular phase of the transfer and the adoption of a more realistic Sun–Earth–Moon four-body model can provide better and more propellant-efficient solution. For this purpose, methods have been developed to compute the invariant tori and their manifolds in this dynamical model.     

Dielectric constant estimation of the uppermost Basal Unit layer in the martian Boreales Scopuli region

An electromagnetic inversion model has been applied to echoes from the subsurface sounding Shallow Radar (SHARAD) to retrieve the dielectric properties of the uppermost Basal Unit (BU) beneath the North Polar Layered Deposits of Mars. SHARAD data have been carefully selected to satisfy the assumption of the inversion model which requires a stratigraphy consisting of mostly plane parallel layers. The resulting values of the dielectric constant have been interpreted in terms of a variable percentage of dust in an ice–dust mixture through the use of a mixing model for dielectric properties. The resulting dust content exceeds 65%, reaching perhaps 95%, depending on the permittivity values assumed for the dust. Such a concentration is higher than that obtained by Selvans et al. (Selvans, M.M., Plaut, J.J., Aharonson, O. [2010]. J. Geophys. Res, 115, E09003). This discrepancy could be justified considering that our observations refer to the uppermost BU layer, whereas Selvans et al. (Selvans, M.M., Plaut, J.J., Aharonson, O. [2010]. J. Geophys. Res, 115, E09003) probed the BU full thickness. Moreover, if the BU is considered spatially inhomogeneous, with very different dust content and thickness (Tanaka, K.L., Skinner, J.A., Fortezzo, C.M., Herkenhoff, K.E., Rodriguez, J.A.P., Bourke, M.C., Kolb, E.J., Okubo, C.H. [2008]. Icarus, 196, 318–358), the discrepancy could be furtherly reconciled.     

U–Pb geochronology and zircon composition of late Variscan S- and I-type granitoids from the Spanish Central System batholith

The Spanish Central System (SCS) batholith, located in the Central Iberian Zone, is one of the largest masses of granite in the European Variscan Belt. This batholith is a composite unit of late- and post-kinematic granitoids dominated by S- and I-type series granite, with subordinate leucogranite and granodiorite. Zircon trace element contents, from two representative S-type and three I-type granitoids from the eastern portion of the SCS batholith, indicate a heterogeneous composition due to magma differentiation and co-crystallisation of other trace element-rich accessory phases. In situ, U–Pb dating of these zircons by SHRIMP and LA-ICP-MS shows 479–462-Ma inherited zircon ages in the I-type intrusions, indicating the involvement of an Ordovician metaigneous protolith, while the S-type intrusions exclusively contain Cadomian and older zircon ages. The zircon crystallisation ages show that these granites have been emplaced at ca. 300?Ma with a time span between 303?±?3?Ma and 298?±?3?Ma. Precise dating by CA-ID-TIMS reveals a pulse at 305.7?±?0.4?Ma and confirms the major pulse at 300.7?±?0.6?Ma. These ages match the Permo-Carboniferous age for granulite-facies metamorphism of the lower crust under the SCS batholith and coincide with a widespread granitic event throughout the Southern Variscides. Ti-in zircon thermometry indicates temperatures between 844 and 784°C for both the S- and I-type granites, reinforcing the hypothesis that these granites are derived from deep crustal sources.     

U–Pb ages of detrital zircons from Paleozoic metasandstones of the Gelnica Terrane (Southern Gemeric Unit, Western Carpathians, Slovakia): evidence for Avalonian–Amazonian provenance

U–Pb (SHRIMP) determinations on detrital zircons from the Early Paleozoic Gelnica Terrane metasandstones and their Permian overlap sediments of the Inner Western Carpathian Southern Gemeric Unit define five age populations based on age-probability plots. The metasandstones were sampled for detrital zircons from six stratigraphic levels, four of them in the Late Cambrian/Ordovician Gelnica Terrane metasandstones and the two in Permian envelope sequence. The data set includes 84 U–Pb ages for individual detrital zircons. These ages are combined with the previously dated inherited zircons from the associated metavolcanites (n?=?31). The majority of the pre-Permian detrital and inherited zircons (95%) belong to the three main populations: population A—the Paleoproterozoic/Neoarchean ages ranging from 1.75 to 2.6?Ga; population B—the Mesoproterozoic ages with the range of 0.9 to 1.1?Ga; population C—the Neoproterozoic ages, ranging from 560 to 807?Ma. The detrital zircon age spectrum from the basal Permian sediments reflects the strong recycling from the underlying Gelnica Terrane, with the presence of the dominant Precambrian C and B populations (94% of total), including the minor populations A. The range of the detrital zircon ages from the Late Permian sandstones is wider, with additional population D, ranging from 497 to 450?Ma and population E with a time span from 369 to 301?Ma. Within the Late Permian detrital zircon assemblage, the Proterozoic population A?+?B?+?C form only 25% of total. The detrital zircon data suggest that the Gelnica Terrane belongs to the peri-Gondwanan terrane with a source area located on the northwestern margin of Gondwana close to Amazonia. This terrane should have travelled a long distance in the Phanerozoic times.     

Shallow water tidal currents in close proximity to the seafloor and boundary-induced turbulence

Velocity measurements with vertical resolution 0.02 m were conducted in the lowest 0.5 m of the water column using acoustic Doppler current profiler (ADCP) at a test site in the western part of the East China Sea. The friction velocity u _* and the turbulent kinetic energy dissipation rate ε _wl(ζ) profiles were calculated using log-layer fits; ζ is the height above the bottom. During a semidiurnal tidal cycle, u _* was found to vary in the range (1–7) × 10⁻³ m/s. The law-of-the-wall dissipation profiles ε _wl(ζ) were consistent with the dissipation profiles ε _mc(ζ) evaluated using independent microstructure measurements of small-scale shear, except in the presence of westward currents. It was hypothesized that an isolated bathymetric rise (25 m height at a 50-m seafloor) located to the east of the measurement site is responsible for the latter. Calculation of the depth integrated internal tide generating body force in the region showed that the flanks of the rise are hotspots of internal wave energy that may locally produce a significant turbulent zone while emitting tidal and shorter nonlinear internal waves. This distant topographic source of turbulence may enhance the microstructure-based dissipation levels ε _mc(ζ) in the bottom boundary layer (BBL) beyond the dissipation ε _wl(ζ) associated with purely locally generated turbulence by skin currents. Semi-empirical estimates for dissipation at a distance from the bathymetric rise agree well with the BBL values of ε _mc measured 15 km upslope.