NW Algeria Research Articles

Quality assessment of reclaimed water for irrigation purpose and aquatic life protection in the Mekerra sub-watershed (NW Algeria)

Quality assessment of reclaimed water for irrigation purpose and aquatic life protection in the Mekerra sub-watershed (NW Algeria)

Upper Pliocene bivalve shell concentrations from the Lower Chelif basin (NW Algeria): Systematics, sedimentologic and taphonomic framework

Sedimentologic and palaeontological investigation of the Upper Pliocene Slama Formation in the Lower Chelif Basin (NW Algeria) led us to collect important bivalve assemblages for taxonomic and taphonomic purposes. A rather comprehensive inventory list of Upper Pliocene bivalves from northwestern Algeria is now available and consists of 30 species, 17 of which are extinct ones. Four principal taphonomic attributes were analysed: bioerosion, encrustation, fragmentation, and abrasion. Physical and biogenic sedimentary structures are used for palaeoenvironmental interpretations. The taphonomic, sedimentologic and ichnological characteristics of most of the deposits suggests they originated from discontinuous processes of winnowing and bypassing of sediments, probably due to the action of storms in shallow waters, mainly in the shoreface depositional environment. The bivalve assemblage is dominated by disarticulated valves and displays significant taphonomic alteration in the shells. Sclerobionts traces in shells particulary affect the oyster shells. Bioerosion traces are predominately those of clionid sponges (Entobia isp.), polychaetes (Maeandropolydora isp. and Caulostrepsis isp.), bivalves (Gastrochaenolites isp.), and of predatory gastropods (Oichnus isp.). Among the sclerobionts, the identified encrusters were juvenile oyster recruits, barnacles, polychaetes (serpulid tubeworms), bryozoans (Microporella sp. and Acanthodesia sp.), and vermetid gastropods (Petaloconchus intortus).

Lower Bashkirian fusulinoideans from the upper part of the Tagnana Formation (Carboniferous, NW Algeria)

The upper member of the Tagnana Formation of the Djebel Bechar Group (informally the Tagnana-3 or Tagnana Ill member) yielded fusulinoideans and other related foraminifera of the genera Pseudoendothyra (rare), Pseudostajfella (Semistaffella) (rare), Millerella, Pseudonovel/a, Plectostaffella, Eostaffella and Mediocris. The presence of Eostaffellina (rare) and Endostaffella is doubtful. The difference between Millerella and Eostaffella cannot be adequately defined by evolute versus involute coiling. Pseudonovella Kireeva, 1949 is redefined to include Seminovella Rauzer-Chernousova, 1951. The foraminifera are from two samples, one from close to the top and the other from near the base of the Tagnana III Member. Conodonts from the same samples, in comparison with the fusulinoidean foraminifera indicate similar or slightly younger ages; combined evidence from conodonts and foraminifera shows that the Tagnana-III Member at its upper boundary is Askynbashky or Akavassky (probably late Akavassky), while its lower boundary is Akavassky or Siuransky (probably late Siuransky) in age.

Quality assessment of water used for human consumption and irrigation purpose in parts of Tafna watershed (NW Algeria)

Quality assessment of water used for human consumption and irrigation purpose in parts of Tafna watershed (NW Algeria)

Bioerosion in Ostrea lamellosa shells from the Messinian of the Tafna basin (NW Algeria)

Bioerosional trace fossils (borings) are reported for the first time in Algeria. Three ichnotaxa observed in the shells of Ostrea lamellosa from the lower Messinian (upper Miocene) deposits of the Tafna basin (NW Algeria) are described. The ichnotaxa are Entobia cf. geometrica, Gastrochaenolites cf. torpedo and Trypanites isp.. Ostrea lamellosa shells are encrusted by balanid barnacles which are bored by Trypanites isp.. The ichnoassemblage is assigned to the Trypanites ichnofacies. Besides the bioerosion and encrustation described herein, specimens permitted the identification of the different phases of the Messinian transgression across the Souk el Khemis shoal.

Latest Pliensbachian to Early Toarcian palynological record in the Traras basin (northwestern Algeria)

The present study of the Tisseddoura limestones and Bayada bed formations in Traras basin (NW Algeria) refines our understanding of the palynological content of latest Pliensbachian- Early Toarcian interval. The analysis of 38 samples allowed us to identify a diversity of most of the characteristic of palynomporphs such as spores (Rotverrusporites tenuis, Cyathidites australis, Cyathidites minor, Reticulatisporites castellatus, Lycopodiumsporites reticulatum, Lycopodiumsporites clavatoides), pollen grains (Classopollis torosus, Spheripollenites subgranulatus, Callialasporites segmentatus, and Cerebropollenites sp. associated with acritarchs (Micrhystridium sp., Umbellasphaeridium sp., Baltisphaeridium sp., Acanthodiacrodium sp.), and algae (Tasmanites puntatus, Tasmanites sp., Tytthodiscus sp., Leiosphaeridia sp., Crassosphaera sp., Botryococcus sp., Tapajonites sp., unidentified Prasinophytes) unknown in this Algerian basin until now. The results of qualitative and quantitative analyses of pollen assemblages generated new stratigraphic information on the lower limit of Bayada beds and on the impact of the anoxic event on the low presence of spores and pollen grains in the Polymorphum-Levisoni Zones. Finally, this palynological study, carried out for the first time in Algeria, allowed us to identify pteridophyta spores, gymnosperms, acritarchs, and algae that show a great similarity with palynomorphs found in some northern and southern Tethyan basins.

Aeromagnetic data analysis for the identification of volcano-sedimentary complex: case of Permo-Triassic of the Traras Mountains, NW Algeria

In this study, the aeoromagnetic data are analyzed and interpreted to characterize the deep structure of the Traras Mountains (NW Algeria). Thus, the aeromagnetic data processing (reduction to pole, analytic signal, horizontal and vertical gradients and upward continuation) allowed, for the first time, to show an image of the sub-surface topography of the volcano-sedimentary complex, whose age is attributed to the Permo-Triassic. In addition, the application of the 3D Euler Deconvolution to the aeromagnetic data reveals the existence of several structures at different depths with mainly NNE–SSW and NW–SE directions. The structural model obtained from these results, shows a perfect correlation between the dynamics of studied Permo-Triassic complex and the local and regional tectonics.

Interplay of Autogenic and Allogenic Processes On the Formation of Shallow Carbonate Cycles in a Synrift Setting (Lower Pliensbachian, Traras Mountains, NW Algeria)

AbstractMeter-scale shallowing-upward cycles are recorded in many carbonate successions around the world. It is often difficult to recognize whether they represent autocycles, formed through intrinsic controls, or allocycles, resulting from orbital forcing or tectonic movements, or both. Here, we review the criteria used in the identification of the two types of cyclicity and apply them to two newly described lower Pliensbachian outcrops in the Traras Mountains, northwestern Algeria. Throughout the investigation of six sections, the deposits are suggested to have formed in intertidal–supratidal to shallow subtidal environments on a tropical ramp in the Western Tethys. In this area, shallowing-upward small-scale peritidal and subtidal cycles have been shown to be, and are assumed to be, ordered. The carbon isotope data mirror the recorded cycles and indicate different lengths of subaerial exposures. These cycles, in a developed within synrift setting, have been interpreted as produced mainly by autocyclic processes, but interacting with allocyclic factors. Peritidal cycles are thought to be generated by progradation of intertidal and supratidal flats into lagoonal sediments, while subtidal cycles are interpreted to have been controlled by lateral migration of shoals. The impact of the minor fluctuations of eustatic sea level is weakly marked, and only long subaerial exposure can reveal the contribution of these fluctuations to the formation of the recorded cycles. Tectonic movements resulting from spreading of the Tethys are interpreted to have controlled cycle distribution and thickness at a regional scale. However, synsedimentary tectonic features are rare in the studied area; this suggests that sediment transport would control the thickness and duration of cycles instead of the rate at which accommodation was created.

The destructive 1790 Oran (NW Algeria) earthquake in a region of low seismicity

The Oran earthquake of 9th October 1790 in NW Algeria caused heavy damage in that city, and originated a tsunami observed in Almeria and Cartagena, SE Spain. It occurred in a region of low seismicity in comparison with other regions east of Algeria. The abundant contemporary documentation analysed in the present study, some of it not used previously, confirms a maximum intensity of IX–X (EMS-98) for Oran city. The estimated focal parameters are: origin time 01 h 15 m or 01 h 30 m UT, duration 1-to-2 min, a macroseismic offshore epicentre at 35.9°N, 0.6°W to explain the generation of the tsunami, and estimated magnitude 6.0–6.5. The rupture is complex, formed by two events, and may have been associated with NE-SW oriented thrust faults present in the area.

Carbonate concretions in Miocene mudrocks in NW Algeria: types, geochemistry, and origins

Carbonate concretions have been recorded in many recent and ancient marine sediments around the world. The Middle Miocene marl of the Tenes area, situated in the northeast of the Lower Chelif Basin in NW-Algeria, contains such carbonate concretions but with a variety of different structures and morphologies. Three different basic types are distinguished: nodular (spheroidal, ellipsoidal, disc, and irregular), stratiform, and tubular concretions, the last locally have a central conduit. The close association between carbonate concretions and synsedimentary deformation structures (synsedimentary faults, slumps) and normal faults, pronounced in the Ounsour Anhas outcrop, indicates synsedimentary instability related to upward fluid movement. The concretions were formed by precipitation of micritic carbonate within the host marl at shallow burial depth, probably in the active microbial methanogenesis zone. Strongly varying δ13C values (− 9.82 to + 5.85‰ PDB) are interpreted as the result of the balance between 13C-enriched (residual CO2 from methanogenesis) and 13C-depleted (microbial organic matter decomposition) CO2 added to the pore solutions. δ18O values (− 2.39 to + 1.71‰ PDB) indicate that carbonate concretion growth occurred during early diagenesis conditions, from marine-derived pore-water.

Challenging asymmetric cements as indicators of vadose diagenesis: “pseudo-gravitational” cements from the lower Pliensbachian of the Traras Mountains in NW Algeria

Asymmetric, pendant cements are considered good indicators for early lithification in the vadose zone. In the present study, asymmetric cements are recorded in thin-sections of a Lower Jurassic limestone from the Traras Mountains (northwest Algeria). Geopetal fabrics, however, indicate that these seemingly “pendant cements” are, in some places, oriented upwards, i.e., they have grown in the opposite direction from that expected, or they grew from grains towards the pore centers. These observations disprove their origin as gravitational cements precipitated from pendant water droplets on the undersides of grains as in the vadose zone. In contrast, a formation in the marine phreatic zone seems more probable. Under high-energy conditions, and after an early lithification stage with isopachous cements in the subtidal zone, strong tidally driven horizontal pore-water flow allowed sufficient seawater to pass through the slightly cemented but still highly permeable rock. Those grain sides, which were oriented towards the pore center, where faster flowing water prevailed, were more exposed to CaCO3-supersaturated percolating seawater and therefore the cements precipitated here show their greatest thickness. In relatively more protected areas around the margins of the pores, asymmetric cements are rarely developed. The resulting rock exhibits an unusual, heterogeneous cementation with preferential centripetal nucleation areas.

Frasnian (Upper Devonian) integrated facies analysis, magnetic susceptibility and sea-level fluctuations in the NW Algerian Sahara

AbstractChanges in the palaeoenvironment are investigated in two representative Frasnian sections of the NW Algerian Sahara, integrating sedimentology and magnetic susceptibility (MS). The Ben Zireg section is characterized by condensed and ferruginous calcareous deposits; in the South Marhouma section the sedimentation rate is high, dominated by muddy nodular limestones with several hypoxic shale intervals. In both sections, sediments were mostly emplaced on pelagic outer ramps below the limit of storm wave-base, evolving through time from proximal to distal setting. Investigations of the temporal evolution of facies and MS data permit a first estimate of the local sea-level trends in NW Algeria. These trends match the overall long-term rise of sea level recognized worldwide from Frasnian Zone 5 upwards. Noteable positive excursions of the sea-level curve related to the semichatovae transgression, as well as to the late Frasnian transgression prior to the late Kellwasser event, can be established in this area. Although the sharp regression of sea level at the upper Kellwasser level can be confirmed from our data, no particular trend is depicted at the transition of conodont zones (Frasnian Zones 12–13) where the presence of the lower Kellwasser level has not yet been clearly recognized.

Terrestrial Gastropoda from the Pleistocene of Beni Saf, NW Algeria

A study of the terrestrial gastropods of the Pliocene-Quaternary succession of the Beni Saf sea cliff, NW Algeria, at the Playa Port locality, is presented herein. The sedimentary succession is subdivided into four lithostratigraphic units, on the basis of their lithologic and biogenic contents: the three first units (A, B and C) are of marine origin; the last unit (D) is of continental origin and includes three beds yielding terrestrial gastropod fossils, which form laterally traceable horizons. Herein, we describe the section's lithology, present stratigraphical considerations regarding its age and thoroughly described its terrestrial gastropod fossil fauna. In total, 13 species are reported here from Beni Saf: 2 caenogastropods (family Pomatiidae) and 11 stylommatophorans (family Achatinidae and superfamily Helicoidea). The sedimentological data indicate that the depositional setting at Beni Saf was a dune system flanked by wadi floodplains deposits (snail levels); the ecological preferences of the gastropods largely agrees with this scenario.

The November 26 and 27, 1927 devastating flood event (NW Algeria): characterization and reconstruction using historical data

The historical records show that the Northwestern Algeria has experienced more than 130 floods, which were sometimes catastrophic. They caused more than 1000 deaths and significant damage. In this work, we try to reconstruct the most devastating and deadly historical flood that occurred on November 26 and 27, 1927. This event is interesting to discuss disaster scenario because of its extent and impacts and the availability of data. For this purpose, we used historical press reports, scientific papers, and archival reports. This work allowed the reconstruction of the hydroclimatic situation during the flood and the regional scale impacts. It presents also the catastrophic flooding of the Ain Sefra river at Mostaganem and that of El Hammam river, as well as the Fergoug dam breaking at Mohammadia. The main factor triggering these floods was the heavy rainfall. Other factors have increased the damage such as the occupation of high-risk areas and the human failure. This event caused 430 killed persons, more than 1200 disaster victims, and around one billion francs losses. These effects evidence the high vulnerability of the Northwestern Algeria to the occurrence of floods. For that, if a similar event occurs in the future, it can be extremely negative.

Miocene sediment mineralogy of the lower Chelif basin (NW Algeria): implications for weathering and provenance

Mineralogical investigations of clay and nonclay minerals were conducted on the Miocene sediments from three sections of the lower Chelif basin, northern Algeria. Bulk rock analyses of Miocene sediments show that these clastic sediments are dominated by variable mineralogical compositions and concentrations. Quartz is the dominant mineral through the three stratigraphic intervals and calcite (except in the upper layers) and dolomite are lacking in the Messinian deposits. The clay mineralogy is dominated by smectite (24%) and mixed-layer illite-smectite (I-S) (22%) during the Burdigalian-Langhian, illite (36%) and kaolinite (28%) in the Tortonian, and illite (49%) and I-S (20%) in the Messinian stratigraphic range. The smectite-(kaolinite+chlorite)-illite ternary diagram shows that, in general, Miocene sediments originated from a mixed mafic and felsic source and were influenced by physical erosion and chemical weathering processes.

Geochemical and qualitative assessment of groundwater of the High Mekerra watershed, NW Algeria

Groundwater constitutes the main source of water supply in the High Mekerra watershed of northwestern Algeria. This resource is currently under heavy pressures to meet the growing needs of drinking water and irrigation. This study assesses the geochemical characteristics of groundwater of the High Mekerra watershed at 21 points distributed across the two main aquifers (Ras El Ma and Mouley Slissen) in the region. Hydrochemical facies of Ras El Ma groundwater are dominantly MgCl and CaCl type, while those of Mouley Slissen groundwater are of CaHCO3 type. Principal component analysis shows a strong correlation between groundwater mineralization and Ca2+, Na+, Cl− and SO42− ions stemming from the dissolution of carbonates, gypsum and anhydrite. Groundwater mineralization evolves from south to north. Geochemical modeling shows that the High Mekerra groundwater is saturated with respect to calcite and dolomite and undersaturated with respect to gypsum and anhydrite. Nitrate concentrations that exceed the WHO standard (50 mg L−1) at several points are linked to the agro-pastoral activities in this region.

Contribution of hydrological modeling to the water resources assessment using soil-moisture accounting model: the case of the wadi Taria (Macta basin, NW Algeria)

Contribution of hydrological modeling to the water resources assessment using soil-moisture accounting model: the case of the wadi Taria (Macta basin, NW Algeria)

Estimation and condition of groundwater recharge in semiarid zone: example from the Ksour Ridge, NW Algeria

In a recharge area characterized by a semiarid or arid climate and a low annual rainfall, aquifers can be hardly recharged adequately, as it was demonstrated by classical monthly hydrological balance computations. The methodology proposed in this work relies on spatial and temporal interpolation of scarce climatic data. This methodology can be used to determine the recharge flow of aquifers in these zones. The AinSefra’s syncline (Western Saharan Atlas, Southwest Algeria) includes the sandstone aquifers of Continental Intercalary and the Plio-Quaternary layers. It forms an excellent example for this application. Three years with different annual rainfalls are chosen in this application: 1983 as dry year, 2006 as average year, and 2008 as humid one. This application requires information about the soil nature, the surface, and the altitude of the recharge areas. The rainfall and the recharge flow of aquifers indicate that the principal recharge areas are the Jurassic outcrops in the humid years when the annual rainfall exceeds 300 mm.

A graphical method to study suspended sediment dynamics during flood events in the Wadi Sebdou, NW Algeria (1973–2004)

Small sub-basins are numerous in Mediterranean area and global sedimentary budgets cannot be obtained without a detailed understanding of the hydroclimatic processes that govern sediment fluxes in these small river systems. In this study, the shape of the relationship between sediment concentration (C) and water discharge (Q) during flood events of a 31-years period (1973–2004) was analyzed at the outlet of the Wadi Sebdou basin (256 km2) in northwest Algeria, using a new graphical analysis method based on features of hysteresis loops. Each flood was decomposed as successive stages – each of which being characterized by a sediment rating curve – and used to quantify the contribution of diverse sediment sources within the basin. Seven common classes of hydrological events (single valued and six hysteresis loops: clockwise, counter-clockwise, eight-shaped, single valued plus one loop, either clockwise or counter-clockwise, and single valued plus at least two loops) were explored. Sediment supply from locally derived sources (or “base load”) was high and reached 77% of total sediment yield for the study period, and was attributed to weathering of bed material or gullies. The remainder portion was derived from hill-slopes, re-suspension of fresh fine deposits in the river bed, or bank collapse. The ratio of suspended sediment load derived from active sediment source varies considerably from one flood to another depending on many factors, such as seasonality and antecedent type of flood. The simpler floods were the most frequent ones but produced less sediment. The most frequent floods were clockwise or anticlockwise (52% of floods) but brought only 34% of the total sediment flux. The 18% of the most complex floods (single valued plus at least two loops) produced more than 53% of the sediments, mainly supplied by base load (84%). Intra-annual variability was very high. Over 31-years, the five biggest floods cumulated 64% of the total sediment flux and were of three classes, the most complex floods being dominant. The largest contribution occurred during one single 33-days long hydrological event with complex form which represented 26% of the total sediment flux. Apart from the five biggest flood events, the base load represented 53%. The biggest floods favour base load as compared to the smallest ones.

Suspended sediment transport in a semiarid watershed, Wadi Abd, Algeria (1973–1995)

Summary A quantification of the fine sediment budget of a wadi (dryland river) in NW Algeria is presented for a period of 22 hydrological years (1973‐1995). The climate is Mediterranean over the Wadi Abd basin (2480 km 2 ), the mean annual precipitation is 250 mm and the mean annual discharge is 1.0 m 3 s � 1 at the gauging station. Regression relationships between water discharge Q and suspended sediment concentration C are calculated from 1432 paired measurements in the Wadi Abd, leading to power-law equations of the type C = aQ b . The variability of coefficients a and b, calculated for 138 floods and flood stages, is analyzed. The median value of b is 0.757, indicating that C is almost proportional to Q 3/4 . Given that the (a, b) pairs are correctly aligned (r 2 = 0.578), the coefficients a and b are not independent. Regression relationships between daily Q and daily suspended sediment concentration and discharge Qs are calculated from 702 input data. The performances of these regression relationships are shown to be equivalent, leading to over-estimations of 20‐25% of the suspended sediment flux. The non-biased C‐Q sediment rating curve is used to extrapolate a time series of C measurements, and thus to analyze the long-term patterns in suspended sediment transport. Average sediment wash-down (136 t km � 2 yr � 1 ) is similar to the mean global value. The ratio of sediment wash-down to the river water discharge is 10.7 · 10 6 tk m 3 , 20 times greater than the average ratio in the Earth’s eastern hemisphere, and illustrates the highly erosive power of wadis. Variability is shown to be significant at the seasonal scale (CV = 89%) and higher at the interannual scale (CV = 139%). The fine sediment flux mainly occurs in autumn (48.4%) and spring (32.7%). Although precipitation decreased, it was more irregular from one year to another over the period 1985‐1995 than during the period 1973‐1985, and the Wadi Abd, which was a perennial river, became intermittent in the late 1980s. This increasing irregularity is accompanied by: an amplification of the variations of discharge, an increase in the average discharge of approximately 20% during the second period, and a higher and more irregular suspended particulate flux. The mean annual suspended