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741.
A new numerical model for simulating estuarine dynamics is introduced here. This model, called General Estuarine Transport Model (GETM), has been specifically designed for reproducing baroclinic, bathymetry-guided flows where the tidal range may exceed the mean water depth in large parts of the domain such that drying and flooding processes are relevant. Several physical and numerical features of the model support exact and stable results for such domains. For the physics, high-order turbulence closure schemes guarantee proper reproduction of vertical exchange processes. Among the specific numerical features, generalised vertical coordinates, orthogonal curvilinear horizontal coordinates, high-order TVD advection schemes and stable drying and flooding algorithms have been implemented into GETM. The model is applied here to simulate the dynamics of estuarine turbidity maxima (ETMs), a complex feature present in most tidal estuaries. First, idealised simulations for a two-dimensional domain in the xz space will be shown to reproduce the basic generation mechanisms for ETMs. Then, a realistic three-dimensional simulation of the Elbe estuary in Northern Germany will be carried out. It is demonstrated that for a given forcing situation the model reproduces a stable ETM at the correct location.Responsible Editor: Phil Dyke 相似文献
742.
R. Gil Hutton 《Earth, Moon, and Planets》1995,71(3):207-210
Using a Super-Schmidt camera installed at the Cesco Observatory we are developing a program conducted to detect asteroids (especially members of the Aten Group) and comets approaching the Earth. The search strategy is based on simulations of the population of objects in this kind of orbits. 相似文献
743.
Manuel Falconi Ernesto A. Lacomba Jaume Llibre 《Celestial Mechanics and Dynamical Astronomy》2000,77(4):325-326
Volume Contents
Volume contents 相似文献744.
Michel Durand-Delga Silvia Gardin Manuel Esteras Hélène Paquet 《Comptes Rendus Geoscience》2005,337(8):787-798
The Lias–Dogger successions of the Tariquide units in the Gibraltar Arc differ from the series of tectonically adjacent units, the Penibetic (Iberia margin) and the Limestone ‘Dorsale’ (Alboran Domain). Lower Lias limestones are eroded and covered by the Domerian, which starts by deposits of open sea, continuous up to the Dogger (J. Musa-type successions), and elsewhere (Los Pastores-type successions) by a thin series (Upper Lias to Upper Dogger), starting by a manganesiferous episode (Ras Leona) and including marls deposited into three episodes, dated by calcareous nannofossils. Faulting events occurred before the Domerian and during the Late Toarcian (Los Pastores). To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005). 相似文献
745.
Manuel A. Aguilar Fernando J. Aguilar Francisco Agüera 《The Photogrammetric Record》2005,20(112):335-350
Generating maps of small areas using conventional aerial photography is of great interest for small engineering firms. The main problem is the high cost of the sophisticated digital photogrammetric workstations usually employed. In this paper, a low-cost close range photogrammetric software package is used to measure the three-dimensional coordinates of points on the land surface from a photogrammetric flight at a scale of approximately 1:5000. Furthermore, the influence of the type of scanner used to digitise photographs (consumer-grade or photogrammetric scanner), the resolution of the digital images and the number of control points required are examined. The root mean square errors obtained at the check points, using a low-cost close range software package, scanning aerial images with a photogrammetric scanner and 24 ground control points, were around 116 mm for X and Y coordinates, and 191 mm for Z. These levels of accuracy allow the generation of planimetric maps at a scale of 1:1500 and topographic maps with a contour interval of around 1 m. When the images were scanned with a consumer-grade scanner, the root mean square errors were around 150 mm for X and Y, and 271 mm for Z. 相似文献
746.
747.
Paula Galego Fernandes Paula Carreira Manuel Oliveira da Silva 《Mathematical Geology》2006,38(6):765-780
The Sines coastal sedimentary basin, a tectonic trough with a NE-SW orientation filled with Mesozoic and Cenozoic deposits,
has two hydrogeological systems: the Mio-Pliocene and the Jurassic. Both systems are supplying water to the entire region
with highly populated and industrialized areas. The aquifers are recharged in the outcrop areas, although the Jurassic aquifer
also receives some contribution from the overlying Miocene rocks. The main groundwater flow direction in the Jurassic aquifer
is E to W towards the Atlantic Ocean.
In order to understand the influence of anthropogenic activities on the water quality, a statistical principal components
analysis (PCA) was performed on the physical–chemical data from groundwater samples in both aquifers. Four components were
obtained in the Jurassic and three in the Miocene. The principal components analyses indicate water–rock interactions as the
major mechanism responsible for the groundwater solutes (mainly calcium-bicarbonate type), from the calcareous and dolomitic
units. Anthropogenic contamination was identified in the influence of the water compositions, corresponding to local polluting
inputs. These were magnesium, sulfate, nitrate, iron and copper for PC 3 in the Jurassic and sodium, chloride, nitrate and
manganese for PC 2 in the Miocene. These account for about 13% of the system total variance in the Jurassic aquifer and near
23% in the Miocene one. 相似文献
748.
Stephanos P. Kilias Manuel Pozo Manuel Bustillo Michael G. Stamatakis José P. Calvo 《Mineralium Deposita》2006,41(7):713-733
The Rubian magnesite deposit (West Asturian—Leonese Zone, Iberian Variscan belt) is hosted by a 100-m-thick folded and metamorphosed Lower Cambrian carbonate/siliciclastic metasedimentary sequence—the Cándana Limestone Formation. It comprises upper (20-m thickness) and lower (17-m thickness) lens-shaped ore bodies separated by 55 m of slates and micaceous schists. The main (lower) magnesite ore body comprises a package of magnesite beds with dolomite-rich intercalations, sandwiched between slates and micaceous schists. In the upper ore body, the magnesite beds are thinner (centimetre scale mainly) and occur between slate beds. Mafic dolerite dykes intrude the mineralisation. The mineralisation passes eastwards into sequence of bedded dolostone (Buxan) and laminated to banded calcitic marble (Mao). These show significant Variscan extensional shearing or fold-related deformation, whereas neither Rubian dolomite nor magnesite show evidence of tectonic disturbance. This suggests that the dolomitisation and magnesite formation postdate the main Variscan deformation. In addition, the morphology of magnesite crystals and primary fluid inclusions indicate that magnesite is a neoformed hydrothermal mineral. Magnesite contains irregularly distributed dolomite inclusions (<50 μm) and these are interpreted as relics of a metasomatically replaced dolostone precursor. The total rare earth element (REE) contents of magnesite are very similar to those of Buxan dolostone but are depleted in light rare earth elements (LREE); heavy rare earth element concentrations are comparable. However, magnesite REE chondrite normalised profiles lack any characteristic anomaly indicative of marine environment. Compared with Mao calcite, magnesite is distinct in terms of both REE concentrations and patterns. Fluid inclusion studies show that the mineralising fluids were MgCl2–NaCl–CaCl2–H2O aqueous brines exhibiting highly variable salinities (3.3 to 29.5 wt.% salts). This may be the result of a combination of fluid mixing, migration of pulses of variable-salinity brines and/or local dissolution and replacement processes of the host dolostone. Fluid inclusion data and comparison with other N Iberian dolostone-hosted metasomatic deposits suggest that Rubian magnesite probably formed at temperatures between 160 and 200°C. This corresponds, at hydrostatic pressure (500 bar), to a depth of formation of ~~5 km. Mineralisation-related Rubian dolomite yields δ
18O values (δ
18O: 12.0–15.4‰, mean: 14.4±1.1‰) depleted by around 5‰ compared with barren Buxan dolomite (δ
18O: 17.1–20.2‰, mean: 19.4±1.0‰). This was interpreted to reflect an influx of 18O-depleted waters accompanied by a temperature increase in a fluid-dominated system. Overlapping calculated δ
18Ofluid values (~+5‰ at 200°C) for fluids in equilibrium with Rubian dolomite and magnesite show that they were formed by the same hydrothermal system at different temperatures. In terms of δ
13C values, Rubian dolomite (δ
13C: −1.4 to 1.9‰, mean: 0.4±1.3‰) and magnesite (δ
13C: −2.3 to 2.4‰, mean: 0.60±1.0‰) generally exhibit more negative δ
13C values compared with Buxan dolomite (δ
13C: −0.2 to 1.9‰, mean: 0.8±0.6‰) and Mao calcite (δ
13C: −0.3 to 1.5‰, mean: 0.6±0.6‰), indicating progressive modification to lower δ
13C values through interaction with hydrothermal fluids. 87Sr/86Sr ratios, calculated at 290 Ma, vary from 0.70849 to 0.70976 for the Mao calcite and from 0.70538 to 0.70880 for the Buxan dolostone. The 87Sr/86Sr ratios in Rubian magnesite are more radiogenic and range from 0.71123 to 0.71494. The combined δ
18O–δ
13C and 87Sr/86Sr data indicate that the magnesite-related fluids were modified basinal brines that have reacted and equilibrated with intercalated siliciclastic rocks. Magnesite formation is genetically linked to regional hydrothermal dolomitisation associated with lithospheric delamination, late-Variscan high heat flow and extensional tectonics in the NW Iberian Belt. A comparison with genetic models for the Puebla de Lillo talc deposits suggests that the formation of hydrothermal replacive magnesite at Rubian resulted from a metasomatic column with magnesite forming at higher fluid/rock ratios than dolomite. In this study, magnesite generation took place via the local reaction of hydrothermal dolostone with the same hydrothermal fluids in very high permeability zones at high fluid/rock ratios (e.g. faults). It was also possibly aided by additional heat from intrusive dykes or sub-cropping igneous bodies. This would locally raise isotherms enabling a transition from the dolomite stability field to that of magnesite.Editorial handling: F. Tornos 相似文献
749.
Dominique Similox-Tohon Manuel Sintubin Philippe Muchez Griet Verhaert Kris Vanneste Max Fernandez Sara Vandycke Hannelore Vanhaverbeke Marc Waelkens 《Tectonophysics》2006,420(3-4):371-387
The archaeological site of Sagalassos (SW Turkey) is located in a region characterized by the absence of any significant recent seismic activity, contrary to adjacent regions. However, the assessment of earthquake-related damage at the site suggests that the earthquakes that have been demonstrated to have struck this Pisidian city in ca. AD 500 and in the middle or second half of the 7th century AD are characterized by an MSK intensity of at least VIII and occurred on a fault very close to the city. Different investigation techniques (archaeoseismology, remote sensing and geomorphology, surface geology and structural data, 2D resistivity imaging and palaeoseismological trenching) have been applied at the archaeological site and its direct surroundings in search for the causative fault of these earthquakes. This multidisciplinary approach shows that each of the different approaches independently provides only partial, non-conclusive information with respect to the fault identification. Integration is imperative to give a conclusive answer in the search for the causative fault. This study has, indeed, revealed the existence of a to date unknown active normal fault system passing underneath ancient Sagalassos, i.e. the Sagalassos fault. A historical coseismic surface rupture event on this fault could be identified. This event possibly corresponds to the devastating Sagalassos earthquakes of ca. AD 500 and the middle or second half of the 7th century AD. Finally, this study demonstrates that in the particular geodynamic setting of SW Turkey archaeological sites with extensive earthquake-related damage form an important tool in any attempt to asses the seismic hazard. 相似文献
750.
Robert W Risebrough Brock W De Lappe Wayman Walker Bernd R.T Simoneit Joan Grimalt Joan Albaiges Jose Antonio Garcia Regueiro Antoni Ballester Inolla Manuel Mariño Fernandez 《Marine pollution bulletin》1983,14(5):181-187
The Mussel Watch concept was applied in a study of man-induced chemical changes in the Ebro Delta on the Catalonian coast to obtain a preliminary assessment of the distribution of synthetic organic compounds, petroleum and biogenic hydrocarbons in the local coastal zone. Mussels, oysters and clams were selected as the indicator organisms. Levels of petroleum accumulated by mussels were generally high, in the order of 100–800 μg?1 dry weight, equivalent to those in mussels in the most polluted harbours and bays of California. The relative distributions of the steranes and pentacyclic triterpanes in the mussels were significantly different from those found in petroleum from a local field, indicating that local petroleum was not contributing to the present contamination. The composition of biogenic compounds was variable, probably reflecting differences in the composition of local plankton communities, PCB levels were high in relation to current levels in mussels from US sites, reflecting continuing PCB use in Spain. The Delta appears to be a point source of a number of organochlorine compounds, including HCB, the DDT compounds, endrin and γ-chlordane. Levels of the DDT compound o,p′-DDD, a pharmacologically active substance, were unexpectedly high; identification was confirmed by GS/MS. Many unidentified peaks were present on EC chromatograms, indicating a more complex pattern of contamination than might be suggested by printed summaries of data. 相似文献