Grain size characteristics of superficial sediments of the Gulf of Tunis (NE Tunisia)     

Hanen Saïdi  Radhia Souissi  Fouad Zargouni 《Arabian Journal of Geosciences》2014,7(8):3365-3387

This work presents a recent grain size study characterizing superficial sediments of the whole sectors of the Gulf of Tunis which extends from Sidi Ali El Mekki to Sidi Daoued. In this study, a total of 112 samples were collected from different depths following 26 profiles perpendicular to the shore and from rivers. The determination of the proportions of coarse and fine fractions and the interpretation of the grain size results lead to dividing the Gulf of Tunis into two principal coasts: (1) the western coast situated between Sidi Ali El Mekki and Borj Cédria, which is characterized by three sedimentary facies: (a) a sandy facies along the coastline, (b) a mixed facies between Ghar El Melh and Raoued, near the Medjerda River, and between La Goulette and Ezzahra, near the Miliane River, and (c) a muddy facies between Ghar El Melh and Kalâat El Andalous and covered by fine to very fine sands, and (2) the eastern coast, which is characterized by a sandy facies and covered by medium to coarse sands. The dominant N–E and N–W waves generate longshore currents that provide sediment transport following the directions N–S, from Sidi Ali El Mekki to Kalâat El Andalous; SE–NW, from Gammarth to Raoued; NE–SW, from Sidi Bou Saïd to La Goulette and from Sidi Daoued to Bir El Jadi; SE–NW, from Hammam-Plage to Ezzahra; and SW–NE, from Port aux Princes to Rtiba.  相似文献   

Photometric study and preliminary elements of the low-mass ratio W UMa system ASAS 021209+2708.3     

Francesco Acerbi  Carlo Barani  Massimiliano Martignoni 《中国天文和天体物理学报》2011,(7)

We present CCD B and V light curves,obtained in the year 2006,and a photometric solution of the low-mass ratio contact binary ASAS 021209+2708.3. With our data we were able to determine six new times of minimum light and refine the orbital period of the system to 0.3181963 days.The light curves are analyzed using the 2003 version of the Wilson-Devinney program and the analysis was performed with and without adding a spot on the surface of one star because the light curves appear to exhibit a typical O’Conne...  相似文献   

High resolution investigation of the 7 μm region of the ethane spectrum     

Carlo di Lauro  Franca Lattanzi  Linda R. Brown  Keeyoon Sung  Jean Vander Auwera  Arlan W. Mantz  Mary Ann H. Smith 《Planetary and Space Science》2012,60(1):93-101

Building upon previous studies, we re-investigated the ethane spectrum between 1330 and 1610 cm^?1 by combining unapodized spectra obtained at room temperature with a Bruker Fourier transform spectrometer (FTS) in Brussels and at 131 K with a Bruker FTS in Pasadena. The maximum optical path differences (MOPD) of the two datasets were 450 and 323.7 cm, corresponding to spectral resolutions of 0.0020 and 0.0028 cm^?1, respectively. Of the 15,000 lines observed, over 4592 transitions were assigned to the ν₆ (at 1379 cm^?1), ν₈ (at 1472 cm^?1), ν₄+ν₁₂ (at 1481 cm^?1) and 2ν₄+ν₉ (at 1388 cm^?1) bands, and another 1044 transitions were located for the ν₄+ν₈?ν₄ hot band (at 1472 cm^?1). Our new analysis included an improved implementation of the Hamiltonian calculation needed to interpret the complex spectral structures caused by numerous interactions affecting these four modes of vibration. From these results, we created the first line-by-line database containing the molecular parameters for over 20,000 ¹²C₂H₆ transitions at 7 μm.  相似文献   

Prospection géophysique pour la recherche d’eau souterraine dans le Nord-Ouest de la Tunisie     

Rihab Guellala  Malek Abidi  Néji Balti  Mohamed Hédi Inoubli 《水文科学杂志》2013,58(3):636-645

RÉSUMÉ

Des sondages électriques verticaux, des enregistrements diagraphiques et des données de forages sont utilisés pour identifier et caractériser les aquifères de la région de Bou Salem (Nord-Ouest de la Tunisie). Les données de résistivité apparente mesurées à chaque sondage électrique vertical pour les différentes distances AB sont interprétées unidimensionnellement. Les enregistrements diagraphiques ont permis la restitution précise des colonnes lithologiques des forages préexistants et par conséquent l’étalonnage des sondages électriques. L’analyse et l’interprétation des données révèlent que les alluvions quaternaires perméables se limitent aux zones proximales des oueds Kasseb et Bouhertma. Cette distribution est contrôlée par les mécanismes de sédimentation dans les plaines d’inondation et par la réactivation des accidents N–S en failles normales durant le Quaternaire récent. Il ressort aussi que les calcaires éocènes et crétacés correspondant au substratum des alluvions quaternaires et caractérisés par des fortes résistivités peuvent constituer d’intéressants aquifères.  相似文献   

Research Paper     

Max J. Egenhofer‡  Eliseo Clementini  Paolino di Felice 《International journal of geographical information science》2013,27(2):129-142

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Stable carbon isotopic ratios of CH₄-CO₂-bearing fluid inclusions in fracture-fill mineralization from the Lower Saxony Basin (Germany) - A tool for tracing gas sources and maturity   总被引：1，自引：0，他引：1  

Volker Lüders  Birgit PlessenRolando di Primio 《Marine and Petroleum Geology》2012,30(1):174-183

The stable carbon isotopic ratios (δ¹³C) of methane (CH₄) and carbon dioxide (CO₂) of gas-rich fluid inclusions hosted in fracture-fill mineralization from the southern part of the Lower Saxony Basin, Germany have been measured online using a crushing device interfaced to an isotopic ratio mass spectrometer (IRMS). The data reveal that CH₄ trapped in inclusions seems to be derived from different source rocks with different organic matter types. The δ¹³C values of CH₄ in inclusions in quartz hosted by Carboniferous rocks range between −25 and −19‰, suggesting high-maturity coals as the source of methane. Methane in fluid inclusions in minerals hosted by Mesozoic strata has more negative carbon isotope ratios (−45 to −31‰) and appears to represent primary cracking products from type II kerogens, i.e., marine shales. There is a positive correlation between increasing homogenization temperatures of aqueous fluid inclusions and less negative δ¹³C(CH₄) values of in co-genetic gas inclusions probably indicating different mtaturity of the potential source rocks at the time the fluids were released. The CO₂ isotopic composition of CH₄-CO₂-bearing inclusions shows slight negative or even positive δ¹³C values indicating an inorganic source (e.g., water-rock interaction and dissolution of detrital, marine calcite) for CO₂ in inclusions. We conclude that the δ¹³C isotopic ratios of CH₄-CO₂-bearing fluid inclusions can be used to trace migration pathways, sources of gases, and alteration processes. Furthermore, the δ¹³C values of methane can be used to estimate the maturity of the rocks from which it was sourced. Results presented here are further supported by organic geochemical analysis of surface bitumens which coexist with the gas inclusion-rich fracture-fill mineralization and confirm the isotopic interpretations with respect to fluid source, type and maturity.  相似文献   

Mediterranean warming is especially due to summer season   总被引：2，自引：2，他引：0  

Giorgio Bartolini  Valentina di Stefano  Giampiero Maracchi  Simone Orlandini 《Theoretical and Applied Climatology》2012,107(1-2):279-295

We created a new homogenized daily minimum and maximum temperature data set (1955–2007) for the central Mediterranean area of Tuscany (Italy). Yearly and seasonal long-term trends of some climatic and extreme climatic indices were investigated. The results highlighted a positive trend for mean temperature of about 0.9°C per 50 years with a slightly more pronounced increase in maximum temperature. Seasonal analysis revealed a by far much greater increase in summer (June, July, August) and spring (March, April, May) temperature in respect of autumn and winter, this finding consistent with most recent Mediterranean evidences. Warm extremes showed an overall tendency to increase, while a slight not significant decrease trend was found in regard to frost days and cold extremes. Comparisons with different patterns of Mediterranean warming confirmed the magnitude of recent very fast rise in temperature, especially during summer. This change could be due to last decades modifications of general circulation patterns and land–temperature, land–precipitation positive feedback processes dependent from soil moisture. All these results confirm that the Mediterranean is a region especially responsive and thus very vulnerable to climate change.  相似文献   

The Tunisian Jurassic aquifer in the North African Sahara aquifer system: information derived from two-dimensional seismic reflection and well logs     

Rafika Ben Lasmar  Rihab Guellala  Mohamed Garrach  Ali Mahroug  Benen Sarsar Naouali  Mohamed Hédi Inoubli 《Hydrogeology Journal》2017,25(8):2281-2301

Southern Tunisia is an arid area where socio-economic activities are dependent on groundwater resources. The presented study aims to better characterize the Jurassic aquifer based on geological and geophysical data, with a view to develop a rational exploitation program. Well logs are used to precisely determine the position and composition of the known Jurassic aquifer layers and to identify others able to produce good quality water. The logs show that limestones, sandstones and dolomites of the Krachoua, Techout and Foum Tataouine formations are the main Jurassic aquifers. Sixty-eight seismic-reflection sections are integrated within this study. The interpolation between the interpreted sections leads to the construction of isochronous isopach maps and geoseismic sections, and their analysis finds that compressive and extensive tectonic deformations have influenced the Jurassic aquifer geometry. The Hercynian orogeny phase manifestation is remarkable in that there are several stratigraphic gaps in the Jurassic sequence. The E–W, NW–SE, and NNW–SSE accidents, reactivated in normal faults since the Permian to Lower Cretaceous epochs, have generated the structures found in the Jurassic series, such as subsided and raised blocks. Their syn-sedimentary activity has controlled the thickness and facies of these series. The Cretaceous, Tortonian and Post-Villafranchian compressions are responsible for the Jurassic-deposits folding in some localities. The highlighted tectonic and sedimentary events have an important impact on the Jurassic aquifer function by favoring the Jurassic aquifer interconnections and their connections with the Triassic and Cretaceous permeable series.  相似文献   

DEM assessment of impact forces of dry granular masses on rigid barriers   总被引：1，自引：1，他引：0  

Francesco Calvetti  Claudio Giulio di Prisco  Emmanouil Vairaktaris 《Acta Geotechnica》2017,12(1):129-144

In the design of sheltering structures/embankments for the mitigation of the risk due to rapid and long spreading landslides, a crucial role is generally played by the assessment of the impact force exerted by the flowing mass on the artificial obstacle. This paper is focused on this issue and in particular on the evaluation of the maximum impact force on the basis of the results obtained by performing an extensive numerical campaign by means of a 3D discrete element code, in which a dry granular mass is schematised as a random distribution of rigid spherical particles. The granular mass is generated just in front of the obstacle: its initial volume, velocity distribution, height, length and porosity are arbitrarily assigned, and the impact process is exclusively analysed. The initial conditions are varied to take a large variety of geometrical/mechanical factors, such as the initial front inclination, its height, the initial void ratio, the length of the impacting mass and the inter-particle friction angle, into consideration. A design formula is also proposed on the base of the obtained results and critically compared with the literature data.  相似文献   

Some observations on the prediction of the dynamic parameters of debris flows in pyroclastic deposits in the Campania region of Italy   总被引：1，自引：0，他引：1  

Anna Scotto di Santolo  Aldo Evangelista 《Natural Hazards》2009,50(3):605-622

Over the last 20 years, many tools have been developed for the prediction of the post-failure behaviour of rapid landslides. However, as pointed out by several researchers, knowledge may be improved by the performance of back-analyses using different models and the evaluation of their reliability. This paper reports the back-analysis, conducted using numerical models, of 57 rapid landslides that have occurred in the Campania region. The back-analysis has been performed using the 2-D DAN_W code (version 2003) with two different rheological models: the Voellmy and the frictional models. The latter has been immediately discarded because it did not match the observed data. Instead, using the Voellmy model, the best-fit values of the parameters (friction μ and turbulence ξ) for different types of flow (channelled, un-channelled and mixed flows) have been researched. With these values a parametric study has been carried out on four representative slope profiles of the Campania region, enabling the prediction of runout, velocity and depth of flow (dynamic parameters) of potential debris flows.

Anna Scotto di SantoloEmail:

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