Tracking deepwater oxygen recovery using sedimentary chironomid assemblages: Peninsula Lake revisited     

Jeziorski  Adam  Nelligan  Clare  Corrigan  Dara  Meyer-Jacob  Carsten  Paterson  Andrew M.  Smol  John P. 《Journal of Paleolimnology》2021,66(4):371-387

Journal of Paleolimnology - Peninsula Lake, Ontario, Canada, is a Precambrian Shield lake that has experienced many environmental stressors since European settlement of the watershed in the...  相似文献   

Lu-Hf garnet geochronology of eclogites from the Balma Unit (Pennine Alps): implications for Alpine paleotectonic reconstructions     

Daniel Herwartz  Carsten Münker  Erik E. Scherer  Thorsten J. Nagel  Jan Pleuger  Nikolaus Froitzheim 《Swiss Journal of Geoscience》2008,101(1):173-189

Three samples of eclogite from the Balma Unit, an ophiolite sheet on top of the Monte Rosa Nappe in the Pennine Alps, were investigated in terms of their P-T evolution, geochemistry, and Lu-Hf geochronology. The paleogeographic origin of this unit is controversial (North Penninic vs. South Penninic). It has been interpreted as a piece of Late Cretaceous oceanic crust, on the basis of ca. 93 Ma U-Pb SHRIMP ages of synmagmatic zircon cores in an eclogite. Trace element and isotope data suggest a mid ocean ridge (MOR) rather than an intraplate or OIB setting for the protoliths of the eclogites. Electron microprobe analyses of representative garnets show typical prograde zoning profiles. Estimated peak metamorphic temperatures of 550–600 Cº most likely did not exceed the closure temperature of the Lu-Hf system. Hence, Lu-Hf ages most likely reflect garnet growth in the studied samples. To minimize inclusion effects on age determinations, a selective digestion procedure for garnet was applied, in which zircon and rutile inclusions are not dissolved. The ages obtained for three samples, 42.3 ± 0.6 Ma (MSWD: 0.47), 42 ± 1 Ma (MSWD: 3.0) and 45.5 ± 0.3 Ma (MSWD: 0.33), are younger than all Lu-Hf ages reported so far for South Penninic Units. Metamorphic zircon domains of the 42.3 Ma sample (PIS1) were previously dated by U-Pb SHRIMP at 40.4 ± 0.7 Ma, indicating that the growth of metamorphic zircon post-dated the onset of garnet growth.These new data put important constraints on the paleogeographic reconstruction of the Alps. The MORB character of the rocks, together with their previously published protolith age, imply that oceanic spreading was still taking place in the Late Cretaceous. This supports a North Penninic origin for our samples because plate tectonic models predict Cretaceous spreading in the North Penninic but not in the South Penninic Ocean. If the Balma Unit is indeed North Penninic, the new Lu-Hf data, in combination with published geochronological data, require that two independent subduction zones consumed the South and North Penninic oceans.  相似文献   

Extracting central places from the link structure in Wikipedia          下载免费PDF全文

Carsten Keßler 《Transactions in GIS》2017,21(3):488-502

Explicit information about places is captured in an increasing number of geospatial datasets. This article presents evidence that relationships between places can also be captured implicitly. It demonstrates that the hierarchy of central places in Germany is reflected in the link structure of the German language edition of Wikipedia. The official upper and middle centers declared, based on German spatial laws, are used as a reference dataset. The characteristics of the link structure around their Wikipedia pages, which link to each other or mention each other, and how often, are used to develop a bottom‐up method for extracting central places from Wikipedia. The method relies solely on the structure and number of links and mentions between the corresponding Wikipedia pages; no spatial information is used in the extraction process. The output of this method shows significant overlap with the official central place structure, especially for the upper centers. The results indicate that real‐world relationships are in fact reflected in the link structure on the web in the case of Wikipedia.  相似文献   

Resonance trapping of circumstellar dust particles by an alleged planet     

H. Scholl  F. Roques  B. Sicardy 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):381-393

The dynamical evolution of dust particles forming a circumstellar disk around Pictoris is followed by numerical simulations on a Connection Machine. The disk appears to be cleared inside a radius of about 20 AU. We integrate simultaneously the orbits of 8,000 dust particles subjected to Poynting-Robertson drag and perturbed by one alleged planet. The simulations show that a planet revolving about Pictoris at a mean distance of 20 AU with a mass of at least 2 * 10^–5 central stellar mass can confine the disk by outer resonance trapping. The azimuthal density distribution of particles which shows very strong variations. appears to be stationary in a frame rotating with the planet.  相似文献   

Genetic population structure of Austropotamobius pallipes (Lereboullet 1858) (Decapoda: Astacidae) in Switzerland, based on allozyme data     

Mathias Lörtscher  Martin Clalüna  Adolf Scholl 《Aquatic Sciences - Research Across Boundaries》1998,60(2):118-129

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History and evolution of Chiron's orbit     

H. Scholl 《Icarus》1979,40(3):345-349

We integrated Chiron's orbit numerically from 6000 bc to ad 18,000. Since Chiron often approaches Saturn closely, <1 AU, the evolution of Chiron's orbit obtained by an accurate integration is only of statistical significance. Slightly different starting values may yield a completely different orbit. Therefore, a cloud of nine variational orbits surrounding Chiron's orbit was also integrated numerically in order to get an idea about possible evolutionary paths. The calculations support the conjecture of S. Oikawa and E. Everhart [Astron. J.84, 134 (1979)] that the dynamical evolution of Chiron's orbit is with a certain statistical probability similar to orbits of short-period comets.  相似文献   

A framework to model shrimp (Pandalus borealis) stock dynamics and to quantify the risk associated with alternative management options, using Bayesian methods     

Hvingel  Carsten; Kingsley  Michael C.S. 《ICES Journal of Marine Science》2006,63(1):68-82

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Revealing Uncertainties in Land Change Modeling Using Probabilities          下载免费PDF全文

Carsten Krüger  Tobia Lakes 《Transactions in GIS》2016,20(4):526-546

Land change models are frequently used to analyze current land change processes and possible future developments. However, the outcome of such models is accompanied by uncertainties that have to be taken into account in order to address their reliability for science and decision‐making. While a range of approaches exist that quantify the disagreement of land change maps, the quantification of uncertainty remains a major challenge. The aim of this article is therefore to reveal uncertainties in land change modeling by developing two measures: quantity uncertainty and allocation uncertainty. We choose a Bayesian Belief Network modeling approach for deforestation in Brazil to develop and apply the two measures to the resulting probability surface. Quantity uncertainty describes the uncertainty about the correct number of cells in a land change map assigned to different land change categories and allocation uncertainty expresses the uncertainty about the correct spatial placement of a cell in the land change map. Thus, uncertainty can be quantified even in those cases where no reference data exist. Informing about uncertainty in probabilistic outcomes may be an important asset when land change projections are being used in science and decision‐making and moreover, they may also be further evaluated for other spatial applications.  相似文献   

Predictable signals in seasonal mean soil moisture simulated with observation-based atmospheric forcing over China     

Kairan Ying  Tianbao Zhao  Xiaogu Zheng  Xiao-Wei Quan  Carsten S. Frederiksen  Mingxing Li 《Climate Dynamics》2016,47(7-8):2373-2395

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Spatial Mapping of Conductive Ground Water Contamination With Electromagnetic Induction     

Dennis D. Weber  James F. Scholl  Douglas J. LaBrecque  Eric G. Walther  Roy B. Evans 《Ground Water Monitoring & Remediation》1984,4(4):70-77

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