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101.
Réka?LukácsEmail author Szabolcs?Harangi Olivier?Bachmann Marcel?Guillong Martin?Dani?ík Yannick?Buret Albrecht?von?Quadt István?Dunkl László?Fodor Jakub?Sliwinski Ildikó?Soós János?Szepesi 《Contributions to Mineralogy and Petrology》2015,170(5-6):52
A silicic ignimbrite flare-up episode occurred in the Pannonian Basin during the Miocene, coeval with the syn-extensional period in the region. It produced important correlation horizons in the regional stratigraphy; however, they lacked precise and accurate geochronology. Here, we used U–Pb (LA-ICP-MS and ID-TIMS) and (U–Th)/He dating of zircons to determine the eruption ages of the youngest stage of this volcanic activity and constrain the longevity of the magma storage in crustal reservoirs. Reliability of the U–Pb data is supported by (U–Th)/He zircon dating and magnetostratigraphic constraints. We distinguish four eruptive phases from 15.9 ± 0.3 to 14.1 ± 0.3 Ma, each of which possibly includes multiple eruptive events. Among these, at least two large volume eruptions (>10 km3) occurred at 14.8 ± 0.3 Ma (Demjén ignimbrite) and 14.1 ± 0.3 Ma (Harsány ignimbrite). The in situ U–Pb zircon dating shows wide age ranges (up to 700 kyr) in most of the crystal-poor pyroclastic units, containing few to no xenocrysts, which implies efficient recycling of antecrysts. We propose that long-lived silicic magma reservoirs, mostly kept as high-crystallinity mushes, have existed in the Pannonian Basin during the 16–14 Ma period. Small but significant differences in zircon, bulk rock and glass shard composition among units suggest the presence of spatially separated reservoirs, sometimes existing contemporaneously. Our results also better constrain the time frame of the main tectonic events that occurred in the Northern Pannonian Basin: We refined the upper temporal boundary (15 Ma) of the youngest counterclockwise block rotation and the beginning of a new deformation phase, which structurally characterized the onset of the youngest volcanic and sedimentary phase. 相似文献
102.
D. Chochol T. Pribulla M. Vaňko P. Mayer M. Wolf P. G. Niarchos K. D. Gazeas V. N. Manimanis L. Brát M. Zejda 《Astrophysics and Space Science》2006,304(1-4):93-96
Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable. 相似文献
103.
Uta Fritze – von Alvensleben 《Astrophysics and Space Science》2002,281(1-2):379-382
Mergers of massive gas-rich galaxies trigger violent starbursts that - over timescales of > 100 Myr and regions > 10 kpc -
form massive and compact star clusters comparable in mass and radii to Galactic globular clusters. The star formation efficiency
is higher by 1–2 orders of magnitude in these bursts than in undisturbed spirals, irregulars or even BCDs. We ask the question
if star formation in these extreme regimes is just a scaled-up version of the normal star formation mode of if the formation
of globular clusters reveals fundamentally different conditions.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
104.
ISLA will be an astronomical observatory, operating at the upper limit of our planet Earth atmosphere, offering space like
observing conditions in most aspects. ISLA can be maintained easily, modified easily if necessary, always kept at the state
of the art and operated for very extended periods without polluting the stratosphere. ISLA is ideally suited to become the
first world space observatory as the observing conditions are very much space-like – diffraction limited angular resolution,
very low ambient temperature, remote control – however ISLA is easily accessible, telescopes and instruments can be continuously
improved and ISLA's costs corresponds only to those of ground-based modern astronomical installations like the ESO-VLT-, KECK-
and GEMINI-observatories. The cost of observing and experimenting on ISLA will be orders of magnitudes lower than those of
building and operating any space telescope, allowing the astronomers of developing nations to participate in the ISLA observatory
within their limited financial possibilities as competent and full partners. ISLA's 4-m and 2-m telescopes will operate diffraction
limited from 0.3 μm in the optical, over the infrared, far-infrared to the sub-mm spectral range. ISLA's individual telescopes
will permit imaging with 20 milli-arcsec spatial resolution in the optical, 5 times better than the Hubble Space Telescope.
ISLA's telescopes can be combined to form an interferometer with a maximum baseline of 250 m with nearly complete coverage
of the u,v plane. Interferometric resolution will be of the order of 20 micro-arcsec for the optical. ISLA will thus offer
spatial resolution comparable or better than the intercontinental VLBI radio interferometers. ISLA's telescope efficiency
will be many orders of magnitude better than comparable ground-based telescopes. The light collecting power of ISLA's interferometric
telescopes will be orders of magnitudes greater than the future space interferometers under discussion. ISLA, being an aviation
project and not a space project, can be realised in the typical time scale for the development of aviation: about 5 years.
ISLA's cost for the whole observatory, including its movable ground station etc. will be of the order of a typical medium
size ESA space mission. ISLA's lifetime will be in excess of many decades, as it can easily be maintained, modernised, repaired
and improved. ISLA will become the origin of a new astronomical international organisation with worldwide participation. ISLA's
telescopes will be of the greatest importance to all astronomical fields, as it will permit to study much fainter, much more
distant objects with microscopic spatial resolution in wavelength regions inaccessible from ground. ISLA's many telescopes
permit easily simultaneous observations at many wavelengths for rapidly varying objects, from continuously monitoring the
surfaces of the planets in our solar system, surfaces of close-by stars, nuclei of galaxies to QSO's.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
105.
De Geer moraine ridges occur in abundance in the coastal zone of northern Sweden, preferentially in areas with proglacial water depths in excess of 150 m at deglaciation. From detailed sedimentological and structural investigations in machine‐dug trenches across De Geer ridges it is concluded that the moraines formed due to subglacial sediment advection to the ice margin during temporary halts in grounding‐line retreat, forming gradually thickening sediment wedges. The proximal part of the moraines were built up in submarginal position as stacked sequences of deforming bed diamictons, intercalated with glaciofluvial canal‐infill sediments, whereas the distal parts were built up from the grounding line by prograding sediment gravity‐flow deposits, distally interfingering with glaciolacustrine sediments. The rapid grounding‐line retreat (ca. 400 m yr?1) was driven by rapid calving, in turn enhanced by fast iceflow and marginal thinning of ice due to deforming bed conditions. The spatial distribution of the moraine ridges indicates stepwise retreat of the grounding line. It is suggested that this is due to slab and flake calving of the ice cliff above the waterline, forming a gradually widening subaqueous ice ledge which eventually breaks off to a new grounding line, followed by regained sediment delivery and ridge build‐up. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
106.
Rudolf?BráZdilEmail author Christian?Pfister Heinz?Wanner Hans?Von?Storch JüRg?Luterbacher 《Climatic change》2005,70(3):363-430
This paper discusses the state of European research in historical climatology. This field of science and an overview of its development are described in detail. Special attention is given to the documentary evidence used for data sources, including its drawbacks and advantages. Further, methods and significant results of historical-climatological research, mainly achieved since 1990, are presented. The main focus concentrates on data, methods, definitions of the “Medieval Warm Period” and the “Little Ice Age”, synoptic interpretation of past climates, climatic anomalies and natural disasters, and the vulnerability of economies and societies to climate as well as images and social representations of past weather and climate. The potential of historical climatology for climate modelling research is discussed briefly. Research perspectives in historical climatology are formulated with reference to data, methods, interdisciplinarity and impacts. 相似文献
107.
A filter composed of a crossed pair of doubly refracting crystals and a polaroid, mounted at the focal plane of the telescope, divides each star image into two images of constant intensity ratio. It is shown that such a filter arrangement is capable of providing reliable photographic calibration for stellar photometry. 相似文献
108.
The effect of latitudinal differential heating on the atmospheric general circulation is studied using a simple general circulation model driven by different heating rates. It is found that an increase in differential heating leads to a strengthening of the general circulation as characterized by an increase in global available potential energy, kinetic energy and atmospheric angular momentum. The strengthening of the circulation results in three circulation regimes characterized by different eddy activities. One is a zonally symmetric Hadley regime with no eddy activity while the other two are Rossby regimes dominated by eddies with intermediate and low wave numbers, respectively. Relative to other global indices, the global relative atmospheric angular momentum is superior in detecting the transition of circulation regimes. The regime changes in mid- and high-latitudes resemble the response of the atmosphere to large changes in Earths rotation rate. 相似文献
109.
Stanis?aw?MazurEmail author Krzysztof?Turniak Michael?Br?cker 《International Journal of Earth Sciences》2004,93(5):758-772
The Kodzko Metamorphic Complex (KMC) in the Central Sudetes consists of meta-sedimentary and meta-igneous rocks metamorphosed under greenschist to amphibolite facies conditions. They are comprised in a number of separate tectonic units interpreted as thrust sheets. In contrast to other Lower Palaeozoic volcano-sedimentary successions in the Sudetes, the two uppermost units (the Orla-Googowy unit and the Kodzko Fortress unit) of the KMC contain meta-igneous rocks with supra-subduction zone affinities. The age of the KMC was previously assumed to be Early Palaeozoic–Devonian, based on biostratigraphic findings in the lowermost tectonic unit. Our geochronological study focused on the magmatic rocks from the two uppermost tectonic units, exposed in the SW part of the KMC. Two orthogneiss samples from the Orla-Googowy unit yielded ages of 500.4±3.1 and 500.2±4.9 Ma, interpreted to indicate the crystallization age of the granitic precursors. A plagioclase gneiss from the same tectonic unit, intimately interlayered with metagabbro, provided an upper intercept age of 590.1±7.2 Ma, which is interpreted as the time of igneous crystallization. From the topmost Kodzko Fortress unit, a metatuffite was studied, which contains a mixture of genetically different zircon grains. The youngest 207Pb/206Pb ages, which cluster at ca. 590-600 Ma, are interpreted to indicate the maximum depositional age for this metasediment. The results of this study are in accord with a model that suggests a nappe structure for the KMC, with a Middle Devonian succession at the base and Upper Proterozoic units at structurally higher levels. It is suggested here that the KMC represents a composite tectonic suture that juxtaposes elements of pre-Variscan basement, intruded by the Lower Ordovician granite, against a Middle Palaeozoic passive margin succession. The new ages, combined with the overall geochemical variation in the KMC, indicate the existence of rock assemblages representing a Gondwana active margin. The recognition of Neoproterozoic subduction-related magmatism provides additional arguments for the hypothesis that equivalents of the Teplá-Barrandian domain are exposed in the Central Sudetes. 相似文献
110.
Jochen Br?cker 《Climate Dynamics》2012,39(3-4):655-667
Proper scoring rules provide a useful means to evaluate probabilistic forecasts. Independent from scoring rules, it has been argued that reliability and resolution are desirable forecast attributes. The mathematical expectation value of the score allows for a decomposition into reliability and resolution related terms, demonstrating a relationship between scoring rules and reliability/resolution. A similar decomposition holds for the empirical (i.e. sample average) score over an archive of forecast–observation pairs. This empirical decomposition though provides a too optimistic estimate of the potential score (i.e. the optimum score which could be obtained through recalibration), showing that a forecast assessment based solely on the empirical resolution and reliability terms will be misleading. The differences between the theoretical and empirical decomposition are investigated, and specific recommendations are given how to obtain better estimators of reliability and resolution in the case of the Brier and Ignorance scoring rule. 相似文献