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141.
Jelena Obradović Jelena Djurdjević - Colson Nebojša Vasić 《Journal of Paleolimnology》1997,18(4):351-364
Lacustrine basins of Neogene age in Serbia were formed either in intramountain valleys-graben and half-graben structures or in the marginal part of the Pannonian sea during Oligocene or at the beginning of Miocene, lasted and ended at the end of Miocene or Pliocene. The formation of the numerous depressions of the Balkan Peninsula, due to tectonic activity, gave lake basins with alluvial, swamp and lacustrine facies. The cycle with these facies was repeated several times. The lakes are mostly meromictic, often permanently stratified (oil-shale). A high rate of sedimentation with thickness up to 2000 m is characteristic for many of these basins. In many lakes phytogenic sedimentation occurs, giving facies with coal and with oil-shales. In this paper only some basins with oil-shales will be discussed, e.g. Valjevo-Mionica, Jadar and Pranjani basin. The characteristics of Vranje and Aleksinac basin will be discussed only in general. The organic rich sequences (oil shales) are characterized by the thin lamination, preservations of fish remains and plant leaves and absence of bioturbation, which needed permanent stratification of water body and anoxic conditions. Paleoclimatic regimes at the time of deposition and diagenesis were warm, subtropic with the changes of humid and dry periods. 相似文献
142.
Ferdinando Bosi Henrik Skogby Tonči Balić-Žunić 《Physics and Chemistry of Minerals》2016,43(6):395-407
A dravite from Yemen of near end-member composition was treated in air and hydrogen atmospheres at 600–900 °C to reveal changes in Mg and Al order over the octahedrally coordinated Y and Z sites, and to explore related changes in the characteristic vibrational bands in the principal (OH)-stretching frequency. Relevant information was obtained using electron microprobe analysis (EMPA), structural refinement (SREF) and polarized infrared (IR) single-crystal spectroscopy. Overall, the EMPA, SREF and IR data show that only minor changes occur during thermal treatment up to at least 800 °C, including variations in structural parameters, Mg–Al order–disorder and (OH)-stretching bands, indicating limited hydrogen loss. Untreated and treated dravite samples have very similar long-range and short-range atomic structures, which may be related to the occurrence of stable Al–Mg extended clusters around the O1 (=W) and O3 (=V) sites: W(F)–Y(MgMgMg)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]; W(OH)–Y(MgMgAl)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]; W(O2–)–Y(AlAlAl)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]. These extended clusters remain stable to temperatures close to the observed start of decomposition (~900 °C). 相似文献
143.
A method for estimating microporosity of fine‐grained sediments and sedimentary rocks via scanning electron microscope image analysis 下载免费PDF全文
This study presents a method of two‐dimensional scanning electron microscope image analysis that directly quantifies microporosity abundance in clay‐rich, fine‐grained sediments. The method is novel in that it is specifically designed to circumvent the challenge to porosity quantification posed by mineral surface charging and topographical artifacts created during Ar‐ion cross‐section polishing. It utilizes the finding that differences in circularity values can be used to distinguish micropores from blemishes in a thresholded image. This method is powerful because it is fast and provides a direct microporosity estimation technique to augment or replace experimental data. The pore size range to which the method is applicable is clear and can be selected depending on the application of the analysis. When used appropriately, the method can be implemented on microporous sediments and sedimentary rock in general. The method is developed using marine muds of Pliocene and Miocene ages from the Nankai margin (burial depths from approximately 200 to 1100 m). The close match between imaging‐derived microporosity and bulk N2 microporosity measurements shows that porosity in these young and relatively shallowly buried sediments is dominated by pores of sizes that can be imaged by scanning electron microscopy. In Kumano, forearc basin sediments of the Nankai Trough, results of this method show a significant increase in microporosity with burial depth, probably due to microporosity preservation during compaction and possibly early volcanic ash diagenesis. 相似文献
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148.
K. Zaninović 《Theoretical and Applied Climatology》1992,45(1):65-70
Summary Limits of warm and cold stress in different climatic regions are determined by means of temperature, wind speed and humidity for the period 1976–1985. These values are measured at 2 PM local time during July for warm stress and at 7 AM local time during January for cold stress. Hvar (20 m ASL) is used to represent maritime climate, Zavian on the top of Mount Velebit (1594 m ASL) and Skrad (668 m ASL) in Gorski Kotar are representative of mountainous climate, and Zagreb (128 m ASL) is representative of continental low-land climate. Values of a biometeorological Temperature-Wind Speed-Humidity (TWH)-index higher than the 98% value of the theoretical distribution fitted to empirical data represent above normal extreme conditions at a given location, and TWH values less than 2% value of the theoretical distribution represent below normal extreme conditions. For similar temperatures, it will be extremely above normal at the top of Mount Velebit (Zavian) whilst normal on the coast (Hvar), and similarly, it will be extremely below normal in Hvar but normal at Zavian.With 4 Figures 相似文献
149.
Gojko Djurašević 《Astrophysics and Space Science》1992,196(2):267-282
For the purpose of analysing light curves of active CB with an accretion disc being at the evolutional phase of an intensive matter exchange between the components a model for light-curve synthesis has been realized where the attention is given to systems like W Ser not sufficiently examined yet with regard that in them the accretion disc is formed around an ordinary star. In the paper one uses the elements presented in the first paper of this series. The model can successfully describe the essential characteristics of the observed light curves due to existence of an accretion disc and a hot spot, as well as those originated in the temperature distribution along the disc radius. The system components are considered in the framework of the nonsynchronous Roche model and the accretion disc of a constant thickness lies in the orbital plane around the star capturing the matter of the neighbouring component.The primary surrounded by the disc is situated relatively well within the Roche oval and its rotation can be significantly nonsynchronous. Near the Lagrange equilibrium pointL
1 flows from the secondary (which fills the Roche limit) the gas stream nourishing the disc. In the zone where the stream touches the lateral side of the disc a hot spot is formed.The proposed model enables estimating of the basic orbital and physical parameters of active type W Ser CB (Djuraevi, 1991) on the basis of photometric measurements by applying the inverse-problem method. 相似文献
150.
Slobodan Ninković 《Astrophysics and Space Science》1987,136(2):299-314
An analysis of the data concerning high-velocity stars from Eggen's catalogue aimed at a determination of the approximate slope of the mass function for the spherical component of our Galaxy, and at estimating the local circular velocity, as well as the local rotation velocity, as by-products, has been performed. Our conclusions are that:
- A linear dependence of the mass on the radius is very likely;
- the value of the limiting radius is most likely equal to (40±10) kpc;
- the two local velocities are approximately equal to each other, being both equal to (230±30) km s?1;
- the local escape velocity appears to be most likely equal to (520±30) km s?1;
- the total mass of a corona, obtained in this way, is (5±1)×1011 M ⊙.