Late Quaternary Stratigraphy, Glacial Limits, and Paleoenvironments of the Marresale Area, Western Yamal Peninsula, Russia     

Steven L. Forman   lafur Inglfsson  Valery Gataullin  William Manley  Hanna Lokrantz 《Quaternary Research》2002,57(3):355

Stratigraphic records from coastal cliff sections near the Marresale Station on the Yamal Peninsula, Russia, yield new insight on ice-sheet dynamics and paleoenvironments for northern Eurasia. Field studies identify nine informal stratigraphic units from oldest to youngest (the Marresale formation, Labsuyakha sand, Kara diamicton, Varjakha peat and silt, Oleny sand, Baidarata sand, Betula horizon, Nenets peat, and Chum sand) that show a single glaciation and a varied terrestrial environment during the late Pleistocene. The Kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying Labsuyakha sand and Marresale formation. Finite radiocarbon and luminescence ages of ca. 35,000 to 45,000 yr from Varjakha peat and silt that immediately overlies Kara diamicton place the glaciation >40,000 yr ago. Eolian and fluvial deposition ensued with concomitant cryogenesis between ca. 35,000 and 12,000 cal yr B.P. associated with the Oleny and the Baidarata sands. There is no geomorphic or stratigraphic evidence of coverage or proximity of the Yamal Peninsula to a Late Weichselian ice sheet. The Nenets peat accumulated over the Baidarata sand during much of the past 10,000 yr, with local additions of the eolian Chum sand starting ca. 1000 yr ago. A prominent Betula horizon at the base of the Nenets peat contains rooted birch trees ca. 10,000 to 9000 cal yr old and indicates a >200-km shift northward of the treeline from the present limits, corresponding to a 2° to 4°C summer warming across northern Eurasia.  相似文献   

Leaf cellulose δD and δO trends with elevation differ in direction among co-occurring, semiarid plant species     

Valery J Terwilliger  Julio L BetancourtSteven W Leavitt  Peter K Van de water 《Geochimica et cosmochimica acta》2002,66(22):3887-3900

The potential to reconstruct paleoclimate from analyses of stable isotopes in fossil leaf cellulose could be enhanced by adequate calibration. This potential is likely to be particularly great in mid-latitude deserts, where a rich store of fossil leaves is available from rodent middens. Trends in δD and δ¹⁸O of leaf cellulose were examined for three species growing across climatic gradients caused by elevation and slope aspect in southeastern Utah, USA. The species differed in morphology (Pinus edulis vs. Yucca glauca), photosynthetic pathway (C₃Y. glauca vs. CAM Yucca baccata) or both (P. edulis vs. Y. baccata). The δD_LCN (leaf cellulose nitrate) and δ¹⁸O_LC (leaf cellulose) values of P. edulis decreased with elevation. Stem water δD values either increased (in spring) or did not change with elevation (in summer). Needle water δD values usually decreased with elevation and differed greatly with leaf age. These results suggest that δ cellulose values of P. edulis record the effects of climate on the isotopic composition of leaf water but not climate effects on meteoric water. In contrast to P. edulis, δD_LCN values of Y. glauca increased with elevation. The δ¹⁸O_LC values of Y. glauca also increased with elevation but less significantly and only on south-facing slopes. The δ cellulose values in both P. edulis and Y. glauca were most significantly related to changes in temperature, although temperature and precipitation were negatively correlated in the study area. Where all three species co-occurred, their δD_LCN values differed but their δ¹⁸O_LC values were the same. The disparity in δD_LCN between Y. baccata and the other species corresponds to differences in biochemical fractionations associated with photosynthetic pathway. Biochemical fractionations may also contribute to differences between the two C₃ species. Knowledge of factors affecting responses of individual plant species to environment may be required to infer climate from δD_LCN and δ¹⁸O_LC.  相似文献   

Activité du gaz radon dans l'air du sol et sismicité locale : exemple du bassin de l'Arax (Arménie)Radon soil-gas concentrations and local seismicity: case of the Arax basin (Armenia)     

Karen Kharatian  Yves Travi  Valery Igoumnov 《Comptes Rendus Geoscience》2002,334(3):179-185

A survey of soil gas radon concentrations has been carried out at three sites, in the seismic area of Armenia, from 1996 to 1999. The seismicity generates opposed behaviours at the different sites. This heterogeneity is related to the sites locations in the tectonic frame. An increase of radon concentration occurs inside the tectonic micro-blocks during local seismic activity. On the contrary, an abrupt co-seismic decrease is recorded close to the fault area. These variations can be due to ‘pore-collapse’ phenomena which expulse the pore-gas and increases Rn concentration in soil at intra-blocs sites, but also to pore-elastic deformations and microfracturing modifications in the fault area. To cite this article: K. Kharatian et al., C. R. Geoscience 334 (2002) 179–185.  相似文献   

The mechanism of formation of the Baikal basin     

Eugene V. Artyushkov  Felix A. Letnikov  Valery V. Ruzhich 《Journal of Geodynamics》1990,11(4)

The Baikal is a deep long and narrow basin in East Siberia which follows a huge fault zone adjoining the Siberian Platform. The basin was formed by rapid subsidence of continental crust during the pas 3–4 Ma. It is bounded by normal faults which indicate extension of the crust during the subsidence. According to seismic reflection profiling data, the intensity of extension is not large (3–7%). It is much smaller than the thinning of the crystalline crust under the basin (up to 38%). The thinning and crustal subsidence can be explained by the transformation of gabbro in the lower crust into dense garnet granulites. The latter rocks (with V_p 7.7−7.8 km/sec) are still located under the remnant part of the crust. Rapid transformation took place due to an inflow of catalyzing fluid along the fault zone from the asthenospheric upwelling. This upwelling, which is at a depth of 80–90 km, caused a general uplift of a broad area in the south of East Siberia.  相似文献   

Jusa and Barsuchi Log Volcanogenic Massive Sulfide Deposits from the Southern Urals of Russia: Tectonic Setting, Structure and Mode of Formation     

Geoffrey P. Glasby    Irina A. Prozherova    Valery V. Maslennikov  Sergey I. Petukhov 《Resource Geology》2007,57(1):24-36

The Jusa and Barsuchi Log volcanogenic massive sulfide (VMS) deposits formed along a paleo island arc in the east Magnitogrosk zone of the Southern Urals between ca 398 and 390 Ma. By analogy with the VMS deposits of the west Magnitogrosk zone, they are considered to be Baimak type deposits, which are Zn‐Cu‐Ba deposits containing Au, Ag and minor Pb. Detailed mapping and textural analysis of the two deposits shows that they formed as submarine hydrothermal mounds which were subsequently destroyed on the sea floor under the influence of ocean bottom currents and slumping. Both deposits display a ratio of the length to the maximum width of the deposit >15 and are characterized by ribbon‐like layers composed mainly of bedded ore and consisting principally of altered fine clastic ore facies. The Jusa deposit appears to have formed in two stages: deposition of colloform pyrite followed by deposition of copper–zinc–lead sulfides characterized by the close association of pyrite, chalcopyrite, sphalerite, galena, tennantite, arsenopyrite, marcasite, pyrrhotite, bornite, native gold and electrum and high concentrations of gold and silver. The low metamorphic grade of the east Magnitogorsk zone accounts for the exceptional degree of preservation of these deposits.  相似文献   

On the covering of a Hill’s region by solutions in the restricted three-body problem     

Valery Kozlov  Ivan Polekhin 《Celestial Mechanics and Dynamical Astronomy》2017,127(3):331-341

We consider two classical celestial-mechanical systems: the planar restricted circular three-body problem and its simplification, the Hill’s problem. Numerical and analytical analyses of the covering of a Hill’s region by solutions starting with zero velocity at its boundary are presented. We show that, in all considered cases, there always exists an area inside a Hill’s region that is uncovered by the solutions.  相似文献   

Signature of the last shelf-centered glaciation at a key section in the Pechora basin,Arctic Russia     

Jan Tveranger  Valery Astakhov  Jan Mangerud  John Inge Svendsen 《第四纪科学杂志》1998,13(3):189-203

The Vastiansky Kon' is the largest exposure of Quaternary deposits in the Pechora lowland, northern Russia. Morphologically the site belongs to the so-called Markhida Moraine; a complex, east–west trending zone of ice-marginal landforms deposited by the Kara Sea Ice Sheet during the last glaciation. The site exhibits a succession of sediments more than 100 m thick that, according to previous studies, covers the interval from the end of the Elsterian to the beginning of the Holocene. Unfortunately both the strong glaciotectonic deformation of the sedimentary succession and few absolute dates have made the chronological interpretation of the section difficult. The present paper reviews previous studies of the site published in Russian, and presents the results of a reinvestigation focusing on the post-Eemian stratigraphy. A marine Eemian clay more than 8 m thick is overlain erosionally by 20 m of fluvial deposits of Late Eemain or Early Weichselian age. The fluvial succession is overlain by a till and a marine clay, which, according to one interpretation, may represent an Early or Middle Weichselian advance of the Kara Ice Sheet followed by a transgression. The clay shows a transition into 15 m of estuarine and fluvial sediments overlain by more than 12 m of tundra–floodplain deposits. The whole succession has been upthrusted glaciotectonically by the last ice advance, which deposited a more than 12 m thick till on top of the section. Based on a number of subtill radiocarbon age-estimates from the site, in the range 25–32 ka BP, the youngest ice advance is considered to be of late Weichselian age, although a Middle Weichselian age cannot be excluded. © 1998 John Wiley & Sons, Ltd.  相似文献   

Viscous waves on a beta-plane and its zonal asymmetry     

Zyryanov  Valery N.  Chebanova  Marianna K. 《Ocean Dynamics》2019,69(4):427-441

Ocean Dynamics - Effects of the viscosity, Earth rotation, and sphericity (beta-effect) on the long-wave dynamics are investigated based on the linear model. The basic equation for the complex...  相似文献   

Spectra of the spreading layers on the neutron star surface and constraints on the neutron star equation of state     

Valery Suleimanov  Juri Poutanen 《Monthly notices of the Royal Astronomical Society》2006,369(4):2036-2048

Spectra of the spreading layers on the neutron star surface are calculated on the basis of the Inogamov–Sunyaev model taking into account general relativity correction to the surface gravity and considering various chemical composition of the accreting matter. Local (at a given latitude) spectra are similar to the X-ray burst spectra and are described by a diluted blackbody. Total spreading layer spectra are integrated accounting for the light bending, gravitational redshift and the relativistic Doppler effect and aberration. They depend slightly on the inclination angle and on the luminosity. These spectra also can be fitted by a diluted blackbody with the colour temperature depending mainly on a neutron star compactness. Owing to the fact that the flux from the spreading layer is close to the critical Eddington, we can put constraints on a neutron star radius without the need to know precisely the emitting region area or the distance to the source. The boundary layer spectra observed in the luminous low-mass X-ray binaries, and described by a blackbody of colour temperature   T _c= 2.4 ± 0.1 keV  , restrict the neutron star radii to   R = 14.8 ± 1.5 km  (for a  1.4-M_⊙  star and solar composition of the accreting matter), which corresponds to the hard equation of state.  相似文献   

Investigation of radio pulsar emission features using power spectra     

Valery M.Malofeev  Sergey A.Tyul'bashev 《天文和天体物理学研究(英文版)》2018,(8)

Since 2013, round-the-clock monitoring of the sky has been carried out simultaneously in 96 beams using a high-sensitivity radio telescope called the Large Phased Array(LPA) at the frequency110.25 MHz. These observations are made under the program of interplanetary plasma investigation.The same data are used to search for pulsars by means of power spectra. To increase the sensitivity of the pulsar search, 500–600 power spectra corresponding to different days of observations are summed. In the integrated spectra of known pulsars, besides expected improvement in signal-to-noise(S/N) ratio for the frequency harmonics, some features are explored in this paper. We present the 27 strongest pulsars which are in a field with declination 21°-42°. The observable details in the integrated power spectra are connected with the presence of pulsar periods of the second(P_2) and third(P_3) class, which have been identified. Empirical relations for calculating these periods are obtained. The value P_2 is estimated for 26 pulsars, and for 15 sources it is made for the first time. The value P_3 is estimated for 13 pulsars,among them these values are given for five sources for the first time.  相似文献