Late Palaeozoic to Triassic evolution of the Turan and Scythian platforms: The pre-history of the Palaeo-Tethyan closure   总被引：2，自引：4，他引：2  

Boris A. Natal'in  A.M. Cell engr 《Tectonophysics》2005,404(3-4):175-202

A number of en échelon-arranged, southwest-facing arc fragments of Palaeozoic to Jurassic ages, sandwiched between two fairly straight east-northeast trending boundaries, constitute the basement of the Scythian and the Turan platforms located between the Laurasian and Tethyside units. They have until now largely escaped detection owing to extensive Jurassic and younger cover and the inaccessibility of the subsurface data to the international geological community. These units are separated from one another by linear/gently-curved faults of great length and steep dip. Those that are exposed show evidence of strike-slip motion. The arc units originally constituted parts of a single “Silk Road Arc” located somewhere south of the present-day central Asia for much of the Palaeozoic, although by the late Carboniferous they had been united into a continental margin arc south of the Tarim basin and equivalent units to the west and east. They were stacked into their present places in northern Afghanistan, Turkmenistan, Caucasus and the northern Black Sea by large-scale, right-lateral strike-slip coastwise transport along arc-slicing and arc-shaving strike-slip faults in the Triassic and medial Jurassic simultaneously with the subductive elimination of Palaeo-Tethys. This gigantic dextral zone (“the Silk Road transpression”) was a trans-Eurasian structure and was active simultaneously with another, similar system, the Gornostaev keirogen and greatly distorted Eurasia. The late Palaeozoic to Jurassic internal deformation of the Dniepr–Donets aulacogen was also a part of the dextral strain in southern Europe. When the emplacement of the Scythian and Turan units was completed, the elimination of Palaeo-Tethys had also ended and Neo-Tethyan arcs were constructed atop their ruins, mostly across their southern parts. The western end of the great dextral zone that emplaced the Turan and Scythian units horsetails just east of north Dobrudja and a small component goes along the Tornquist–Teisseyre lineament.  相似文献   

Molecular formulae of marine and terrigenous dissolved organic matter detected by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry     

Boris P. Koch  Matthias Witt  Thorsten Dittmar 《Geochimica et cosmochimica acta》2005,69(13):3299-3308

The chemical structure of refractory marine dissolved organic matter (DOM) is still largely unknown. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) was used to resolve the complex mixtures of DOM and provide valuable information on elemental compositions on a molecular scale. We characterized and compared DOM from two sharply contrasting aquatic environments, algal-derived DOM from the Weddell Sea (Antarctica) and terrigenous DOM from pore water of a tropical mangrove area in northern Brazil. Several thousand molecular formulas in the mass range of 300-600 Da were identified and reproduced in element ratio plots. On the basis of molecular elemental composition and double-bond equivalents (DBE) we calculated an average composition for marine DOM. O/C ratios in the marine samples were lower (0.36 ± 0.01) than in the mangrove pore-water sample (0.42). A small proportion of chemical formulas with higher molecular mass in the marine samples were characterized by very low O/C and H/C ratios probably reflecting amphiphilic properties. The average number of unsaturations in the marine samples was surprisingly high (DBE = 9.9; mangrove pore water: DBE = 9.4) most likely due to a significant contribution of carbonyl carbon. There was no significant difference in elemental composition between surface and deep-water DOM in the Weddell Sea. Although there were some molecules with unique marine elemental composition, there was a conspicuous degree of similarity between the terrigenous and algal-derived end members. Approximately one third of the molecular formulas were present in all marine as well as in the mangrove samples. We infer that different forms of microbial degradation ultimately lead to similar structural features that are intrinsically refractory, independent of the source of the organic matter and the environmental conditions where degradation took place.  相似文献   

Basin evolution and palaeoenvironmental variability of the thermokarst lake El'gene‐Kyuele,Arctic Siberia          下载免费PDF全文

Philipp Schleusner  Boris K. Biskaborn  Frank Kienast  Juliane Wolter  Dmitry Subetto  Bernhard Diekmann 《Boreas: An International Journal of Quaternary Research》2015,44(1):216-229

Thermokarst lakes are a widespread feature of the Arctic tundra, in which highly dynamic processes are closely connected with current and past climate changes. We investigated late Quaternary sediment dynamics, basin and shoreline evolution, and environmental interrelations of Lake El'gene‐Kyuele in the NE Siberian Arctic (latitude 71°17′N, longitude 125°34′E). The water‐body displays thaw‐lake characteristics cutting into both Pleistocene Ice Complex and Holocene alas sediments. Our methods are based on grain size distribution, mineralogical composition, TOC/N ratio, stable carbon isotopes and the analysis of plant macrofossils from a 3.5‐m sediment profile at the modern eastern lake shore. Our results show two main sources for sediments in the lake basin: terrigenous diamicton supplied from thermokarst slopes and the lake shore, and lacustrine detritus that has mainly settled in the deep lake basin. The lake and its adjacent thermokarst basin rapidly expanded during the early Holocene. This climatically warmer than today period was characterized by forest or forest tundra vegetation composed of larches, birch trees and shrubs. Woodlands of both the HTM and the Late Pleistocene were affected by fire, which potentially triggered the initiation of thermokarst processes resulting later in lake formation and expansion. The maximum lake depth at the study site and the lowest limnic bioproductivity occurred during the longest time interval of ～7 ka starting in the Holocene Thermal Maximum and lasting throughout the progressively cooler Neoglacial, whereas partial drainage and an extensive shift of the lake shoreline occurred ～0.9 cal. ka BP. Correspondingly, this study discusses different climatic and environmental drivers for the dynamics of a thermokarst basin.  相似文献   

Some general relations of the development of complex molecular objects at early stages of biosphere formation as a consequence of the physical properties of condensed medium     

V. I. Baranov  L. A. Gribov  V. A. Dement’ev  I. V. Mikhailov 《Geochemistry International》2016,54(11):1011-1018

We analyzed the character of molecular transformations under conditions of condensed media, in which intermolecular interactions always occur. It was shown that, instead of discrete transfer of external energy into the molecule, the energy characteristics of the condensed medium (appearance of zones) could result in gradual accumulation of internal energy in reaction centers owing to sequential thermal collisions with particles of the medium initiating the chemical reaction. This does not require high temperatures. The established physical properties related to the energy characteristics of condensed media could play an important role in molecular transformations and, consequently, formation of complex molecular objects at early stages of biosphere formation.  相似文献   

Results of test experiment comparing measurement data of three adjacent ADCP bottom stations     

V. B. Piotukh  V. I. Baranov  S. B. Kuklev  O. I. Podymov 《Oceanology》2016,56(4):601-613

The results of a test experiment comparing quasi-synchronous data of three adjacent acoustic Doppler current profilers (ADCPs) deployed on the shelf bottom of the Black Sea in September 2014 are considered. The direct aim of the experiment was quantitative comparison of data from different ADCPs placed in maximally similar conditions to simultaneously measure the sea current parameters at one geographic point. The goals and the scheme of the experiment, methods for processing the measurement results, main results, and their interpretations and analysis, including practical results and conclusions, are described.  相似文献   

Modern modes of provenance and dispersal of terrigenous sediments in the North Pacific and Bering Sea: implications and perspectives for palaeoenvironmental reconstructions   总被引：1，自引：0，他引：1  

Rong Wang  Boris K. Biskaborn  Arne Ramisch  Jian Ren  Yongzhan Zhang  Rainer Gersonde  Bernhard Diekmann 《Geo-Marine Letters》2016,36(4):259-270

During expedition 202 aboard the RV Sonne in 2009, 39 seafloor surface sediment sites were sampled over a wide sector of the North Pacific and adjoining Bering Sea. The data served to infer land–ocean linkages of terrigenous sediment supply in terms of major sources and modes of sediment transport within an over-regional context. This is based on an integrated approach dealing with grain-size analysis, bulk mineralogy and clay mineralogy in combination with statistical data evaluation (end-member modelling of grain-size data, fuzzy cluster analysis of mineralogical data). The findings on clay mineralogy served to update those of earlier work extracted from the literature. Today, two processes of terrigenous sediment supply prevail in the study area: far-distance aeolian sediment supply to the pelagic North Pacific, and hemipelagic sediment dispersal from nearby land sources via ocean currents along the continental margins and island arcs. Aeolian particles show the finest grain sizes (clay and fine silt), whereas hemipelagic sediments have high abundances of coarse silt. Exposed sites on seamounts and the continental slope are partly swept by strong currents, leading to residual enrichment of fine sand. Four sediment sources can be distinguished on the basis of distinct index minerals revealed by statistical data analysis: dust plumes from central Asia (quartz, illite), altered materials from the volcanic regions of Kamchatka and the Aleutian Arc (smectite), detritus from the Alaskan Cordillera (chlorite, hornblende), and fluvial detritus from far-eastern Siberia and the Alaska mainland (quartz, feldspar, illite). These findings confirm those of former studies but considerably expand the geographic range of this suite of proxies as far south as 39°N in the open North Pacific. The present integrated methodological approach proved useful in identifying the major modern processes of terrigenous sediment supply to the study region. This aspect deserves attention in the selection of sediment core sites for future palaeoenvironmental reconstructions related to aeolian and glacial dynamics, as well as the recognition of palaeo-ocean circulation patterns in general.  相似文献   

Calorimetric determination of the standard enthalpy of formation of stannite,Cu<Subscript>2</Subscript>FeSnS<Subscript>4</Subscript>     

T. A. Stolyarova  A. V. Baranov  E. G. Osadchii 《Geochemistry International》2018,56(1):75-77

The standard enthalpy of formation of stannite (Cu₂FeSnS₄) was calculated from the calorimetric measurements of the reactions of its formation from simple synthetic sulfides: Cu₂S + FeS₂ + SnS → Cu₂FeSnS₄ and ₂CuS + FeS + SnS → Cu₂FeSnS₄. Using published data for the binary sulfides, the standard enthalpy of formation of stannite from the elements was determined as ΔfH°_298.15(Cu₂FeSnS₄) =–(417.28 ± 2.28) kJ mol^–1.  相似文献   

Deficit of Large Aftershocks as an Indicator of Afterslip at the Sources of Earthquakes in Subduction Zones     

Shebalin  P. N.  Vorobieva  I. A.  Baranov  S. V.  Mikhailov  V. O. 《Doklady Earth Sciences》2021,498(1):423-426

Doklady Earth Sciences - A relative decrease in the fraction of large aftershocks in the first days after earthquakes in subduction zones is demonstrated, and a connection of this phenomenon with...  相似文献   

Influence of friction on the motion of quasigeostrophic vortices     

Boris Moro 《地球物理与天体物理流体动力学》2013,107(3-4):209-225

Abstract

Who show through numerical experiments that friction may enhance westward motion of vortices on the beta-plane and establish a relation betwen the dissipation coefficients and westward aceleration. This suggests an explanation fot the dunamics of westward intensification.  相似文献   

Response of littoral chironomid communities and organic matter to late glacial lake—level,vegetation and climate changes at Lago dell’Accesa (Tuscany,Italy)     

Laurent Millet  Boris Vannière  Valérie Verneaux  Michel Magny  Jean Robert Disnar  Fatima Laggoun-Défarge  Anne Véronique Walter-Simonnet  Gilles Bossuet  Elena Ortu  Jacques-Louis de Beaulieu 《Journal of Paleolimnology》2007,38(4):525-539

This study focuses on the response of lacustrine littoral chironomid communities to late glacial changes in limnological, environmental and climate conditions in the Mediterranean context. Late glacial chironomid (Diptera: Chironomidae) assemblages, organic petrography and geochemistry were analysed in a sediment core from the littoral zone of Lago dell’Accesa (Tuscany, Italy), where the lake-level fluctuations and the vegetation history have been previously reconstructed. Comparison of the chironomid stratigraphy to other proxies (pollen assemblages, organic petrography and geochemistry, lake-level) and regional climate reconstruction suggested the predominant influence of lake-level changes on the littoral chironomid fauna. The main lowering events that occurred during the Oldest and the Younger Dryas were followed by higher proportions of taxa typical of littoral habitats. A complementary study of organic matter suggested the indirect impact of lake-level on the chironomids through changes in humic status and habitat characteristics, such as the type of substrate and aquatic macrophyte development. Several chironomid taxa, such as Glyptotendipes, Microtendipes and Cricotopus type patens, were identified as possible indicators of low lake-level in the late glacial records. Nevertheless, this study suggested that parallel analyses of organic matter and chironomid assemblages may be needed to circumvent misinterpretation of littoral chironomid assemblage stratigraphy. There was a weak response of the chironomid assemblages to small lake-level lowerings that corresponded to the Older Dryas and Preboreal oscillations. A higher level of determination, e.g. to the species group level, may be necessary to increase the sensibility of the indicators to lake-level changes.  相似文献