Mapping of groundwater quality in the Turonian aquifer of Oum Er-Rabia Basin, Morocco: a case study

This study takes the groundwater of the Moroccan limestone aquifer of Oum Er-Rabia as an example of statistical and cartographical approaches in water resources management. Statistical analyses based on frequency distribution and PCA methods revealed the homogeneity of waters with the existence of abnormal points and have helped to assess correlations between the studied variables. The mapping approach illustrated that waters are influenced by the lithology of the surrounding rocks and are of Ca–Mg–HCO₃, Ca–Mg–Cl–SO₄, and mixed types according to the Piper classification. The quality of water is of high to medium, north of the basin, but it is of medium to bad, NE and south, due to excessive contents of chloride, sulfate and nitrate. According to the US Salinity Laboratory classification, water used for irrigation in the eastern and the southern parts of the basin should take into consideration the drainage conditions, the nature of plants and the addition of gypsum doses.

Processes of water–rock interaction in the Turonian aquifer of Oum Er-Rabia Basin, Morocco

Possible water–rock interaction processes, in the Moroccan basin of Oum Er-Rabia, were discussed by a geochemical study of groundwater from the Turonian limestone aquifer, the most important water resource in the region. Different types of water according to the classification of Piper were defined. Waters have shown an evolution from dominant CHO₃–Ca–Mg type through mixed to SO₄–Cl–Ca–Mg type. The use of geochemical diagrams and chemical speciation modeling method has shown that water–rock interaction is mainly controlled by carbonate and anhydrite dissolution, ion exchange and reverse ion exchange processes. Water–rock equilibrium conditions are favorable for the precipitation of calcite, dolomite, kaolinite and magnesian smectite.     

Groundwater pollution risk mapping for the Eocene aquifer of the Oum Er-Rabia basin, Morocco

Sustainable development requires the management and preservation of water resources indispensable for all human activities. When groundwater constitutes the main water resource, vulnerability maps therefore are an important tool for identifying zones of high pollution risk and taking preventive measures in potential pollution sites. The vulnerability assessment for the Eocene aquifer in the Moroccan basin of Oum Er-Rabia is based on the DRASTIC method that uses seven parameters summarizing climatic, geological, and hydrogeological conditions controlling the seepage of pollutant substances to groundwater. Vulnerability maps were produced by using GIS techniques and applying the “generic” and “agricultural” models according to the DRASTIC charter. Resulting maps revealed that the aquifer is highly vulnerable in the western part of the basin and areas being under high contamination risk are more extensive when the “agricultural” model was applied.     

Hydrochemical and isotopic characteristics of groundwater in the Souss Upstream Basin, southwestern Morocco

Heterogeneous shallow Plio-Quaternary formations of the Souss Plain represent the most important aquifer in southern High Atlas Mountains in Morocco. The present work was conducted in the Souss Upstream Basin to identify the chemical characteristics and the origin of groundwater in an aquifer under semi-arid climate. Isotopic and hydrochemical compositions combined with geological and hydrogeological data were used for this purpose. The total dissolved solids vary from 239 to 997 mg l⁻¹, and the following groundwater types are recognized: Ca²⁺–Mg²⁺–HCO₃⁻, Ca²⁺–Mg²⁺–SO₄²⁻ and Ca²⁺–Mg²⁺–Cl⁻. The groundwater is saturated and slightly supersaturated with respect to carbonate minerals and undersaturated with respect to evaporite minerals, which means that the groundwater composition is largely controlled by the dissolution of carbonate rocks known in the basin. The isotopic contents of groundwaters ranged from −8‰ to −5.2‰ for δ¹⁸O, from −52‰ to −34‰ for δD, and from 0 to 5.5 TU for tritium. The hydrogen (δD) and oxygen (δ¹⁸O) isotope signatures reveal a significant infiltration before evaporation takes place, indicating a major recharge directly from fractures in the crystalline and limestone formations of Atlas Mountains (above 800 m a.s.l.) and infiltration of surface water in the alluvial cones at the border of the Atlas basins. The very low tritium values suggest that the groundwater recharge follows a long flow path and a mixing between old and modern water is shown. However, a slight evaporation effect is noted in the southern part of the basin close to the Anti-Atlas Mountains.     

Environmental impact of an urban landfill on a coastal aquifer (El Jadida, Morocco)

The El Jadida landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 150 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the ground. At the site of this landfill, the groundwaters circulate deeply (10–15 m) in the Cenomanian rock (calcareous–marl), which is characterised by an important permeability from cracks. The soil is sand–clay characterized by a weak coefficient of retention.The phreatic water ascends to the bottom of three quarries, which are located within the landfill. These circumstances, along with the lack of a leachate collection system, worsen the risks for a potential deterioration of the aquifer.To evaluate groundwater pollution due to this urban landfill, piezometric level and geochemical analyses have been monitored since 1999 on 60 wells. The landfill leachate has been collected from the three quarries that are located within the landfill. The average results of geochemical analyses show an important polluant charge vehiculed by landfill leachate (chloride = 5680 mg l⁻¹, chemical oxygen demand = 1000 mg l⁻¹, iron = 23 000 μg l⁻¹). They show also an important qualitative degradation of the groundwater, especially in the parts situated in the down gradient area and in direct proximity to the landfill. In these polluted zones, we have observed the following values: higher than 4.5 mS cm⁻¹ in electric conductivity, 1620 and 1000 mg l⁻¹ respectively in chlorides and sulfate (), 15–25 μg l⁻¹ in cadmium, and 60–100 μg l⁻¹ in chromium. These concentrations widely exceed the standard values for potable water.Several determining factors in the evolution of groundwater contamination have been highlighted, such as (1) depth of the water table, (2) permeability of soil and unsaturated zone, (3) effective infiltration, (4) humidity and (5) absence of a system for leachate drainage. So, to reduce the pollution risks of the groundwater, it is necessary to set a system of collection, drainage and treatment of landfill leachates and to emplace an impermeable surface at the site of landfill, in order to limit the infiltration of leachate.     

Vulnerability mapping of the Turonian limestone aquifer in the Phosphates Plateau (Morocco)

Turonian limestones are an important source of water indispensable for industrial, urban and agricultural development in the Phosphates Plateau. This is an elaboration of a vulnerability map of the aquifer, based on a multicriterion approach according to the DRASTIC charter that serves as a tool for assessment, management and protection of the groundwater quality.     

Zarafasaura oceanis, a new elasmosaurid (Reptilia: Sauropterygia) from the Maastrichtian Phosphates of Morocco and the palaeobiogeography of latest Cretaceous plesiosaurs

Though the Maastrichtian Phosphates of Morocco have yielded very rich marine vertebrate assemblages, plesiosaurs remain very scarce in these strata. The only hitherto recognized taxon was Plesiosaurus mauritanicus Arambourg, 1952, regarded here as a nomem dubium. Here we describe a new genus and species of elasmosaurid plesiosaur, Zarafasaura oceanis, which represents the first valid elasmosaurid plesiosaur described from the latest Cretaceous of Africa, and the second one from this continent. A phylogenetic analysis of plesiosauroids indicates that Zarafasaura oceanis has close affinities with elasmosaurids from the Late Cretaceous of North America and Japan. Among its distinctive suite of characters, the general shape and organisation of its squamosal and palate are unique among elasmosaurids. This new taxon completes our understanding of Late Cretaceous plesiosaur palaeobiodiversity and palaeobiogeography, and shows that Maastrichtian plesiosaurs were characterized by a quite high degree of endemism. They were also highly diversified and distributed worldwide, which supports the hypothesis of a catastrophic extinction of plesiosaurs at the K/T boundary.     

Recharge mechanism and hydrochemistry evaluation of groundwater in the Nuaimeh area, Jordan, using environmental isotope techniques

The relationship between the stable isotopic and chemical composition of precipitation and groundwater was studied in the Nuaimeh area of the Ajloun Highlands in Jordan. The isotopic composition values of precipitation and groundwater are almost identical. The spatial variation of stable isotopes in precipitation is mainly due to the effect of seasonal temperature, altitude and amount. The groundwater reveals identical variation in isotopic composition to the precipitation due to direct recharge and the karstic nature of the outcropping Turonian aquifer. Tritium levels in wells are high and their content is similar to the weighted mean value of tritium content in precipitation, indicating local recharge and low residence time. The ¹⁴C activity in the tritiated groundwater is found to be about half of the ¹⁴C activity of precipitation in the region. A geochemical evolution through dissolution of carbonate by water–carbonate rock interactions reduced the atmospheric ¹⁴C activity from 114 to 61 pmc in the groundwater. A ¹⁴C of around 61 pmc and 7.6 TU values are considered the initial concentration for the recharge in the shallow carbonate aquifer in the Yarmouk Basin. The large fluctuation of water level in observation wells during the rainy season indicates the sensitivity and direct response of the aquifer to the recharge. The chemical composition of the groundwater (Ca²⁺–HCO₃^–) gives emphasis to the short duration of water–rock interaction and indicates dissolution of the carbonate aquifer. The elevated concentrations of Cl^– and NO₃^– in groundwater are attributed to anthropogenic sources.

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Resumen Fue estudiada la relación entre la composición isotópica estable y la composición química, tanto de la precipitación como del agua subterránea, en el área de Nuaimeh en las montañas de Ajloun, en Jordania. Los valores de la composición isotópica de la precipitación y del agua subterránea son casi idénticos. La variación espacial de los isótopos estables en la precipitación, es debida principalmente al efecto de la temperatura estacional, a la altura y a la cantidad. El agua subterránea muestra una variación idéntica a la precipitación en cuanto a la composición isotópica, debido a la recarga directa y a la naturaleza cársica del acuífero Turoniano aflorante. Los niveles de tritio en los pozos son altos y su contenido es similar al valor medio ponderado del contenido de tritio en la precipitación, indicando una recarga local y un tiempo de residencia corto. Se ha encontrado que la actividad de ¹⁴C en el agua subterránea tritiada, es alrededor de la mitad de la actividad del ¹⁴C en la precipitación para la región. La evolución geoquímica ocurrida a partir de la disolución del carbonato, por las interacciones roca carbonatada–agua, redujeron la actividad atmosférica del ¹⁴C desde 114 en porcentaje de carbono moderno (pcm) hasta 61 pcm en el agua subterránea. Los valores del ¹⁴C cercanos a 61 pcm y de 7.6 unidades de tritio, se han considerado como las concentraciones originales para la recarga en el acuífero carbonatado somero de la Cuenca de Yarmouk. Una gran fluctuación en el nivel de agua de los pozos de observación, durante la estación lluviosa, indica la sensibilidad y la respuesta directa del acuífero frente a la recarga. La composición química del agua subterránea (Ca²⁺–HCO₃^–), enfatiza en la corta duración de la interacción de agua–roca, e indica disolución del acuífero carbonatado. La concentración elevada de Cl^– y NO₃^– en el agua subterránea, se atribuye a fuentes antropogénicas.

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Résumé Dans la région montagneuse dAjloun de Jordanie on a étudié la relation entre la composition chimique et isotopique des précipitations et des eaux souterraines. La composition isotopique est presque identique dans précipitations et les eaux souterraines. La variation spatiale de la teneur en isotopes stables dans les précipitations est déterminée en principal par les variations saisonnière de la température, laltitude ainsi que par la quantité des précipitations. A cause de la recharge directe et de la nature karstique des affleurements de laquifère dage touronienne, les eaux souterraines présentent la même composition isotopique que les précipitations. La teneur en ³H mesurée dans les forages présente des valeurs élevées, proches de la valeur moyenne des précipitations, ce quindique une recharge locale et un temps court de résidence. On a déterminé pour lactivité de ¹⁴C une valeur proche de la moitié trouvée dans les précipitations. Lévolution géochimique par dissolution des carbonates pendant linteraction entre leau et les roche a diminué lactivité du ¹⁴C, de la valeur de 114 pcm en atmosphère à 61 pcm dans les eaux souterraines. Dans laquifère calcaire de surface de bassin Yarmouk, on a considéré comme de concentrations initiales, les valeurs de 61 pcm pour ¹⁴C et 7.2 UT pour ³H. Les grandes fluctuations des niveaux des eaux souterraines observées dans les forages pendant les saisons pluvieux montrent la sensibilité ainsi que la réponse directe de laquifère au recharge. La composition chimique des eaux souterraines (Ca²⁺–HCO₃^–) montre de plus le temps court de linteraction entre leau et la roche, en indiquant aussi la dissolution de laquifère calcaire. Les taux élevées de la concentration en Cl^– et NO₃^– dans les eaux souterraines ont été attribuées aux sources humaines.

     

An extension to the DRASTIC model to assess groundwater vulnerability to pollution: application to the Haouz aquifer of Marrakech (Morocco)

An extension to the DRASTIC model is proposed in order to assess aquifer vulnerability to pollution. In contrast to the DRASTIC model, which considers the unsaturated and saturated zones together and computes a global intrinsic vulnerability index, the suggested approach discriminates between the aquifer vertical vulnerability (a concept related to the pollutant percolation) and the groundwater susceptibility (a concept that depends on the behaviour and uses of the groundwater). This approach is applied to the Haouz aquifer (Morocco) that supplies water to the Marrakech area. This aquifer is widely overexploited and there is evidence that the groundwater quality is threatened by various sources of pollution. Evaluation of the vertical vulnerability indicates that the aquifer mainly presents a moderate-to-weak vertical vulnerability. The zones potentially most favourable to pollutant percolation are mainly located in Central Haouz, along or near the surface wadis. The aquifer susceptibility is high in places located near the N’Fis, Baaja and Issil wadis. Everywhere else, low-to-moderate susceptibility is observed. This new approach therefore enables areas of vertical vulnerability and areas of susceptibility to be delineated separately. As a result, it constitutes a valuable decision-making tool for optimising the management of aquifer water resources and land-use planning.     

Modelling groundwater flow of the Trifa aquifer, Morocco

Trifa is the most productive agricultural plain of north-eastern Morocco. The development of agricultural activities during the last few decades has been mainly based on imported water for irrigation. However, irrigation requirements have become so large that groundwater is used as a secondary source to supply the agricultural and domestic water needs, causing a depletion of the groundwater resources, especially during dry periods. A hydrological and a hydrogeological model for the Trifa plain have been developed, which yield information on relevant parameters such as groundwater recharge, and estimate the amount of pumped groundwater needed to meet the irrigation needs. The models (MODFLOW and WetSpass) provide insight into the status and evolution of the groundwater reserves. The results of the study are useful to predict the sustainability of the groundwater resources in the Trifa plain and to evaluate possible management actions. A reduction in groundwater abstraction by at least 25% may be necessary to achieve sustainable conditions.

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Resumen Trifa es la planicie agrícola más productiva del noreste de Marruecos. El desarrollo de las actividades agrícolas durante las últimas décadas se ha basado principalmente en agua importada para riego. Sin embargo, los requerimientos de riego han llegado a ser tan grandes ocasionando que se utilice el agua subterránea como una fuente secundaria para abastecer las necesidades de agua para uso doméstico y agrícola, lo que causa un agotamiento de los recursos de agua subterránea, especialmente durante periodos secos. Se ha desarrollado un modelo hidrogeológico e hidrológico para la planicie Trifa el cual aporta información de parámetros relevantes tal como recarga de agua subterránea y estima la cantidad de agua subterránea que necesita bombearse para satisfacer las necesidades de riego. Los modelos (MODFLOW y WetSpass) aportan una idea acerca del estado actual y la evolución de las reservas de agua subterránea. Los resultados de este estudio son útiles para predecir la sostenibilidad de los recursos de agua subterránea en la planicie Trifa y para evaluar posibles acciones de gestión. Puede ser necesario reducir la explotación de agua subterránea en por lo menos 25% para alcanzar condiciones sostenibles.

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Résumé Trifa est la plaine agricole la plus productive du Nord-Est marocain. Le développement de l’activité agricole durant ces dernières décennies a essentiellement reposé sur l’irrigation. Néanmoins les besoins de l’irrigation sont devenus tels que l’eau souterraine est utilisée comme ressource secondaire, pour combler la demande en eau domestique et agricole, induisant un rabattement d’autant plus important durant les périodes sèches. Un modèle hydrologique et hydrogéologique de la plaine de Trifa a été développé sur base des paramètres les plus importants, tels la recharge, et permet d’estimer le pompage nécessaire des eaux souterraines pour combler les besoins de l’irrigation. Les modèles (MODFLOW et WetSpass) apportent une bonne connaissance de l’état et de l’évolution des réserves souterraines. Les résultats de l’étude sont utiles pour prédire la longévité des ressources et pour évaluer différents scénarios de gestion. Une réduction de l’extraction de 25% serait nécessaire pour atteindre un état durable.

     

水-岩相互作用模拟的研究进展

水-岩相互作用的地球化学模拟已在模型建立和软件的开发方面取得了较大的进展.地球化学模型发展经历了从反向模拟到正向模拟,以及到现在的反应性溶质运移模拟的发展过程.许多计算模拟软件被开发出并投入到实际应用中,现在的模拟技术已能处理较大范围内温度变化、压力变化、组分变化,以及各种地质条件下的水-岩地球化学作用.许多水-岩相互作用问题要回答地质作用的过去历史,要解释或预测未来可能水环境变化,通过模拟已获得满意的解决.目前水-岩作用地球化学模拟取得的重要进步是动力学模型和耦合运移模拟已取得了实质性进展,并应用于实际研究之中.     

Oceanic events and biotic effects of the Cenomanian-Turonian anoxic event, Tarfaya Basin, Morocco

Profound biotic changes accompanied the late Cenomanian δ¹³C excursion and OAE2 in planktic foraminifera in the Tarfaya Basin of Morocco. Planktic foraminifera experienced a severe turnover, though no mass extinction, beginning with the rapid δ¹³C excursion and accelerating with the influx of oxic bottom waters during the first peak and trough of the excursion. Species extinctions equaled the number of evolving species, though only the disaster opportunists Guembelitria and Hedbergella thrived along with a low oxygen tolerant benthic assemblage. The succeeding δ¹³C plateau and organic-rich black shale deposition marks the anoxic event and maximum biotic stress accompanied by a prolonged drop in diversity to just two species, the dominant (80–90%) low oxygen tolerant Heterohelix moremani and surface dweller Hedbergella planispira. After the anoxic event other species returned, but remained rare and sporadically present well into the lower Turonian, whereas Heterohelix moremani remained the single dominant species. The OAE2 biotic turnover suggests that the stress to calcareous plankton was related to changes in the watermass stratification, intensity of upwelling, nutrient flux and oxic levels in the water column driven by changes in climate and oceanic circulation. Results presented here demonstrate a 4-stage pattern of biotic response to the onset, duration, and recovery of OAE2 that is observed widely across the Tethys and its bordering epicontinental seas.     

Groundwater nitrate pollution in the Essaouira Basin (Morocco)

The Essaouira Basin (Morocco) contains a multi-layered aquifer situated in fractured and karstic materials from the Middle and Upper Cretaceous (the Cenomanian, Turonian and Senonian). Water percolates through the limestone and dolomite formations of the Turonian stage either through the marls and calcareous marls of the Cenomanian or through the calcareous marly materials of the Senonian. The aquifer system may be interconnected since the marl layer separating the Turonian, Cenomanian and Senonian aquifers is thin or intensively fractured. In that case, the water is transported through a network of fractures and stratification joints. This paper describes the extent of the nitrate pollution in the area and its origin. Most of the wells and drillholes located in the Kourimat perimeter are contaminated by nitrates with some concentrations over $\text{400 }\text{mg}\text{l}{}^{\mathrm{?1}}$. Nitrate contamination is also observed in the surface water of the Qsob River, which constitutes the natural outlet of the multi-layered complex aquifer system. In this area, agriculture is more developed than in the rest of the Essaouira Basin. Diffuse pollution of the karstic groundwater body by agricultural fertiliser residues may therefore partially explain the observed nitrate pollution. However, point pollution around the wells, springs and drillholes from human wastewater, livestock faeces and the mineralisation of organic debris close to the Muslim cemeteries cannot be excluded.     

Evolution of groundwater salinity in the unconfined aquifer of Bou-Areg, Northeastern Mediterranean coast, Morocco

The Bou-Areg plain in the Mediterranean coast at the North-eastern of Morocco is characterized by a semi-arid climate. The aquifer consists of two sedimentary formations of Plio-quaternary age: the upper formation of fine silts and the lower one of coarse silts with sand and gravels. The aquifer is underlain by marly bedrock of Miocene age that dips toward the coastal lagoon of Bou-Areg. The hydrodynamic characteristics vary between 10⁻⁴ and 10⁻³ m/s; and transmissivities range between 10⁻⁴ and 10⁻¹ m²/s. The general direction of flow is SW to NE, toward the lagoon. The aquifer is crossed by the river Selouane, which also ends in the lagoon. The groundwater is characterized by a high salinity that can reach 7.5 g/l. The highest values are observed in the upstream and in the downstream sectors of the aquifer. The temporal evolution of the physico-chemical parameters depends on the climatic conditions and piezometric variations. The analysis of the spatio-temporal distribution of the physico-chemical parameters suggests different sources of groundwater salinization: the seawater intrusion, the influence of marly gypsum-bearing terrains, and the influence of anthropogenic products as the agricultural fertilizers, which cause great nitrate concentrations that vary between 80 and 140 mg/l.     

A revised ammonoid biostratigraphy for the Aptian of NW Africa: Essaouira-Agadir Basin,Morocco

A revised ammonoid biostratigraphy is presented for the Aptian of NW Africa, Essaouira-Agadir Basin (EAB), Morocco, based on detailed analysis of 5 key sections. A number of bio-events are documented and 26 genus and 43 species fully documented, forming the largest published Aptian ammonite collection made from NW Africa. The section at Tiskatine is documented as the type section, and 8 zones and subzones are defined, of which 5 are new. This work allows correlation of the Aptian of the EAB to the Standard Mediterranean Ammonite Scale (SMAS).Two main hiatuses are identified at the scale of the basin scale: a major one that includes most of the lower Aptian and the base of the upper Aptian and a second one encompass the top of the upper Aptian and the base of the lower Albian. The ammonite fauna displays a clear Tethyan palaeobiogeographic character affected by a fairly high degree of endemism at the genus and species level. The new genus and species Elsaisabellia tiskatinensis is introduced.     

青海共和盆地地热流体地球化学特征及热储水-岩相互作用过程

地热流体地球化学组成及其运移规律和成因机制研究对地热资源勘查和开发利用具有重要意义。当前,青海省地热资源开发利用程度低,更缺乏针对地热流体地球化学特征进行深入研究的系统性工作。青海共和盆地是青藏高原北缘的一个断陷盆地,盆地内地热资源丰富。本文以共和盆地及周围部分山区的地热系统为研究对象,基于系统地球化学采样和测试开展了地热流体地球化学组成及热储水-岩相互作用过程分析,认为:从共和下更新统热储、新近系热储到鄂拉山构造岩浆带再到瓦里贡山构造岩浆带,地热水中SiO₂含量依次升高,反映热储温度依次升高;上述地热地区热储中原生铝硅酸盐矿物的溶解和蚀变矿物的形成是控制地热水中阳离子含量的最重要的水文地球化学过程,而补给水下渗和地热水径流及升流过程中盐类矿物的溶滤则是水中阴离子(特别是 {\mathrm{SO}}_4^{2-}和Cl^-)的主要来源。     

The Selloum Basin: new element of the Middle Liassic paleogeography in the southern Middle Atlas (Morocco)

A comparative study of the Middle Liassic series in the south western part of the Middle Atlas system leads to the definition of three new formations called Fellat 1, 2 and 3. They mainly involve gravity-flow deposits related to the breakup of the regional carbonate platform in a subsiding area, the Selloum Basin. The creation of this basin provides evidence for a rifting stage during the Carixian–Domerian interval, inducing the separation of the Selloum unit with respect to the Middle Atlasic trough and its possible connection with the High Atlasic sedimentary domain.     

A baby mosasauroid (Reptilia,Squamata) from the Turonian of Morocco – Tethysaurus ‘junior’ discovered?

New Middle Turonian mosasauroid remains were discovered in the same large-sized nodule that yielded a specimen referred to Tethysaurus nopcsai Bardet et al., 2003, from the Goulmima region (southern Morocco). They comprise isolated, fragmentary cranial elements (skull and mandible) and some vertebrae. Their very small size suggests a juvenile condition, an observation supported also by anatomical (spongious nature of numerous bone parts), micro-anatomical (loose inner spongiosa) and histological (numerous remains of calcified cartilage deep into the centrum; radial vascular canals) data. These bones belonged to a basal mosasauroid that cannot be distinguished from Tethysaurus nopcsai to which taxon we tentatively assign the material.