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451.
Influence of lithostratigraphy on the retreat of an unconsolidated sedimentary coastal cliff (St. Lawrence estuary,eastern Canada) 下载免费PDF全文
Gabriel Joyal Patrick Lajeunesse Antoine Morissette Pascal Bernatchez 《地球表面变化过程与地形》2016,41(8):1055-1072
This paper investigates the processes involved in unconsolidated cliff recession using LiDAR surveys (2005, 2010 and 2013) and aerial photographs (1964–2012) at Pointe‐au‐Bouleau, on the north shore of the St. Lawrence estuary, in eastern Canada. The high lithostratigraphic variability of the sediments allowed for the identification of stratigraphic and lithological variables that explain the evolution of coastal cliffs. Space‐for‐time substitution was also used to assess how lithostratigraphy controls the evolution of emerged glaciomarine coastal cliffs over decadal to centennial timescales. This case study presents new quantitative data that contributes to a better understanding of the role of sediment architecture, stratigraphy and geomorphology on coastal evolution. The methodological approach includes the development of a new conceptual model suitable for identifying erosion on cliff coastlines. The high spatial resolution methodology (<5 cm) used herein demonstrates the need for further research using LiDAR data in order to quantify the processes involved in the evolution of coastal cliffs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
452.
We propose an analytical method, namely the SORTAN method, to determine the sense of slip on faults as induced by stresses. This method is useful to infer the sense of motion along faults whose surface cannot be directly accessed, such as faults imaged in the subsurface. Because the SORTAN method is based on the Wallace–Bott hypothesis, we assume that the shear stress vector applied to a given fault is parallel to the slip vector on this fault. The assumptions allow for simplification of the method that in turn implies very short calculation times. A concise formalism is adopted. We introduce the stress ratio ' that accounts for (1) the type of stress regime (i.e., strike-slip, reverse or normal) and (2) the degree of anisotropy of the stress state. The formalism of the SORTAN method permits an easy exploration and imaging of the complete collection of slip motions that may theoretically occur on fault planes. The input parameters are the fault plane orientation, the type and anisotropy of the stress regime, and the azimuth of the horizontal stress axes. 相似文献
453.
Jean-Marie Auzende Mathilde Cannat Pascal Gente Jean-Pierre Henriet Thierry Juteau Jeffrey Karson Yves Lagabrielle Catherine Mével Maurice Tivey 《地学学报》1994,6(2):143-148
The objective of the 20 Nautile dives of the recent Kanaut cruise was to study the southern wall of the Kane Fracture Zone from its eastern intersection with the Mid-Atlantic Ridge (MAR) to 5 Myr in age. The geological mapping shows four successive massifs, wrench faulted and slightly tilted. The transform-facing walls of these massifs exhibit outcrops of fresh and serpentinized peridotites, gabbros and basalts. The entire crustal exposure is cataclased and metamorphosed to greenschist facies. 相似文献
454.
We present a new method to solve the problem of initial orbit determination of any binary system. This method is mainly based
on the material available for an observer, for example relative positions at a given time of the couple in the “plane of sky”,
namely the tangent plane to the celestial sphere at the position of the primary component. The problem of orbit determination
is solved by splitting in successive stages in order to decorrelate the parameters of each other as much as possible. On one
hand, the geometric problem is solved using the first Kepler’s law from a single observing run and, on the other hand, dynamical
parameters are then inferred from the fit of the Kepler’s equation. At last, the final stage consists in determining the main
physical parameters involved in the secular evolution of the system, that is the spin axis and the J2 parameter of the primary if we assume that it is a quasi-spherical body. As a matter of fact there is no need to make too
restrictive initial assumptions (such as circular orbit or zero eccentricity) and initial guesses of parameters required by
a non-linear least-squares Levenberg–Marquardt algorithm are finally obtained after each stage. Such a protocol is very useful
to study systems like binary asteroids for which all of the parameters should be considered a priori as unknowns. As an example of application, we used our method to estimate the set of the Pluto–Charon system parameters from
observations collected in the literature since 1980. 相似文献
455.
456.
Enhancement of regional variations in salinity and temperature in a coral reef lagoon, New Caledonia
Sylvain Ouillon Pascal Douillet Renaud Fichez Jean-Yves Panch 《Comptes Rendus Geoscience》2005,337(16):231
The variability in salinity and temperature in the southwest lagoon of New Caledonia (2100 km2) under non-storm conditions is analysed using a 4-year dataset (1997–2001). Seasonal and interannual variations in salinity are amplified nearshore. Temperature is larger in bays than in the open lagoon during summer, the reverse is true in winter. El Niño Southern Oscillation (ENSO) related nearshore temperature variations parallel those at regional scale, but with seasonal variations amplified. Haline stratification, if any, is enhanced in coastal areas. To cite this article: S. Ouillon et al., C. R. Geoscience 337 (2005). 相似文献
457.
458.
Michel L. Schlegel Pascal Reiller Nicole Barré Valérie Moulin 《Geochimica et cosmochimica acta》2006,70(22):5536-5551
The molecular environment of iodine in reference inorganic and organic compounds, and in dry humic and fulvic acids (HAs and FAs) extracted from subsurface and deep aquifers was probed by iodine L3-edge X-ray absorption spectroscopy. The X-ray absorption near-edge structure (XANES) of iodine spectra from HAs and FAs resembled those of organic references and displayed structural features consistent with iodine forming covalent bonds with organic molecules. Simulation of XANES spectra by linear combination of reference spectra suggested the predominance of iodine forming covalent bonds to aromatic rings (aromatic-bound iodine). Comparison of extended X-ray absorption fine structure (EXAFS) spectra of reference and samples further showed that iodine was surrounded by carbon shells at distances comparables to those for references containing aromatic-bound iodine. Quantitative analysis of EXAFS spectra indicated that iodine was bound to about one carbon at a distance d (I-C) of 2.01(4)-2.04(9) Å, which was comparable to the distances observed for aromatic-bound iodine in references (1.99(1)-2.07(6) Å), and significantly shorter than that observed for aliphatic-bound iodine (2.15(2)-2.16(2) Å). These results are in agreement with previous conclusions from X-ray photoelectron spectroscopy and from electrospray ionization mass spectrometry. These results collectively suggest that the aromatic-bound iodine is stable in the various aquifers of this study. 相似文献
459.
The effect of the small fraction of clays on the rheological behaviour of alpine debris flow is poorly understood. This is partly due to the complexity of the debris flow mineralogy and the broad particle size distribution. This study has investigated this issue by simulating an alpine debris flow with a mixture of well characterized fractions and then varying the clay fraction composition. Four samples were tested, ranging from a clay fraction made up of only kaolinite (1:1 type clay) to samples where 80 per cent of the kaolinite is replaced by bedeillite (a 2:1 type clay similar to smectite). Changing the content of 2:1 type clay has a strong influence on the behaviour of the whole material, despite its low weight fraction of around 2 per cent. The tests carried out on these reconstituted materials were compared with the results obtained for natural debris flow materials and showed some common trends: in particular, the rheological parameters for materials with and without 2:1 clays with respect to yield stress as a function of solid content. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
460.
A drop calorimetric study, between 900 and 1800 K, of amorphous SiO2, NaAlSi3O8, NaAlSi2O6, NaAlSiO4 and KAlSi3O8 shows the increase in heat capacity which results from glass transitions. For these glasses, the fictive temperature has a negligible effect on the heat capacity above room temperature, but it has an important influence on the enthalpy of formation as obtained from solution calorimetry. From these results and published Cp and enthalpy of solution data, several properties have been calculated: the enthalpies of fusion of high albite, nepheline, Jadeite and high sanidine, the thermodynamic functions of amorphous NaAlSi3O8 and KAlSi3O8 between 0 and 2000 K, and some mixing properties of liquids along the join SiO2-NaAlSi3O8. The latter data suggest that these liquids behave more closely as athermal solutions than as regular solutions. 相似文献