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51.
Deeper water black shales, overlain by coccolith-bearing marlstones representing the incipient Paratethys (example: Early Oligocene; Austrian Molasse Basin), have sedimentary characteristics similar to those of the Holocene Black Sea since 7500 years bp. Framboid pyrite size, biomarker and C–N-isotope data additionally indicate that isolation of the Paratethys resulted in Black Sea-type characteristics during nannoplankton zone NP 23.In contrast to the estuarine circulation across the Bosphorus since 7500 years bp, marine conditions prevailed in the incipient Paratethys during NP 21/22. Nitrogen was fixed and low organic carbon accumulation rates prevailed. In both settings a vertical density water-column stratification was accompanied by photic zone anoxia, and by anaerobic methane oxidation in the Paratethys. In the Paratethys increased run off, starting in NP 22, led to estuarine circulation during NP 23. During this period cyclic blooms of calcareous nannoplankton resulted in high calcite accumulation rates which diluted the coeval clay sedimentation. Similar sedimentary features in the Black Sea and the Paratethys during the earliest Oligocene are result from opposite paleoceanographic developments, both leading to estuarine circulation patterns. In the Black Sea, permanent photic zone anoxic conditions were established 7500 years bp in response to the first invasion of saline Mediterranean waters into the former freshwater lake. In contrast, brackish surface water in the Paratethys resulted from nutrient-rich freshwater diluting the marine water body. 相似文献
52.
Recent observations provide strong evidence for the BL Lac object OJ287 exhibiting a 11.6±0.5 yr periodicity with a double-peaked
maxima in its optical flux variations. Several models have been proposed for the optical behavior. The 2005 November outburst
in OJ287 gives us a surprising result since calculation based on the periodicity was predicting such an outburst in late 2006.
Here we suggest a new model, it can not only explain the optical quasi-periodic behavior, but also the radio flares behavior
which is and simultaneous with the optical flares. We propose that OJ287 is a binary pair of super-massive black holes, both
of them creating a jet. The quasi-periodic double peaks would be due to the relativistic beaming effect on the emission coming
from the double helix jets. We used “core flares” to explain the large lags between light curves at different frequencies,
and the assumption of two jets appear to be merged with each other partly in the radio frequency emitting regions provides
a viable interpretation that we can see only a broad maximum which contains two radio flares that we cannot distinguish. 相似文献
53.
东川拖布卡金矿矿化层位与找金方向 总被引:10,自引:3,他引:7
超大型拖布卡金矿的发现,表明东川地区具备找金前景.“黑层”是金的成矿前提,断裂加蚀变是成矿必备条件,基性与中性岩脉在容矿层中的侵位,是找富金的重要标志.金成矿全过程应是多旋回(晋宁、华力西、燕山、喜马拉雅山)成矿作用,且受剪切破碎带控制的黑层型金矿. 相似文献
54.
In zones washed by rain (façades, pinnacles, pilasters), fine siliceous sandstones are covered by a black varnish, which gives a dirty appearance to monuments. In composition, structure and areas covered by it, it differs from the usual black gypsum crust. Experiments carried out on blocks covered by black varnish show the modifications due to their growth. Results show that despite their low thickness and the coherence of the stone below, the accumulation of hydrophobic matters and the wetting-drying cycles modify the transfer properties of sandstones several centimeters below the surface. Thus, although sandstones seem to be protected by the black varnish, in the long run, a flake detachment process, in the areas covered by it, affects them. Therefore, damage to sandstones by black varnish can be explained by the fact that a wetting and drying cycle modifies the pore network. 相似文献
55.
We examine the behaviour of accretion flow around a rotating black hole in presence of cooling. We obtain global flow solutions
for various accretion parameters that govern the accreting flow. We show that standing isothermal shock wave may develop in
such an advective accretion flow in presence of cooling. This shocked solution has observational consequences as it successfully
provides the possible explanations of energy spectra as well as generation of outflows/jets of various galactic and extra-galactic
black hole candidates. We study the properties of isothermal shock wave and find that it strongly depends on the cooling efficiency.
We identify the region in the parameter space spanned by the specific energy and specific angular momentum of the flow for
standing isothermal shock as a function of cooling efficiencies and find that parameter space gradually shrinks with the increase
of cooling rates. Our results imply that accretion flow ceases to contain isothermal shocks when cooling is beyond its critical
value. 相似文献
56.
Pb-Pb dating of black shales from the Lower Cambrian and Neoproterozoic strata, South China 总被引:2,自引:0,他引:2
Black shales occur widely in the Lower Cambrian and Neoproterozoic strata on the Yangtze Platform, South China. In this study, Lower Cambrian black shales from Xiuning section and Late Neoproterozoic black shales from Weng’an section were studied and Pb isotopic compositions were analyzed following a stepwise acid-leaching technique. The 206Pb/204Pb ratios in both sections show large variations, from 18.906 to 43.737 in the Weng’an section and from 24.811 to 38.110 in the Xiuning section. In contrast, the ranges for 207Pb/204Pb and 208Pb/204Pb values in both sections are relatively smaller from 15.649 to 17.126 and 37.744-38.199 in the Weng’an section, and from 16.034 to 16.783 and 38.602-39.391 in the Xiuning section, respectively. These data yielded two Pb isotope isochron ages of 536±39 and 572±36 Ma, respectively. These ages well accord with other published data and we suggest that they represent the depositional ages for the Lower Cambrian Hetang Formation and the upper Neoproterozoic Doushantuo Formation in South China. 相似文献
57.
Structural specific features of the sedimentary succession on the continental margin of the South Crimea in the Black Sea have been examined in the Yalta Area using geomorphologic, acoustic, and lithologic methods. Alternation of regressive and transgressive sequences has been ascertained in sediment sections formed on the shelf and in the Yalta deep-sea fan due to Quaternary oscillations of the basin level. The analysis of sediment sections resulted in revealing a leading role of sedimentary material transference from upper hypsometric levels to lower ones in the sediment accumulation. 相似文献
58.
A. L. Meysner 《Moscow University Geology Bulletin》2009,64(4):214-219
A fault was traced along the southwestern margin of the Shatsky Rise. It extends to land where it crosses the Mountainous Crimea. Interpretation and analysis of marine seismic and magnetic survey data, as well as geological data on land, allow stating that the fault originated during the rift evolution stage of the East Black Sea Basin. Currently, the fault is in the sea and is a channel for migrating hydrocarbon fluids. Another fault was traced from the West Caucasus into the sea, where it separates the Shatsky Rise into two structural units. 相似文献
59.
Black holes are extremely dense and compact objects from which light cannot escape. There is an overall consensus that black holes exist and many astronomical objects are identified with black holes. White holes were understood as the exact time reversal of black holes, therefore they should continuously throw away material. It is accepted, however, that a persistent ejection of mass leads to gravitational pressure, the formation of a black hole and thus to the “death of while holes”. So far, no astronomical source has been successfully tagged a white hole. The only known white hole is the Big Bang which was instantaneous rather than continuous or long-lasting. We thus suggest that the emergence of a white hole, which we name a ‘Small Bang’, is spontaneous - all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed rather their effect can only be detected around the event itself. γ-ray bursts are the most energetic explosions in the universe. Long γ-ray bursts were connected with supernova eruptions. There is a new group of γ-ray bursts, which are relatively close to Earth, but surprisingly lack any supernova emission. We propose identifying these bursts with white holes. White holes seem like the best explanation of γ-ray bursts that appear in voids. We also predict the detection of rare gigantic γ-ray bursts with energies much higher than typically observed. 相似文献
60.
Anisotropic emission of gravitational waves during the merger of black holes induces a recoil velocity on the centre of mass of the binary and the final merger product can then be ejected from its host galaxy. We consider ejected black holes which stay on bound orbits around their host haloes. A recoiled black hole which moves on an almost radial orbit outside the virial radius of its central galaxy, in the cold dark matter background, reaches its apapsis in a finite time. Due to small dark matter velocity dispersion at high redshifts and also the small black hole velocity near the apapsis passage a high-density wake forms around these black hole. Gamma-ray emission can result from the enhancement of dark matter annihilation in these wakes. The diffuse high-energy gamma-ray background from the ensemble of such black holes in the Hubble volume is also evaluated. 相似文献