Fine-Grained Aluminosiliciclastic Rocks of the Middle Riphean Stratotype Section in the Southern Urals: Formation Conditions,Composition and Provenance Evolution   总被引：2，自引：0，他引：2  

Maslov  A. V.  Krupenin  M. T.  Ronkin  Yu. L.  Gareev  E. Z.  Lepikhina  O. P.  Popova  O. Yu. 《Lithology and Mineral Resources》2004,39(4):357-381

General trends of the formation of Middle Riphean fine-grained aluminosiliciclastic rocks in the Bashkir Meganticlinorium are considered. It is shown that Yurmatinian shales do not contain any significant pyroclastic admixture. Judging from the relatively constant Th/Cr ratio throughout the Yurmatinian section, the tectonic regime in the study territory during the early Middle Riphean is suggested to be rather stable. The main paleoclimatic indices and indicators of the pelitic material maturity (CIA, CIW, IVC, PIA, and Ce/Y) suggest that paleodrainage systems in the early Middle Riphean were dominated by humid climate that gave way to the arid or semiarid type in the middle Yurmatinian. The low Mo/Mn ratio and some other indicators of redox conditions in shales from all Yurmatinian lithostratigraphic units show that no explicit reducing conditions existed in the basin during the early Middle Riphean. The shales were characterized by the increase in K₂O/Al₂O₃ ratio, gradual enrichment in REE, and growth of LREE/HREE and La_N/Yb_N ratios toward the middle Yurmatinian, indicating the gain of an appreciable amount of slightly weathered arkosic aluminosiliciclastic material in the sedimentary basin about 1220–1200 Ma ago. The REE distribution and the UCC- and AUC-normalized shale compositions suggest that the eroded upper crust was compositionally close to the UCC. The occurrence of mafic and ultramafic rocks is also inferred. Data points of Yurmatinian shales plotted in the Cr–Ni, Eu/Eu*–Gd_N/Yb_N, and (La/YB)_N–Yb_N diagrams are localized between the fields of Upper Archean and post-Archean rocks or within the latter field. Hence, post-Archean igneous and metamorphic complexes prevailed in paleodrainage systems of the early Middle Riphean. This is also confirmed by the model Nd ages.  相似文献   

A multi-proxy approach for revealing recent climatic changes in the Russian Altai   总被引：2，自引：0，他引：2  

Olga V. Sidorova  Matthias Saurer  Vladimir S. Myglan  Anja Eichler  Margit Schwikowski  Aleksander V. Kirdyanov  Marina V. Bryukhanova  Oksana V. Gerasimova  Ivan A. Kalugin  Andrey V. Daryin  Rolf T. W. Siegwolf 《Climate Dynamics》2012,38(1-2):175-188

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ¹³C and δ¹⁸O in cellulose chronologies obtained for the period 1779–2007 and cell wall thickness (CWT) for 1900–2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ¹³C data contain a strong summer temperature signal, while δ¹⁸O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ¹³C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ¹⁸O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction.  相似文献   

Spatial and temporal variability of the frequency of extreme daily rainfall regime in the La Plata Basin during the 20th century   总被引：1，自引：1，他引：0  

Olga C. Penalba  Federico A. Robledo 《Climatic change》2010,98(3-4):531-550

We analyzed trends, interdecadal variability, and the quantification of the changes in the frequency of daily rainfall for two thresholds: 0.1 mm and percentile 75th, using high quality daily series from 52 stations in the La Plata Basin (LPB). We observed increases in the annual frequencies in spatially coherent areas. This coherence was more marked in austral summer, autumn, and spring, during which the greatest increases occurred in southern Brazil, especially during extreme events. In winter, the low and middle basins of the Río Uruguay and Río Paraná showed negative trends, some of which were significant. Interdecadal variability is well defined in the region with more pronounced positive jumps west of the basin between 1950 and 2000. This variability was particularly more marked during periods of extreme rainfall in summer, autumn, and spring, unlike in winter when extreme daily rainfall in the lower Rio Paraná basin decreased by up to 60%. The changes in the past century during extreme rainfall produced modifications in the annual rainfall cycle. The annual cycle of both indices was broader during the last period which is mainly explained by the strong decreases in winter.  相似文献   

Fractionation analysis of transport engine-generated soot particles with respect to hygroscopicity     

Elena D. Kireeva  Olga B. Popovicheva  Natalia M. Persiantseva  Mikhail A. Timofeyev  Natalia K. Shonija 《Journal of Atmospheric Chemistry》2009,64(2-3):129-147

Combustion-derived particles emitted by various transport engines are analyzed with respect to their morphology and composition. Soot particles collected behind an aircraft gas turbine engine combustor, in the diesel engine exhaust pipe, and at the end of ship pipe demonstrate heterogeneous morphological structures and different chemical identities. Individual particle analysis allows the characterization of emitted soot particles into three fractions, namely C-O, C-O-S, and Fe-C-O, with the dominant presence of chain soot agglomerates, irregular internally mixed soot, and particles of distinct morphology, respectively. The influence of oxygen and sulfur concentrations on the ability of soot to uptake water is proposed as a method for categorizing transport engine-generated particles. Categories of hydrophobic and hydrophilic particles within non-hygroscopic soots can be defined based on the amount of water uptake relative to several reference laboratory-made soots comparable to transport engine emissions. This method of characterizing hydrophobic/hydrophilic and hygroscopic soots in combustion emissions will help to determine the potential impacts of the combustion emissions on CCN/IN formation in the atmosphere.  相似文献   

Present rate of uplift in Fennoscandia from GRACE and absolute gravimetry   总被引：2，自引：0，他引：2  

Holger Steffen  Olga Gitlein  Heiner Denker  Jürgen Müller  Ludger Timmen 《Tectonophysics》2009,474(1-2):69

Fennoscandia is a key region for studying effects of glacial isostatic adjustment. The associated mass variations can be detected by the Gravity Recovery and Climate Experiment (GRACE) satellite mission, which observes the Earth's gravity field since April 2002, as well as by absolute gravimetry field campaigns. Since 2003, annual absolute gravity (AG) measurements have been performed in Fennoscandia by the Institut für Erdmessung (IfE, Institute of Geodesy) of the Leibniz Universität Hannover, Germany, within a multi-national cooperation. This offers a unique opportunity for validation and evaluation of the GRACE results. In this preliminary study, the GRACE results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the FG5-220 gravimeter of the IfE.The results from GRACE monthly solutions provided by different analysis centres show temporal gravity variations in Fennoscandia. The included secular variations are in good agreement with former studies. The uplift centre is located west of the Bothnian Bay, the whole uplift area comprises Northern Europe. Nevertheless, the differences between the GRACE solutions are larger than expected and the different centre-specific processing techniques have a very strong effect on possible interpretations of GRACE results. The comparison of GRACE to the AG measurements reveals that the determined trends fit well with results from GRACE at selected stations, especially for the solution provided by the GFZ. Variations of land hydrology clearly influence results from GRACE and the AG measurements.  相似文献   

Planetary dynamics in the system α Centauri: The stability diagrams     

E. A. Popova  I. I. Shevchenko 《Astronomy Letters》2012,38(9):581-588

The stability of the motion of a hypothetical planet in the binary system ?? Cen A?CB has been investigated. The analysis has been performed within the framework of a planar (restricted and full) three-body problem for the case of prograde orbits. Based on a representative set of initial data, we have obtained the Lyapunov spectra of the motion of a triple system with a single planet. Chaotic domains have been identified in the pericenter distance-eccentricity plane of initial conditions for the planet through a statistical analysis of the data obtained. We have studied the correspondence of these chaotic domains to the domains of initial conditions that lead to the planet??s encounter with one of the binary??s stars or to the escape of the planet from the system. We show that the stability criterion based on the maximum Lyapunov exponent gives a more clear-cut boundary of the instability domains than does the encounterescape criterion at the same integration time. The typical Lyapunov time of chaotic motion is ??500 yr for unstable outer orbits and ??60 yr for unstable inner ones. The domain of chaos expands significantly as the initial orbital eccentricity of the planet increases. The chaos-order boundary has a fractal structure due to the presence of orbital resonances.  相似文献   

Shock Wave Effects from the Impacts of Cosmic Objects with Diameters from 20 m to 3 km     

Glazachev  D. O.  Popova  O. P.  Podobnaya  E. D.  Artemieva  N. A.  Shuvalov  V. V.  Svetsov  V. V. 《Izvestiya Physics of the Solid Earth》2021,57(5):698-709

Izvestiya, Physics of the Solid Earth - Abstract—Destruction on the Earth’s surface caused by a shock wave is one of the most important and dangerous effects from asteroid and comet...  相似文献   

Open star clusters in the spiral arms of our Galaxy     

M. E. Popova  A. V. Loktin 《Astronomy Letters》2008,34(8):551-557

We consider the age distributions of open star clusters attributed to three segments of Galactic spiral arms. The smoothed distributions of clusters on the age-Galactocentric angle plane show a great nonuniformity. The time dependence of the formation rate of Galactic disk clusters recovered by taking into account selection effects and dynamical evolution of clusters shows that, on average, the formation rate of open star clusters decreases with time. This is in agreement with the increase in star formation rate into the past, as follows from the study of this process by the method of stellar population synthesis. The present time is the epoch of a current maximum of the cluster formation rate. In addition to the current maximum, there have been at least three more maxima with a period of 300–400 Myr and a duration of no more than 300 Myr. The age distributions are consistent with the pattern of star formation governed by the successive passages of density waves through each examined volume of the Galactic disk. The spiral structure becomes more complex when passing from the inner regions of the Galaxy to its outer regions.  相似文献   

Meridional circulation and dynamo waves     

H. Popova  D. Sokoloff 《Astronomische Nachrichten》2008,329(7):766-768

The effect of meridional circulation on spherical shell dynamos is considered in the Parker approximation. We demonstrate that the type of the exited solution crucially depend on the intensity of the meridional circulation. If the circulation is equatorward or if it is polarward however do not exceed some critical value, an oscillating solution in form of an equatorward traveling wave is excited. If the polarward meridional circulation becomes too intensive the solution becomes steady growing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

乌兹别克斯坦入境旅游者行为差异研究     

左冰  Olga Kim 《世界地理研究》2017,(3):147-156

随着旅游活动的全球化,跨文化旅游者的消费行为成为学界关注的热点问题。本文以地处丝绸之路黄金节点的乌兹别克斯坦为案例地,通过深入调研,分析了不同文化类别国家的旅游者在乌兹别克斯坦的旅游行为和感知差异,并借用霍夫斯泰德的文化差异理论对其进行解释。研究发现:(1)乌兹别克入境旅游者普遍年龄比较大,受教育水平高,停留时间长,更愿意花钱,并想获得真正的深度体验,寻找真实性;(2)不同文化类别游客在旅游目的、旅行方式、停留时间、游览空间等方面具有不同特征;(3)西方游客以精神性体验为主,关注文化体验和建筑,并希望在旅途中找到快乐;俄罗斯游客以世俗体验为主,追求休闲和美食;亚洲游客则两者兼而有之,表现为重视与本族群的关系、景点的文化价值和关心服务质量。研究对于了解丝绸之路旅游者的消费特征,推动中乌旅游合作和丝绸之路旅游发展具有重要意义。  相似文献