Early Neoproterozoic Granite-Gneisses of the Junggar Alataw (Southeastern Kazakhstan): Age, Petrogenesis and Tectonic Implications     

Nadezhda KANYGINA  Andrey TRETYAKOV  Dmitriy ALEXEIEV  Kirill DEGTYAREV  Anfisa SKOBLENKO  Natalia SOLOSHENKO  Boris ERMOLAEV 《《地质学报》英文版》2024,98(1):67-82

The combined petrographic, petrological, geochemical and geochronological study of the Neoproterozoic gneisses of the Sarychabyn and Baskan complexes of the Junggar Alataw of South Kazakhstan elucidate the Precambrian tectonic evolution of the Aktau–Yili terrane. It is one of the largest Precambrian crustal blocks in the western Central Asian orogenic belt. The U-Pb single-grain zircon ages indicate that granite-gneisses formed from the same source and crystallised in the early Neoproterozoic ca. 930–920 Ma. The chemical composition of gneisses corresponds to A2-type granites. The whole-rock Nd isotopic characteristics (εNd(t) = ?4.9 to ?1.0 and TNd(DM-2st) = 1.9 to 1.7 Ga) indicate the involvement of Paleoproterozoic crustal rocks in magma generation. Early Neoproterozoic ca. 930–920 Ma A-type granitoids in the Aktau–Yili terrane of South and Central Kazakhstan might reflect within-plate magmatism adjacent to the collisional belt or a local extension setting in back-arc areas of the continental arc.  相似文献   

Lateglacial and Holocene environmental history of the central Kola region,northwestern Russia revealed by a sediment succession from Lake Imandra     

Matthias Lenz  Larisa Savelieva  Larisa Frolova  Anna Cherezova  Matthias Moros  Marlene M. Baumer  Raphael Gromig  Natalia Kostromina  Niyaz Nigmatullin  Vasili Kolka  Benrd Wagner  Grigory Fedorov  Martin Melles 《Boreas: An International Journal of Quaternary Research》2021,50(1):76-100

Bolshaya Imandra, the northern sub-basin of Lake Imandra, was investigated by a hydro-acoustic survey followed by sediment coring down to the acoustic basement. The sediment record was analysed by a combined physical, biogeochemical, sedimentological, granulometrical and micropalaeontological approach to reconstruct the regional climatic and environmental history. Chronological control was obtained by ¹⁴C dating, ¹³⁷Cs, and Hg markers as well as pollen stratigraphy and revealed that the sediment succession offers the first continuous record spanning the Lateglacial and Holocene for this lake. Following the deglaciation prior to c. 13 200 cal. a BP, the lake's sub-basin initially was occupied by a glacifluvial river system, before a proglacial lake with glaciolacustrine sedimentation established. Rather mild climate, a sparse vegetation cover and successive retreat of the Scandinavian Ice Sheet (SIS) from the lake catchment characterized the Bølling/Allerød interstadial, lasting until 12 710 cal. a BP. During the subsequent Younger Dryas chronozone, until 11 550 cal. a BP, climate cooling led to a decrease in vegetation cover and a re-advance of the SIS. The SIS disappeared from the catchment at the Holocene transition, but small glaciers persisted in the mountains at the eastern lake shore. During the Early Holocene, until 8400 cal. a BP, sedimentation changed from glaciolacustrine to lacustrine and rising temperatures caused the spread of thermophilous vegetation. The Middle Holocene, until 3700 cal. a BP, comprises the regional Holocene Thermal Maximum (8000–4600 cal. a BP) with relatively stable temperatures, denser vegetation cover and absence of mountain glaciers. Reoccurrence of mountain glaciers during the Late Holocene, until 30 cal. a BP, presumably results from a slight cooling and increased humidity. Since c. 30 cal. a BP Lake Imandra has been strongly influenced by human impact, originating in industrial and mining activities. Our results are in overall agreement with vegetation and climate reconstructions in the Kola region.  相似文献   

Fog and stratus formation on the coast of Brazil   总被引：1，自引：0，他引：1  

Natalia Fedorova  Vladimir Levit  Dmitry Fedorov   《Atmospheric Research》2008,87(3-4):268

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Behavior of planetary dynamos under the influence of external magnetic fields: Application to Mercury and Ganymede     

Natalia Gómez-Pérez  Johannes Wicht 《Icarus》2010,209(1):53-1693

For planets with strong intrinsic magnetic fields such as Earth and Jupiter, an external magnetic field is unlikely to affect the internal dynamo, but for bodies with weak intrinsic fields in appropriate environments, such as Mercury and Ganymede, the interaction with nearby field sources may determine the internal dynamics and overall behavior of their liquid iron cores. On the basis of simulations of such interactions using numerical models for fluid flow and dynamo generation, the parameter regimes for stable dipolar and multipolar reversing dynamo magnetic fields established for isolated systems can be substantially changed by the action of external sources. Relatively weak external background fields (as low as 2% of the averaged undisturbed field at the core-mantle boundary) may change the energy balance and alter the regime over which natural isolated dynamos operate.  相似文献   

A GIS-Based Ground Water Contamination Risk Assessment Tool for Pesticides   总被引：4，自引：0，他引：4  

Michael G. Sinkevich Jr  .  M. Todd Walter  Arthur J. Lembo Jr  .  Brian K. Richards  Natalia Peranginangin  Sunnie A. Aburime  Tammo S. Steenhuis 《Ground Water Monitoring & Remediation》2005,25(4):82-91

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Interactive maps for visual exploration of grid and vector geodata     

Gennady Andrienko  Natalia Andrienko  Valeri Gitis 《ISPRS Journal of Photogrammetry and Remote Sensing》2003,57(5-6):380

This article considers two types of tools used for the analysis of spatial data: computational tools for grid data and visualization-based interactive exploratory techniques. The main purpose is to demonstrate that computational and visual techniques are complementary, and their combined use in data analysis may produce a synergistic effect. To this end, we describe two example scenarios of data analysis in the evaluation of potential damage from earthquakes and in analysis of forest resources. The analyses were performed with the use of CommonGIS, featuring the availability of powerful geocomputational tools and interactive visualization-related facilities that can be efficiently used in combination in a desktop environment or via the World Wide Web.  相似文献   

Permian palaeomagnetism of East Kazakhstan and the amalgamation of Eurasia     

Natalia M. Levashova  Kirill E. Degtyarev  Mikhail L. Bazhenov  Adam Q. Collins  Rob Van der Voo 《Geophysical Journal International》2003,152(3):677-687

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Inter-annual and seasonal variations of energy and water vapour fluxes above a Pinus sylvestris forest in the Siberian middle taiga   总被引：2，自引：0，他引：2  

Nadejda M. Tchebakova  Olaf Kolle  Daniil Zolotoukhine  Almut Arneth  Julie M. Styles  Natalia N. Vygodskaya  E.-Detlef Schulze  Olga Shibistova  Jon Lloyd 《Tellus. Series B, Chemical and physical meteorology》2002,54(5):537-551

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Coastal cooling/heating events: Laboratory experiments     

Natalia Demchenko  Irina Chubarenko 《Acta Geophysica》2007,55(1):56-64

We report the results of laboratory experiments on water heating/cooling, performed in 5 m long water channel with a slope. About 63 series of photos were analyzed: for 3 locations, for 3 bottom slopes (3.7, 6.7 and 12 degrees) and for different Ra numbers. It was pointed out that there exist two types of mixing characterizing different circulations in the presence of slope: gravity current and undersurface jet; the thermal bar is the region where one type of mixing is replaced by another; the highest speed and flowrate are at the break point; the flow is three-dimensional.  相似文献   

Testing the applicability of a Marine Biotic Index (AMBI) to assessing the ecological quality of soft-bottom benthic communities, in the South America Atlantic region   总被引：2，自引：0，他引：2  

Muniz P  Venturini N  Pires-Vanin AM  Tommasi LR  Borja A 《Marine pollution bulletin》2005,50(6):624-637

Recently, several monitoring programmes have been undertaken to evaluate the impact of different anthropogenic activities, upon a range of coastal ecosystems located in the South-western Atlantic. In the present contribution, the applicability of the AZTI's Marine Biotic Index (AMBI) is tested, to establish the benthic health of the ecosystem using these data sets. As the AMBI was created previously for use in European estuarine and coastal environments, its general applicability to new geographical locations is discussed. In general, the results are in agreement with those obtained using traditional univariate and multivariate methods. Some inconsistent results are observed, when low abundances and/or number of taxa are recorded in the samples. Moreover, when the macrofauna samples are dominated by large nematodes, the classification of the benthic ecosystem health using AMBI is not consistent with previous results achieved applying other statistical techniques. Thus, parallel to the application of this index to a wider extend, the complementary use of different indices and/or methods is recommended to assess confidently the environmental quality of a coastal area.  相似文献