Marker tephra layers in the late quaternary deposits of the Sea of Okhotsk as evidence of catastrophic eruptions in the Nemo caldera complex (Onekotan Island, Kuril Islands)     

A. N. Derkachev  M. V. Portnyagin 《Stratigraphy and Geological Correlation》2013,21(5):553-571

On the basis of complex studies of tephra layers (morphology of volcanic glass particles, chemical composition of glass particles and minerals, and REE distribution), marker tephra layers (K2, K3) were distinguished in the stratigraphic columns in the area of the Sea of Okhotsk. The areas of distribution of tephra layers and their age datings were determined. Tephra layers are shown to be similar in their chemical composition. They are correlated with strong explosive eruptions in the Nemo caldera complex on Onekotan Island (northern part of the Kuril Islands) in the Late Pleistocene.  相似文献   

Glacial and palaeoenvironmental history of the Cape Chelyuskin area, Arctic Russia     

Per Möller  Grigorij Fedorov  Maxim Pavlov  Marit-Solveig Seidenkrantz  & Charlotte Sparrenbom 《Polar research》2008,27(2):222-248

Quaternary glacial stratigraphy and relative sea-level changes reveal at least two glacial expansions over the Chelyuskin Peninsula, bordering the Kara Sea at about 77°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raised-beach sequences mapped to altitudes of at least up to ca. 80 m a.s.l. Chronological control is provided by accelerator mass spectrometry ¹⁴C dating, electron-spin resonance and optically stimulated luminescence geochronology. Major glaciations, followed by deglaciation and marine inundation, occurred during marine oxygen isotope stages 6–5e (MIS 6–5e) and stages MIS 5d–5c. These glacial sediments overlie marine sediments of Pliocene age, which are draped by fluvial sediment of a pre-Saalian age, thereby forming palaeovalley/basin fills in the post-Cretaceous topography. Till fabrics and glacial tectonics record expansions of local ice caps exclusively, suggesting wet-based ice cap advance, followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains and the Severnaya Zemlya archipelago, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with the exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice neither impacted the Chelyuskin Peninsula nor Severnaya Zemlya, and barely touched the northern coastal areas of the Taymyr Peninsula.  相似文献   

An attempt to build a new completely analytical theory of the Uranian satellites: The results achieved and the results to be obtained     

Maxim Varfolomeev 《Planetary and Space Science》2008,56(14):1773-1777

An attempt to build a new theory of the main Uranian satellites is being made at the Sternberg Astronomical Institute. The main difference compared to GUST86 theory is that the new theory is planned to be completely analytical. To do this, the secular frequencies of the satellites should be calculated taking into account the secular perturbations of the second order and, partly, of the third order. This allows to improve the secular frequencies and make them more close to those obtained from numerical integration. Nevertheless, discrepancies remain, which indicate that more terms in the analytical development are needed. Some other advantages of the new theory are also discussed.  相似文献   

The sodium exosphere of Mercury: Comparison between observations during Mercury's transit and model results     

Alessandro Mura  Peter Wurz  Helmold Schleicher  Dominique Delcourt  Stefano Orsini  Maxim L. Khodachenko 《Icarus》2009,200(1):1-11

In this study we compare the sodium exosphere observations made by Schleicher et al. [Schleicher, H., and 4 colleagues, 2004. Astron. Astrophys. 425, 1119-1124] with the result of a detailed numerical simulation. The observations, made during the transit of Mercury across the solar disk on 7 May 2003, show a maximum of sodium emission near the polar regions, with north prevalence, and the presence of a dawn-dusk asymmetry. We interpret this distribution as the resulting effect of two combined processes: the solar wind proton precipitation causing chemical alteration of the surface, freeing the sodium atoms from their bounds in the crystalline structure on the surface, and the subsequent photon-stimulated and thermal desorption of the sodium atoms. While we find that the velocity distribution of photon desorbed sodium can explain the observed exosphere population, thermal desorption seems to play a minor role only causing a smearing at the locations where Na atoms are released on the dayside. The observed and simulated distributions agree very well with this hypothesis and indicate that the combination of the proposed processes is able to explain the observed features.  相似文献   

Activation of the Blandford–Znajek mechanism in collapsing stars     

Serguei S. Komissarov  Maxim V. Barkov 《Monthly notices of the Royal Astronomical Society》2009,397(3):1153-1168

The collapse of massive stars may result in the formation of accreting black holes in their interiors. The accreting stellar matter may advect substantial magnetic flux on to the black hole and promote the release of its rotational energy via magnetic stresses (the Blandford–Znajek mechanism). In this paper we explore whether this process can explain the stellar explosions and relativistic jets associated with long gamma-ray bursts. In particular, we show that the Blandford–Znajek mechanism is activated when the rest mass–energy density of matter drops below the energy density of the magnetic field in the near vicinity of the black hole (within its ergosphere). We also discuss whether such a strong magnetic field is in conflict with the rapid rotation of the stellar core required in the collapsar model, and suggest that the conflict can be avoided if the progenitor star is a component of a close binary. In this case the stellar rotation can be sustained via spin-orbital interaction. In an alternative scenario the magnetic field is generated in the accretion disc, but in this case the magnetic flux through the black hole ergosphere is not expected to be sufficiently high to explain the energetics of hypernovae by the BZ mechanism alone. However, this energy deficit can be recovered via the additional power provided by the disc.  相似文献   

New Data on the Geology of Osborn Plateau,Indian Ocean     

Levchenko  O. V.  Marinova  Yu. G.  Portnyagin  M. V.  Werner  R.  Lobkovsky  L. I. 《Doklady Earth Sciences》2019,489(2):1469-1473

Doklady Earth Sciences - The Osborn Plateau is a large intraplate rise in the eastern part of the Indian Ocean, which has been poorly studied by the geological and geophysical methods. In cruise...  相似文献   

An intercomparison between the GSWM, UARS, and ground based radar observations: a case-study in January 1993     

S. E. Palo  M. E. Hagan  C. E. Meek  R. A. Vincent  M. D. Burrage  C. McLandress  S. J. Franke  W. E. Ward  R. R. Clark  P. Hoffmann  R. Johnson  D. Kürschner  A. H. Manson  D. Murphy  T. Nakamura  Yu. I. Portnyagin  J. E. Salah  R. Schminder  W. Singer  T. Tsuda  T. S. Virdi  Q. Zhou 《Annales Geophysicae》1997,15(9):1123-1141

The Global-Scale Wave Model (GSWM) is a steady-state two-dimensional linearized model capable of simulating the solar tides and planetary waves. In an effort to understand the capabilities and limitations of the GSWM throughout the upper mesosphere and thermosphere a comparative analysis with observational data is presented. A majority of the observational data used in this study was collected during the World Day campaign which ran from 20 January to 30 January 1993. During this campaign data from 18 ground-based observational sites across the globe and two instruments located on the UARS spacecraft were analyzed. Comparisons of these data with the simulations from the GSWM indicate that the GSWM results are in reasonable agreement with the observations. However, there are a number of cases where the agreement is not particularly good. One such instance is for the semidiurnal tide in the northern hemisphere, where the GSWM estimates may exceed observations by 50%. Through a number of numerical simulations, it appears that this discrepancy may be due to the eddy diffusivity profiles used by the GSWM. Other differences relating to the diurnal tide and the quasi-two-day wave are presented and discussed. Additionally, a discussion on the biases and aliasing difficulties which may arise in the observational data is alos presented.  相似文献   

Textural evolution of synthetic fluid inclusions in quartz during reequilibration,with applications to tectonic reconstruction   总被引：4，自引：0，他引：4  

Maxim O. Vityk  Robert J. Bodnar 《Contributions to Mineralogy and Petrology》1995,121(3):309-323

Experimental reequilibration of synthetic 10 wt% NaCl-H₂O inclusions in natural quartz reveals that reequilibration textures show distinct differences depending upon the P-T path followed by the inclusion after formation. These differences combined with other geological information may be used to determine whether the sample (rock) followed a dominantly isothermal or isobaricP-T path following entrapment. The intensity and style of inclusion reequilibration features is related to the direction and magnitude of the departure of theP-T path from the original isochore for the inclusion. Thus, fluid inclusion reequilibration textures not only permit inclusionists to determine whether the rocks followed an isothermal or isobaric retrogradeP-T path, but also the magnitude of departure of this path from one that is isochoric. Editorial responsibility: J. Touret  相似文献   

Predicting dynamic failure of dense granules from static compression tests     

R.E. Maxim  A.D. SalmanM.J. Hounslow 《International Journal of Mineral Processing》2006

This paper shows how static failure loads can be used to predict impact failure of granules. A theoretical model is presented that gives the maximum force experienced during impact and equates this to experimentally measured static failure load to define a critical impact velocity for impact failure. A granule will fail if the predicted theoretical maximum force during impact due to the impact velocity is greater than the real force required to produce failure in that particular granule.  相似文献   

The source of platinum group elements in basalts of the ophiolite complex of the Kamchatsky Mys Peninsula (Eastern Kamchatka)     

D.P. Savelyev  S.V. Palesskii  M.V. Portnyagin 《Russian Geology and Geophysics》2018,59(12):1592-1602

Contents of platinum group elements (PGE—Os, Ir, Ru, Rh, Pt, and Pd) and rhenium in basalts of different geochemical types from the ophiolite complex of the Kamchatsky Mys Peninsula have been determined by the isotope dilution-mass spectrometry method. The total contents of PGE in different basalts are commensurate (1.4-3.6 ppb), but the element ratios vary considerably. A specific feature of the rocks is the low degree of PGE fractionation (Pd/Ir = 0.9-6.6, Pt/Pd = 1.0-7.3), which makes them similar to the Hawaiian tholeiitic basalts and picrites. The most fractionated PGE pattern is observed for alkali basalt (Pd/Ir = 6.6), and the least fractionated one, for E-MORB (Pd/Ir = 1.7). The similarity of the PGE patterns of basalts of different geochemical types suggests their similar mantle sources. We propose a model explaining the geochemical features of the basalts of the Kamchatsky Mys ophiolite complex by an impurity of the Earth’s core material in the plume source. The Ir/Pd-Ru/Pd and Pd/10-Ir-Ru discrimination diagrams can be used to identify enriched (plume) basalts based on their PGE content.  相似文献