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121.
Mirosław Jastrzębski 《International Journal of Earth Sciences》2009,98(8):1901-1923
Structural, petrological and geochronological data from marbles and mica schists combined with those from highly disputable
gneisses and eclogites of the Orlica-Śnieżnik Dome (OSD), gave new insights into Variscan evolution of eastern borderland
of the West Sudetes. It is shown that the Variscan tectonometamorphic evolution of the OSD began with E–W oriented subhorizontal
shortening (D1 stage) related to the collision of the West Sudetes terranes and the Brunovistulian terrane. The shortening
led to generally upright folding, which resulted in formation of the steep N–S trending metamorphic planar fabric S1, thickening
of the lithosphere and burial of the Stronie Formation under greenschist facies conditions. As a consequence of subsequent,
near-coaxial gravity-controlled vertical shortening (D2), the S1 foliation was deformed in tight recumbent folds F2. The flattening
strain was associated with the progression to amphibolite-facies conditions (from ca. 510 upto ca. 620°C) and uplift from
depths corresponding to 9–10 kbar to depths corresponding to 7–8 kbar. On microscale, the flattening strain is documented
by rotation of the mineral fabric overgrown by syn-D2 prograde garnet porphyroblasts. The Sm–Nd Grt–WR isochron age, correlated with the D2 event yields 346.5 ± 4.4 Ma. Further
deformation and progressive metamorphism led to development of the subhorizontally disposed S2 axial plane schistosity, which
terminated at the metamorphic temperature peak. During retrogression but still under ductile conditions of deformation, the
S2 planes were reactivated during successive top-to-the-N shear movement of the OSD (D3 stage). Due to the mutual interaction
of the OSD with the adjacent terranes the shear deformations were localized within marginal parts of these units. Finally,
as a result of the NE–SW and the NW–SE oriented shortenings (D4 stage and D5 stage, respectively), both the structural surfaces
and metamorphic isograds were regionally folded with W(NW)-ward plunges. A synthesis of new and existing data shows an overall
similarity in sequence of Variscan deformations (D1–D2–D3) in the West Sudetes borderland to that observed in the eastern
flank of the Moldanubian domain. 相似文献
122.
First-arrival traveltime tomography was applied to high-resolution seismic data acquired over a known quick-clay landslide scar near the Göta River in southwest Sweden in order to reveal the geometry and physical properties of clay-related normally consolidated sediments. Investigated area proved to be a challenging environment for tomographic imaging because of large P-wave velocity variations, ranging from 500 to 6000 m/s, and relatively steeply-dipping bedrock. Despite these challenges, P-wave velocity models were obtained down to ca. 150 m for two key 2D seismic profiles (each about 500-m long) intersecting over the landslide scar. The models portrait the sandwich-like structure of marine clays and coarse-grained consolidated sediments, but the estimated resolution (20 m) is too small to distinguish thin layers within this structure. Modelled velocity structures match well the results of reflection seismic processing and resistivity tomography available along the same profiles. 相似文献
123.
Michał Malinowski 《Acta Geophysica》2013,61(6):1437-1456
Controlled-source seismology (CSS) is the primary source of information regarding the fine structure of the lithosphere. The aim of this paper is to provide an overview of the methods that are commonly used to derive Earth models from CSS data with the focus on the wide-angle reflection/refraction method. Some outlook on the future of the CSS is presented with the special emphasis on the full-wavefield based methods like full-waveform inversion, which brings high level of objectivity into modeling, as well as significantly increases spatial resolution. It is stressed that the researchers should be aware of the limitations of how the elastic parameters transcribe into the actual rock properties which should stimulate them to go beyond the simple P-wave modeling and to build multiparameter Earth models based either on the seismic data or constrained by additional geophysical fields in order to derive sound geological interpretation of their models. 相似文献
124.
Journal of Atmospheric Chemistry - In this study, the aerosol removal coefficients based on 7Be, 210Pb and 210Po radionuclides in the urban air, in Lodz, Poland, were investigated over 3 years,... 相似文献
125.
Boundary-Layer Meteorology - The Obukhov length, although often adopted as a characteristic scale of the atmospheric boundary layer, has been introduced purely based on a dimensional argument... 相似文献
126.
The environmental conditions of the Szczecin Bay, which existed prior to Szczecin Lagoon, have been reconstructed on the basis of the stable carbon and oxygen isotope (18O and 13C) analysis and radiocarbon dates obtained for subfossil shells of Cerastoderma (Cardium) glaucum. The shells in the collected core were well preserved in their life positions, representing a geochemical record of past temperature variation over the middle Holocene. Three major periods with different thermal conditions have been distinguished in the interval ~ 6000–4300 cal yr BP, when the important Littorina regional transgression took place. During the first period, 6000–5250 cal yr BP, water temperature decreased by 1.4°C, and then remained constant over the second period (5250–4750 cal yr BP). In contrast, during the third period (4750–4300 cal yr BP) both δ-values were highly variable and the mean summer temperature (March–November) increased by about 3.5°C. During first two periods, δ18O and δ13C were significantly correlated, indicating stability of the environmental conditions. 相似文献
127.
Empirical frequency distributions of multiplicative cascade weights, or breakdown coefficients, at small timescales are analyzed
for 5-min precipitation time series from four gauges in Germany. It is shown that histograms of the weights, W, are strongly deformed by the recording precision of rainfall amounts. A randomization procedure is proposed to statistically
remove the artifacts due to precision errors in the original series. Evolution of the probability distributions of W from beta-like for large timescales to combined beta-normal distribution with a pronounced peak at W ≈ 0.5 for small timescales is observed. A new 3N-B distribution built from 3 separate normal, N, distributions and one beta,
B, distribution is proposed for reproduction of the empirical histograms of W at small timescales. Parameters of the 3N-B distributions are fitted for all gauges and analyzed timescales. Microcanonical
cascades models with a generator based on 3N-B distributions are developed and their performance at disaggregating precipitation
at 1280-min intervals down to 5-min intervals is evaluated. 相似文献
128.
Ryszard Kryza Jolanta Muszer Joanna Haydukiewicz Czesław August Marta Jurasik Nickolay Rodionov 《International Journal of Earth Sciences》2011,100(6):1227-1235
A Lower Carboniferous platform sedimentary sequence (the Paprotnia Beds) in the Bardo Unit of the central Sudetes (NE part
of the Bohemian Massif, SW Poland) is biostratigraphically well dated, based on rich macro- and micro-fossil evidence, as
Late Viséan (late Asbian, crenistria, Go III α zone). The beds contain several bentonite layers, one of which was dated using the U–Pb SHRIMP method on volcanic
zircons and yielded an age of 334 ± 3 Ma. This date fits well to the recently established chronostratigraphic limits of the
Viséan, and is consistent with the newest isotopic age constraints of 336.5–332 Ma for the Asbian boundaries. 相似文献
129.
Suzanne?E.?HollinsEmail author Jennifer?J.?Harrison Brian?G.?Jones Atun?Zawadzki Henk?Heijnis Stuart?Hankin 《Journal of Paleolimnology》2011,46(4):579-596
In this study, we combined grain size and geochemical analyses with radioisotope analysis of lead-210 (210Pb), caesium-137 (137Cs) and radiocarbon (14C) ages to reconstruct the sedimentation history of two urbanised coastal lagoons in south-east Australia. Towradgi and Fairy
Lagoons were both found to exhibit slow initial sedimentation of less than 1 mm year−1 prior to anthropogenic influences. Land clearing in the catchments increased runoff and erosion in the creeks feeding into
the estuaries, and has resulted in progradation of fluvial material into the estuarine systems with a marked increase in sedimentation
to between 2 and 7 mm year−1. The upper 20–50 cm of the sediment column in both lagoons contained elevated concentrations of heavy metals such as Pb,
Cu, Ni and Zn. This pollution trend was found to be consistent with the history of industrialisation and urbanisation in the
region, which expanded rapidly post World War 2. The total metal concentrations were consistent with other urbanised/industrialised
estuaries around the world. Despite the fairly disturbed nature of these coastal lagoons, the use of 210Pb, 137Cs and 14C dating in combination with bulk geochemical analyses allowed detailed reconstruction of sedimentation history. 相似文献
130.
Emily?LeydenEmail author John?Tibby Adriana?García Atun?Zawadzki 《Journal of Paleolimnology》2011,46(4):637-647
Bombah Broadwater is a shallow coastal lake within the Ramsar-listed Myall Lakes system on the mid-north coast of New South
Wales, Australia. Increased nutrient and sediment loads resulting from catchment modification are thought to have instigated
the loss of aquatic plants in the lake, causing it to “switch” from a clear, macrophyte dominated system (similar to the conditions
in present day Myall Lake) to a turbid, phytoplankton dominated system. To assess this hypothesis, charophytes, foraminifera
and aquatic fauna remains from an 800 year sediment record were examined. The sediment chronology was established using 14C, 210Pb and 137Cs radiometric dating and sediment composition. Interestingly, a clear increase in charophytes since European arrival conflicted
with the hypothesised aquatic plant loss. Hence, it appears Bombah Broadwater has not undergone a change in stable state since
European arrival. An additional and unexpected finding in the patterns of the foraminifera and testate amoeba suggest that
Bombah Broadwater has freshened substantially since European arrival. This freshening may have resulted from increased catchment
run off as a result of the clearance of catchment vegetation. Since catchment vegetation clearance is widespread in Australia,
this finding raises the possibility that post-settlement freshening of coastal lakes may be a common occurrence. 相似文献