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1.
M. S. Barash 《Oceanology》2016,56(6):863-875
The second of the five great mass extinctions of the Phanerozoic occurred in the Late Devonian. The number of species decreased by 70–82%. Major crises occurred at the Frasnian–Famennian and Devonian–Carboniferous boundary. The lithological and geochemical compositions of sediments, volcanic deposits, impactites, carbon and oxygen isotope ratios, evidence of climate variability, and sea level changes reflect the processes that led the critical conditions. Critical intervals are marked by layers of black shales, which were deposited in euxinic or anoxic environments. These conditions were the main direct causes of the extinctions. The Late Devonian mass extinction was determined by a combination of impact events and extensive volcanism. They produced similar effects: emissions of harmful chemical compounds and aerosols to cause greenhouse warming; darkening of the atmosphere, which prevented photosynthesis; and stagnation of oceans and development of anoxia. Food chains collapsed and biological productivity decreased. As a result, all vital processes were disturbed and a large portion of the biota became extinct. 相似文献
2.
L. Z. Reznitskii V. P. Kovach I. G. Barash Yu. V. Plotkina K. -L. Wang H. -Y. Chiu 《Stratigraphy and Geological Correlation》2018,26(5):489-513
The results of U—Th—Pb (LA-ICP-MS) geochronological studies of detrital zircons from terrigenous rocks of the Dzhida terrane of the Central Asian Fold Belt (CAFB) are presented. The data obtained allow us to distinguish the following age maxima (Ma): 578 and 634 (Vendian); 720, 823, and 919 (Late Riphean); 1922, 2090, 2225, and 2321 (Early Proterozoic). A number of zircons have Late Archean age in the interval of 2670–2980 Ma. Taking into account Late Cambrian age (504–506 Ma) of intrusive rocks that intruded the Dzhida terrane, a possible sedimentation period of sequences of this terrane is estimated to be in the interval of 580–510 Ma (from Vendian to Late Cambrian). The possible provenance areas of terrigenous sediments are proposed and the previously proposed models of geodynamic evolution of the Dzhida terrane are correlated with new geochronological data. 相似文献
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4.
M. S. Barash 《Oceanology》2013,53(6):739-749
The consideration of the conditions during the mass extinctions has shown that a series of factors, including mutually independent tectonic movements, variations in the sea level and climate, volcanism, asteroid impacts, changes in the composition of the atmosphere and hydrosphere, the dimming of the atmosphere by aerosols at volcanism and impact events, etc., had a harmful affect during some periods of time (a hundred thousand years to millions of years). Some of the listed events occurred for a long period of time and could not have caused the abrupt catastrophic death of organisms on a global scale. The examination of the hierarchy of the major events allows us to distinguish the primary terrestrial (volcanism) and cosmic (impact events) reasons for the mass extinctions. The coeval mutually independent events testify to the common external reasons for the higher order beyond the solar system. These events are suggested to be related with the orbital movement of the solar system around the galaxy’s center, the intersection of the galactic branches, and the oscillations of the solar system’s position relative to the galactic plane. These reasons influence the processes on the Earth, including the internal and external geospheres, and activate the impacts of asteroids and comets. Under their effect, two main subsequences of events are developed: terrestrial, leading to intense volcanism, and cosmic impact events. In both cases, harmful chemical elements and aerosols are vented to the atmosphere, thus resulting in the greenhouse effect, warming, the dimming of the atmosphere, the prevention of photosynthesis, the ocean’s stagnation, and anoxia with the following reduction of the bioproductivity, the destruction of the food chains, and the extinction of a significant part of the biota. 相似文献
5.
M. S. Barash 《Oceanology》2012,52(2):238-248
At the end of the Permian, at the boundary between the Paleozoic and Mesozoic (251.0 ± 0.4 Ma), the largest mass extinction
of organisms on the Earth occurred. Up to 96% of the species of marine invertebrates and ∼70% of the terrestrial vertebrates
died off. A lot of factors were suggested and substantiated to explain this mass mortality, such as the disappearance of environmental
niches in the course of the amalgamation of the continental plates into Pangea, sea level fluctuations, anoxia, an elevated
CO2 content, H2S intoxication, volcanism, methane discharge from gas-hydrates, climate changes, impact events (collisions with large asteroids),
or combinations of many of these reasons. Some of these factors are in subordination to others, while others are independent.
Almost all of these factors developed relatively slowly and could not cause the sudden mass mortality of organisms globally.
It could have happened when large asteroids, whose craters have been discovered lately, fell to the Earth. It is suggested
that the impact events “finished off” the already suppressed biota. A simultaneous change in many of the factors responsible
for the biodiversity, including those not connected in a cause-and-effect relationship, proves the existence of a common extrater-restrial
cause that affected both the changes in the internal and external geospheres and the activation of asteroid attacks (the Sun’s
transit of spiral arms of our galaxy, the Sun’s oscillations perpendicularly to the galactic plane, etc). 相似文献
6.
M. S. Barash 《Oceanology》2011,51(4):640-651
The mass death of organisms at the Cretaceous-Tertiary boundary (KT boundary) resulted in the extinction of approximately
half of marine genera. Some taxa had degraded by the end of the Cretaceous to become eventually extinct either before or precisely
at the KT boundary. Most of them became extinct immediately at this boundary. The terminal Cretaceous was marked by changes
in many environmental processes, which influenced the biota. These included tectonic events, powerful basalt eruptions, falls
of large asteroids (impact events), anoxia, transgressions and regressions, cooling and warming episodes, and the chemistry
of the atmosphere and seawater. All these factors, except for impact events, could stimulate degradation of some groups of
organisms, not their extinction. The Cretaceous-Tertiary boundary was marked by major impact events, which are reflected in
the occurrence of the Chicxulub, Shiva, Boltysh, Silverpit, and, probably some other impact craters. Some known craters were
left by asteroids at that time or slightly earlier. At least as many asteroids undoubtedly fell into the ocean. The combination
of many factors in the terminal Cretaceous harmful for organisms and seemingly unrelated to each other may be likely explained
only by a single supreme cause beyond the Solar System. 相似文献
7.
M. S. Barash 《Earth, Moon, and Planets》1995,71(3):467-468
The Tunguska 1908 explosion's region as an international park of studies of the Ecological Consequences of Collisions of the Earth with the Solar System Small Bodies 相似文献
8.
M. S. Barash 《Doklady Earth Sciences》2016,466(2):119-122
In the interval of the Triassic–Jurassic boundary, 80% of the marine species became extinct. Four main hypotheses about the causes of this mass extinction are considered: volcanism, climatic oscillations, sea level variations accompanied by anoxia, and asteroid impact events. The extinction was triggered by an extensive flooding of basalts in the Central Atlantic Magmatic Province. Furthermore, a number of meteoritic craters have been found. Under the effect of cosmic causes, two main sequences of events developed on the Earth: terrestrial ones, leading to intensive volcanism, and cosmic ones (asteroid impacts). Their aftermaths, however, were similar in terms of the chemical compounds and aerosols released. As a consequence, the greenhouse effect, dimming of the atmosphere (impeding photosynthesis), ocean stagnation, and anoxia emerged. Then, biological productivity decreased and food chains were destroyed. Thus, the entire ecosystem was disturbed and a considerable part of the biota became extinct. 相似文献
9.
M. S. Barash 《Oceanology》2006,46(6):848-858
An analysis of the biota development in response to the changing abiotic factors shows that long relatively stable periods of transgression, high-energy hydrodynamics, and diverse ecological niches are favorable for a growth of biodiversity and the abundance of organisms. Biota reduction is determined by sharp environmental changes, particularly by multiple alteration of opposite development trends (transgression-regression, warming-cooling, and others). In addition, events harmful for the development of organisms such as global anoxia in the oceans, powerful eruptions of trap basalts and volcanism, and collision of the earth with extraterrestrial bodies negatively influence the biota evolution. The impact of different factors is particularly notable during biotic crises. The abiotic factors influencing the biota development are determined by three fundamental causes: terrestrial, orbital, and extraterrestrial. Frequently, these causes and relevant factors were synchronous or almost synchronous in terms of geological time. Inasmuch as there is no cause-effect relationship between them, we can assume that large-scale environmental changes are determined by general extraterrestrial factors originating beyond the solar system. 相似文献
10.
Oceanology - Ideas about the geomagnetic field’s influence on evolution and biodiversity are controversial. The quantitative distribution of datum levels of oceanic microplankton during the... 相似文献