Ali Mrabet

Carbonate, evaporite, siliciclastic transitions in Quaternary rift sediments of the northwestern Red Sea

Abstract The Quaternary and Recent coastal environments of the Egyptian Red Sea and Gulf of Suez are characterized by rapid lateral variations: carbonates, evaporites and siliciclastic sediments exist in close proximity. Although the climate is exceptionally dry, the numerous wadis draining high hinterland relief deliver important quantities of coarse clastics to coastal environments during the rare periods of flash-flooding. However, because this efficient supply is sporadic, coastal waters are contaminated for short, catastrophic periods which are followed by a rapid return to clear water, carbonate sedimentation. The warm, arid conditions, on the other hand, favour both carbonate (reef) production and evaporite mineral precipitation. Rapid lateral transitions between continental siliciclastic and marine carbonate facies are favoured by a particular morphology closely related to the active distensional tectonic setting within the Red Sea rift. Block faulting, which began in the early Miocene and continues today, has resulted in numerous, subparallel grabens and horsts situated between the onshore basement relief and the coast. The structural depressions (grabens) tend to trap much of the episodic siliciclastic input, favouring permanent carbonate production in the nearby littoral environments.

Evaporite, carbonate, and siliciclastic transitions in the Jurassic sequences of southeastern Tunisia

Abstract Evaporite, carbonate and siliciclastic transitions occur within the Jurassic deposits of southeastern Tunisia. These facies are grouped into four major transgressive-regressive sequences corresponding to various environments of deposition. The latter include sabkha, subaqueous evaporite basin, carbonate tidal flats to shallow marine platform, bioherms and mixed siliciclastic ramp. Rapid lateral and vertical variations in thicknesses and facies are controlled by tectonic, climatic and eustatic factors. East-west and NW-SE fault systems generated a down-faulted graben (Tataouine basin) bordered by two uplifted horsts (Tebaga Mole and Libyan Craton) and have acted as an evaporite depocenter or as a siliciclastic trap. Eustatic-related transgressions occurring during Late Lias, Bajocian, Early/Middle Callovian, and probable Upper Callovian-Oxfordian have led to opening and/or deepening of the marine basin accompanied by carbonate sedimentation rapidly replacing evaporite or siliciclastic deposition. This Jurassic example not only confirms that tectonics and, to a lesser extent, climate largely controlled evaporite, carbonate, and siliciclastic transitions; it also demonstrates that sea-level changes may be another factor controlling such transitions in these ancient deposits.

Neocomian deltaic complex in Central Tunisia: a particular example of ancient sedimentation and basin evolution

Abstract Sedimentologic and stratigraphic study of the Neocomian series of Central Tunisia has demonstrated that these sediments form a regressive megasequence dominated by development of a deltaic complex. This deltaic complex consists of three prograding environments: (1) a clayey prodelta passing seawards into a deep marly-calcareous shelf; (2) a delta platform characterized by coarsening upward sequences of mouth bars and fining upward sequences of channel bars, and intercalated with oolitic carbonate beds; and (3) a fluvial plain with coarse sands deposited in braided channels. The general organization of deposits and the progradation of the environments is comparable to many modern deltaic systems. However, it differs from modern deltas by the absence of classic deltaic form and by the intimate association of siliciclastic and carbonate sediments reflecting fluctuating terrigenous supply and minor marine ingressions. Non-marine sedimentation occurred mainly on a fluvial plain deficient both in swamps and in tidal flats; the coarse sand was deposited not by a single river but in numerous braided channels. The construction of this deltaic complex within the weakly subsiding Central Tunisia basin was controlled by three main factors: (1) a semi-arid paleoclimate; (2) tectonic movements occurring at the end of Jurassic and Neocomian; and (3) a hinterland, the Saharan platform, lacking both relief and channelized drainage systems.

Comparison between active surveillance and passive detection of zoonotic cutaneous leishmaniasis in endemic rural areas in Central Tunisia, 2009 to 2014

Abstract Objective To assess the contribution of active surveillance of zoonotic cutaneous leishmaniasis (ZCL) in rural areas in Sidi Bouzid from 2009 to 2014 in comparison with the passive case detection, and describe the pattern of the disease. Methods The monitoring was based on the notification of all new cases in primary health care facilities, among pupils in all schools and a community-based active ZCL surveillance was also performed. The medical staff of health care facilities reviewed and confirmed cases notified in schools. Results From July 2009 to June 2014, a total of 856 (51.1% male, 48.9% female) cases were enrolled; the average incidence rate of the disease was 2 514.4 per 100 000 inhabitants. The median age was 11 years (inter quartile range: 7-28) and 68.9% were aged less than 20 years. Most ZCL lesions arose between August and January and 46.1% of cases were reported between July 2013 and June 2014. Active surveillance reported more cases mainly in the delegation of West Sidi Bouzid and most cases (66.7%) were reported by the health care centers. Conclusions The present study showed ZCL was still endemic in rural areas in Sidi Bouzid Governorate. Active surveillances cost-effectiveness is not certain thus, it would be rational to improve routine passive detection of ZCL in Sidi Bouzid than to continue active research of cases.

The vaccination program and chemoprophylaxis in Tropics

Introduction : military deployment to a tropical country will expose soldiers to infectious diseases. Some of these diseases can be avoided by immunization before departure. Our objective is to establish an immunization and chemoprophylaxis planning to protect deployed troops. Methods : first step is to gather medical intelligence from institutional website as WHO, Atlanta CDC, to identify preventable infectious diseases frequent in the country of deployment. Second step is to make the list of vaccines. Vaccination can be divided in two groups: mandatory vaccines depending on national policy (boost) and specific vaccine depending on the geographical area of the deployment (complete vaccination). Finally, we create a timeline for vaccination. For malaria, the chemoprophylaxis is required and must be continued for some time after the end of mission. Results : we deploy 5000 Tunisian soldiers in DR of Congo with MONUC from 2000 to 2010 (500 every year). The timeline of vaccination was: boost for mandatory vaccination: Diphtheria-Tetanus, Typhoid, Polio and Meningitis > 3 months before deployment; complete vaccination for specific immunization: Hepatitis A, Hepatitis B and Yellow Fever >30 to 15 days before deployment; boost at 6 months, in mission, for Hepatitis A and B; chemoprophylaxis: Doxycyline or Mefloquine, begins at day-7 and until 30 days after returning. Conclusion : the results of this vaccination program was satisfying, with a protection of 100% and no lethal case of malaria. Side effects were minor fever and local symptoms, with no immune or neurologic reaction. For chemoprophylaxis, observance was not good, especially for doxycycline.

Distant peer-tutoring for developing countries

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