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291.
Prof. Dr. Klaus -J. Reutter Marlies Teichmüller Rolf Teichmüller Giorgio Zanzucchi 《International Journal of Earth Sciences》1983,72(3):861-893
The rocks of the Northern Apennines predominantly consist of non-metamorphic terrigeneous deposits (flysches and molasses) some of which are preorogenic, some synorogenic and others postorogenic with respect to the nappe tectonics (Miocene). As plant fragments frequently occur in these sediments, a study of coal rank based on reflectance measurements on vitrinites (% Rm = mean value of the random reflectance in non polarized light) contributes to the clarification of the relation between the orogenic and the palaeogeothermal development. The determination of the Rm values of more than 180 samples from outcrops and three deep drillings revealed some important features. Within the pile of Liguride and Tuscanide nappes, the coal rank increases from the uppermost nappe to the lower nappes until lowgrade metamorphism is reached in the Lower Tuscanides. In the single nappes the rank decreases from the Tyrrhenian coast (internal zone) towards the Po Plain (external zone). This regional trend is disturbed only locally by young post-coalification tectonics. In the uppermost Liguride nappe (M. Antola Unit) a pre-Oligocene (i. e. pre-Apenninic) thermal event was detected. Postorogenic heating is connected with the magmatic activity of Late Miocene to Pleistocene age in Tuscany. Except for these preorogenic and postorogenic thermal events, the main coalification is generally younger than the emplacement of the nappes in the nappe pile during the Apenninic orogeny in the Miocene, but it is older than the last thrust movements and the final tensional tectonics in the internal zones of the chain. For these reasons, the main regional thermal event has to be considered as synorogenic or, more precisely, as late-synorogenic. 相似文献
292.
A.M Celál Şengör Si̇lva Büyükaşikoğlu Nezi̇hi̇ Canitez 《Journal of Structural Geology》1983,5(2):211-216
Data for the post-Serravallian, ‘neotectonic’ evolution of the Pontides in northern Turkey indicate predominant ENE-WSW shortening with complementary NNW-SSE extension. We present a new fault plane solution for the Bartin earthquake (3 September 1968) and compare its mechanism with the movement picture of other neotectonic faults in the Pontides and northern Greece together with that of the Thessaloniki earthquake (20 May 1978). The general strain pattern exhibited by these structures agrees remarkably well with that inferred from early Tortonian-early Pleistocene structures reported from within the North Anatolian fault zone, which have been interpreted as indicating a possible reversal of the sense of movement along the North Anatolian transform fault. Here, we argue that such ‘incompatible’ structures may be related to the overall E-W shortening of Anatolia and the southern parts of the Black Sea resulting from the sideways continental escape from around the African and the Arabian promontories, rather than to hypothetical reversal of motion along the North Anatolian fault, for which there is no evidence other than the above-mentioned ‘incompatible’ structures. This new model also has important implications for seismicity and earthquake risk in regions contained within the southern part of the Black Sea plate. 相似文献
293.
294.
Ramzi Touchan Elena Xoplaki Gary Funkhouser Jürg Luterbacher Malcolm K. Hughes Nesat Erkan Ünal Akkemik Jean Stephan 《Climate Dynamics》2005,25(1):75-98
This study represents the first large-scale systematic dendroclimatic sampling focused on developing chronologies from different
species in the eastern Mediterranean region. Six reconstructions were developed from chronologies ranging in length from 115 years
to 600 years. The first reconstruction (1885–2000) was derived from principal components (PCs) of 36 combined chronologies.
The remaining five, 1800–2000, 1700–2000, 1600–2000, 1500–2000 and 1400–2000 were developed from PCs of 32, 18, 14, 9, and
7 chronologies, respectively. Calibration and verification statistics for the period 1931–2000 show good levels of skill for
all reconstructions. The longest period of consecutive dry years, defined as those with less than 90% of the mean of the observed
May–August precipitation, was 5 years (1591–1595) and occurred only once during the last 600 years. The longest reconstructed
wet period was 5 years (1601–1605 and 1751–1755). No long term trends were found in May–August precipitation during the last
few centuries. Regression maps are used to identify the influence of large-scale atmospheric circulation on regional precipitation.
In general, tree-ring indices are influenced by May–August precipitation, which is driven by anomalous below (above) normal
pressure at all atmospheric levels and by convection (subsidence) and small pressure gradients at sea level. These atmospheric
conditions also control the anomaly surface air temperature distribution which indicates below (above) normal values in the
southern regions and warmer (cooler) conditions north of around 40°N. A compositing technique is used to extract information
on large-scale climate signals from extreme wet and dry summers for the second half of the twentieth century and an independent
reconstruction over the last 237 years. Similar main modes of atmospheric patterns and surface air temperature distribution
related to extreme dry and wet summers were identified both for the most recent 50 years and the last 237 years. Except for
the last few decades, running correlation analyses between the major European-scale circulation patterns and eastern Mediteranean
spring/summer precipitation over the last 237 years are non-stationary and insignificant, suggesting that local and/or sub-regional
geographic factors and processes are important influences on tree-ring variability over the last few centuries. 相似文献
295.
Christine Franke Thomas Frederichs Mark J. Dekkers 《Geophysical Journal International》2007,170(3):1053-1066
Low-temperature rock magnetic measurements have distinct diagnostic value. However, in most bulk marine sediments the concentration of ferrimagnetic and antiferromagnetic minerals is extremely low, so even sensitive instrumentation often responds to the paramagnetic contribution of the silicate matrix in the residual field of the magnetometer. Analysis of magnetic extracts is usually performed to solve the problems raised by low magnetic concentrations. Additionally magnetic extracts can be used for several other analyses, for example electron microscopy or X-ray diffraction. The magnetic extraction technique is generally sufficient for sediments dominated by magnetite. In this study however, we show that high-coercivity components are rather underrepresented in magnetic extracts of sediments with a more complex magnetic mineralogy. We test heavy liquid separation, using hydrophilic sodium polytungstenate solution Na6 [H2 W12 O40 ], to demonstrate the efficiencies of both concentration techniques. Low-temperature cycling of zero-field-cooled, field-cooled and saturation isothermal remanent magnetization acquired at room temperature was performed on dry bulk sediments, magnetic extracts, and heavy liquid separates of clay-rich pelagic sediments originating from the Equatorial Atlantic. The results of the thermomagnetic measurements clarify that magnetic extraction favours components with high spontaneous magnetization, such as magnetite and titanomagnetite. The heavy liquid separation is unbiased with respect to high- and low-coercive minerals, thus it represents the entire magnetic assemblage. 相似文献
296.
297.
Y.-H. Sung C. L. Ciobanu A. Pring J. Brügger W. Skinner N. J. Cook M. Nugus 《Mineralogy and Petrology》2007,90(3-4):249-270
Summary The Cu–Fe–Au–Mo (W) deposits in southeastern Hubei are an important component of the Middle–Lower Yangtze River metallogenic
belt. Molybdenite from the Fengshandong Cu- (Mo), Ruanjiawan W–Cu- (Mo), Qianjiawan Cu–Au, Tongshankou Cu–Mo and Tonglüshan
Cu- (Fe) deposits yielded Re–Os ages of 144.0 ± 2.1 Ma, 143.6 ± 1.7 Ma, 137.7 ± 1.7 Ma, 142.3 ± 1.8–143.7 ± 1.8 Ma and 137.8
± 1.7–138.1 ± 1.8 Ma, respectively. Phlogopite from the Tieshan Fe- (Cu) deposit yielded an Ar–Ar age of 140.9 ± 1.2 Ma. These
data and other published isotopic ages (Re–Os molybdenite and Ar–Ar mica ages) for the Cu–Fe–Au–Mo (W) deposits in the Middle–Lower
Yangtze River metallogenic belt show that Cu–Fe–Au–Mo (W) mineralisation in the Tongling, Anqing, Jiurui and Edong ore districts
developed in a narrow time span between 135.5 and 144.9 Ma, reflecting an important regional metallogenic event. An integrated
study of available petrological and geochronological data, together with relationships to magmatism and the regional geodynamic
framework, indicate that the Cu–Fe–Au–Mo (W) mineralisation in the Middle–Lower Yangtze River belt occurred during a regime
of lithospheric extension. This extension is probably related to Late Mesozoic processes of lower crustal delamination and
lithospheric thinning in East China. 相似文献
298.
Siegfried Siegesmund Akos Török Andre Hüpers Christian Müller Werner Klemm 《Environmental Geology》2007,52(2):385-397
High levels of SO2 and particulate pollution enable the rapid development of gypsum-rich weathering crusts in Budapest. Two types of white crusts,
thin and thick ones, and two forms of black crusts, laminar and framboidal ones, were studied in limestone buildings of the
parliament and Citadella. The percentage of crust cover and damage categories were documented on selected walls. Petrographic,
XRD, XRF and sulphur isotope analyses were performed under laboratory conditions to understand the mechanism of crust formation.
White crusts found both on exposed and sheltered walls display a calcite-rich layer with gypsum, while black crusts are enriched
with gypsum. The sulphur isotopic composition of white and black crusts overlaps, but the crusts are slightly enriched in
heavy isotopes compared to rainwater. S content, Si/Al ratios and particulates in black crusts suggest that air pollution
(SO2, dust) contributes to black crust formation. The accumulation of sulphur and Zn enrichment of white crusts were also documented
indicating that under high pollution levels, even these compound can accumulate on exposed facades. 相似文献
299.
300.