排序方式: 共有67条查询结果,搜索用时 15 毫秒
51.
52.
Britta Trautwein István Dunkl Wolfgang Frisch 《International Journal of Earth Sciences》2001,90(3):703-713
The thermotectonic evolution of the East Alpine Rhenodanubian flysch zone (RDFZ) and the collisional history along the orogenic front is reconstructed using apatite fission-track (FT) thermochronology. The apatite FT data provides evidence for a burial depth of at least 6 km for the samples, which were totally reset. Burial was not deeper than 11 km, since the zircon fission-track system was not reset. The RDFZ represents an accretionary wedge with a complex burial and cooling history due to successive and differential accretion and exhumation. The sedimentary sequences were deposited along a convergent margin, where accretion started before Maastrichtian and lasted until Miocene. Accretion propagated from a central area (Salzburg-Ybbsitz) both to the west and to the east. In the west, accretion lasted from Middle Eocene to Early Oligocene, reflecting underplating of the RDFZ by the European continental margin sediments. In the east, where three nappes (Greifenstein, Kahlenberg and Laab nappes) can be distinguished, the exhumation started between Late Oligocene and Early Miocene. The Kahlenberg and Laab nappes show total resetting of the apatite FT ages, while in the Greifenstein nappe there is only partial resetting. According to a new paleogeographic reconstruction, the Kahlenberg and Laab nappes were placed on top of the Greifenstein nappe by an out-of-sequence thrust. 相似文献
53.
István Szynyogh 《Meteorology and Atmospheric Physics》1993,52(1-2):49-57
Summary A simple systematic method has been developed to investigate the laws of conservation for approximating model equations. The main purpose of this paper is to identify these model equations as approximations of continuous Hamiltonian systems. If this identification is possible, the laws of conservation of the model system can be investigated as for a finite dimensional Hamiltonian system. Obviously, this method can be applied only in the case where the original continuous equations are Hamiltonian. The applicability of the general method has been verified by using three well-known finite-difference schemes as examples. These examples show that this technique is a possible systematic way to construct new conservative finite-difference approximations, as well as to identify the conserved quantities of well-known schemes. 相似文献
54.
István Berényi 《GeoJournal》1994,32(4):403-414
55.
István Dódony 《Physics and Chemistry of Minerals》1997,24(1):39-49
Polygonal serpentine (PS) from selected serpentinite were studied using transmission electron microscopy. Fiber axis selected-area
electron diffraction (SAED) patterns and electron micrographs reveal orthogonal and monoclinic lizardite polytypes. The PS
models by Chisholm (1992) and Baronnet et al. (1994) do not fit SAED measurements. Experimental results are matched with calculated
diffraction geometry and intensities, as well as with simulated images, indicating inversion of the tetrahedral layer at sector
boundaries. The structural relationships between chrysotile and PS are discussed.
Two types of 30-sectored PS are distinguished. In “regular PS” the fiber axis is [100], in “helical PS” the fiber axis points
into a [uν0] direction with large u value (u≫ν). Helical PS can be regarded as a lizardite analogue of helical chrysotile.
Received December 6, 1995/Revised, accepted May 8, 1996 相似文献
56.
István Kovács Attila Demény György Czuppon Christophe Lécuyer Francois Fourel Qun-Ke Xia Jia Liu Zsanett Pintér Edit Király Kálmán Török Ábel Szabó Etienne Deloule György Falus Tamás Fancsik Zoltán Zajacz Judit Sándorné Kovács Beatrix Udvardi 《Contributions to Mineralogy and Petrology》2016,171(5):38
57.
Szabolcs Harangi Kata Molnár Axel K. Schmitt István Dunkl Ioan Seghedi Ágnes Novothny Mihály Molnár Balázs Kiss Theodoros Ntaflos Paul R. D. Mason Réka Lukács 《第四纪科学杂志》2020,35(1-2):232-244
Late Pleistocene tephras derived by large explosive volcanic eruptions are widespread in the Mediterranean and surrounding areas. They are important isochronous markers in stratigraphic sections and therefore it is important to constrain their sources. We report here tephrochronology results using multiple criteria to characterize the volcanic products of the Late Pleistocene Ciomadul volcano in eastern–central Europe. This dacitic volcano had an explosive eruption stage between 57 and 30 ka. The specific petrological character (ash texture, occurrence of plagioclase and amphibole phenocrysts and their compositions), the high-K calc-alkaline major element composition and particularly the distinct trace element characteristics provide a strong fingerprint of the Ciomadul volcano. This can be used for correlating tephra and cryptotephra occurrences within this timeframe. Remarkably, during this period several volcanic eruptions produced tephras with similar glass major element composition. However, they differ from Ciomadul tephras by glass trace element abundances, ratios of strongly incompatible trace elements and their mineral cargo that serve as discrimination tools. We used (U-Th)/He zircon dates combined with U-Th in situ rim dates along with luminescence and radiocarbon dating to constrain the age of the explosive eruptions of Ciomadul that yielded distal tephra layers but lack of identified proximal deposits. 相似文献
58.
Pál Sümegi Sándor Gulyás Dávid Molnár Gábor Bozsó István Fekete László Makó Péter Cseh Mihály Molnár Balázs P. Sümegi Peter Almond Christian Zeeden Tünde Törőcsik Janina J. Nett András Markó Frank Lehmkuhl 《第四纪科学杂志》2021,36(8):1364-1381
The 10 m thick Madaras loess–palaeosol profile is one of the Hungarian outcrops that yielded Upper Palaeolithic artefacts in 1966. To clarify the nature of the deposits and establish a reliable litho- and chronostratigraphy, a profile was opened and sampled at 25 cm intervals on the northern side of the brickyard in 1975. Analyses focused on grain size, carbonate content and the mollusc fauna. The chronology was based on the mollusc composition and a single date from the archaeological layer at the depth of ca 7 m below the surface. The 1975 profile was destroyed by mining but the reposited samples allowed an extended analysis of this important Marine Isotope Stage 2 record to which archaeological features were directly assigned. A new absolute chronology was built based on 11 14C dates. Environmental magnetic, geochemical and palaeoecological investigations allowed a refined view of site evolution with reliable chronology for the Last Glacial Maximum. Our results corroborated those of previous investigations done on other coeval loess–palaeosol sequences of the Southern Carpathian Basin. This also allowed for a temporal correlation to another local record with the published high-resolution chronology of the same brickyard and enabled modelling of local-scale heterogeneity of the environment in the long run. 相似文献
59.
Seasonal evaporation cycle in oxbow lakes formed along the Tisza River in Hungary for flood control
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
As a result of water regulation, dykes (i.e., embankments against floods) were constructed along the Tisza River and meanders were cut to control the floods in the region. These cut‐off meanders resulted in oxbow lakes that are important locations for nature conservation. We collected water samples over 5 years in 7 campaigns to measure the δ18O (‰) and δ2H (‰) ratios in 45 oxbow lakes from the Upper Tisza Region (NE‐Hungary). We applied Random Forest Regression involving climatic data to reveal the connection with the stable isotopes. We determined that isotope ratios changed as a function of time, due to evaporation and a varying water supply (precipitation and groundwater). The average difference in the isotopic ratios for the river and oxbows increased from spring to winter, but decreased between the oxbows on both sides of the dyke. We found that isotope ratios were determined by the maximum monthly temperature in the case of oxbows in the active floodplain, whereas in case of oxbows on the reclaimed side, this was also influenced by the maximum monthly temperature, and the cumulative evaporation. As direct measurement of evaporation is difficult to evaluate, stable isotope measurements provided an effective quantitative alternative to estimate evaporation. Measuring the seasonality of the δ18O and δ2H is important to interpret the results and these data are useful to water management experts to identify the lakes at risk of running dry. 相似文献
60.
Superposition of burial and hydrothermal events: post‐Variscan thermal evolution of the Erzgebirge,Germany
下载免费PDF全文
![点击此处可从《地学学报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Reinhard Wolff István Dunkl Jan‐Michael Lange Christian Tonk Thomas Voigt Hilmar von Eynatten 《地学学报》2015,27(4):292-299
The post‐Variscan thermal history of the Erzgebirge (Germany) is the result of periods of sedimentary burial, exhumation and superimposed hydrothermal activity. The timing and degree of thermal overprint have been analysed by zircon and apatite (U–Th)/He and apatite fission track thermochronology. The present‐day surface of the Erzgebirge was exhumed to a near‐surface position after the Variscan orogeny. Thermal modelling reveals Permo‐Mesozoic burial to temperatures of up to 80–100 °C, although the sedimentary cover thins out towards the north resulting in maximum burial temperatures of less than 40 °C. This thermal pattern was locally modified by Cretaceous hydrothermal activity that reset the zircon (U–Th)/He thermochronometer along ore veins. The thermal models show no significant regional exhumation during Cenozoic times, indicating that the peneplain‐like morphology of the basement is a Late Cretaceous feature. 相似文献