NE Algeria Research Articles

Robustness of DRASTIC Method for Groundwater Vulnerability Case of Wadi Nil Aquifer in Jijel, NE Algeria

DOI:10.17014/ijog.9.2.229-246The alluvial water table of Wadi Nil is characterized by an abundance of groundwater, attributed to the high rainfall (1,000 mm/yr on average) of the region, the good permeability of its aquifer (10-3 to 10-4 m/s), and its significant thickness (35 to 100 m). Its waters are used for drinking water as well as for irrigation. In recent years (2000-2020), significant growth in terms of urban, agricultural, and industrial activities has developed on the plain, and has generated a significant amount of waste and effluents. In order to protect the groundwater resource, a map of the vulnerability of the water table to pollution, intended to guide public policies, has been drawn up. The DRASTIC method is a method chosen for the creation of this map, in view of its efficiency and reliability. The results obtained show that the groundwater consists of three zones: the first zone - of moderate vulnerability - is located in the outcrop areas of the marl formations (central part of the plain); the second - of high vulnerability - occupies most of the plain, composed mainly of the wadi alluvial formations; and finally the third - of very high vulnerability - is located in the downstream part of the groundwater, where the aquifer formations are sandy. The statistical analyses and sensitivity analysis of DRASTIC parameters highlight the importance of the parameters «water depth, recharge, and impact of the vadose zone» in the elaboration of the vulnerability map of the studied area, and show that the approach is relatively robust. Nevertheless, if the “water depth” and “recharge” parameters can be constrained by field measurements, the “impact of vadose zone” parameter appears to be the most delicate, because it is both sensitive and associated with uncertainties

Crassatella baudeti (Coquand, 1862) du Cénomanien de Batna (NE algérien) : paléobiogéographie, paléoécologie et biostratigraphie

The lower Cenomanian strata from the Batna region (NE Algeria) constitute the richest and most diversified deposits in terms of macro-invertebrates, mainly dominated by bivalves both in terms of specimens and taxa. Among them, Crassatellidae are restricted to the lower Cenomanian stratigraphical levels. They are represented by the single species Crassatella baudeti. The species is easily distinguished by its flattened boat anchor shape and quite strong commarginal lamellae, and is very abundant. It is present in levels ranging from Sharpeiceras schlueteri Subzone to Cunningtoniceras inerme Zone. The species is, therefore, a good marker of the last levels of the lower Cenomanian and the beginning of the midlle Cenomanian. A precise palaeontological description and an environmental discussion were conducted. Thus, Cr. baudeti would be indicative of a shallow environment, with cold but calm waters, normal salinity and moderately soft substrate. Recorded exclusively from the Cenomanian of a few Tethys localities, the exclusive presence of Cr. baudeti reflects a specific thermal gradient and climatic zonation.

A preliminary mineralogical and physicochemical characterization of the Neogene clays from the Timgad Basin (Massif of Aur\xe8s, NE Algeria): potential use in the manufacturing of bricks and ceramic industry

This study aims at the mineralogical and physicochemical characterization of the clay formations of the Miocene age from the Timgad Basin (Massif of Aurès, NE Algeria), in order to evaluate their possible valorization, notably for their potential use in the manufacturing of bricks and ceramic industry. For this purpose, four samples were taken from a clay-dominated formation that outcrops 5 km east of the Timgad city. Each sample was collected, prepared, and analyzed by the appropriate analytical methods of characterization such as X-ray diffraction, X-ray fluorescence, and scanning electron microscopy. Moreover, other complementary analyses are performed in this study such as laser granulometry and geotechnical tests. The results of the different tests revealed that the clay formations of the Timgad Basin are non-refractory clays and characterized by medium plasticity. These clays are constituted of more than 50% of fine fraction, mainly represented by kaolinite in association with non-negligible proportions of illite, chlorite, mixed-layer clay minerals, and traces of smectite. Besides, this clayey assemblage is accompanied by some proportion of quartz and calcite, as well as traces of hematite, feldspar, and gypsum. In the light of these results and in combination with the particle size distribution, as well as the results of geotechnical tests, it is concluded that the Neogene clays of the Timgad Basin present high limits of Atterberg. Consequently, their use in the field of manufacturing of bricks and terra cotta ‘Terre Cuite’ products is subordinated to a preliminary treatment with addition of a degreasing agent, in the form of coarse sand, in order to improve their plasticity.Article HighlightsMineralogical and physicochemical properties of the Neogene clays from the Timgad Basin have been investigated.The studied clays have ideal mineralogical composition and physicochemical properties thus making them applicable in the manufacturing of bricks and ceramic industry.Addition of coarse sand to the Neogene clays will greatly improve the plasticity of these raw materials.

Social-ecological dimensions of Marine Protected Areas and coastal fishing: How fishermen's local ecological knowledge can inform fisheries management at the future “Taza” MPA (Algeria, SW Mediterranean)

The aim of this paper is to examine fishermen's Local Ecological Knowledge (LEK) relating to Marine Protected Area (MPA) planning and the overlap with fisheries management in the future “Taza” MPA (Algeria, SW Mediterranean). The case study focuses on both commercial and recreational coastal fisheries from the fishing harbour of Ziama (NE Algeria). In this area, coastal fishing is carried out by professional small-scale fishers and purse seiners for commercial fishery and by recreational boat fishers for recreational fishery. While there have been some science-based studies in the characterization of this coastal fishery by using direct observation of landings as a method for estimating catch and fishing effort, fishermen's LEK remains under-utilized in this Social-Ecological System (SES). To address this knowledge gap, perceptions regarding: (1) biological and ecological impacts of coastal fisheries, (2) marine ecosystem health and (3) attitudes towards the proposed MPA regulations were analyzed in order to assess potential social-ecological impacts which can inform more accurately on MPA planning and fisheries management in the future. To this end, thirty face-to-face semi-structured interviews with fishers at Ziama harbour were carried out between June and September 2017. The study found that the future establishment of the “Taza” MPA may affect the fisheries in this area in the short-term, and in particular the jobs and livelihoods of professional fishers by limiting the fishing area through new fishing restrictions. The fishermen's LEK provided some capacity to understand the heterogeneity of the SES in place and may be used as a tool to evaluate the outcome of fishery management actions. The results indicate higher acceptance rates among recreational than professional fishers regarding no-take zones. Professional fishers were proportionately more likely to oppose the new regulations, though 53% of the fishers surveyed were uncertain about the future positive impacts of the MPA. The LEK provides managers with a level of detail about the prediction and prevention of fishermen opposition, and can point out opportunities for improving conservation policy with respect to social acceptance.

Optical sorting technology for waste management from the Boukhadra iron ore mine (NE Algeria)

Mining processes in the iron ore mine of Boukhadra, Tebessa (NE Algeria) generated thousands of tons of mining wastes every year, which represents a real threat to the environment, leading to hazardous effects for the resident population of the region. The aim of this study is the selective sorting of the Boukhadra mining wastes for valorization. This will facilitate the recycling of the mineral substances (limestone, iron, marls) on the one hand and it makes it possible to minimize the volume of stocks and their environmental impacts on the other hand. To do this, and taking into account the chemical properties of wastes, we recommend an optical separation management using a color camera and a microprocessor linked to the ejection system (valve or pump), the color measurement tests performed on Boukhadra waste rocks samples using Matlab codes converted from Algorithms showed that each rock has a specific color (Red Green Blue value) or RGB. For this purpose, the use of three optical separators that sort according to algorithmic commands (RGB interval) will contribute to the separation of the Boukhadra mining wastes and consequently simplify their reuse.

Shallow marine trace-fossils from the Middle Miocene of the Tebessa Basin (NE Algeria) and their paleoenvironmental implications

The northeastern part of Algeria is characterized by Meso–Cenozoic fossiliferous deposits. All the previous studies have been focused on invertebrate and vertebrate body fossils from this region. In the present paper we provide the first ichnological study from the region of Ouenza, Tebessa Wilaya (northeastern Algeria). An ichnoassemblage composed of eight ichnotaxa, namely cf. Archaeonassa isp., Arenicolites isp., Diplocraterion isp., Helminthopsis isp., Palaeophycus tubularis, Skolithoscf. linearis, cf. Taenidium isp., and Thalassinoides isp., reported from the lower Langhian (Middle Miocene) of Aïn Sidi Salah locality (Tebessa Basin) is discussed. These trace-fossils belong to the Skolithos and proximal Cruziana ichnofacies indicating deposition within a shallow marine (littoral). The large size of Thalassinoides suggests well-oxygenated setting, under moderate- to high-energy conditions, with occasional storm events. Keywords: trace-fossils, paleoenvironments, shallow marine, Middle Miocene, Tebessa.

Origin of the Mizab barite vein-type deposit, Ain Mimoun (NE Algeria): evidence from fluid inclusion and S-, O- and C-stable isotope studies

Origin of the Mizab barite vein-type deposit, Ain Mimoun (NE Algeria): evidence from fluid inclusion and S-, O- and C-stable isotope studies

Assessment of relative-active tectonics in rhumel-smendou basin (ne Algeria) – observations from the morphometric indices and hydrographic features obtained by the digital elevation model

Assessment of relative-active tectonics in rhumel-smendou basin (ne Algeria) – observations from the morphometric indices and hydrographic features obtained by the digital elevation model

New genera and species of ostracods from the El Ma El Abiod Miocene Basin (Tébessa, NE Algeria)

Two new ostracod genera of the family Trachyleberididae Sylvester-Bradley, 1948, each based on a new species, are described and commented here. The specimens were collected in Tortonian sediments cropping out at El Hadjra Safra in the El Ma El Abiod basin (region of Tébessa, north-eastern Algeria).

The main events of the July–August 2020 Mila (NE Algeria) seismic sequence and the triggered landslides

The main events of the July–August 2020 Mila (NE Algeria) seismic sequence and the triggered landslides

Impact of Land use Changes on Landslides Occurrence in Urban Area: The Case of the Constantine City (NE Algeria)

The city of Constantine (NE Algeria), the third largest city of the country (2.374 inhabitants/km2) is facing frequent damaging landslides that constitute a constraint to future development and land use planning. The main goals of this study are to evaluate the effect of land use changes on the spatial distribution of landslide hazard occurrence and give an example of landslide hazard assessment as useful tool within the context of long-term land use planning in the urban area of Constantine. For this purpose, the adopted methodology requires four steps: (i) Data collection and construction of a spatial database related to the historical landslides, land use, building and population inventory; (ii) landslide inventory and land use mapping for the period of 1970 to 2011 based on the analysis of aerial photographs, high resolution satellite images, historical records verified and completed by extensive field observations, (iii) analysis of the effects of land use changes on the spatial distribution of landslide occurrence for different periods 1970 and 2011; (iv) landslide hazard map, obtained by using the frequency ration (FR) under GIS and (v) evaluate the impact of human-induced land use changes on hazard occurrence. For that, we, firstly, compared the landslide inventory map with land use maps of different periods of 1970 and 2011 that showed that since 1970, the density of landslides increases with increasing of urban areas. In 2011, the high landslide density is concentrated on the following four layers: the urban area layer (41%), the agriculture land layer (39%), the grass area layer (15%) and the forest land layer (5%). The effect of the expansion of urban zone in agriculture, grass and pasture area have increase landslide densities over time. Secondly, we compared the landslide hazard map to these land use maps and we found that 40% of the high hazard zones and 50% of the moderate hazard zones fall in the urbanized area. The obtained results show a clear impact of the changed land use where human action is an important triggering and/or accelerating factor of landslides in the urban area of Constantine. Nowadays, about 72,749 inhabitants and 25,255 buildings are located in landslides threatened area. Therefore, landslide hazard maps should, always, guide the land use and urbanization in landslides prone areas.

Cenomanian (Upper Cretaceous) bivalves from the Hameimat Massifs, north of Tebessa, Algeria: Systematics, biostratigraphy, palaeoecological and taphonomical remarks

In the eastern Saharan Atlas, particularly in the northern area of Tebessa Province (NE Algeria), the widely outcropping Cenomanian strata display a highly diversified macrofauna, among which bivalves are prominently represented. Twenty-eight bivalve species are here reported for the first time from the Cenomanian of Hameimat Massifs. Based on the stratigraphic distribution of these bivalves, five bivalve zones were recognized, i.e., Costagyra olisiponensis - Gyrostrea delettrei, Rhynchostreon suborbiculatum - Exogyra conica, Ceratostreon flabellatum, Ilymatogyra africana, and Pycnodonte vesicularis vesiculosa - Rastellum carinatum zones. Correlation to the ammonite biozones of the same region as follows: the Costagyra olisiponensis - Gyrostrea delettrei and the Rhynchostreon suborbiculatum - Exogyra conica zones occur respectively in the Sharpeiceras schlueteri and Mantelliceras saxbii subzones of the lower Cenomanian Mantelliceras mantelli Zone. The Ceratostreon flabellatum Zone is correlated with the middle Cenomanian Acanthoceras rhotomagense Zone. The Ilymatogyra africana Zone is correlated with the upper Cenomanian Calycoceras naviculare and the Metoicoceras geslinianum zones. Finally, the Pycnodonte vesicularis vesiculosa - Rastellum carinatum Zone represents the uppermost Cenomanian. Detailed analysis of biometrical and morphological features of these bivalve specimens provides the most reliable tool within the scope of palaeo-environmental reconstitution and the many palaeo-ecological variables that had driven the development and distribution of these macro-invertebrates. Comparison of these new data to those of adjacent south Tethyian areas supports the homogeneity of the Cenomanian bivalve faunas. Such an affinity underlines more vividly the favorable marine communications and currents driving the geographic dispersal of these bivalves during the Cenomanian.

Assessment of groundwater and soil pollution by leachate using electrical resistivity and induced polarization imaging survey, case of Tebessa municipal landfill, NE Algeria

In the last decade, the anarchical discharges have severely degraded the environment quality in Tebessa province. Due to the exudation and the percolation of leachate through the retention tanks, the Tenoukla Technical Landfill Center (TLC) is considered as the main source of the aquifer and soil pollution in the Tebessa basin. Our research intended to investigate the groundwater and soil pollution extent within and close the municipal landfill, southeast of Tebessa city, NE Algeria. For this task, we used geochemistry analysis based on atomic absorption spectrometry and geophysics prospecting based on electrical resistivity tomography (ERT) and induced polarization (IP) techniques. The chemical results showed strong soil/water contamination by high levels of mineralization (3.5 μg/g of Pb, 7.1 μg/g of Cd, 0.09 μg/g of Cu, and.05 μg/g of Zn). The IP and ERT image indicated large zones of decomposed waste bodies saturated with highly conducting leachate (resistivity’s value varies from 3 to 10 Ω m). This high mineralization concentration in the vadose zone is due to the leakage of the leachate, through the permeable Cenomanian marly limestone. Cd, Pb, Cu, Zn, Fe, and Mg element concentration in sediments caused the degradation of water quality. These results confirm a general trend of pollution towards the downstream area. Soil exchangeable bases were higher in the vadose zone compared to the saturated one. Our study gives a good example of the potential of the ERT/IP method for the hydrogeological investigation and for the pollution characterization especially in landfill sites. These tools could help decision-makers in our study area or in a similar environment for monitoring environmental parameters, reduce the risk, and avoid critical pollution situations caused by the leachate resulting from landfills. We highly recommended initiating a depollution plan for a both soil and water.

Using a multi-disciplinary approach to characterize groundwater systems in arid and semi-arid environments: The case of Biskra and Batna regions (NE Algeria)

This study presents a multi-disciplinary approach for the hydrogeological assessment and characterization of water resources in typical arid and semi-arid areas with high anthropogenic pressure, and where environmental conditions and political context prevent extensive field surveys. The use of a three-dimensional (3D) hydrogeological conceptual model, integrating hydrochemical and multi-isotope data, is proposed for the Batna and Biskra area (NE Algeria).Geological data were assembled in 3D geological software, from which a 3D hydrogeological conceptual model was constructed, which included the delineation of groundwater flow directions. The isotopic characterization, including deuterium and oxygen isotopic composition of water (δ2H and δ18O), and tritium (3H), provided information regarding recharge sources, flow pathways and residence times of groundwaters. Hydrochemical parameters, measured on the same samples, supported the interpretation of isotope data. All data were processed in a geographic information system (GIS) environment. The effectiveness of this approach was tested on a complex system of aquifers with high hydrogeological heterogeneity. Results show the important role the tectonic setting of an area can play in the hydrogeology and hydrochemistry of its principal groundwater systems. The fault network in the study region connects different aquifers, resulting in the mixing of groundwaters. The region most influenced by geological structures is the southern part of the study area, close to Biskra city. In fact, besides a limited contribution of recharge from rain and surface water derived from flood events, the recharge of the Cenozoic aquifers seems to proceed from the ascension of deeper Cretaceous groundwaters through the fault network, as indicated by temperature, bulk chemistry and in particular δ2H, δ18O and 3H results. In contrast, results suggest that the recharge of the low mineralized Maastrichtian waters is primarily influenced by local precipitation and runoff in the mountainous northern part of the study area. Tritium content, low salinity, and bulk chemistry all suggest such waters to be a mix of pre-bomb (deeper flow-lines within the aquifer) and recent water, with no contribution from the deepest Continental Intercalaire groundwaters.The proposed approach reduces ambiguity about the studied aquifer systems, greatly improves the conceptual understanding of their behaviour, and could provide insights into the vulnerability of the aquifers to different anthropogenic pollution phenomena. The methodology used appears to be a valid tool that could be applied to other geographical areas, to inform the design and implementation of efficient management strategies aimed at improving the quality and availability of water resources. Moreover, three-dimensional modelling methods are becoming increasingly applied to different aspects of groundwater management, to obtain a detailed picture of subsurface conditions.

Rock mass properties and their suitability as a foundation for a rolled compacted concrete gravity dam: case study of Beni Haroun dam (Mila, NE Algeria)

Dams are generally designed and built to resist the most severe destabilizing conditions. Their failures have caused severe damages and loss of lives through history. The investigations carried out on failed dams have, in most cases, unveiled that foundation problems are usually the cause. These problems are very often related to the condition of discontinuities dissecting the rock foundations. Being weak, they are the preferred planes for deformation and rupture causing the collapse of the whole structure. This study deals with the rock mass properties and their suitability as rock foundation for Beni Haroun dam, the largest dam in Algeria. The dam is located in the north-eastern part of Algeria on Wadi El-Kebeir, approximately 40 km from its outfall in the Mediterranean Sea. The dam is a roller-compacted concrete type with a height of 120 m, a crest length of 710 m, and a water storage capacity of approximately 1 billion m3. The dam is founded on Ypresian limestone rock mass. The present study was carried out both in the field and in a laboratory. The field study included geological mapping of the engineering, an intensive discontinuity survey, and sampling. Laboratory tests were conducted to determine shear strength, uniaxial compressive strength, tensile strengths, and Young’s modulus of rock samples. The shear strength of discontinuity was evaluated according to the criterion developed by Barton and Choubey. The joint roughness coefficient was calculated through a statistical approach using the parameter Z2, and an empirical approach based on a visual comparison with standard profiles of the Barton–Choubey roughness. The quality of the rock mass was estimated using Rock Mass Rating (RMR) and Geological Strength Index (GSI) systems. The stability of the dam foundation was assessed using the DMR system and the Hoek and Brown failure criteria. The rock mass of the dam foundation is the Ypresian limestone formation and is of fair quality. This study has shown that this rock mass is adequate as foundation for Beni Haroun RCC dam.

Hydrodynamic functioning of rhythmic springs: a case of M’Chaki spring (Jijel – NE Algeria)

Rhythmic springs are characterized by a rhythmic flow attributable to a hydraulic phenomenon of filling and emptying one or several siphonic reservoirs located upstream of the springs. The M’Chaki spring is the only rhythmic spring in Algeria. The present research was carried out to determine its hydrodynamic functioning on the basis of understanding the hydrodynamic and chemical responses of the spring as well as the geological conditions of the area. Hydrodynamic results indicate that the M’Chaki spring has two types of flow: one is permanent, while the other one is rhythmic, characterized by a cyclicity ranging from 30 min up to 2 h 16 min during the year. Comparison of the spring’s discharge between low and high water periods shows that the discharge of permanent flow varies between 24 and 100 L/s, and the maximum rhythmic flow discharge varies between 70 and 280 L/s, indicating the contribution of rainfalls to supplying the spring. Cycle’s analysis (from 37 up to 60 min) during one day shows that the rhythmic flow is linked to 3 siphonic reservoirs. Hydrochemical study confirmed the obtained hydrodynamic results and indicated that the origin of the permanent water flow is less superficial than the rhythmic water flow. It mentioned also that the siphonic reservoirs were carved in Triassic brecciated formations and highly fractured Liassic carbonate formations. Combining geological, hydrodynamic and hydrochemical data enabled us to propose a conceptual scheme to reveal the disposition of siphonic reservoirs and to explain the functioning of the M’Chaki spring.

The EPIK multi-attribute method for intrinsic vulnerability assessment of karstic aquifer under semi-arid climatic conditions, case of Cheria Plateau, NE Algeria

Karst aquifers supply an important freshwater resource for MENA (Middle East and North Africa) semi-arid regions. Their functioning conditions reveal often several contaminations. The Cheria carbonate aquifer (NE Algeria) has never had management tools to deal with the pollution of this resource. The outlining and protection of the vulnerable areas are essential to ensure the water purity and the consumer health. Based on the EPIK multicriteria analysis method, we aim in our study to assess the karstic aquifers intrinsic-vulnerability to contamination in the Cheria Plateau. This method has been already applied for contamination problems in Northeast Algeria. It uses a conceptual scheme that considers epikarst, protective cover, infiltration, and karst network as parameters. In addition, it also uses the interpolation of the geophysics data to define the conditioning attributes. The resulting vulnerability map categorizes all the basin vulnerable areas and the groundwater protection zones. Nearly 30% of the study area was judged as highly vulnerable to anthropogenic pollution, whereas around 10% is moderately vulnerable. These results confirm that the karst aquifer of the Cheria Plateau is severely polluted by chemical pesticides resulting from farming activity. In addition to the surrounding agricultural lands, the underground of Cheria city was found as extremely vulnerable to pollution (F < 19). Our study delimited boundaries for the karst aquifer protection zones and for an integrated resource management in this region. It recommends applying this method for comparable problems.

Groundwater modelling of the Tebessa-Morsott alluvial aquifer (northeastern Algeria): A geostatistical approach

This paper studies aquifer's hydrodynamic behavior by combining a flow-simulation model with transmissivity optimization (cokriging) in order to provide an optimal management scheme for the groundwater aquifer. The use of a cokriging approach improves the transmissivity data which are insufficient for the database of the groundwater flow simulation model. The obtained results are then used to model the groundwater flow of the Tebessa-Morsott shallow aquifer, located in NE Algeria, under a steady and transient regime. The results of the model calibration for the steady-state (year 2010) show that the recharge by rainfall and leakage rate are similar compared to those calculated by the analytical approach, (84,354 m3/day for the recharge and 36,986 m3/day for pumped water flow rate). The results of the transient regime show the alluvial aquifer affected by large drawdowns reaching 40 m over 20 years (year 2030 scenario) due to increase in water exploitation from pumping wells to answer water needs of the Tebessa region.

Vestiges of a fore-arc oceanic crust in the Western Mediterranean: Geochemical constraints from North-East Algeria

The present day architecture of the Western Mediterranean mainly results from the interplay of different lithospheric plates and the Cenozoic consumption of various branches of the Alpine Tethys and Neo-Tethys Oceans. Identifying relics of these oceanic domains in the peri-Mediterranean belts enables pinpointing the earliest stages of this evolutionary framework. In NE Algeria, the Kef Lakhal Complex (Edough Massif) is composed of amphibolites and meta-gabbros metamorphosed under amphibolite facies conditions and thrust onto the northern African margin during earliest Miocene. Geochemical analyses reveal that amphibolites and metagabbros have major and trace element signatures characteristic of tholeiitic basalts and gabbros and display N-MORB (La/SmN = 0.7–0.9) to E-MORB (La/SmN = 1.1–1.2) affinities. Enrichments in U and alkalis (Cs, Rb) and high 87Sr/86Sri ratios on bulk rocks and minerals (up to 0.70856) are typical of seawater alteration and indicate that the Kef Lakhal Complex represents a piece of altered oceanic crust. Parental magmas were derived from a Depleted Mantle source (WR εNdi = 8.2–9.9 and εHfi = 10.4–14.4) that preserved some canonical MORB ratios (Ti/Eu = 5700–7600 and Y/Ho = 27.4–29.0), but which was contaminated by a component akin to recycled oceanic crust and associated sediments (Ce/Pb = 10.5–22.2; 206Pb/204Pbi = 18.41–18.74; 207Pb/204Pbi = 15.49–15.59; 208Pb/204Pbi = 37.73–38.37). The sedimentary component is consistent with a volcaniclastic origin and substantiates an intra-oceanic setting. The geochemical characteristics of the Kef Lakhal rocks are comparable to present day (Mariana, W Pacific Ocean) or fossil (Xigaze, SE Tibet) fore-arc oceanic crust. An overview of the Western Mediterranean geodynamic indicates that the most likely period for initiating formation of a fore-arc corresponds either to the Early/Late Cretaceous or to the Middle Eocene. 40Ar/39Ar dating on amphibole further indicate that after thrusting onto the African margin, the Kef Lakhal Complex cooled down to c.550 °C at 18.14 ± 0.27 Ma (2σ).

Cenomanian Cephalopods of Bellezma-Aures mountains, NE Algeria: Taxonomy and biostratigraphy

The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria is well exposed and rich in macroinvertebrates, including cephalopods. Twenty-five ammonite species and two nautiloid species from the Thénièt El Manchar, Djebel Metrassi and Djebel Bouarif sections are described and seven assemblage zones proposed as provisional working units: Mantelliceras mantelli–Sharpeiceras laticlavium Assemblage Zone (lower Cenomanian), Mantelliceras dixoni Assemblage Zone (uppermost lower Cenomanian), Cunningtoniceras inerme Assemblage Zone (lower middle Cenomanian), Acanthoceras rhotomagense and Acanthoceras cf. rhotomagense Assemblage Zone (middle middle Cenomanian), Acanthoceras amphibolum Assemblage Zone (upper middle Cenomanian), Acanthoceras jukesbrownei Assemblage Zone (uppermost middle Cenomanian), and Neolobites vibrayeanus Assemblage Zone (lower upper Cenomanian). The lower Cenomanian Mantelliceras mantelli–Sharpeiceras laticlavium Zone is subdivided into the Submantelliceras aumalense, Sharpeiceras schlueteri and Mantelliceras saxbii subzones. The base of the middle Cenomanian is marked by the disappearance of species of Mantelliceras and the appearance of the scleractinian coral Aspidiscus cristatus (Lamarck, 1801), associated with Cunningtoniceras inerme (Pervinquière, 1907). The middle Cenomanian contains abundant A. cristatus and species of Acanthoceras, i.e., A. cf. rhotomagense (Defrance in Brongniart, 1822), A. jukesbrownei (Spath, 1926) and A. amphibolum Morrow, 1935. An ammonite zonal scheme is then applied to the Cenomanian exposed in the Bellezma-Aures mountains located on the southern Tethys margin in Algeria.