Geochemical evidence of aeolian deposits in European soils     

Andreas J. Scheib  Manfred Birke  Enrico Dinelli  GEMAS Project Team 《Boreas: An International Journal of Quaternary Research》2014,43(1):175-192

Hafnium (Hf) and zirconium (Zr) concentrations measured in over 4100 agricultural soil samples from Europe were assessed with the focus on their relationship to the distribution of aeolian deposits, such as loess and coversands. Comparison of extractable (aqua regia; ICP‐MS) and total (XRFS) concentrations shows that only 1.0 to 1.7% of the total Hf and Zr is chemically extractable because of the resistant nature of their host minerals. Resistate minerals, such as zircon, are commonly found in the predominantly silty fraction of loess deposits. In this study a statistical analysis of total Hf and Zr soil data from areas with and without loess was carried out to derive threshold values of 10 mg kg^?1 (Hf) and 318 mg kg^?1 (Zr). These values were subsequently applied across the project area in an attempt to indicate the presence of aeolian deposits. The spatial distribution of above‐threshold concentrations suggests a more extensive and coherent loess belt across central and eastern Europe, providing additional evidence of loess across Brittany, Aquitaine and near the Vosges mountains in France as well as in the basins of central and northern Spain. Above‐threshold concentrations were also detected in loess regardless of its thickness, emphasising the importance of the abundance of zircon in the upper part of the soil profile rather than the actual thickness of the deposit. Soil data however, failed to indicate various loess facies within most of the Pannonian Basin, suggesting that this approach only works where deposits contain a sufficient amount of zircon. This may also explain why the extensive coversands across northern Germany and Poland were largely undetected. This study demonstrates that continental‐scale soil geochemical data can help identify and map the distribution of zircon‐rich loess and coversand, and subsequently enhance and improve current knowledge of the extent of these deposits.  相似文献   

Submersible structural study of Tamayo transform fault: East Pacific Rise, 23°N (project RITA)     

L. Pastouret  Cyamex Scientific Team 《Marine Geophysical Researches》1981,4(4):381-401

A submersible structural study of Tamayo transform fault, the second field study of an oceanic transform, was conducted with the diving saucer CYANA as part of the international project RITA. On the basis of the surface ship surveys and deep-tow traverses made prior to the diving program, the four successful dives of CYANA established the geometry of the presently active shear zones and demonstrated that the median ridge of the Tamayo transform is tectonically inactive. The dive results require the presence, in an area marked by diapir-like bodies, of an extensional relay zone linking the two offset shear zones which trend about 110°.P. CHOUKROUNE, Laboratoire de Géologie structurale, Université de Rennes I, avenue du Général-Leclerc, 35042-Rennes Cédex, France; P. J. FOX, State University of New York at Alban, Albany, New York, 12222, USA; M. SEGURET, Laboratoire de Géologie structurale Université des Sciences et Techniques du Languedoc, Place Eugéne-Bataillon, 34060, Montpellier Cédex, France; J. FRANCHETEAU, H. D. NEEDHAM, Centre Océanologique de Bretagne, B. P. 337, 29273, Brest Cédex, France; T. JUTEAU, Laboratoire de Minéralogie-Pétrographie, Université Louis-Pasteur, 1 rue Blessig, 67084, Strasbourg, Cédex, France; R. D. BALLARD, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543, USA; W. NORMARK, United States Geological Survey, Pacific-Arctic Branch of Marine Geology, Menlo Park, California, 94025, USA; A. CARRANZA, Centro de Ciencias del Mar y Limnologia, Ciudad Universitaria, Mexico 20 DF, Mexico; D. CORDOBA, J. GUERRERO, Instituto de Geologia, UNAM, Ciudad Universitaria, Mexico 20 DF Mexico; C. RANGIN, UNAM,now at Université de Paris VI, France.  相似文献   

The Continuous Plankton Recorder: concepts and history, from Plankton Indicator to undulating recorders   总被引：1，自引：0，他引：1  

P. C. Reid  J. M. Colebrook  J. B. L. Matthews  J. Aiken  Continuous Plankton Recorder Team 《Progress in Oceanography》2003,58(2-4):117

Alister Hardy conceived the Continuous Plankton Recorder (CPR) survey in the 1920s as a means of mapping near-surface plankton in space and time, interpreting the changing fortunes of the fisheries and relating plankton changes to hydrometeorology and climatic change. The seed he planted has grown to become the most extensive long-term survey of marine organisms in the world and the breadth of his vision becomes ever more apparent. The survey has now run for over 70 years and its value increases with every passing decade. Operating from ‘ships of opportunity’ the machines used are robust, reliable and easy to handle. Wherever possible, all the sampling and analytical methods have not been changed to maintain the consistency of the time series. Computerisation and the development of new statistical approaches have increased our ability to handle the large quantities of information generated and enhance the sensitivity of the data analyses. This overview, based on almost 900 papers, recounts the various phases in the history of the survey. It starts with the Indicator Survey (1921–1934), the deployment of the first CPR on the Discovery Expedition (1924–1927) and the early CPR survey in the North Sea (1931–1939). The survey reopened in 1946 after the Second World War and expanded across the North Atlantic to North America from 1959. Taxonomic studies were initiated and an emphasis was placed on patterns of distribution, which were seen to reflect the varying oceanographic conditions. The years 1968–1976 saw further expansion with operations even in the American Great Lakes, publication of a Plankton Atlas and initial evidence for a downward trend in plankton biomass. At about this time electronic instrumentation was attached to CPRs to make additional measurements and work was started on the development of a new generation of undulating Continuous Plankton and Environmental Recorders (CPERs). In 1976 the survey moved to Plymouth. Scientific priorities in the UK changed in the subsequent decade and funding became more difficult to secure even though some of the CPR papers being published at the time are now regarded as classics in plankton ecology. In 1988 the UK Natural Environment Research Council (NERC) decided to close the survey. An international rescue operation led to the creation of the Sir Alister Hardy Foundation for Ocean Science (SAHFOS) in 1990, which has continued with consortium funding from a number of countries, and from 1999 again included NERC. The scientific rationale of the survey has gained credibility as concern over climate change and other anthropogenic effects has grown and as the key role that plankton plays as an indicator of large-scale environmental conditions becomes ever more apparent. Recently, the survey became an integral component of the Global Ocean Observation System (GOOS) and expanded into the North Pacific. It plays a complementary role in many large international and multidisciplinary projects and is providing inspiration, advice and support to daughter surveys elsewhere in the world. At the start of a new millennium, Hardy’s vision from the 1920s is a powerful driving force not just in international biological oceanography, but in global environmental science.  相似文献   

滇西兰坪盆地五茂林剖面下白垩统景星组沉积相   总被引：1，自引：0，他引：1       下载免费PDF全文

吴根耀  矢野孝雄  谭明清 《古地理学报》2004,6(3):380-384

实测了云南西部兰坪盆地东部下白垩统下部景星组的五茂林剖面,建立了曲流河、三角洲和湖泊3种沉积序列,其中三角洲序列在云南下白垩统中属首次建立。分析了粗碎屑岩的组成,将该剖面上出露的砾岩分成4类。早白垩世时兰坪盆地属丹那沙林-高黎贡弧的弧后盆地,景星组自下而上为曲流河沉积、三角洲沉积和湖泊沉积,且随湖侵发生,湖泊向西扩大。  相似文献   

Dawn; the Vesta–HED connection; and the geologic context for eucrites,diogenites, and howardites     

Harry Y. McSween Jr.  Richard P. Binzel  M. Cristina De Sanctis  Eleonora Ammannito  Thomas H. Prettyman  Andrew W. Beck  Vishnu Reddy  Lucille Le Corre  Michael J. Gaffey  Thomas B. McCord  Carol A. Raymond  Christopher T. Russell  the Dawn Science Team 《Meteoritics & planetary science》2013,48(11):2090-2104

The Dawn mission has provided new evidence strengthening the identification of asteroid Vesta as the parent body of the howardite, eucrite, and diogenite (HED) meteorites. The evidence includes Vesta's petrologic complexity, detailed spectroscopic characteristics, unique space weathering, diagnostic geochemical abundances and neutron absorption characteristics, chronology of surface units and impact history, occurrence of exogenous carbonaceous chondritic materials in the regolith, and dimensions of the core, all of which are consistent with HED observations and constraints. Global mapping of the distributions of HED lithologies by Dawn cameras and spectrometers provides the missing geologic context for these meteorites, thereby allowing tests of petrogenetic models and increasing their scientific value.  相似文献   

Reconstruction of RHESSI Solar Flare Images with a Forward Fitting Method     

Aschwanden  Markus J.  Schmahl  Ed  Team  the RHESSI 《Solar physics》2002,210(1-2):193-211

We describe a forward-fitting method that has been developed to reconstruct hard X-ray images of solar flares from the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), a Fourier imager with rotation-modulated collimators that was launched on 5 February 2002. The forward-fitting method is based on geometric models that represent a spatial map by a superposition of multiple source structures, which are quantified by circular gaussians (4 parameters per source), elliptical gaussians (6 parameters), or curved ellipticals (7 parameters), designed to characterize real solar flare hard X-ray maps with a minimum number of geometric elements. We describe and demonstrate the use of the forward-fitting algorithm. We perform some 500 simulations of rotation-modulated time profiles of the 9 RHESSI detectors, based on single and multiple source structures, and perform their image reconstruction. We quantify the fidelity of the image reconstruction, as function of photon statistics, and the accuracy of retrieved source positions, widths, and fluxes. We outline applications for which the forward-fitting code is most suitable, such as measurements of the energy-dependent altitude of energy loss near the limb, or footpoint separation during flares. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022469811115  相似文献   

新建岩石地层单位的基本要求——以多索曲组的创建为例     

孙崇仁 《青海国土经略》1995,(1)

本文介绍了岩石地层单位的基本概念,今后新创或修订岩石地层单位应提供的资料和说明,并以多索曲组的创建为例,对有关基本要求进一步予以说明。  相似文献   

Geology and activity around volcanoes on Io from the analysis of NIMS spectral images     

Sylvain Douté  Rosaly Lopes  Robert Carlson  the Galileo NIMS Team 《Icarus》2004,169(1):175-196

The last two successful flybys of Io by Galileo in 2001 (orbits I31, I32) allowed the Near Infrared Mapping Spectrometer to enrich its collection of IR spectral image cubes of the satellite. These data cover hemispheric portions of Io, several volcanic centers as well as their surroundings with a spatial resolution ranging from 2 to 93 km pixel⁻¹. They map thermal emission from the hot-spots and the distribution of solid SO₂ in the 1.0-4.7 μm spectral range. We obtain maps of SO₂ abundance and granularity from the NIMS data using the method of Douté et al. (2002, Icarus 158, 460-482). The maps are correlated to distinguish four different physical units that indicate zones of SO₂ condensation, metamorphism and sublimation. We relate these information with visible images from Galileo's Solid State Imaging System and with detailed mapping of the thermal emission produced by Io's surface. Our principal goal is to understand the mechanisms controlling how lava, pyroclastics and gas are emitted by different types of volcanoes and how these products evolve. The 800 km diameter white ring of fallout created by a violent “Pillanian” eruption during summer of 2001 is at least partly composed of solid SO₂ and has enriched preexisting regional deposits. Orange materials have been recently or are currently emplaced 240 km south from the main eruption site, possibly as sulfur flows. A similar event may have taken place in the past at Ababinili Patera (12.5° N, 142° W). Carefull study of SO₂ maps covering the Emakong region also suggests that sulfur forms the bright channel-fed flow emerging from the south eastern side of the caldera. Within the main caldera of Tvashtar Catena completely cooled patches of crust exist. Elsewhere, the caldera is still cooling from previous episodes of flooding. We confirm that Amirani emits constantly large amount of SO₂ gas by interaction of fresh lava with the volatiles of the underlying plains. Nevertheless SO₂ frost is not the major component of the bright white ring seen in the SSI images. Over the whole Gish Bar region, SO₂ frost seems barely stable and is constantly regenerated. The stability increases along gray filamentary structures which could be faults filled with materials having peculiar thermal properties. Northwest of Gish Bar Patera, a localized bright deposit shows an unusual spectral signature potentially indicative of H₂O molecules forming ice crystals or being trapped in a nonidentified matrix. The Chaac region may present a thickened old crust reducing the geothermal flux to levels lower than 0.5 W m⁻² and thus creating a cold trap for SO₂. Looking at the abundance and degree of metamorphose of SO₂, we establish the relative age of different flows and ejecta for the Sobo Fluctus. Finally the assumption that the white patches in visible images indicate SO₂ rich deposits is once again challenged. In the Camaxtli region we identify a topographically controlled compact white deposit showing only moderate SO₂ abundance. In contrast, we detect two spots of quite pure SO₂ ice on the gray flanks of Emakong. Furthermore, the close association of fumarolic SO₂ and red S₂ already noted for several volcanic centers is observed at Tupan.  相似文献   

青海南部地区煤炭资源勘查思路     

白生海  余存莲  李喜萍 《青海国土经略》1997,(1)

青海南部及其毗邻地区,是青海省乃至全国工业基础最薄弱、社会经济最落后的地区。煤炭资源紧缺,是制约其经济发展的重要因素之一。查明煤炭资源赋存状况,探讨聚煤规律,指出进一步找煤勘探的方向,科学、合理地开发煤炭资源,以带动其它资源开发,使该区尽快脱贫致富,意义重大。  相似文献   

Probing the Formation and Evolution of early-type galaxies: the SAURON project     

E. Emsellem  The Sauron Team 《Astrophysics and Space Science》2002,281(1-2):363-366

We are conducting a systematic study of a carefully selected sampleof nearby E/S0 galaxies and Sa bulges using the unique panoramic integral-fieldspectrograph SAURON, mounted at the WHT. The goal of the SAURON projectis to fully map the gaseous/stellar kinematics and the stellar populations of a representative sample of 80 early-type galaxies up to 1 Re,probing different environments (clusters, field). These data, used in combination with existing ground-based and HST observations, and fed to the theoretical machinery we have developed, will allow to determine theintrinsic dynamical structure of the galaxies. We will also measure the masses of central black holes, relate the internal dynamics to the ageand metallicity of the stellar populations, and establish the historyof metal enrichment as a function of Hubble type and environment. Some brief results on two targets observed during the SAURON campaign will serve as an illustration of the unique and high quality data we are currently gathering. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献