Numerical simulation and validation of ocean waves measured by an Along-Track Interferometric Synthetic Aperture Radar   总被引：1，自引：0，他引：1  

张彪  何宜军 《中国海洋湖沼学报》2008,26(1):1-8

A new nonlinear integral transform of ocean wave spectra into Along-Track Interferometric Synthetic Aperture Radar （ATI-SAR） image spectra is described. ATI-SAR phase image spectra are calculated for various sea states and radar configurations based on the nonlinear integral transform. The numerical simulations show that the slant range to velocity ratio （R/V）, significant wave height to ocean wavelength ratio （Hi2）, the baseline （2B） and incident angle （0） affect ATI-SAR imaging. The ATI-SAR imaging theory is validated by means of Two X-band, HH-polarized ATI-SAR phase images of ocean waves and eight C-band, HH-polarized ATI-SAR phase image spectra of ocean waves. It is shown that ATI-SAR phase image spectra are in agreement with those calculated by forward mapping in situ directional wave spectra collected simultaneously with available ATI-SAR observations. ATI-SAR spectral correlation coefficients between observed and simulated are greater than 0.6 and are not sensitive to the degree of nonlinearity. However, the ATI-SARoPhase image spectral turns towards the range direction, even if the real ocean wave direction is 30. It is also shown that the ATI-SAR imaging mechanism is significantly affected by the degree of velocity bunching nonlinearity, especially for high values of R/V and H/2.  相似文献   

Pre‐Holocene age of Humboldt's 1430 eruption of the Orotava Valley,Tenerife, Canary Islands     

J.C. Carracedo  B. Singer  B. Jicha  F.J. Pérez Torrado  H. Guillou  E.R. Badiola  R. Paris 《Geology Today》2010,26(3):101-104

Errors in the interpretation of clouds, fumarolic activity and forest fires as volcanic eruptions in Tenerife, mainly in relation with Teide volcano, are common in references by passing navigators and other eyewitness accounts from the fifteenth and sixteenth centuries. In the case of the most common, historical, multiple‐vent fissure eruptions in the Canaries, vent locations provided by these accounts are frequently uncertain or are clearly erroneous and often conflict with geological evidence. Significant examples are the general association of the latest eruption of Teide volcano, dated at 1150 ± 140 bp , with the reference made by Christopher Columbus in 1492 to an eruption ‘on the flanks of Teide’, which actually corresponds to an eruptive vent (Boca Cangrejo volcano) situated in the NW Rift, dated at 400 ± 110 bp . Similar conflicting vent locations occurred in the 1730–36 eruption of Lanzarote and the 1677 eruption of La Palma. This article considers the volcanic cones located in the Orotava Valley, erroneously assigned by Chevalier de Borda and Alexander von Humboldt to a 1430 ad eruption. Geological evidence and radiocarbon dating of charcoal underlying the lapilli, and ⁴⁰Ar/³⁹Ar dating of one of the lava flows, show that these volcanic cones and lavas correspond to an eruption that took place about 30 000 yr bp . Analysis of the influence of these erroneous ages for the recent volcanism of Tenerife shows an overestimation of eruptive hazards of this island.  相似文献   

Iron environment in a montmorillonite from Gola del Furlo (Marche,Italy). A synchrotron radiation XANES and a Mössbauer study   总被引：1，自引：0，他引：1  

E. Paris  A. Mottana  P. Mattias 《Mineralogy and Petrology》1991,45(2):105-117

Summary The iron environment and oxidation state has been determined by XANES spectroscopy in a montmorillonite sample from Gola del Furlo (Marche, Italy). A comparison with the XANES spectra of Fe^2– in a natural hematite from Elba (Italy) and of Fe 21 in a synthetic Fe[C0₃] (the fine structures in the spectra of which have also been clarified in detail on the basis of the known crystal structures) permits recognizing that in this sheet silicate Fe is mostly in the trivalent oxidation state and in a distorted octahedral coordination. Mössbauer spectroscopy confirms the XANES assignment, but it also shows that minor octahedral Fee+ is present besides the predominant octahedral Fe^3—.

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Zusammenfassung Synchroton Radiation XANES und Mössbauer-Studien zur Vertielung des Eisens im Montmorillonit aus Gola del Furlo(Marche, Italien) Die Verteilung und die Oxidationsstufe des Eisens eines Montmorillonites aus Gola del Furlo (Marche, Italien) wurden untersucht. Ein Vergleich der XANES Spektren dieses Schichtsilikates mit denen von FeFe³⁺ eines natürlichen Hämatites von Elba (Italien) und von Fe²⁺ eines synthetischen Fe[C0₃], wobei die Details der Spektren auf Grund der Kenntnis der bekannten Kristallstruktur geklärt werden konnten, zeigt, daß Eisen großteils in dreiwertiger Form und in verzerrter oktaedrischer Koordination vorliegt. Mössbauer-Studien bestätigen die Ergebnisse der XANES Untersuchungen, zeigen aber auch, daß untergeordnet Fe e+ an Stelle von Fe³⁺ in der oktaedrischen Position eingebaut wird.

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大别山北部黄土岭片麻岩的锆石U-Pb年龄和氧同位素组成：古老的原岩和多阶段历史   总被引：6，自引：0，他引：6  

夏群科郑永飞  葛宁洁EtienneDELOULE 《岩石学报》2003,19(3):506-512

利用阴极发光和离子探针技术，对大别山北部黄土岭片麻岩的锆石进行了内部结构、U-Pb年龄和氧同位素组成的系统分析。黄土岭片麻岩的锆石具有核-幔-边三层结构，核部是原岩的岩浆锆石，形成时代为-2800Ma；幔部是变质重结晶的产物，变质作用的时代为-2000Ma；边部则是在-110Ma从部分熔融体里结晶出来的增生锆石，是受大别山燕山期构造-岩浆事件影响的反映。黄土岭片麻岩和麻粒岩中-2800Ma和-2000Ma的年龄，以及麻粒岩中约3400Ma的残留锆石年龄均可以与扬子崆岭群变质岩对比。由此可以推断，北大别在构造属性上属于扬子板决，扬子与华北板决的缝合线应在北大别以北。锆石的核-幔-边具有不同的氧同位素组成，氧同位素数据表明黄土岭片麻岩的原岩是S型花岗岩，在-2000Ma和-110Ma的事件中都有外来物质(流体或熔体)的加入。  相似文献   

Late Ordovician glaciation in southern Turkey   总被引：1，自引：0，他引：1  

O. Monod  H. Kozlu  J.-F. Ghienne  W. T. Dean  Y. Günay  A. Le Hérissé  F. Paris  & M. Robardet 《地学学报》2003,15(4):249-257

ABSTRACT We present a new survey of several Palaeozoic sections in both the Taurus range and the Border Folds that documents typical glacial features including a glacial pavement and striated dropstones (Halevikdere Formation) and demonstrates the former presence of an ice sheet in southern and south-eastern Turkey. Evidence for the late Ashgill (Hirnantian) age of this episode is provided by macro- and microfossils found within the glacial formation. The extension of ice-related deposits into the northernmost part of the Arabian Platform (Mardin region) implies a much wider distribution of the Ordovician ice sheet than was previously believed, and strongly suggests that southern Turkey lay close to Egypt during the Lower Palaeozoic.  相似文献   

Diagenetic controls on the isotopic composition of carbonate‐associated sulphate in the Permian Capitan Reef Complex,West Texas     

Theodore M. Present  Melissa Gutierrez  Guillaume Paris  Charles Kerans  John P. Grotzinger  Jess F. Adkins 《Sedimentology》2019,66(7):2605-2626

Late Palaeozoic‐age strata from the Capitan Reef in west Texas show facies‐dependent heterogeneity in the sulphur isotopic composition of carbonate‐associated sulphate, which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater. However, diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate‐associated sulphate. These processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest, outer shelf, shelf margin and slope depositional settings. This study used a new multicollector inductively‐coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures. Carbonate rocks representing peritidal facies in the Yates and Tansill formations preserve the sulphur isotopic composition of Guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes. However, sulphur isotopic data indicate that limestones deposited in reef and slope facies in the Capitan and Bell Canyon formations largely incorporate sulphate from anoxic marine‐phreatic pore fluids isotopically modified from seawater by microbial sulphate reduction, despite generally preserving the carbon and oxygen isotopic compositions of Permian seawater. Some early and all late meteoric calcite cements have carbonate‐associated sulphate with a sulphur isotopic composition distinct from that of Permian seawater. Detailed petrographic and sedimentary context for carbonate‐associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms. The results of this study indicate that carbonate rocks that diagenetically stabilize in high‐energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawater's sulphur isotopic composition.  相似文献   

X‐ray tomography of tsunami deposits: Towards a new depositional model of tsunami deposits          下载免费PDF全文

Simon Falvard  Raphaël Paris 《Sedimentology》2017,64(2):453-477

X‐ray computed microtomography is used to obtain high resolution imagery of a historical tsunami deposit in Andalusia, Spain (1755 Lisbon tsunami). The technique allows characterization of grain‐size distribution, structures, component analysis and sedimentary fabric of fine‐grained unconsolidated tsunami deposits at resolutions down to particle scale. The results are validated by comparing to data obtained using other techniques such as laser diffraction, anisotropy of magnetic susceptibility and X‐ray microfluorescence on the same deposits. Specific technical details such as sampling, scanning and image processing methods, and further improvements are addressed. The use of X‐ray computed microtomography provides new insights into the stratigraphy of the deposits and gives access to significantly more detailed view of key sedimentary features such as mudlines, rip‐up clasts, crude laminations, convolutions, floating outsized clasts and contacts between successive units. This analysis of the 1755 tsunami deposits using X‐ray computed microtomography allows the proposal of new hypotheses for the sedimentary processes forming tsunami deposits. Deposition by settling is limited and the section analysed here is dominated by a high shear stress leading to the development of traction carpets, with laminated mudlines corresponding to the basal frictional region of these carpets. The onset of the tsunami backwash is marked by a micro‐vortex resembling Kelvin–Helmoltz instabilities.  相似文献   

Revision of the age of magnetization of the Montmartin red beds, Normandy, France     

H. Perroud  M. Robardet  R. Van der  Voo N. Bonhommet  F. Paris 《Geophysical Journal International》1985,80(2):541-549

Summary. A new roadcut has enabled us to sample the south-dipping limb of the Montmartin syncline for a palaeomagnetic reevaluation of an earlier result published by Jones, Van der Voo & Bonhommet. In combination with the results previously published in 1979 for the north-dipping beds of the syncline, a conclusively negative fold test is obtained. The resulting magnetization (declination/inclination =206°/-3°, α₉₅= 12°, palaeopole at 38°S, 325°E) is interpreted to be of Late Carboniferous age, not Late Devonian as thought earlier. Simultaneously, we have re-evaluated the age of the rocks, previously thought to be Late Devonian on the basis of Acritarchs, Chitinozoans and spores. It has not been possible to reconfirm these fossils, not even in the same samples as studied originally; in contrast, the regional presence of Early Palaeozoic fossils suggests to us an age similar to that of other red beds in the Arrnorican Massif, which have been dated as Early Ordovician. The geodynamic implications of our finding that the Montmartin rocks are completely remagnetized, however, are of no great consequence for the geodynamics of the Hercynian belt. Pre-folding magnetization obtained from Silurian and Devonian rocks in Spain and Germany argue for the same conclusion as reached erroneously in our earlier study, namely that the Armorican Massif and adjacent parts of Hercynian Europe were adjointed to North America, Great Britain, the Baltic Shield and the Russian Platform since at least Late Devonian time. If a Medio-European ocean existed during the Palaeozoic, it was virtually closed before the mid-Devonian and of insignificant width during Culm deposition in Early Carboniferoirs time.  相似文献