Age of the Thornton Beach, California, Mammoth Fossil Updated     

Andrei M. Sarna-Wojcicki  Charles E. Meyer  John W. Hillhouse  N. Timothy Hall  Garniss H. Curtis 《Quaternary Research》1996,45(3):327-331

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Ferropericlase—a lower mantle phase in the upper mantle     

Gerhard P. Brey  Vadim Bulatov  Andrei Girnis  Jeff W. Harris  Thomas Stachel   《Lithos》2004,77(1-4):655-663

Experiments on compositions along the join MgO–NaA³⁺Si₂O₆ (A=Al, Cr, Fe³⁺) show that sodium can be incorporated into ferropericlase at upper mantle pressures in amounts commonly found in natural diamond inclusions. These results, combined with the observed mineral parageneses of several diamond inclusion suites, establish firmly that ferropericlase exists in the upper mantle in regions with low silica activity. Such regions may be carbonated dunite or stalled and degassed carbonatitic melts. Ferropericlase as an inclusion in diamond on its own is not indicative of a lower mantle origin or of a deep mantle plume. Coexisting phases have to be taken into consideration to decide on the depth of origin. The composition of olivine will indicate an origin from the upper mantle or border of the transition zone to the lower mantle and whether it coexisted with ferropericlase in the upper mantle or as ringwoodite. The narrow and flat three phase loop at the border transition zone—lower mantle together with hybrid peridotite plus eclogite/sediments provides an explanation for the varying and Fe-rich nature of the diamond inclusion suite from Sao Luiz, Brazil.  相似文献   

Influence of syn-sedimentary faults on orogenic structure: examples from the Neoproterozoic–Mesozoic east Siberian passive margin     

Andrei K. Khudoley  Georgiy A. Guriev 《Tectonophysics》2003,365(1-4):23

The east margin of the Siberian craton is a typical passive margin with a thick succession of sedimentary rocks ranging in age from Mesoproterozoic to Tertiary. Several zones with distinct structural styles are recognized and reflect an eastward-migrating depocenter. Mesozoic orogeny was preceded by several Mesoproterozoic to Paleozoic tectonic events. In the South Verkhoyansk, the most intense pre-Mesozoic event, 1000–950 Ma rifting, affected the margin of the Siberian craton and formed half-graben basins, bounded by listric normal faults. Neoproterozoic compressional structures occurred locally, whereas extensional structures, related to latest Neoproterozoic–early Paleozoic rifting events, have yet to be identified. Devonian rifting is recognized throughout the eastern margin of the Siberian craton and is represented by numerous normal faults and local half-graben basins.Estimated shortening associated with Mesozoic compression shows that the inner parts of ancient rifts are now hidden beneath late Paleozoic–Mesozoic siliciclastics of the Verkhoyansk Complex and that only the outer parts are exposed in frontal ranges of the Verkhoyansk thrust-and-fold belt. Mesoproterozoic to Paleozoic structures had various impacts on the Mesozoic compressional structures. Rifting at 1000–950 Ma formed extensional detachment and normal faults that were reactivated as thrusts characteristic of the Verkhoyansk foreland. Younger Neoproterozoic compressional structures do not display any evidence for Mesozoic reactivation. Several initially east-dipping Late Devonian normal faults were passively rotated during Mesozoic orogenesis and are now recognized as west-dipping thrusts, but without significant reactivation displacement along fault surfaces.  相似文献   

Correlation and interpretation of paleosols and loess across European Russia and Asia over the last interglacial-glacial cycle     

Nathaniel W Rutter  Dean RokoshMichael E Evans  Edward C LittleJiri Chlachula  Andrei Velichko 《Quaternary Research》2003,60(1):101-109

Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle.  相似文献   

Low-temperature magnetization and AC susceptibility of magnetite: effect of thermomagnetic history   总被引：2，自引：0，他引：2  

Andrei Kosterov 《Geophysical Journal International》2003,154(1):58-71

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Environments of the Russian Plain during the Middle Valdai Briansk Interstade (33,000–24,000 yr B.P.) Indicated by Fossil Mammals and Plants     

Anastasia K. Markova  Alexandra N. Simakova  Andrei Yu. Puzachenko  Lev M. Kitaev 《Quaternary Research》2002,57(3):391

Abundant mammal (45 localities) and plant (52 sections) fossil data collected from the Russian Plain deposits of the Middle Valdai Briansk Interstade indicate a period of noticeable warming. These materials were jointly analyzed. The data were organized in the database software PARADOX and then moved to the GIS program ARC/INFO. Mathematical methods as well as traditional research methods were used for the analysis. The reconstructed biogeographical provinces illustrate the specific environmental and climatic conditions of the Briansk Interstade. Analogues of modern natural zones did not exist at this time on the Russian Plain. The Briansk landscapes reflect the moderate-cool climate of this period, when the majority of northern subarctic plant and mammal species extended their ranges considerably to the south to the Central Russian Plain. At the same time, steppe species penetrated farther north and west. This combination shows that the continuous forest zone was destroyed during the Briansk Inter-stade. Five biogeographical provinces have been reconstructed from the north to the south for the Russian Plain during the Briansk warming on the basis of joint analysis of mammalian and botanical data.  相似文献   

Directed Evolution of the Biosphere: Biogeochemical Selection or Gaia?     

Andrei G. Lapenis 《The Professional geographer》2002,54(3):379-391

At the end of the nineteenth and the beginning of the twentieth centuries, a few Russian scientists proposed an interrelated hypothesis on the coevolution of life and the environment. Because political, linguistic, and cultural barriers between Russia and the rest of the world existed through most of the twentieth century, many of their concepts are not well known in Western science. The synthesis of their works presented in this article leads to the concept of directed evolution of the global ecosystem. Similar to the influential Gaia hypothesis, this concept predicts evolution of the global ecosystem toward conditions generally favorable for organisms. Unlike the Gaia hypothesis, however, the directed evolution in works of Russian scientists results from the superposition of “micro–forces” controlled on local and regional scales by the universal criterion of biogeochemical selection.  相似文献   

Automatic detection and correction algorithms for magnetic saturation in the SMFT/HSOS longitudinal magnetograms     

徐海清  刘锁  苏江涛  邓元勇  Andrei Plotnikov  白先勇  陈洁  杨潇  郭晶晶  王晓帆  宋永亮 《天文和天体物理学研究(英文版)》2021,(3):158-166

A longitudinal magnetic field often suffers the saturation effect in a strong magnetic field region when the measurement is performed at a single-wavelength point and linear calibration is adopted.In this study,we develop a method that can judge the threshold of saturation in Stokes V/I observed by the Solar Magnetic Field Telescope(SMFT)and correct it automatically.The procedure is to first perform the second-order polynomial fit to the Stokes V/I vs.I/I_m(I_m is the maximum value of Stokes I)curve to estimate the threshold of saturation,then reconstruct Stokes V/I in a strong field region to correct for saturation.The algorithm is demonstrated to be effective by comparing with the magnetograms obtained by the Helioseismic and Magnetic Imager(HMI).The accuracy rate of detection and correction for saturation is~99.4%and~88%respectively among 175 active regions.The advantages and disadvantages of the algorithm are discussed.  相似文献   

Nudging of vertical profiles of meteorological parameters in one-dimensional atmospheric model: A step towards improvements in numerical simulations   总被引：1，自引：0，他引：1  

D. Bala Subrahamanyam  S. Indira Rani  Radhika Ramachandran  P. K. Kunhikrishnan 《Ocean Science Journal》2008,43(4):165-173

In this article, we describe a simple yet effective method for insertion of observational datasets in a mesoscale atmospheric model used in one-dimensional configuration through Nudging. To demonstrate the effectiveness of this technique, vertical profiles of meteorological parameters obtained from GLASS Sonde launches from a tiny island of Kaashidhoo in the Republic of Maldives are injected in a mesoscale atmospheric model — Advanced Regional Prediction System (ARPS), and model simulated parameters are compared with the available observational datasets. Analysis of one-time nudging in the model simulations over Kaashidhoo show that incorporation of this technique reasonably improves the model simulations within a time domain of +6 to +12 Hrs, while its impact on +18 Hrs simulations and beyond becomes literally null.  相似文献   

Forbidden transition probabilities of astrophysical interest among low-lying states of V III     

Andrei Irimia 《Journal of Astrophysics and Astronomy》2007,28(2-3):157-166

Electric and magnetic multipole transitions among low-lying states of doubly ionized vanadium were computed using the multi-configuration Hartree-Fock (MCHF) method with Breit-Pauli (BP) corrections to a non-relativistic Hamiltonian. Energy levels were determined up to and including 3d ²(¹ G)4s b ² G _7/2 and computed energies were found to be in good agreement with experiment and other theories. In addition to Einstein A _ki coefficients for some E2 and M1 transitions, lifetime data and selected weighted oscillator strengths are also reported.  相似文献