Showing papers in "Journal Of African Earth Sciences in 2022"

Gold-bearing listwaenites in ophiolitic ultramafics from the Eastern Desert of Egypt: Subduction zone-related alteration of Neoproterozoic mantle?

Abstract: Dike-like variable listwaenites with significant Au (up to 25 ppm) are exposed along fault zones in serpentinites at Um Khasila-Um Huweitat (Kh-H) and Malo Grim (MG) in central and southern Eastern Desert of Egypt, respectively. The protoliths of serpentinites were mainly Neoproterozoic fore-arc mantle olivine-rich peridotites. The Kh-H serpentinites are similar to those formed in the mantle wedge, but the MG serpentinites are similar to those formed in the subducted oceanic slab. Serpentinization fluids sourced from dehydrated subducted sediments and oceanic crust. However, the Kh-H serpentinites received more lighter fluids mobile trace elements relative to MG serpentinites (av. Ba/Th = 312 vs. 0.79; av. U/Th = 466 vs. 0.018; av. As/Sm = 0.057 vs. 0.76; av. Cs × depleted mantle = 5075 vs. 7272). The Kh-H listwaenites are allometamorphic, formed by the intrusion of gabbro-diorite and the release of the subducted slab-derived CO2 into the mantle wedge serpentinites giving talc-carbonate (Type I) with high K2O (av. 3.27 wt%), Sr (av. 1131 ppm), Rb (av.165 ppm), Ba (av.407 ppm), and Zr (av. 23 ppm). The MG listwaenites, which have substantially lower K2O, Na2O, TiO2, and Al2O3 concentrations, are autometamorphic and were generated by the loss of SiO2 and addition of CO2 into the subducted serpentinites. With temperature decrease, in Kh-H listwaenites magnesite was overgrown by ankerite, while in MG listwaenites carbonate changed from magnesite to dolomite to calcite. SiO2-bearing fluids could have mixed from continental crust during Kh-H ophiolite emplacement, forming silica-rich listwaenite (Type III) with enriched K2O, TiO2, As, Ba, W and Th. This could be linked to carbonation of serpentinites in MG, forming silica-carbonate listwaenite (Type II) with enriched MnO, Sc, Cr, As, Sr, Cs, Ba, Pb, and U. Mixing of silicification fluids with the Kh-H altered serpentinites most likely increased gold concentration in the enclosed listwaenites. In the MG listwaenites, however, there is no correlation between Au content and SiO2/(CaO + MgO) ratios, indicating that gold was frequently concentrated by the carbonation process.

Assessment of heavy metal contamination and health risk in the coastal sediments of Suez Bay, Gulf of Suez, Egypt

Abstract: Urban and industrial wastewaters, and the weathering of rocks are the main anthropogenic and natural sources of heavy metals (HMs) in coastal worldwide environments. The present work examined the content, distribution, potential sources, and ecological risks of HM contamination in the coastal sediments of Suez Bay, Egypt. Six pollution and health risk indices and multivariate statistical tools were applied. The ranges of HMs (μg/g) were in order: Fe (239–983), Mn (4.70–189), Cr (1.75–19.49), Co (0.04–12.87), Zn (0.78–15.57), Ni (0.78–10.90), Cu (0.23–7.53), Pb (0.74–6.92), Cd (0.10–0.97), and Hg (0.11–0.89). The results of pollution load index (PLI) and modified contamination degree (mCdeg) indicated that the Suez Bay area seems to be free from pollution. However, some individual sites recorded high concentrations of Cd and Hg, which might be attributed to the presence of some ports, industrial activities, sewage, shipbuilding workshops and heavy traffic of commercial ships. Moreover, the assessment of the carcinogenicity risks by dermal absorption was in order Cr > Pb > Cd for adults and children. However, the study area does not suffer from any potential carcinogenic risk because the total cancer risk (LCR) was less than 1 × 10−6.

Assessment of rainfall-induced landslide susceptibility in Artvin, Turkey using machine learning techniques

Abstract: In this study, the performances of machine learning models, such as artificial neural networks (ANN), gradient-boosting machines (GBM), random forest (RF) and support vector machines (SVM) in rainfall-induced landslide susceptibility mapping were evaluated. For this purpose, the Arhavi, Hopa and Kemalpaşa districts of Artvin, which is one of the highest rainfall areas in Turkey, were identified as the study area. A landslide inventory comprising 533 landslide polygons (3959 pixels at 10-m resolution) was used; 70% of the pixels showing the landslides were used for training the models and the remaining 30% were used to validate the models. For landslide susceptibility modelling, 13 factors associated with landslides were considered. The area under the receiver operating characteristic curve was found to reveal the predictive capabilities of the models. As a result, the prediction rates of the ANN, SVM, RF and GBM models were found to be 93.8%, 94.8%, 96.1%, and 97%, respectively. According to the results, the GBM outperformed other models.

Mantle source characteristics of the late Neoproterozoic post-collisional gabbroic intrusion of Wadi Abu Hadieda, north Arabian-Nubian Shield, Egypt

Abstract: This article presents geochemical and mineralogical data for the Neoproterozoic Abu Hadieda mafic intrusion (AHMI), which exposed at the boundary between the northern and central domains of the Eastern Desert of Egypt, to study its magma source and petrogenesis. Field relations indicate that the AHMI is younger than the syn-tectonic tonalite-granodiorite, but older than post-collisional monzogranite and alkali feldspar granite. The AHMI is neither deformed nor metamorphosed and keep the primary texture and mineralogy indicating a post-collisional setting. It consists mainly of medium to high-K calk-alkaline pyroxene-hornblende gabbro with minor diorite. The low Mg# (32–41) values of the gabbro are typical of young post-collisional mafic intrusion in the Arabian-Nubian Shield (ANS). Geothermobarometric calculations suggest that the pyroxene-hornblende gabbro was crystallized at relatively high pressure (0.6 GPa) and temperature (800–915 °C). The samples show a general enrichment in LREEs and LILEs (e.g., Sr, Ba, K) relative to HREEs and HFSEs (e.g., Nb, Ta, Hf, Ti, Zr). The chemical and mineralogical signatures are consistent with evolution of the AHMI from emplacement of a primitive partial melt derived from a lithospheric mantle source that had previously been metasomatized, in an early stage of ANS evolution, by subduction-related melts. Remobilization and melting of this lithospheric source occurred in a post orogenic setting, likely driven by crustal thinning and extension.

Comparison of analytic network process and artificial neural network models for flash flood susceptibility assessment

Abstract: Floods are natural risks with devastating consequences for the environment, people and the economy. Gabes Catchment is regularly devastated by floods owing to urban sprawl, population growth, unregulated municipal systems and indiscriminate land use. However, mitigation of flood impacts can be achieved via flood implementation forecasting systems. In this study, Analytical Network Process (ANP) and Artificial Neural Network (ANN) models were integrated into a Geographic Information System (GIS) to identify and classify flood-prone areas. A geographic information database was derived from the existing geological map, digital elevation model (DEM), precipitation and land-use data. The evaluation of different factors can affect the flood analysis. The ranked and normalized indicators were then weighted and classified with an ANP model to establish the training database. The normalized layers, combined with the training site maps, were then fed to a multilayer perceptron neural network (MLP) to yield a flood risk map. Using a field survey, historical flood data, and satellite imagery, 226 flood locations were identified and classified into 70% training data sets and 30% validation data. Results obtained from ANP and ANN showed that 10% and 14% of all areas were classified as high and very high flood susceptibility, respectively. The performance of both models was assessed using the operational characteristic of the ROC model. The Area Under the Curve ‘AUC’ of ANP and ANN models were 0.861 and 0.876, respectively. The obtained results show the similarity and comparability of the used methods. These results corroborate the perception of susceptibility in the population of the city of Gabes. The study outcomes are of great value to policy makers and state authorities in order to achieve greater awareness and adopt strategies for the preparation and management of the environment in the future for the city of Gabes.

Eburnean/Trans-Amazonian orogeny in the Nyong complex of southwestern Cameroon: Meta-basite geochemistry and metamorphic petrology

Abstract: New and published geochemical, petrologic, and geo-thermobarometric data of meta-basites were combined to constrain the geodynamic evolution of the Paleoproterozoic Nyong complex (NyC) in southwestern Cameroon, a part of the Central African tectonic belt. Their geochemical signatures, including (La/Yb)N = 0.53–56.26, slightly positive Eu anomalies (0.21–1.04), abundance of Pb and U, negative Nb–Ta anomalies, and REE depletion, suggest various degrees of partial melting of mostly spinel-bearing mantle sources. In addition, the meta-basite protoliths can be classified as IAB-, E-MORB-, N-MORB-, and exceptionally OIB-compositional types with minor crustal contamination. Petrologically, the meta-basites are characterized by coronitic textures, marked by microblasts and porphyroblasts of garnet surrounded by plagioclase or by both plagioclase and clinopyroxene, indicating metamorphic recrystallization under decompression. Our new geo-thermobarometric data outline various segments of an overall clockwise pressure‒temperature path. In the different meta-basite samples, the pressure peak at eclogite-facies conditions (∼625 °C, 11.7 kbar) was followed by nearly isobaric heating to amphibolite-facies conditions (600–690 °C, 11.5 kbar) or decompression and heating to amphibolite- (∼740 °C, 10.8 kbar) and granulite-facies (∼800 °C, 10.0 kbar) conditions. The retrograde path evolved from granulite- (850–750 °C, 11.3–7.6 kbar) and amphibolite- (790–550 °C; 12.4–3.0 kbar) to epidote-amphibolite- (∼600‒490 °C, 8.0–7.6 kbar) and greenschist-facies (∼400 °C, 4.2 kbar) conditions. Combining the new with published, in general high to middle temperature-middle pressure data from various rock types, with published high temperature-high pressure data from eclogites highlights distinct burial-exhumation paths for the NyC rocks: these paths document a clockwise pressure-temperature evolution, typical for a collisional setting associated with the Rhyacian-Orosirian Eburnean/Trans-Amazonian orogeny in Cameroon. The eclogite data outline a deep burial–isothermal decompression evolution, typical for a subduction setting predating the collisional setting.

Delineation of groundwater potential zones in KwaZulu-Natal, South Africa using remote sensing, GIS and AHP

Abstract: The present study aimed to spatially identify groundwater potential (GWP) zones in KwaZulu-Natal (KZN), South Africa (SA) using Geographic Information Systems (GIS) and remote sensing-based multi-criteria analysis. This study is the first to utilise these tools in delineating groundwater in KZN, which is a process dominated by outdated, expensive, and time-consuming in-situ methods. Remote sensing images were used instead of traditional data sampling, which provided a cheaper, faster, and sufficient way of acquiring specific information in data-scarce KZN. Remotely sensed spatial thematic layers viz. geology, lineament density, slope, drainage density, rainfall, land use/land cover, and evapotranspiration were processed and developed using GIS and weighted using the Analytical Hierarchy Process (AHP). The thematic layers were subsequently aggregated using the GIS Weighted Overlay Method to develop a groundwater potential index map. Indices from the map were correlated with 113 borehole logs using the Receiver Operating Characteristic Curve (ROC) and Area Under the Curve (AUC) to validate the results. The resultant GWP map computed that approximately 47.3 Km2 (2%) of the total area falls under Excellent GWP, 24405.4 Km2 (27.45%) under good GWP, 50950.5 Km2 (57.3%) under moderate GWP, and the poor and very poor GWP zones constitute around 13380.8 Km2 (15.1%) and 135.6 Km2 (1%) of KZN. The spatial mapping revealed that the AHP-based GWP map exhibited a very good correlation with borehole data (AUC = 72.6%, n = 113), indicating the accuracy of the AHP as a rating method. The use of freely available remote sensing data and modeling techniques provided a relatively inexpensive groundwater identification method that can successfully replace the rudimentary methods.

Is the Anti-Atlas of Morocco still uplifting?

Abstract: Topographic elevation of orogenic belts in the results of several processes and contributions occurring at different temporal and spatial scales, from short-to long-term and from the surface up to the mantle. Disentangle surface evolution on key areas may then encode for deeper ongoing processes. In this concern, the Anti Atlas of Morocco is a prominent mountain belt with moderate relief and with a long deformation history not recorded during the Cenozoic. The modern topography of the Anti-Atlas is resulted from late Miocene uplift driven by mantle processes. In this study, we address the question if mantle processes are still affecting the topography of the Anti-Atlas by providing new clues on the late Miocene-Quaternary uplift history of the north-western margin of the mountain belt. We analyze and compare the river long profiles and related morphometric features of channels draining the Souss Basin of the Anti-Atlas in western Morocco with analog and numeric similar scenarios. We find that the steepness of the rivers, the χ, ksn, slope and local relief show limited values. Moreover, the channels are characterized by Quaternary fluvial conglomerates lying at high elevation. The projection of the non-re-equilibrated river profile runs below the lower part of the channel. We explore the mechanism that could produce this feature by both numerical and analog models. The analogue and numerical long river profiles from modeling show similar morphometric features compared to the natural case when the uplift rate is diminished or set to zero. We speculate that in the Anti Atlas, uplift may have waned over Quaternary time leading to a spatial change in the critical point of sedimentation, triggering valley infilling at high elevation, and in turn a slow burying of the Anti-Atlas.

Synchrotron scanning sheds new light on Lumkuia fuzzi (Therapsida, Cynodontia) from the Middle Triassic of South Africa and its phylogenetic placement

Abstract: Lumkuia fuzzi is a small non-mammalian cynodont from the Middle Triassic of South Africa. It has traditionally been phylogenetically identified as a basal Probainognathia, but some studies place it more basally as the sister-group to Eucynodontia. Lumkuia is known from a single specimen comprising a skull and partial skeleton. Only the skull has been thoroughly described. Here we use synchrotron X-ray computed tomography to describe the dental series and postcranial skeleton of Lumkuia. The shoulder girdle, forearm, manual phalanges, partial vertebral column, and ribs are described. To assess the effect of these new observations on the phylogenetic position of Lumkuia, the scoring of this taxon is updated and new characters are added to two previous analyses, one supporting Lumkuia as a Probainognathia and the other in which the taxon is usually retrieved as a basal Eucynodontia. Our phylogenetic analyses all unambiguously support the position of Lumkuia as a basal Probainognathia. The most commonly retrieved synapomorphies shared by Lumkuia and the probainognathians are cranial (absence of an ectopterygoid and pineal foramen), postcranial (the procoracoid does not contribute to the glenoid fossa), and palaeoneurological (reduction of the external nasal ramus of the maxillary canal, presence of a cochlear canal) characters. The degree of skeletal ossification and stages of dental replacement and wear support that the specimen is a subadult. The forelimbs were adapted to sprawling and occasional scratch-digging, thus suggesting a facultative fossorial ecology for Lumkuia.

Integration of remote sensing and geophysical data for the extraction of hydrothermal alteration zones and lineaments; Gabal Shilman basement area, Southeastern Desert, Egypt

Abstract: In the Gabal Shulman area of the southeastern desert of Egypt, ASTER and geophysical aeromagnetic data provide useful information for detecting hydrothermal alteration zones and structural features at the surface and subsurface. The band ratio of the data from ASTER, constrained energy minimization (CEM) and Crósta algorithms help to identify new potential alteration zones in the study region. The aeromagnetic data were used to enhance the exploration study in the study area. The Horizontal Gradient Magnitude (HGM) filter was used to map the lineaments in the area. The statistical analysis of the lineaments shows that the main directions controlling the study area are northwest, north, north-northeast, and northeast. Finally, the results of ASTER and the geophysical aeromagnetic data show the presence of new hydrothermal alteration zones in the study region. These alteration zones are mostly associated with two main structures trending NNW-SSE and N-S, mainly along tectonic shear zones (thrust faults) and contacts between serpentinites and basic metavolcanics.

Composition, weathering, and provenance of beach sands adjacent to volcanic rocks in the northern Gulf of Guinea, SW Cameroon

Abstract: The southern coastal portion of the Tertiary Cameroon Volcanic Line (CVL), in the Gulf of Guinea, is bordered by Pan-African granitoids, metamorphic rocks, and Cretaceous sedimentary successions, which are prone to contribute sediments to the nearby Limbe beach. To better constrain the weathering intensity and provenance of the beach sediments, the mineralogy and chemical composition of these sediments were analyzed. The low values of SiO2/Al2O3 ratios and Zircon-Tourmaline-Rutile (ZTR) index, coupled with high Index of Compositional Variability (ICV) indicate compositionally immature sediments. This is further supported by the presence of rock forming minerals such as olivine, pyroxene, and amphibole. The Th/Sc versus Zr/Sc binary and Al2O3–TiO2–Zr ternary diagrams suggest that the studied sediments have not experienced recycling. The Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), the A–CN–K and (A-K)-C-N triangular diagrams indicate that the Limbe beach sediments were undergone moderate to intense weathering. Several provenance discrimination diagrams based on Al2O3, TiO2, Zr, TiO2, La/Sc, and Th/Co, and the ternary plot of V–Ni–Th*10, and the comparison of chondrite normalized rare earth elements (REE) patterns of the studied sediments with potential source rocks suggest that the source area is composed of mafic rocks of CVL. This indicates that the granitic, metamorphic, and sedimentary rocks close to the volcanic structure do not significantly contribute to the sedimentation of the studied beach. In addition, the results of this study indicate that longshore currents do not influence the chemical composition of the sediments.

Styles of Fe–Ti–V ore deposits in the Neoproterozoic layered mafic-ultramafic intrusions, south Eastern Desert of Egypt: Evidence for fractional crystallization of V-rich melts

Abstract: The Korab Kansi and Abu Ghalaga Neoproterozoic mafic-ultramafic intrusions in the South Eastern Desert (SED) of Egypt host economic Fe–Ti–V oxide deposits, ∼41 million tons for Abu Ghalaga ores. The Korab Kansi deposits are composed of titanomagnetite with subordinate ilmenite layers in dunites, gabbros and troctolites. The Abu Ghalaga ores consist of hemo-ilmenite and ilmenite with subordinate magnetite and titanomagnetite lenses in norites , gabbros and anorthosites . The difference in calculated oxygen fugacity ( f O2 : ∼ ΔFMQ–1.24 to −3.28 for Korab Kansi ores and +0.21 to −0.3 for Abu Ghalaga ores) during subsolidus re-equilibration is consistent with different dominant iron and titanium oxides, magnetite and hematite , respectively. Ilmenite in both deposits is enriched in Nb, Ta, Zr, Hf and V, but is poor in Cr and Ni relative to coexisting magnetite, which belongs to magmatic Fe–Ti–V deposits. The Korab Kansi and Abu Ghalaga ore deposits are rich in Ti, Fe, V, Nb, Ta and Hf with subordinate S, Cu, Ga and Zn at high f O2 . The Abu Ghalaga gabbroic intrusion crystallized from ferrobasaltic magmas of tholeiitic affinity at lower temperature (∼1082 °C) and pressure (5.1 kbar) than the Korab Kansi intrusion (∼1180 °C, 8.3 kbar). The Korab Kansi ore deposits mainly formed by fractional crystallization of olivine followed by in situ crystallization of Fe–Ti oxides from ferropicritic/ferrobasaltic parent melts at the floor of the magma chamber . The Abu Ghalaga ores formed as a result of more advanced fractional crystallization of ferrobasaltic parent melts. The Abu Ghalaga Fe–Ti oxides in massive ores at the base of the intrusion grew in situ, whereas most ore lenses in the middle to the top of the intrusion precipitated from immiscible oxide melts that separated from the parental magma in association with floatation of plagioclase and sulfide crystals at a late magmatic stage. Both Fe–Ti ore deposits formed from similar mantle-derived magmas but Korab Kansi ores formed as early fractionates, whereas Abu Ghalaga ores formed late. The Korab Kansi ilmenite is rich in vanadium (up to 3.8 wt% V 2 O 5 ) relative to that of other magmatic deposits. Its parental melt may have formed from locally Fe–Ti–V enriched part of the Neoproterozoic mantle due to interaction with upwelling asthenosphere or a mantle plume . Controlling factors for formation of economic SED Fe–Ti–V deposits were the V-rich ferropicritic/ferrobasaltic compositions of the parental magmas, and addition of H 2 O to cause high magma ƒ O2 . • Microtexture, mineralogy and chemistry of Fe–Ti–V ore deposits in mafic-ultramafic intrusions. • Evidence for fractional crystallization of V-rich melts and formation of Fe–Ti oxide deposits. • Role of in situ crystallization and immiscible separation for genesis of Fe–Ti–V ore deposits. • Controlling factors for economic Fe–Ti–V deposits in Egypt, and explaining high V in deposits.

Application of Geophysics in geo-environmental diagnosis on the surroundings of the Hulene-B waste dump, Maputo, Mozambique

Abstract: This study aims to identify superficial and underground heavy metals contamination and outline contamination plumes on the surroundings of the Hulene-B waste dump. The electrical resistivity method was applied in 4 profiles of 400 m, 2D resistivity. The interpretation of the resistivity values allowed to identify three anomalous zones with possible contamination: (i) North (profile 2) with East-West orientation, perpendicular to the waste dump with resistivity values < 30.0 Ω m; (ii) West of the waste dump and Northwest (profiles 1 and 3), with an orientation parallel the waste dump, with resistivity values of <21.9 Ω m; and (iii) Southwest (profile 4) with perpendicular orientation to the waste dump with resistivity of <14.7 Ω m. Thus, the most notorious anomalies in the western limit (profiles 1, 2 and 4) can be associated with soil and subsoil contamination by heavy metals associated with possible contamination plumes that show a movement to the east-west direction and dissolve when in contact with the groundwater in the south and center of the depressive area. Results of the analysis of the spatial distribution of anomalous values show a decrease with distance from the main source of contamination - the Hulene-B waste dump.

Main structural lineaments of the southern Cameroon volcanic line derived from aeromagnetic data

Abstract: The Cameroon Volcanic Line (CVL) is an African-only active alkaline intraplate feature that ranges in age from Oligocene to recent, with volcanoes crossing the oceanic-continental boundary. Because of its Cenozoic tectonic processes and magmatic features associated to seismic and volcanic activity, studies of the CVL geodynamic are of great importance. Despite its shear zone features, detailed structural geophysical studies of the southern CVL remain elusive. In this work, we use high-resolution airborne magnetic data to reveal geophysical signatures of the CVL. We apply a combination of derivative and phased filters and an improved cross-correlation approach to delineate geological structures of the southern CVL and propose an interpretation from aeromagnetic data. Derivative and phased filters highlight three distinct magnetic domains, with high positive and negative amplitudes. Rata Mount and Rumpi Hills, for example, show a NE-SE trend and a high magnetic amplitude. This finding might be explained by different types of rocks, consisting of the Upper Cretaceous basalt and sandstone sequences. The intensity of the enhanced horizontal gradient amplitude (EHGA) is well associated with geological features and its effects on a topographic relief. From the cross-correlation analysis, we successfully obtained the magnetization direction of a few specific anomalies.

Contrasting Paleoproterozoic granitoids in the Kerdous, Tagragra d’Akka, Agadir-Melloul and Iguerda inliers (western Anti-Atlas, Morocco)

Abstract: The northern margin of the West African Craton is characterized by Paleoproterozoic siliciclastic sediments intruded by ca. 2.1-2.0 Ga Eburnean granitoids. New geochronological data highlight the occurrence of a Rhyacian (2.10 Ga) tonalitic to trondhjemitic magmatic suite, followed by an Orosirian (2.040-2.035 Ga) magmatic suite composed of coeval calc-alkaline diorites, mesocratic granites and leucogranites. Whole-rock major and trace element compositions indicate that: (i) the Rhyacian tonalites and trondhjemites suggest a subduction environment, an island-arc arc or an active continental margin; (ii) the Orosirian plutonic rocks show a geochemical heterogeneity; (iii) the chemical features of diorites correspond to calc-alkaline M-type suites; (iv) granodiorites and granites are typical calc-alkaline I-type granitoids, and (iv) leucogranites, with peraluminous composition, reflect a crustal melting. While the Rhyacian magmatic event indicates a subduction environment, the Orosirian magmatic event is more complex, and the geochemical signatures imply involvement of mantellic magmas and crustal melting. The contemporaneity of these Orosirian magmatic suites and their siliciclastic sedimentary host-rocks suggest a back-arc geodynamic context, similar to what was described in the Reguibat Rise, Mauritania.

Groundwater potential characterisation over the Voltaian basin using geophysical, geological, hydrological and topographical datasets

Abstract: The delineation of prospective zones of groundwater resources has been carried out over the Voltaian basin as a viable alternative source of potable water resource to complement increasing demand for domestic and industrial consumption, owing to the danger posed to surficial water resources within the basin by various anthropogenic activities. In achieving this objective, the groundwater potential of the area was assessed by generating a groundwater potential map (GPM) derived by integrating nine (9) evidential layers obtained from geological, geophysical, hydrological, and topographical datasets in geospatial setting using geographic information systems (GIS). The integration of these nine evidential layers was preceded by the assignment of a weight to each evidential layer based on the fuzzy analytical hierarchy process (FAHP) multi-criteria decision making (MCDM) technique. The assignment of weights to these 9 layers using the FAHP approach was done by three decision-makers (DMs) and dwelled on their relative relevance to groundwater resource delineation within the Voltaian basin. The three DMs employed in weighting these layers have expertise in applying geophysical, geological, hydrological and topographical datasets in groundwater prospecting. The weights obtained for the various evidential layers were subjected to normalisation and subsequently consolidated to produce the GPM using a fuzzy gamma operator value of 0.9 in GIS. The efficiency of the GPM was tested using the Nash-Sutclliffe efficiency (NSE) test and the Index of Agreement test. In all, 0.095%, 10.57%, 44.879%, 40.973%, and 3.974% of the study area were delineated as very high, good, moderate, poor, and very poor groundwater zones, respectively by the GPM. The NSE test yielded a value of 0.9996, and the Index of Agreement produced a value of 0.9999. In this regard, results obtained show that FAHP-based model produced is efficient and subsequently good for groundwater prediction over the Voltaian basin.

Formation of gold-bearing listvenite in the mantle section of the Neoproterozoic Bir Umq ophiolite, Western Arabian Shield, Saudi Arabia

Abstract: Serpentinized peridotite and associated listvenites of Neoproterozoic age outcrop in the Bir Umq area of western Saudi Arabia. The mantle section of the Bir Umq ophiolite is extensively serpentinized. Serpentinite host samples are low in Al2O3 (0.48–0.75 wt%) and CaO (0.28–1.24 wt%) and have high Mg# (0.90–0.92), indicating a strongly depleted mantle protolith, typically associated with supra-subduction zone environments and more specifically with fore-arc settings. Listvenite bodies of various shapes and sizes developed by alteration of serpentinite. Listvenites occupy the hanging walls of a stack of thrust faults, while serpentinite dominates the footwalls. Based on mineralogical composition and whole-rock geochemistry, the listvenites of Bir Umq are distinguished into carbonate listvenite and silica-carbonate listvenite; the latter is further divided into mineralized and non-mineralized samples. Carbonate listvenite is high in MgO, Fe2O3, and CaO, but depleted in SiO2. Silica-carbonate listvenite is characterized by the presence of rhythmic banding of quartz and carbonate minerals and by the presence of fuchsite. The Bir Umq listvenites preserve various stages of the progressive alteration and metasomatic transformation of their ultramafic protoliths due to interaction with hydrothermal fluids enriched in CO2, SiO2, Au, K, and other fluid-mobile elements. The association with thrusting suggests that faults acted as conduits for fluids derived from metamorphism of the underlying units during subduction and obduction. Schistosity and deformation fabrics in carbonate listvenite imply that initial listvenitization took place at conditions similar to the conditions of serpentinization. On the other hand, the absence of deformation fabrics in silica-carbonate listvenite suggests that it postdates serpentinization and therefore represents a separate and later fluid infiltration event. Finally, the mineralized silica-carbonate listvenite is highly enriched in fluid-mobile elements Zn, Pb, Cu, Ag, and most notably Au; this enrichment is not correlated with silica content. This suggests that yet a third fluid infiltration event is responsible for the mineralization and Au enrichment. Au concentrations are 0.84–2.31 ng g−1 in host serpentinite, 26–403 ng g−1 in carbonate listvenite, 152–545 ng g−1 in non-mineralized silica-carbonate listvenite, and 2286–3712 ng g−1 in mineralized silica-carbonate listvenite.

Hydrogeochemistry of the groundwater system of the transboundary basement and volcanic aquifers of the Bulal catchment, Southern Ethiopia

Abstract: The evaluation of groundwater geochemistry of transboundary aquifers has an important role in the management and sustainable use of groundwater resources in arid and semi-arid regions. This study presents the results of an integrated hydrogeochemical study of the Bulal transboundary aquifers located in the Borena zone, along the Ethiopia-Kenya border. The main aquifers are basic volcanic rocks, subordinate felsic pyroclastic deposits, and metamorphic basement rocks. These aquifers are overlain by alluvio-lacustrine sediments, eluvial soil and regolith. The groundwaters are dominated by Na+ and HCO3− and mixed water types. Silicate weathering and evaporation are the dominant hydrogeochemical processes controlling the chemistry of the groundwaters in most parts of the catchment. However, dissolution of evaporitic minerals might have also played a significant role in adding major ions into the groundwater system. Groundwater in the volcanic aquifers are Na–HCO3, Ca–Mg–HCO3, Na–Ca–HCO3 and Na–Cl–SO4 water types while Ca–Mg–HCO3, Na–Ca–Cl–SO4 and Ca–Mg–SO4 water types are dominant in the metamorphic basement aquifers. The groundwater in the catchment mainly evolved from Na–HCO3 in the west, Ca–Mg–HCO3 in the north, and Na–Ca–Cl–SO4 in the central east and southeast to Na–Ca–HCO3 type in the southern low-lying areas along the groundwater flow direction. The study has significant implications for the management of groundwater quality in the region.

Characterizing terranes and a Neoproterozoic suture zone in Central Hoggar (Tuareg Shield, Algeria) with airborne geophysics and Landsat 8 OLI data

Abstract: Integration of multisource data into a geographic information system has been a powerful tool to characterize contrasting terranes and their boundaries, such as suture zones with oceanic rocks juxtaposed to continental blocks. We present an integration study of geological, Landsat 8 OLI, and airborne geophysical data for the Wadi Takalous region (Central Hoggar, Algeria), covering the SAA (Sérouenout, Aghefsa, Aguendis) domain, rich in juvenile oceanic rocks, flanked by two continental domains, LATEA (Laouni, Aouilène, Tefedest, Egéré-Aleksod and Azrou N'Fad) to the West, and TAI (Tazat and Assodé-Issalane) to the East. The Sérouenout terrane, comprising tectonic slices of metamafic-ultramafic rocks (including eclogites) enveloped by metapelites and covered by Eopaleozoic sandstones , stands out for its low magnetic intensities and low radiometric responses. To the East, granitic rocks with abnormally high radiometric responses and high magnetic intensities highlight the TAI domain, a basement block rich in Pan-African collisional and post-collisional intrusions. To the West of Sérouenout terrane, a heterogeneous magnetic and radiometric pattern characterizes the eastern LATEA that has been interpreted as a Neoproterozoic passive margin. Our integrated data also suggests that the Afara terrane is more likely correlated with LATEA (instead of TAI). Deep magnetic lineaments outline major shear zones marking terrane boundaries, such as the crustal-scale (hundreds-km long and dozens-km thick) 7°30′E thrust zone limiting the SAA and TAI domains. Structures and kinematic indicators related to collisional deformation point to an overall NE-SW to E-W crustal shortening which induced thrusting and tight folding, followed by strike-slip shear zones related to transpressional deformation in late orogenic stage. In this scenario, the SAA domain may represent an accretionary complex associated to a Pan-African suture zone and thrust onto the LATEA passive margin. • GIS data integration for litho-structural analysis and lithological discrimination. • Radiometric characterization of Pan-African granitic intrusions. • Major Neoproterozoic suture zone along the 7°30′E shear zone (7°30′E SZ). • Aeromagnetic characterization of amalgamated terranes in Central Hoggar. • Renatt-type granites are present in Assodé-Issalane terrane and along the 7°30′E SZ.

Across and along-strike crustal structure variations of the western Afar margin and adjacent plateau: Insights from receiver functions analysis

Abstract: We used teleseismic receiver function analysis to image the crustal structure beneath 24 broadband seismic stations densely deployed along two profiles traversing different structural units across the western Afar margin. Our high-resolution receiver function results image pronounced spatial variations in the crustal structure along the profiles and provide improved insights to understand how strain is partitioned in the crust during rifting. Beneath the western plateau next to northern Afar, the crust is likely felsic-to-intermediate in composition (average Vp/Vs 1.74), with a step like thinning of the crust from an average of 38 km beneath the western plateau to an average of 22 km beneath the marginal graben. Consistently thicker crust is observed beneath the southern profile (central Afar), showing four distinct regions of uniform crustal thickness: 1) an average crustal thickness of 42 km beneath the western plateau; 2) 34 km beneath the foothills area; 3) 28 km beneath the marginal graben and the wide extensional basin and 4) 21 km beneath the central rift axis. We use crustal thickness results to estimate a stretching factor β of 2.2 and 2.7 for central Afar and northern Afar respectively. Our estimated values are lower than β > 3.0 predicted from plate reconstructions, and we interpret that the variations are best explained by 2–5 km magmatic addition into the crust. The crustal composition beneath the southern profile is more complex with elevated Vp/Vs ratios ranging between 1.79 and 1.85 beneath the western plateau and marginal graben. This is consistent with a greater mafic component and best explained by crust altered by intrusions due to significant pre and syn-rift magmatic activity. Abnormally high Vp/Vs ratios of more than 1.90 are observed beneath the axial rift zone of central Afar, which most likely suggests the localization of partial melt within the crust.

Delineation of the aquifer structure and estimation of hydraulic properties on the flanks of Mount Meru, Northern Tanzania

Abstract: Understanding of the aquifer structure and its hydraulic properties provides comprehensive knowledge for proper groundwater utilisation and management. This study delineated the aquifer structure using litho-hydrostratigraphical cross-sections, and estimated the hydraulic parameters using single well pumping tests for various locations on and around Mount Meru. Results show that, the aquifer system on the flanks of Mount Meru is a sloping aquifer with sloping beds. On the far east of the eastern flank, the aquifer is composed of debris avalanche deposits, while on the north-eastern and west flanks the aquifer is composed of weathered fractured lava, whereas on the south-western flank, the aquifer is composed of different layers: pyroclastics on the top, weathered fractured lava, weathered pyroclastics, and weathered fractured lava at the bottom. The aquifer is semi-confined on the north-eastern and western flanks; on the north-eastern flank, the overlying debris avalanche deposits acting as an aquitard, while on the western flank, the overlying layers: pyroclastics and unweathered lava acting as an aquitard and aquiclude, respectively. The aquifer is unconfined on the far east of the eastern flank and south-western flank. The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth, while variable, both at the shallow depth of hand-dug wells and the larger depth of boreholes, on the south-western flank; indicating aquifer heterogeneity. On the north-eastern flank, the topmost part of the aquifer, exploited by hand-dug wells, has a low transmissivity (T = 1.3 m 2 /d) and potential for smaller withdrawals for local water supply with limited consumption, while the upper part of the aquifer, captured by boreholes, has an intermediate transmissivity (T = 35 m 2 /d) and potential for local water supply, whereas the deeper part of the aquifer has a high transmissivity (T = 788 m 2 /d) with potential of somewhat regional importance. On the western flank, the aquifer has a very low transmissivity (T = 0.4 m 2 /d) and potential for local water supply with limited consumption. On the south-western flank, on average, the topmost part of the aquifer, exploited by hand-dug wells, has very low to intermediate transmissivity (range of T: 0.3–21 m 2 /d), leading to variable potential for smaller withdrawals for local water supply (private consumption), whereas the deeper part of the aquifer, captured by boreholes, has low to intermediate transmissivity (range of T: 9–43 m 2 /d) and potential for local water supply. • Volcanic aquifer system. • Sloping aquifer with sloping beds. • Aquifer heterogeneity. • The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth. • The transmissivity of the aquifer is variable, both at the shallow depth and the larger depth on the south-western flank. • The aquifer system has variable potential; the potential varying from smaller withdrawals for local water supply with limited consumption in some areas to potential of somewhat regional importance in another area.

Data-driven multi-index overlay gold prospectivity mapping using geophysical and remote sensing datasets

Abstract: The comparative relevance of each geospatial component of mineralization differs from one geological terrane to the other because various sought-after mineral deposit-types synonymously differ in different geological terranes. Hence, the possibility of employing a conceptual model to obtain a relationship or a quantitative function between various geospatial features (evidential layers) with respect to the mineral being sought is laudable, though these features may not necessarily have a generically related effect with the mineral being sought. As a consequence, there is the need to employ a technique that has the capacity to recognize the efficient and inefficient geospatial indicators of the mineral deposit-type being sought. In view of this, this study employed the logistic function, concentration-area fractal model and the prediction-area (P-A) plot to transform and discretize the continuous value of each evidential layer as well as generating intersection points of prediction rate indicators that are essential in obtaining the normalized densities, which were subsequently employed in generating the objective weight for each evidential layer in a data-driven way. The P-A and the normalized density techniques employed were vital in recognizing the indicator and non-indicator criteria. The results obtained acknowledged the potassium concentration layer as a non-indicator of gold mineralization within the study area and subsequently recognized the hydroxyl bearing mineral concentration layer as the most plausible indicator criteria among the six evidential layers (lineament density, iron concentration, hydroxyl concentration, gravity anomaly, magnetic anomaly and potassium concentration) employed in this study. These five indicator criteria were integrated to generate a mineral prospectivity map (MPM) over the study area based on the data-driven multi-index overlay approach adopted. The prediction rate for each of the 6 evidential layers (5 of which were the indicator criteria) as well as the MPM produced indicates that, the generation of objective weights in a data-driven manner via normalized density enhances the predicting ability of the MPM produced in comparison with the individual evidential layers.

Radiogeochemistry, uranium migration, and radiogenic heat of the granite gneisses in parts of the southwestern Basement Complex of Nigeria

Abstract: The radiogeochemistry of granite gneisses in Akunu-Akoko (AK) and Ayere (AY) areas of the southwestern Basement Complex of Nigeria was studied using gamma-ray spectrometry, and geostatistical analysis and modeling. This study was aimed at determining the concentrations of radionuclides (K, U, and Th) in these rocks, as well as alteration scenarios, nature and rates of uranium migration (UM), levels of radiological hazards, and rate of radiogenic heat production (RHP). The interquartile (lowest Q1 < highest Q2 < highest Q3) elemental concentrations for 40 K, 238 U, and 232 Th were 0.23 < 3.75<4.06%; 1.00 < 4.20<5.40 ppm; and 4.10 < 16.10<30.20 ppm, respectively, within the minimum and maximum limits of BDL (below detection limit) to 5.23%, BDL–9.70 ppm, and 0.40–60.20 ppm. The average activity concentrations of 40 K, 238 U, and 232 Th with values of 629.28, 38.58, and 49.96 B q k g − 1 , respectively, were above their crustal averages in the order of AK3

U-Pb zircon age constraints on the vertebrate assemblages and palaeomagnetic record of the Guadalupian Abrahamskraal Formation, Karoo Basin, South Africa

Abstract: The rich fossil record of the Permo-Triassic Beaufort Group of the main Karoo Basin serves as a reference sequence for tetrapod biochronology and provides a unique window into the evolution of terrestrial ecosystems between the Guadalupian and Middle Triassic. Absolute temporal constraints on the Beaufort Group have improved in the last decade with the application of U-Pb zircon geochronology but precise ages have not yet been reported for its basal Abrahamskraal Formation. Consequently, the age of the Eodicynodon Assemblage Zone and the lower boundary of the Tapinocephalus Assemblage Zone have remained less clear than younger Permian biozones. An improvement in temporal constraints also has implications for the correlation of palaeomagnetic logs reported from the Abrahamskraal Formation. In this paper we present new CA-ID-TIMS U-Pb geochronology from tuff beds that provide the first high-resolution chronostratigraphy for the upper two thirds of Abrahamskraal Formation. These ages constrain the base of the Tapinocephalus Assemblage Zone to be older than 264.4 Ma, and closely constrain the boundary between its two subzones to ca. 262 Ma. Combined with published ages from the overlying Teekloof Formation, our data show the Tapinocephalus Assemblage Zone is latest Wordian to late Capitanian in age. These complement previously published CA-ID-TIMS U-Pb ages for younger Beaufort rocks and suggest that the normal polarity interval observed in the middle Abrahamskraal Formation represents a normal (probably third) chron within the mixed-polarity Illawarra Superchron.

Integration of hydrochemical and isotopic characteristics for identifying groundwater recharge sources of the Eocene carbonate aquifer, Western desert, Egypt

Abstract: The Western Desert is considered as one of the most promising areas for groundwater resource and development in Egypt. The Eocene carbonate aquifer is one of the most exploited aquifers for development in the Egyptian Western Desert, especially in the area west of El-Minia in central Egypt. The present study aims to assess the hydrochemistry of the Eocene carbonate aquifer and the possible recharge sources to this aquifer in the western desert west of El-Minia district. Fifteen groundwater samples from the Eocene carbonate aquifer were analyzed for major ions, heavy metals, oxygen-18, and deuterium to assess the hydrochemistry and isotopic compositions in this area. TDS concentrations ranged from 510 to 1408 mg/l. However, the cluster analysis of the Eocene groundwater samples in the present work, reveals two main groups (A and B) with different chemical and isotopic characteristics. The chemical composition of the studied samples showed that the main chemical facies are Na–Cl, Na–Ca–HCO 3, and Na–Cl–HCO 3 . Silicate weathering control the majority of groundwater samples of the Eocene aquifer, while carbonate dissolution governing the deep groundwater of Eocene carbonate aquifer. Isotope ratios of oxygen ( 18 O) and hydrogen ( 2 H) were used to identify the recharge sources, which showed relatively depleted 18 O and 2 H isotopic ratios and relative mixing of groundwater from the Eocene Limestone with paleowaters from the deep Nubian aquifer and water from the Nile River. However, the mixing ratio depends mainly on the distance from the Nile River, depth to groundwater, and local geologic structures also contribute to the mixing pattern. The present study indicates the need for a detailed structural study to detect the locations and properties of fractures as it plays a vital role in feeding the Eocene aquifer from the underlying aquifer. Integration of hydrogeochemical data and isotopic compositions provide a better understanding of the geochemical processes that control the groundwater hydrochemistry of the Eocene carbonate aquifer west of El-Minia, Egypt and in areas with similar conditions. • Isotopic signature of Eocene Carbonate Aquifer. • Hydrochemical characteristics of Eocene Carbonate Aquifer. • Recharge source of Eocene Carbonate Aquifer. • Effects of distance from River Nile on recharge of Eocene Carbonate Aquifer.

The buried Variscan granites and associated structures in the High Moulouya basin from gravity data and their role during the Triassic-Liassic extensional tectonics (Moroccan Meseta-Atlas domain).

Abstract: The High Moulouya Basin (HMB) occupies a key location between the Southern Middle Atlas and the Central High Atlas. Gravity data from the HMB show the presence of three gravity lows . Borehole data show a thin Meso-Cenozoic cover in the HMB that eliminates the possibility that these lows are due to sedimentary rocks. The gravity anomalies may therefore be related to hidden granitic bodies within the Paleozoic basement. In order to map these granite bodies and associated structures, gravity data sets were processed and enhanced using various mathematical techniques, transformations, and 2D gravity modeling. The following were either better defined or revealed: i) The High Moulouya Batholith is a large NE-SW trending batholith that crops out partially in the Aouli-Mibladen and Boumia Paleozoic inliers. Our study shows the continuity of this batholith with a 90 km long and 30 km wide granitic structure. ii) The Hidden Engil granite is a subcircular, relatively small granite body (20 × 18 km) located at the Middle Atlas's eastern boundary. The hidden granite of Zebzat (30 × 10 km) represents a narrow E-W trending pluton bounded by the High Atlas tectonic structures on its southern boundary. The tectonic influence of these granite bodies may explain, to some extent, the stability of the HMB throughout the development of the Atlasic subsiding basins. The two Atlas basins are separated by the High Moulouya granite-cored intrabasinal high. As shown by the horizontal gradient and Euler deconvolution methods, during Triassic-Liassic NW-SE extensional events, the formation of the Middle and High Atlas basins was guided by Variscan inherited faults bounding the granitic bodies of the HMB. The main factors responsible for the formation of the High Moulouya granite-cored intrabasinal high are the isostatic compensation that follows the granite emplacement during the Variscan orogeny, the distribution of strain and deformation around the granite bodies during the Triassic-Liassic extensional tectonics and their concomitant buoyancy forces. • Presence of three granitic bodies totally or partially hidden in the High Moulouya basin, Moroccan Eastern Meseta. • The newly recognized High Moulouya batholith is the largest granite batholith in the Moroccan Variscan belt. • Isostatic compensation, distribution of strain and deformation around the granite bodies and their concomitant buoyancy forces are the main factors responsible of the formation of the High Moulouya granite-cored intrabasinal high.

Petrogenesis and tectonic setting of the Pan-African Deng-Deng intrusive complex in the Lom series, Eastern Cameroon

Abstract: The Deng-Deng intrusive complex belongs to the Central African Fold Belt (CAFB) in eastern Cameroon and includes granodiorite and diorite. Both rocks are classified as metaluminous to slightly peraluminous, high-K calc-alkaline, and I-type granitoids (A/CNK <1.1). Primitive mantle-normalized trace-element patterns display large-ion lithophile elements (LILE) enrichment, such as Rb, Cs, Ba and K, and depletion in high-field-strength elements (HFSEs), such as Nb, Ti, Ta and P. The studied rocks are enriched in LREEs relative to HREEs and exhibit weak negative Eu anomalies (Eu/Eu* = 0.61–0.92 and 0.59–0.67 for the granodiorite and diorite, respectively), suggesting active continental margin arc affinity. The emplacement temperatures of these granitoids are estimated between 775 and 806 °C. Combined with their diagnostic ratios (e.g., Th/Ta, Rb/Sr, Nb/La, and La/Sm), we propose that the Deng-Deng granitoids were sourced by mixing between mafic magma derived from the lithospheric mantle and felsic magma derived from partial melting of a lower crust in a convergent margin setting.

Aeromagnetic data of the Kelâat M'Gouna inlier (Jbel Saghro, Eastern Anti-Atlas, Morocco): Geotectonic and mining implications

Abstract: The Kelâat M'Gouna inlier (KM'G) is located in the Eastern Anti-Atlas of Morocco, north of the West African Craton (WAC). It offers outcrops of great lithological diversity and has a polycyclic tectonic history. Its bedrock bears traces of the Pan-African orogeny, and its Adoudou-Cambrian cover was affected by the Hercynian orogeny. Therefore, the KM'G inlier is a privileged geological region for a geo-structural study to evaluate its mining potential. In this study, high-resolution aeromagnetic and surface geological data were used to map the structural architecture of the inlier and determine its relationship to the spatial distribution of mineral deposits and showings. Several filters and operators such as Reduction to Pole (RTP), Upward Continuation (UC), Centre for Exploration Targeting (CET) and Tilt Derivative (TDR) were applied to the aeromagnetic data to reveal important magnetic signatures such as magnetic lineaments/domains in the study area. The TDR and UC subdivided the area into two magnetic morpho-structural domains: to the north, a domain dominated by negative anomalies (labeled NMA1, NMA2 and NMA3), which coincide with the Sidi Flah fault and the Azlag and Ibantarn granites; to the south, a domain dominated by positive anomalies (labeled PMA4 and PMA6) which are deeply rooted. CET and TDR have been applied to map structural complexity and depth estimation. Four main magnetic lineament trends were deduced (NE-SW, Sub E-W, NW-SE, and Sub N–S) with variable depths ranging from 45 to 2120 m. A thorough structural scheme was developed based on the CET and TDR outputs and surface geological data. This scheme shows that the main deposits and mineral occurrences are known from the KM’G geological map are in areas with high magnetic lineament density values. Thus, several potential mineralization zones in the study area have been delineated. These results should guide the exploration of possible metal deposits in the KM’G inlier.

Flood hazard and susceptibility assessment in a semi-arid environment: A case study of Seyad basin, south of Morocco

Abstract: Flood, is a constant phenomenon, especially in semi-arid and flood plain regions are one of the most destructive natural hazards endangering a people's life, property, and physical and economic well-being. This paper focuses on hydraulic modelling using the HEC-RAS model in combination with the Watershed Modeling System (WMS) tools and compares the results to the Flood Hazard Index (FHI) method using GIS in the Seyad Basin situated in the southwestern region of Morocco with an area of 1512.85 km2. The goal of the study is to evaluate flood hazards in the Seyad Basin in which the cities of Taghjijt, Aday, Amtoudi, and Tagriante are located. The HEC-RAS approach combines the hydraulic surface water flow model and the digital terrain model data. This combination allows the mapping of the flood zones by using the WMS tools. This approach predicts flood occurrence probability for different times and determines the intensity of the flood (depth and velocity of floodwater) using the existing hydrological data. On the other hand, the Flood Hazard Index method (FHI) presents a multi-criteria index to assess areas prone to flood hazards, using six physical parameters: permeability, slope, distance from rivers, land use, drainage density, and flow accumulation. A weight is calculated from the analytic hierarchy process method and applied to each parameter. HEC-RAS method allows the mapping of a flood with a flood water surface profile that shows the flood depth for Annual Exceedance Probability (AEP). At the same time, FHI permits establishing flood hazard levels without showing the water depth. In both approaches, six simulations were performed with the return periods of 10, 20, 50, 100, 200, and 500 years. The simulation revealed that the most susceptible areas to flooding are the areas along the Wadi Seyad.

Cenozoic tectono-sedimentary evolution of the Upper Moulouya continental basins (Moroccan Atlas system): Insights from lithostratigraphy, structural analysis and paleostress reconstruction

Abstract: The Upper Moulouya massif (UMM) is located at the junction between the Middle and the High Atlas mountain ranges where outcrop a segment of the Moroccan Variscan belt and its unconformably overlying Meso-Cenozoic cover. In this paper, we propose the Cenozoic tectono-sedimentary evolution of the continental series filling the intramontane basins of the UMM using a multidisciplinary approach with multiscale geological-structural and paleostress analyses. The lithostratigraphic study shows that these series correspond to Oligo-Neogene fluvio-lacustrine sequences, alluvial fans deposits, and alluvial outwash plains, associated with volcanic rocks. Structural and paleostress analyses provide a complex tectono-sedimentary evolution marked by the superposition of four tectonic phases with changes in paleostress orientations. These tectonic phases are consistent with strike-slip tectonic regimes associated with compressional, transpressional, transtensional and extensional episodes: (i) the first tectonic phase is characterized by NW-SE trending σ1 axis, and NE-SW trending σ3 axis, with NNW-SSE to N–S sinistral strike-slip faults, ENE-WSW to E-W dextral strike-slip faults, and NE-SW reverse faults cross cutting the Mesozoic and Oligo-Miocene series; (ii) the second tectonic phase is characterized by ENE-WSW to E-W σ1 axis, and NNW-SSE to N–S σ3 axis where the subsidence of Pliocene lake basins is probably controlled by ENE-WSW to E-W extensional faults and NE-SW transtensional faults; (iii) the third phase is marked by NNE-SSW to NE-SW trending σ1 axis, and WNW-ESE to NW-SE trending σ3 axis, with submeridian dextral strike-slip faults, subequatorial sinistral strike-slip faults, NE-SW normal faults, and NW-SE reverse faults; (iv) the last tectonic phase is characterized by NNW-SSE to N–S σ1 axis, and ENE-WSW to E-W σ3 axis responsible for subequatorial reverse faults, submeridian normal faults, NE-SW sinistral strike-slip faults, and NW-SE dextral strike-slip faults.