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Reznitsky L. Z. Sklyarov E. V. Cametti G. Armbruster T. Suvorova L. F. Ushchapovskaya Z. F. Barash I. G. 《Geology of Ore Deposits》2018,60(7):607-615
Geology of Ore Deposits - A new mineral was discovered in Cr–V-bearing marbles of the Sludyanka Complex from the Pereval marble quarry, Sludyanka district, southern Baikal region, Russia. It... 相似文献
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Timothy W. Barash Charles G. Doll Jr. John A. Collins George H. Sutton Sean C. Solomon 《Marine Geophysical Researches》1994,16(5):347-363
A problem in the use of ocean bottom seismometers is the difficulty in leveling the sensors while ensuring good coupling to the seafloor. We have investigated the coupling characteristics of the seismic sensors in the new ONR ocean bottom seismometer. In the deployable sensor package for that instrument, a three-component seismometer set is suspended on a 2-axis passive leveling gimbal and is immersed in a viscous fluid. We report tests, conducted in a seismic vault, comparing the output of a gimbaled seismometer set to that of a set rigidly coupled to the ground. Our results show that the degree to which the gimbaled set is coupled to ground motion is a function of the viscosity of the coupling fluid. The coherence between the two sensor sets is poor (<0.4) at some frequencies within the band of interest (0.15 to 20 Hz) and on some components when the viscosity of the coupling fluid is comparatively low (14 Pa-s or 0.16 kSt kinematic viscosity). In addition, the outputs of some components over portions of this frequency band are attenuated and are phase-shifted relative to the outputs of the set rigidly coupled to the ground. Coherence and phase response similarity improve as the viscosity of the coupling fluid is increased. With a coupling fluid viscosity of 980 Pa-s (10 kSt), coherence and phase agreement between the two sensor sets is good (>0.9) across nearly the entire band of interest on all three components. A simple analytical model of the gimbaled seismometer set as a damped, driven, compound-pendulum provides a basis for understanding the test results. 相似文献
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M. S. Barash A. G. Matul G. Kh. Kazarina T. A. Khusid A. Abelmann N. Biebow D. Nürnberg R. Tiedemann 《Oceanology》2006,46(4):501-512
The distribution of diatoms, radiolarians, planktonic and benthic foraminifers, and sediment components in the fraction >0.125 mm was analyzed in the core obtained from the central Sea of Okhotsk within the frameworks of the Russian-German KOMEX project. The core section characterizes the period 190–350 ka, which corresponds to marine-isotopic stages (MIS) 7 to 10. During glacial MIS 10 and MIS 8, the basin accumulated terrigenous material lacking microfossils or containing them in low abundance, which reflects, along with their composition, heavy sea-ice conditions, suppressed bioproductivity, and bottom environments aggressive toward calcium carbonate. Interglacial MIS 9 was characterized by elevated bioproductivity with accumulation of diatomaceous ooze during the climatic optimum (328 to 320 ka). The water exchange with the Pacific was maximal from 328 to 324 ka ago. Environments became moderate and close to the present-day ones at the end of the optimum exhibiting the possible existence of a dichothermal layer with substantial amounts of the surface Pacific water still flowing into the basin. Similar to interglacial MIS 5e and MIS 1, the “old” Pacific water determined near-bottom environments in the central Sea of Okhotsk during that period, although the influx of terrigenous material was higher, probably reflecting a more humid climate of the region. Slight warming marked the terminal MIS 8 (approximately 260 ka ago). The paleoceanographic situation during interglacial MIS 7 was highly variable: from warm-water to almost glacial. The main climatic optimum of MIS 7 occurred within 220–210 ka, when the subsurface stratification increased and the dichothermal layer developed. Bottom environments during the studied time interval, except for the optimum of interglacial MIS 9, resembled those characteristic of glacial periods: the actively formed “young” Okhotsk water displaced the “old” Pacific deep water. 相似文献
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E. B. Sal’nikova A. B. Kotov V. I. Levitskii L. Z. Reznitskii A. I. Mel’nikov I. K. Kozakov V. P. Kovach I. G. Barash S. Z. Yakovleva 《Stratigraphy and Geological Correlation》2007,15(4):343-358
Geochronological data obtained in this work and previously known results of U-Pb geochronology suggest that principal metamorphic events, which took place in eastern part of the Irkut block (the Sharyzhalgai marginal ledge of the Siberian platform basement), correspond in age to (1) about 2.8 Ga, (2) 2649 ± 6 to 2562 ± 20 Ma, and (3) 1865 ± 4 to 1855 ± 5 Ma. Structural and metamorphic reworking of the earliest event originated under conditions of the granulite facies, whereas conditions of granulite and amphibolite facies were characteristic of the second and third events. Metasomatites after carbonate rocks originated in eastern part of the Sharyzhalgai ledge during the Early Proterozoic metamorphic event that lasted approximately 20 m.y. Being combined with age data, which are known at present for the reference syn-and post-collision granitoids in the Siberian platform basement and flanking foldbelts, new geochronological results show that accretion of basement blocks to the Siberian craton progressed from the east to the west between 1900 and 1840 Ma. To a first approximation, this geochronological interval characterizes time span of the Paleoproterozoic ocean closure and ultimate time, when the craton and supercontinent Columbia became amalgamated. 相似文献
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S. I. Shkolnik E. F. Letnikova A. V. Maslov M. D. Buyantuev L. Z. Reznitskii I. G. Barash 《Doklady Earth Sciences》2017,475(1):739-742
The results of geochemical, mineralogical, and isotope (U–Pb and Sm–Nd) studies of metasedimentary manganese-bearing rocks from the Itantsa Formation of the Ikat terrane are presented. It is found that the carbonate-effusive-shale complex of the Itantsa Fm. formed under the continental margin environment, with volcanic activity accompanying sedimentation, in the interval of 650–540 Ma ago. 相似文献
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M. S. Barash 《Oceanology》2009,49(3):385-395
Climate fluctuations with the optimum in the Early Eocene and subsequent cooling were the main abiotic factor that controlled the development of the oceanic biota in the Paleogene. The Paleogene represented the transitional stage from the greenhouse climate of the Mesozoic to the partly glacial Neogene and was characterized by changes in the distribution of the temperatures in the ocean with the replacement of the dominant latitudinal thermal circulation by the largely meridional thermohaline one. The climate changes were also determined by other factors: the opening and closure of seaways between basins, the position of major currents, volcanic activity, the sea-level fluctuations, the composition of the hydro- and atmosphere, and others. These changes were, in turn, determined by factors of higher order, primarily, by tectonic movements: vertical and horizontal (motions of lithospheric plates). The contribution of impact events to this process is also highly probable. All these factors influenced, via the hydrological and hydrochemical parameters of the water column, the evolution of the oceanic biota: their distribution areas, the sizes of the organisms, the diversity of the communities, the bioproductivity, and the mass extinction (for example, the extinction of 30–50% of the benthic foraminifers at the Paleocene-Eocene transition in response to the abrupt temperature increase). The Eocene-Oligocene transition (38 Ma ago) was marked by a global biotic crisis, the most significant one in the Cenozoic, when the abyssal part of the ocean was filled with cold water to form the psychrosphere. At least five major impact events, which preceded the Oligocene mass extinction of the biota, occurred in the terminal Eocene (36–35 Ma ago). 相似文献
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The Slyudyanka crystalline complex is located within the composite Khamar-Daban metamorphic terrane, the part of the Central
Asian fold belt. Geochemical composition of the basic crystalline schists of the Slyudyanka Group (subterrane) metamorphosed
under the high-temperature subfacies of the granulite facies suggests that their protoliths were tholeiitic basalts. Their
geochemical signatures are intermediate between mid-ocean ridges and island arc basalts, best approximating back-arc basin
basalts. The types of the metamorphic rocks of the Slyudyanka Group and their combination in sequences also most correspond
to accumulation in back-arc basins. It was concluded that the high-grade metavolcanic rocks retain main geochemical signatures
of protoliths, which allows the reconstruction of their paleogeodynamic settings, including back-arc basins. 相似文献