Hydrogeochemical and isotopic evolution of water in the Complexe Terminal aquifer in the Algerian Sahara     

A. Guendouz  A. S. Moulla  W. M. Edmunds  K. Zouari  P. Shand  A. Mamou 《Hydrogeology Journal》2003,11(4):483-495

The hydrogeochemical and isotopic evolution of groundwaters in the Mio–Pliocene sands of the Complexe Terminal (CT) aquifer in central Algeria are described. The CT aquifer is located in the large sedimentary basin of the Great Oriental Erg. Down-gradient groundwater evolution is considered along the main representative aquifer cross section (south–north), from the southern recharge area (Tinrhert Plateau and Great Oriental Erg) over about 700 km. Groundwater mineralisation increases along the flow line, from 1.5 to 8 g l^?1, primarily as a result of dissolution of evaporite minerals, as shown by Br/Cl and strontium isotope ratios. Trends in both major and trace elements demonstrate a progressive evolution along the flow path. Redox reactions are important and the persistence of oxidising conditions favours the increase in some trace elements (e.g. Cr) and also NO₃ ^?, which reaches concentrations of 16.8 mg l^?1 NO₃-N. The range in ¹⁴C, 0–8.4 pmc in the deeper groundwaters, corresponds with late Pleistocene recharge, although there then follows a hiatus in the data with no results in the range 10–20 pmc, interpreted as a gap in recharge coincident with hyper-arid but cool conditions across the Sahara; groundwater in the range 24.7–38.9 pmc signifies a distinct period of Holocene recharge. All δ¹⁸O compositions are enriched relative to deuterium and are considered to be derived by evaporative enrichment from a parent rainfall around ?11‰ δ¹⁸O, signifying cooler conditions in the late Pleistocene and possibly heavy monsoon rains during the Holocene.  相似文献   

Examples of geomorphologic and geological hazards in Algeria     

D. Machane  Y. Bouhadad  G. Cheikhlounis  J.-L. Chatelain  E. H. Oubaiche  K. Abbes  B. Guillier  R. Bensalem 《Natural Hazards》2008,45(2):295-308

We present three geomorphologic and geological phenomena that have occurred in Algeria in recent years: (i) the Bab El Oued mudflow on 11 November 2001, which claimed several hundred lives, (ii) a soil collapse induced by sand liquefaction triggered by the Boumerdes earthquake (M _w = 6.8) on 21 May 2003, and (iii) landslides that are threatening Constantine city, for which a hazard map is presented using a qualitative approach. We briefly describe and analyze these natural disasters, and in the first two cases propose the application of geophysical techniques such as ambient noise recordings and electrical imagery to help evaluate their extent and potential threat. Finally a landslide hazard map of Constantine is proposed.  相似文献   

The use of environmental isotopic and hydrochemical tracers to characterize the functioning of karst systems in the Tlemcen Mountains,northwest Algeria     

H. Azzaz  M. Cherchali  M. Meddi  B. Houha  J. M. Puig  A. Achachi 《Hydrogeology Journal》2008,16(3):531-546

The functioning of karst systems in the Tlemcen Mountains, Algeria, was studied using environmental isotopic and chemical parameters. The weakly enriched values of ¹⁸O suggest a fast infiltration of water through the karst systems. The deuterium (²H) excess in groundwater and tritium (³H) in precipitation show that the region is subjected to Mediterranean and Atlantic influences with a predominance of the former. The isotopic gradient, in combination with topographic and geologic criteria, allows the recharge areas of the main karst systems to be estimated. The results of ¹³C, ¹⁴C and ³H analysis show that the majority of present waters come from perched systems and mixture waters influenced by three clusters (“ante-thermonuclear” waters, “thermonuclear” waters, and present waters) that generally emerge from semi-confined systems. The oldest waters are relatively rare and are stored in deeply confined systems. These results are consistent with the hydrochemical and the hydrogeological findings. The results have important implications in groundwater protection.  相似文献   

Assessment of seawater pollution by heavy metals in the neighbourhood of Algiers: use of the sea urchin, Paracentrotus lividus, as a bioindicator     

Soualili  Dina; Dubois  Philippe; Gosselin  Pol; Pernet  Philippe; Guillou  Monique 《ICES Journal of Marine Science》2008,65(2):132-139

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The Ain Temouchent (Algeria) Earthquake of December 22<Superscript>nd</Superscript>, 1999     

A. K.?Yelles-ChaoucheEmail author  H.?Djellit  H.?Beldjoudi  M.?Bezzeghoud  E.?Buforn 《Pure and Applied Geophysics》2004,161(3):607-621

—On December 22^nd, 1999 an earthquake of Magnitude M_w : 5.7 occurred at Ain Temouchent (northwest Algeria). This moderate seismic event was located in a region characterized by a low seismic activity where few historical events have been observed. The earthquake, with a maximum intensity of VII (MSK scale), caused serious damages to the Ain Temouchent city and its surroundings. In the epicentral area, 25 people died and about 25,000 people were made homeless. Some minor breaks have been observed in several areas in the field. They were mainly related to minor collapses in the landscape or in volcanic cavities. The focal mechanism has been studied by using broadband data at regional and teleseismic distances, and different methods. The fault-plane solution has been estimated from first motions of P wave. Depth and source time function have been estimated from the modeling of body waveforms. Scalar seismic moment and source dimension have been obtained from spectral analysis. Results show thrust motion, with a horizontal pressure axis oriented in a NW-SE direction, a depth of 4 km and a simple source time function with time duration of 5 s. Scalar seismic moment estimated from waveform modeling is 4.7 × 10¹⁷ Nm, and spectral analysis gives a value of 1.7 × 10¹⁷ Nm and a source radius of 7.5 km.  相似文献   

Hydrochemical and isotopic behaviour of a Saharan phreatic aquifer suffering severe natural and anthropic constraints (case of Oued-Souf region, Algeria)     

A. Guendouz  A. S. Moulla  B. Remini  J. L. Michelot 《Hydrogeology Journal》2006,14(6):955-968

An approach combining the use of water dissolved chemical species and isotopic fingerprints has been used to understand the behavior of a phreatic aquifer and to determine the origin of its different water components. This aquifer is located in the large sedimentary basin of the Great Oriental Erg (Algeria) and overlies two deeper aquifers: the Complexe Terminal (CT) and the Continental Intercalaire (CI). Besides the deterioration of its groundwater quality, its water table has risen during the last 20 years. A water budget surplus between 950 and 2500 l s^?1 was estimated. Down-gradient groundwater evolution (south-north) has shown that the mineralisation increases from 1.23 to 5.20 g l^?1 due to evaporite minerals dissolution. Chemical and isotopic data demonstrated that in addition to rainfall there is a contribution from the CT and CI aquifers. The latter are tritium-free and less mineralized than the phreatic aquifer. Their radiocarbon contents are very low (<10 pmC, percent modern Carbon) (Pleistocene recharge) whereas quite the contrary is observed for the superficial aquifer which exhibits fairly high and variable C-14 activities (50–100 pmC), evidence of recent recharge. On the basis of tritium contents, two groundwater groups were identified for the phreatic aquifer.  相似文献   

Groundwater geochemistry of Ain Azel area,Algeria     

Lazhar Belkhiri  Lotfi Mouni 《Chemie der Erde / Geochemistry》2014

Hydrogeochemical data for 18 groundwater samples and 11 hydrochemical parameters were subjected to Q- and R-mode cluster analysis and inverse geochemical modeling. Q-mode cluster analysis resulted in three distinct water types (brackish water type, saline water type and highly saline water type). R-mode cluster analysis led to the conclusion that the water–rock interaction is the major source of contamination for the groundwater in the area. Geochemical modeling results show that carbonates, gypsum, halite, carbon dioxide (gas), and chlorite are dissolving, whereas Ca-montmorillonite, gibbsite, illite, K-mica, kaolinite, and quartz are mostly precipitating along different flow paths in the groundwater system of the area.  相似文献   

Seismogenic potential and earthquake hazard assessment in the Tell Atlas of Algeria   总被引：1，自引：0，他引：1  

A. Aoudia  F. Vaccari  P. Suhadolc  M. Meghraoui 《Journal of Seismology》2000,4(1):79-98

Seismotectonic zonation studies in the Tell Atlas of Algeria, a branch of the Africa-Eurasia plate boundary, provide a valuable input for deterministic seismic hazard calculations. We delineate a number of seismogenic zones from causal relationships established between geological structures and earthquakes and compile a working seismic catalogue mainly from readily available sources. To this catalogue, for a most rational and best-justified hazard analysis, we add estimates of earthquake size translated from active faulting characteristics. We assess the regional seismic hazard using a deterministic procedure based on the computation of complete synthetic seismograms (up to 1 Hz) by the modal summation technique. As a result, we generate seismic hazard maps of maximum velocity, maximum displacement, and design ground acceleration that blend information from geology, historical seismicity and observational seismology, leading to better estimates of the earthquake hazard throughout northern Algeria. Our analysis and the resulting maps illustrate how different the estimate of seismic hazard is based primarily on combined geologic and seismological data with respect to the one for which only information from earthquake catalogues has been used.  相似文献   

EARTHQUAKE HAZARD MAPPING IN THE MAGHREB COUNTRIES: ALGERIA,MOROCCO, TUNISIA     

D. BENOUAR  G. L. MOLAS  F. YAMAZAKI 《地震工程与结构动力学》1996,25(10):1151-1164

This paper presents new seismic hazard maps of the Maghreb countries by using newly re-evaluated earthquake data catalogue in the region under consideration. For this region, there is a clear need to use common procedure and data bases through the whole Maghreb region so that seismic hazard assessments are consistent from country to country. An effort is made to assess the seismic hazard and to construct earthquake hazard maps in terms of expected horizontal and vertical PGA for a 10 per cent chance of being exceeded, expected intensity (MSK), all in an economic life time of 50 and 100 years. Also, a return period seismic hazard map for PGA≥140cm/s² is presented. For engineering applications, earthquake hazard maps for structures with different periods are also constructed.  相似文献   

Late Tournaisian (Carboniferous) brachiopods from Mouydir (Central Sahara,Algeria)     

Bernard Mottequin  Marie Legrand‐Blain 《Geological Journal》2010,45(4):353-374

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