ST
Chargé de Cours
Activité scientifique
Profil chercheur
Enseignant-chercheur à l’Université de Yaoundé I. Grade : Chargé de Cours.
Publications scientifiques
Arcange Duviol Tsanga, Armel Zacharie Ekoa Bessa, Durane Chougong Tchatchouang, Same Moutongo Jacques-David, Gerardine Saurelle Ngokam, Dairou Bachirou et 2 autre(s)
Arabian Journal of Geosciences
Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, Arcange Duviol Tsanga, Sandje Domadjingar Habib, Danielle Ndzie Mbazoa, Suzi Phalone Kaptchouang Kamlo et 3 autre(s)
Journal of African Earth Sciences
Annick Kwewouo Janpou, Plastini Florentin Ngami, Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Théophile Njanko, Tebogo Kelepile et 1 autre(s)
Journal of Sedimentary Environments
André Jules Ouambeti-Wickon, Gabriel Ngueutchoua, Doria Grace Takenne, Prince Emilien Danguene, Armand Sylvain Ludovic Wouatong
Watershed Ecology and the Environment
• Industrialization encourages the gradual accumulation of heavy metals in sediments. • Current industrial waste management methods can prevent contamination of the river. • The toxicity of sediments is discussed to highlight the risk of ecological pollution. The study, based on heavy metals such as cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), vanadium (V), zinc (Zn) and iron (Fe) in the sediments of the Ouaka river watershed, aimed to determine the concentration profiles of the various contaminated zones and to assess the sources of pollution of these sediments, which are of both human and natural origin. These profiles were established against a backdrop of heavy industrial activity (discharges from the Ngakobo sugar refinery and the Bambari cotton gear factory), agricultural activity (with the use of chemical fertilizers and pesticides) and mining activity (artisanal gold mining), all of which may be responsible for heavy metal contamination of the sediments in this watershed. A total of 34 sediment samples were collected and analyzed by inductively coupled plasma mass spectrometry. Results for heavy metal concentrations (mg/kg) ranged from 0.006 to 0.019 for Cd; 1.7 to 7.11 for Co; 11.5 to 30.8 for Cr; 2.3 to 7.4 for Cu; 2.7 to 13.4 Ni; 1.36 to 25.99 for Pb; 11 to 18 for V; 7.9 to 20 for Zn and 11356.2 to 17875.5 for Fe. These values are significantly lower in the sediments studied than the reference values used in the upper continental crust. To assess the degree of contamination in these sediments, the enrichment factor, contamination factor, geo-accumulation index and pollutant load index were calculated. The result is that, with the exception of Pb in sample B15, which is moderately enriched, the other heavy metals are only slightly enriched, and this is confirmed by the geo-accumulation index and pollutant load index, which show the absence of contamination and pollution in this catchment. The results of this work will enable the Central African Republic to control the intensive discharge of industrial and mining residues, and also to limit the use of chemical fertilizers in agriculture in favor of natural fertilizers.
Tsanga Arcange Duviol, Ekoa Bessa Armel Zacharie, Gabriel Ngueutchoua, Chougong Tchatchouang Durane, Jacques-David Same Moutongo, Ngokam Gerardine Saurelle et 2 autre(s)
SSRN Electronic Journal
Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, John S. Armstrong‐Altrin, Gabriel Ngueutchoua, Elisé Sababa
Thalassas An International Journal of Marine Sciences
Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, John S. Armstrong‐Altrin, Gabriel Ngueutchoua, Elisé Sababa
Research Square
Abstract A mineralogical survey was conducted in the Gulf of Guinea sands to assess the transport history, depositional environment, weathering conditions and, provenance. Heavy mineral assemblages are abundant in augite, followed by opaque minerals, diopside, zoisite, enstatite, tourmaline, zircon, rutile, sillimanite, garnet, apatite, hornblende, epidote, kyanite, chloritoid and staurolite. The variety of this minerals show that the sands studied come from the igneous source rocks, mainly from a metamorphic source, in particular the gneisses and basalts, which is consistent with the geology of the study area. The bulk mineralogy detected using XRD and the chemical properties obtained by SEM-EDS reveals that the sands were dominated by quartz. Nineteen microtextures were observed on heavy minerals like hornblende, chloritoid, sillimanite, garnet, augite and staurolite, which were subsequently classified as mechanical (13 features), chemical (4 features), and combined mechanical and chemical (2 features) origins. The dominance of mechanical features suggest that the grains underwent high-energy transport. The abundance of angular and subangular heavy minerals indicate distance or nearby source. The mineral composition suggests that the source rocks underwent moderate weathering. The sub-rounded and rounded heavy minerals indicate a long transport. The predominance of heavy minerals in sediments suggest that the nearby source rocks are rich in heavy minerals.
Francis Temgo Sopie, Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, Archange Duviol Tsanga, Patrice Roland Liyouck, Théophile Njanko et 1 autre(s)
Earth and Planetary Science
Sandy sediments collected along the southern part of the Cameroonian coast have been analyzed geochemically by ICP MS methods to investigate the distribution characteristics, contamination levels and related ecological risks. In these sediments, the concentration (mg/kg) of selected elements are in order Fe > Mn > Cr > V > Th > Ni > U > Co. Indices of pollution such as index of geoaccumulation, where values of all elements in the sediments were < 0, except Th in the sediments station of Yoyo II, and Cr in sediment of all stations were Igeo > 0. The contamination factor shows that the station of Yoyo II has values of CF < 1, such as Fe, V, Ni and Co. While Uranium, Th and Mn values vary from 1 to 3 and 3 to 6, and for Cr values of CF > 6. However, Kribi and Campo stations show that all the elements have values of CF < 1, except Cr which has values of CF > 6. The degree of contamination values ranges between (9.48-37.13) for the station of Yoyo II, (8.84-17.62) for the Kribi station, and (6.52-13.56) for the Campo station. The pollution loading index values at all sampling stations are lower than 1. The potential ecological risk (Er and RI), indicates that this coastal area is a low risk region. Pearson correlation, cluster analysis and principal component analysis supported that heavy metals (Fe, Mn, Cr, V, Ni and Co) have common human influences while radionuclides (Th and U) have a natural source. The presence of human activities such as domestic waste, intensive farming and the processing of industrial products could be potential sources of anthropogenic environmental pollution, thereby threatening the environmental concerns of the entire study area.
Armel Zacharie Ekoa Bessa, Victorine Ambassa Bela, Gabriel Ngueutchoua, Yasser A. El‐Amier, Francis Aonsi Kamani, Leonel Ngueudong Zebaze et 5 autre(s)
Earth Systems and Environment
Durane Tchatchouang Chougong, Gabriel Ngueutchoua, Emmanuel Henock Dicka, Armel Zacharie Ekoa Bessa, Gisèle Flodore Youbouni Ghepdeu, Ulrich Joël Filicien Bilounga et 3 autre(s)
Earth Systems and Environment
Wilson Y. Fantong, Therese L. L. Jokam Nenkam, Pierre Nbendah, Sharon Bih Kimbi, Ernest Chi Fru, Brice Tchakam Kamtchueng et 4 autre(s)
Environmental Geochemistry and Health
Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Annick Kwewouo Janpou, Yasser A. El‐Amier, Odilia-Alexandra Njike Njome Mbella Nguetnga, Ulrich Romaric Kankeu Kayou et 3 autre(s)
Earth Systems and Environment
Gabriel Ngueutchoua, Armel Zacharie Ekoa Bessa, John Takem Eyong, David Demanou Zandjio, Hadjidjatou Baba Djaoro, Lionel Tchami Nfada
Journal of African Earth Sciences
Kenfack Nguemo Gatien Romuald, Paul Tématio, Gabriel Ngueutchoua, Tata Cathryn Ntoboh, Ngounou kouokam Annyck Channele, H. Wabo et 4 autre(s)
International Journal of Sciences: Basic and Applied Research
Major and trace element geochemistry have been used to unravel the tectonic setting, source rock composition, and depositional environment of sedimentary rocks in the Mamfe formation. Field studies reveal both sub tabular and tabular outcrops indicating a post tectonic sedimentary activity for the subtabualar outcrops. Major element geochemistry reveals a moderate to high proportion (50-75wt %) of silica for the analyzed samples. New discriminant diagrams constructed for usage of adjusted major elements shows samples plotting on collision, arc and rift. Another discriminant plot for adjusted major element combined with trace elements shows samples plotting on active and passive tectonic setting. Ratios of highly immobile trace elements such as Cr/Th, Th/Sc, Th/Co, and La/Sc conclude a felsic source rock for the studied rocks of the Mamfe formation. Trace elements ratios for redox conditions and marine-continental discrimination such as Ni/Co, U/Th, V/Cr, Th/U, and Y/Ho show that the sedimentary rocks of the formation were deposited in a shallow oxygenated continental fluvio-lacustrine environment.
Armel Zacharie Ekoa Bessa, Yasser A. El‐Amier, Elvine Paternie Edjengte Doumo, Gabriel Ngueutchoua
Annual Research & Review in Biology
International audience
Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Paul‐Désiré Ndjigui
Arabian Journal of Geosciences
Gabriel Ngueutchoua, Leopold Darlus Ngantchu, Martine Youbi, Simon Ngos, Véronique Kamgang Kabeyene Beyala, Kevin Petsouonko Yifomju et 1 autre(s)
International Journal of Geosciences
Geochemical data of fifteen Cretaceous sediment samples from Kumba area in the Douala sub-basin are presented to determine the provenance, source rock weathering, tectonic setting and paleo-oxidation conditions of the depositional setting of these rocks. For this purpose, the whole-rocks were analyzed for their major and trace element, including rare earth elements (REEs), contents by ICP-AES and ICP-MS methods respectively. On the basis of their major element composition, the rocks have been classified mainly as Fe-shale, shale, arkose and Fe-sandstone. For the provenance, the plot of Zr vs. TiO2, Y/Ni vs. Cr/V, TiO2 vs. Al2O3 diagrams, high LREE/HREE ratios (5.84 to 20.91) and negative and positive Eu anomalies (Eu/Eu*= 0.87 to 1.62) suggest that the studied rocks were mainly derived from felsic igneous rocks with lesser contribution of mafic components. The higher values of paleo-weathering indices such as Plagioclase Index of Alteration (PIA) and Chemical Index of Weathering (CIW), ranging from 79.63 to 99.90 and 87.57 to 99.92 respectively, suggest that the sediments and their potential source rocks experienced intense weathering. Whereas the variable Chemical Index of Alteration (CIA) values (63.01 to 99.50) coupled with high content of K2O (up to 7.5) in most samples could be indicative of K-addition diagenetic processes. The A-CN-K plot also suggests a possible K-addition. The redox conditions during the sedimentation were suboxic to oxic as evidenced by the Ce anomalies of 0.88 to 1.03. This is also confirmed by the values of Ni/Co (less than 7), U/Th (less than 1.25) and Cu/Zn (mostly less than 1). Tectonic discrimination diagrams (e.g., SiO2-K2O/Na2O and Th-Sc-Zr/10) show that these rocks were deposited mainly in an active continental margin setting, and in various tectonic environments. This reflects probably the recycling effect experienced by the samples studied.
P. L. Kenfack, Pierre Ricard Njiké Ngaha, Georges Emmanuel Ekodeck, Gabriel Ngueutchoua
Geosciences
The deposits of the Douala sub-basin stand among the Gulf of guinea best-studies series. In spite of continuous oil prospecting production in the area, there is still a paucity of published information and data on the palynology of the Douala sub-basin. This study aimed at reconstructing the palaeoenvironments from d inoflagellates cysts identified in surface samples collected among deposits of the Nkappa formation. Ten surface samples fro m three different localities (M iang, Fiko and Bwapaki) were collected, studied and analyzed for their lithological and palynological contents. This essentially comprised the field description of lithological and textural characteristics of facies. The laboratory work was based on treatment and extraction of dinoflagellates cysts from shales samples selected for the study, using the standard palynological method applied in the laboratory of micropaleontology of PETROCI (Ivory Coast). Hence, four lithological units were delineated made up of dark to grayish shales, fine, med ium and coarse sandstones. A total of sixteen dinoflagellates cysts were recovered and identified fro m the samples. They all belong to the class Dinophyceae but are subdivided into four families (Gonyaulacaceae, Perid iniaceae, Areoligeraceae and Protoperidiniaceae). The dominant dinocysts grains are those of Areoligera sp, glaphyrocysta sp, Paleocystodinium golzowense and Cerodiniu m sp. Correlation with other studies carried in the neighbouring basin and event over the world allo w g iving a Maastrichtian-Paleocene age to the formation studied. Palaeoecological interpretations from the above data suggest of shallow marine coastal environments where waters are warm and have a normal salinity.
P. L. Kenfack, Paul Tématio, M. Kwekam, Gabriel Ngueutchoua, P. R. Njike
Journal of Petroleum Technology and Alternative Fuels
The Ngwa sedimentary sequence is situated on the southern flank of the Bambouto volcano. Analysis of petrography, lithostratigraphy, mineralogy, morphology and morphometry enabled the reconstruction and interpretation of their stratigraphic architecture, depositional and paleogeographic setting, the origin of the sediments and the geological history of this region. The lithostratigraphic sequence of the Ngwa sedimentary deposits reveals two major phases of sedimentation: (i) Conglomerates with pelitic sandstone matrix, pelitic sandstone and carbonaceous clayey shale with lignite intercalations; and (ii) conglomerates and arkosic sandstones. Pebbles from the Ngwa conglomerates are sub-rounded to spherical. The grain size distribution of the sandstones indicates a high amount of very fine clay particles. The sediments of Ngwa are well sorted. The homometrical character of sandstones is related to their fluvial origin. The presence of sillimanite and kyanite testifies to the metamorphic provenance of a part of the Ngwa sediments while the basaltic pebbles indicate the volcanic origin of the other part. During the Miocene, Ngwa area experienced detrital sedimentation with alternation of volcanic phases related to volcanic activity at Mount Bambouto. Key words: Ngwa, Cameroon, lithofacies, detrital sedimentation, Miocene.
Gabriel Ngueutchoua, Pierre Giressè
Marine and Petroleum Geology
Jean Benkhelil, Pierre Giressè, Claude Poumot, Gabriel Ngueutchoua
Marine and Petroleum Geology
Pierre Giressè, Gabriel Ngueutchoua
Some 80 Kullenberg core samplings associated with high- resolution seismic reflection surveys allowed the analysis of the main sedimentary bodies of the Cameroon shelf as a result of the last glacio-eustatic movements. In some 16 core sections, it was possible to date the last oscillations of the shoreline--before or after the last glacial low-stand emersion--using 14 C. The high-stand of the isotopic stage 3 may not have reached -50 m. The last glacial low-stand was very near -130 m and for the first time on the West-African margin, the steps of the regressive process were analyzed and compared to the author9s eustatic graphs. On the outer shelf, a metric veneer of bioclastic gravels of the reef type was deposited between 14 and 12 ka B.P., during the very active eustatism phase at the beginning of the transgression. A pause in the transgression between 12 and 11 ka B.P. as a result of the Younger Dryas temporary cooling was often observed in the inherited morphostructural depressions which allowed the record. The bioclastic debris were extensively spread and reworked during this 12-11 ka B.P. relative stability of the shoreline. Some of these successions were considered at the wide scale of the Guinea Gulf shelves which show the same pattern. Hiatuses were observed as a result of the last low-stand, but the recorded stratigraphical lacunae do not seem closely related to the depth and to the emergence episode. A better conservation is probably associated with the subsiding property of narrow basins of aggrading sedimentation: inversely, the roofs of the shoals have been frequently planed off.
Pierre Giressè, J.P. Megope-Foonde, Gabriel Ngueutchoua, J. C. Aloisi, Martin Kuété, Jacques Monteillet
Le plateau camerounais a fait l'objet d'une prospection sismique haute resolution (env. 1000 km) et de prelevements de surface (env. 100 carottages et 450 dragages). La geometrie des corps sedimentaires et la succession des paleoenvironnements ont ete analysees en fonction d'une chronostratigraphie qui est basee sur pres de 50 datations au radiocarbone. Dans la partie septentrionale, on observe successivement (1) des depots vaso-silteux de la regression pre-holocene (accumules dans les depressions du substratum pliocene), (2) des sols hydromorphes, des depots lamines paraliques et des vases a mangrove signalent l'approche de la transgression holocene, (3) des sables des paleodeltas remanies au debut de la transgression (it) et (4) enfin un prisme vaseux (phn) atteignant 20 a 40 m pres de la cote qui a ete alimente principalement par la sanaga et les rivieres de la baie de douala. Dans la partie meridionale, a l'ecart des flux des principales rivieres, les depots holocenes se limitent a des placages centimetriques a metriques issus pour partie des eaux nigeriennes. En consequence, on observe pratiquement a l'affleurement une succession pleistocene: (1) sables verts glauconieux de bas-niveau (18000 bp), (2) sables calcaires a tendance recifale (12000 bp) indiquant une hesitation de la transgression. Les flux actuels de la sanaga et des rivieres de la baie de douala semblent representatifs des flux moyens holocenes, si l'on s'en tient a l'evaluation massique des depots accumules sur le plateau et le haut de la pente
Pierre Giressè, Jean-Claude Aloïsi, Martin Kuété, Jacques Monteillet, Gabriel Ngueutchoua
Quaternary International
André Jules Ouambeti-Wickon, Gabriel Ngueutchoua, Doria Grace Takenne, Armand Sylvain Ludovic Wouatong, Prince Emilien Danguene
Journal of Geoscience and Environment Protection
The sediments of the Ouaka River were analyzed on the basis of samples taken from the banks during the dry season. These sediments consist of gravel, sand and silt-clay. These sediments are being studied in a context where the sand from the Ouaka River is going to be used for major construction work on road infrastructure and administrative buildings. In this context, the granulometric analysis of these sediments revealed the dominance of medium sands, silt-clays and, secondarily, coarse sands. The grading curves for these sediments show a sigmoidal “S” shape, indicating that they were deposited in a river and in a depositional environment with relatively high hydrodynamic energy. These sediments, transported and deposited by various hydrodynamic energies, are linked to the massive arrival of materials from secondary watercourses tributary to the Ouaka River. Most of the gravel moves by rolling. Most sand moves by saltation. Silt-clays move essentially by suspension. The Passega diagram describes transport of these gravels by rolling over the bottom. The combined Friedman, Moiola and Weiser diagrams show sediments of fluvial origin and those influenced by sand dunes from the Chad Basin. Analysis of the linear discriminant functions reveals a turbulent fluvial environment with shallow marine beach inputs in turbulent waters. This marine influence is linked to the presence of limestone in the catchment, which is generally formed in a marine palaeoenvironmental context. As part of this study, the distribution of heavy minerals was highlighted in order to determine the origin of sediments from the Ouaka River. These sediments contain mainly tourmaline, rutile, sillimanites, opaque minerals and other heavy minerals. The majority of the sediments are mineralogically immature to sub-mature since the Zircon-Tourmaline-Rutile maturity index is less than 75%.
Arcange Duviol Tsanga, Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, John S. Armstrong‐Altrin
Journal of Sedimentary Environments
Christel Sobdjou-Kemteu, Réné Toyama, Milan Stafford Tchouatcha, Usman Abubakar, Soureiyatou Fadil-Djenabou, Abakar Mahamat et 3 autre(s)
Arabian Journal of Geosciences
André Jules Ouambeti-Wickon, Gabriel Ngueutchoua, Armand Sylvain Ludovic Wouatong, Doria Grace Takenne, Prince Emilien Danguene, Yannick Steve Ngagoum-Kontchipe et 1 autre(s)
Research Square
Annick Kwewouo Janpou, Armel Zacharie Ekoa Bessa, Roger Firmin Donald Ntouala, Tebogo Kelepile, Gabriel Ngueutchoua, John S. Armstrong‐Altrin
Journal of the Geological Society of India
Abstract Petrographical, mineralogical and geochemical studies were carried out on the beach sands of Limbe (South-West Cameroon) to highlight their provenance, source rocks alteration and the tectonic framework. The Limbe beach sediments were classified as sandy litharenite type. The sediments were derived from mafic and andesite source rocks. The sediments are composed of quartz, olivine, augite, amphibole, pyroxene, plagioclase, potassium feldspar, muscovite and biotite, indicating the primary phases of magmatic source rocks; kaolinite and illite in the secondary phase; and rutile in their residual composition. The presence of ferromagnesian minerals indicates that they were derived from the mafic rocks, which are the basalts of the Cameroon Volcanic Line (CVL). However, the presence of quartz associated with plagioclase and feldspars suggests that alkaline granites played a minor role in the sedimentation of the Limbe beaches. Total Quartz - Total Feldspar - Total Lithic Fragments (Qt-Ft-Lt) mineralogical relationships demonstrate that these beach sediments would be formed in an undissected arc tectonic context, typical of volcanic sources with high relief producing black sands or sands enriched in iron oxides. Their microscopic characteristics of angular to subangular shapes suggest that the magmatic sources are proximal to the shoreline deposits. The characteristics of microporosity, iron oxide inclusions, conchoidal fracture, heavy mineral grains, and opaque minerals support this proximal source. The conchoidal fractures defining the angularity of these beach sediments would suggest its derivation from crystalline rocks. The predominance of heavy minerals suggests that the rocks proximal to the beach have been altered. The abundance of primary minerals associated with these secondary heavy minerals justifies the existence of unweathered lithic grains in the source rocks and an alteration that occurred under a tropical monsoon climate that ranged from semi-humid to humid. The use of the multi-element tectonic discrimination diagram implies an arc framework that is compatible with the geology of the study area.
Armel Zacharie Ekoa Bessa, V. Ambassa-Bela, A. T. Ndzié-Mvindi, John S. Armstrong‐Altrin, Gabriel Ngueutchoua, Mohamed Abioui et 1 autre(s)
Doklady Earth Sciences
Abstract In order to identify the sedimentary processes, depositional environment, and provenance, the study used sieving and SEM-EDS to analyze the particle size and quartz grain microtextures from sediments in the central part of the Gulf of Guinea. Samples were collected from three locations (Yoyo, Mbiako, Mouanko) for grain size analysis and particle size parameters such as mean, sorting, skewness, and kurtosis were determined. In general, the sediments are dominated by medium-grained sands (81.14%). The descriptive statistics and bivariate relationship plots of different particle size parameters show that the sediments are medium to fine, moderately well classified, fine-to-very fine skewed towards fine with platykurtic. Most of the sands come from a river-type environment, as well as beaches, and transported by saltation. The transport mode of the fine sands is dominated by suspension transport. Rolling is the dominant mode of transport for coarse sands. Twenty-five features were known and clustered according to their types of origin. Among them, eighteen features characterize the mechanical origin, four belong to the chemical origin, and three represents mechanical/chemical origin. Quartz microtextures show that the mechanical, mechanical/chemical, and chemical are mostly associated with fluvial, littoral, and aeolian processes. The quartz grains in the sediments from the central part of the Gulf of Guinea are resulting mostly from crystalline source rocks. Furthermore, shapes (angular, subangular, sub-rounded) indicate that these sediments were transported by a medium to high-energy environment, short transport or quick deposition. Moreover, occurrence of sub-rounded grains militated for far-source materials.
Christel Kemteu Sobdjou, B. C. Mfayakouo, Gabriel Ngueutchoua, R. G. N. Kenfack, S. Ngos
Geological Journal
The Lower Cretaceous syn‐rift deposits of the Douala Basin (Mundeck Formation), located in the equatorial West African margin were investigated in order to determine the palaeoenvironment and organic matter source, redox conditions, palaeoclimate, and tectonic settings, based on facies, organic and inorganic geochemical analyses. The sediments consist of pebble, coarse, medium‐ to fine‐grained sandstone, siltstone, and grey to black fossiliferous shales. The shales are characterized by an average total organic carbon (TOC) of 1.02%, fair to poor source generative potential with present‐day hydrogen index values, which range from 31 to 350 mg HC/g TOC suggesting that the shale contains Type III kerogens with mainly gas generative potential. The organic particles are dominated by phytoclasts (40% on average) and non‐fluorescent amorphous organic matter (34% on average). The palynomorphs represent about 26% on average with a large amount of pollen grain and a minor amount of dinoflagellate cysts and microforaminifera test linings. The inferred depositional environment of the studied sediments is an alluvial fan to fluvio‐lacustrine with shallow marine incursion. This depositional environment received the contribution of aquatic algae and microorganisms with a large amount of terrestrial organic matter, evidenced by the presence of some dinoflagellate cysts and microforaminifera test linings, and relatively higher amounts of SiO 2 , Al 2 O 3 , and phytoclasts. The presence of trace elements such as Ba, Sr, V, Ni, Co and Cr in the analysed samples and their ratio, suggest suboxic to anoxic conditions of deposition with low salinity. The warm to cold and dry climatic conditions prevailed during the deposition of the Mundeck deposits and sediments from active continental margin setting during the lower Cretaceous periods in the Douala Basin as confirmed by inorganic geochemical data. This study sheds light on the early stage of the evolution of the Douala Basin which could be integrated into the context of a mid‐Jurassic to lower Cretaceous regional evolution of the opening of a passive margin. This evolution is characterized by an alluvial fan, fluviatile, lacustrine, lagoon and marine depositional system. This depositional system is recognized as part of the petroleum system recognized within the syn‐rift deposits in the others basins along the West African margin, where giant hydrocarbons have been discovered.
Patrice Roland Liyouck, Gabriel Ngueutchoua, John S. Armstrong‐Altrin, Aristide Nadine Sonfack, Yannick Steve Kontchipe Ngagoum, Armel Zacharie Ekoa Bessa et 3 autre(s)
Journal of African Earth Sciences
Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, John S. Armstrong‐Altrin, Francis Aonsi Kamani, Estelle Diane Biami Nya, Gabriel Ngueutchoua
Solid Earth Sciences
The provenance of clastic sediments in stream beds, river terraces, rivers, swamps, lakes and beaches from different geological settings was investigated based on their compositional and geochemical variations. The geochemistry data of 622 sediment samples from 22 sites in the Cameroon were compiled to infer the provenance. The results suggest that, their mineralogy is dominated by quartz, low amount of feldspars, clay minerals, heavy minerals, ferric minerals, and rock fragments. The SiO2/Al2O3 ratio indicate that the sediments of Cameroonian region are mostly rich in quartz and clay-minerals. The enrichment of K2O/Na2O ratio implies plagioclase disintegration as K-feldspar during weathering and/or K-reintroduction in the system during diagenesis. The sediments are rich in light rare earth elements (LREE) and classified as shale, Fe-shale, Fe-sand, wacke, arkose, litharenite, sublitharenite, and quartzarenite. The sediments are composed of detritus derived from felsic igneous rocks, which correspond to the geology of the source areas. Weathering indices such as chemical index of alteration (CIA), chemical index of weathering (CIW), plagioclase index of alteration (PIA) and, A–CN–K (A=Al2O3, CN=CaO∗ + Na2O, K=K2O) plot indicated that the source rocks are subjected to low, moderate and intense weathering.
Francis Temgo Sopie, Gabriel Ngueutchoua, John S. Armstrong‐Altrin, Théophile Njanko, Aristide Nadine Sonfack, Yannick Steve Ngagoum Kontchipe et 2 autre(s)
Journal of Earth System Science
Annick Kwewouo Janpou, Gabriel Ngueutchoua, Armel Zacharie Ekoa Bessa, John S. Armstrong‐Altrin, Ulrich Romaric Kankeu Kayou, Odilia-Alexandra Njike Njome Mbella Nguetnga et 4 autre(s)
Journal of African Earth Sciences
Arcange Duviol Tsanga, Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Gerardine Saurelle Ngokam, Same Moutongo Jacques-David, Victorine Ambassa Bela et 3 autre(s)
Journal of African Earth Sciences
The hinterland of Campo is marked by Archean, Paleoproterozoic, and Cretaceous geological formations. Petrographic, mineralogical and geochemical analyzes of beach sediment samples were performed to determine the origin, alteration, and paleoclimate of the various coastal sediment layers and to reconstruct the structural context of the source region. The beach sediments are fine to medium-grained in size. Morphoscopic examination showed a predominance of very angular and shiny quartz grains. These data reflect a relatively close source with transport in a fluvial environment. The Chemical Index of Alteration (CIA: average = 79.94%), Plagioclase Index of Alteration (PIA: average = 85.31%), as well as the A–CN–K and (A-K)-C-N triangular diagram, show that the weathering affected the source area rocks. The ratios of SiO2/Al2O3, K2O/Na2O, and the chemical composition variation index (ICV ∼ 1.32) show that the sediment samples are immature to mature in terms of texture and chemical composition. Al2O3/TiO2 ratio values ranged from 3.04 to 33.44, indicating an intermediate to felsic rock signature, confirmed by Zr vs TiO2, La/Sc, and Th/Co binary diagrams. Geochemical results reveal a passive marginal continental environment. The passive margin emerged during the opening of the South Atlantic Ocean, which is compatible with the overall geology and structural setting of the studied area.
Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Francis Aonsi Kamani, Mohamed Abioui, Annick Kwewouo Janpou et 3 autre(s)
Arabian Journal of Geosciences
John Takem Eyong, Gabriel Ngueutchoua, Mbesse Cécile Olive, Ntsama Atangana Jacqueline, Moïse Bessong, Paul B. Wignall et 1 autre(s)
Journal of African Earth Sciences
Nguo Sylvestre Kanouo, Arnaud Patrice Kouske, Gabriel Ngueutchoua, A. S. Venkatesh, Prabodha Ranjan Sahoo, Emmanuel Archelaus Afanga Basua
Minerals
The core of detrital zircons from the southern Meiganga gold-bearing placers were analyzed by Laser Ablation Split Stream analytical techniques to determine their trace element abundances and U-Pb ages. The obtained data were used to characterize each grain, determine its formation condition, and try to trace the provenance. The Hf (5980 to 12,010 ppm), Y (27–1650 ppm), U (25–954 ppm), Th (8–674 ppm), Ti (2–256 ppm), Ta, Nb, and Sr (mainly <5 ppm), Th/U (0.06–2.35), Ti zircon temperature (617–1180 °C), ∑REE (total rare earth element) (98–1030 ppm), and Eu/Eu* (0.03 to <1.35) are predominant values for igneous crustal-derived zircons, with very few from mantle sources and of metamorphic origin. Crustal igneous zircons are mainly inherited grains crystallized in granitic magmas (with some charnockitic and tonalitic affinities) and a few from syenitic melts. Mantle zircons were crystallized in trace element depleted mantle source magmatic intrusion during crustal opening. Metamorphic zircons grown in sub-solidus solution in equilibrium with garnet “syn-metamorphic zircons” and in equilibrium with anatectic melts “anatectic zircons” during crustal tectono-metamorphic events. The U-Pb (3671 ± 23–612 ± 11 Ma) ages distinguish: Eoarchean to Neoproterozoic igneous zircons; Neoarchean to Mid Paleoproterozoic anatectic zircons; and Late Neoproterozoic syn-metamorphic grains. The Mesoarchean to Middle Paleoproterozoic igneous zircons are probably inherited from pyroxene-amphibole-bearing gneiss (TTGs composition) and amphibole-biotite gneiss, whose features are similar to those of the granites, granodiorites, TTG, and charnockites found in the Congo Craton, south Cameroon. The youngest igneous zircons could be grains eroded from Pan-African intrusion(s) found locally. Anatectic and syn-metamorphic zircons could have originated from amphibole-biotite gneiss underlying the zircon-gold bearing placers and from locally found migmatized rocks that are from the Cameroon mobile belt, which could be used as proxies for tracking gold.
Aristide Nadine Sonfack, Gabriel Ngueutchoua, Yannick Steve Ngagoum Kontchipe, Francis Temgo Sopie, David Guimolaire Nkouathio, Armand Sylvain Ludovic Wouatong et 3 autre(s)
Journal of African Earth Sciences
Durane Tchatchouang Chougong, Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Rose Fouateu Yongué, Sylvie Carole Ondo Ntyam, John S. Armstrong‐Altrin
Journal of African Earth Sciences
Yannick Steve Ngagoum Kontchipe, Francis Temgo Sopie, Gabriel Ngueutchoua, Aristide Nadine Sonfack, David Guimolaire Nkouathio, Robinson Tchatchueng et 2 autre(s)
Arabian Journal of Geosciences
Alexandrine N’nanga, Gabriel Ngueutchoua, Emile Ekomane, Paul Tématio
Arabian Journal of Geosciences
Sonfack Aristide Nadine, Gabriel Ngueutchoua, Ngagoum Kontchipe Yannick Steve, Sopie Francis Temgo, Nkouathio David Guimolaire, Wouatong Armand Sylvain Ludovic et 3 autre(s)
Journal of African Earth Sciences
Armel Zacharie Ekoa Bessa, Gabriel Ngueutchoua, Emile Ekomane, Salomon Bertrant Bissé, Bokanda Ekoko Eric, Durane Tchatchouang Chougong et 2 autre(s)
Solid Earth Sciences
This work reports the mineralogical and geochemical characterization of the Moloundou swamp sediments in order to deduce their tectonic setting, source rock composition, weathering conditions and maturity. These sediments show sandy to loamy sand in nature; they are pale olive to greenish and contain organic matter in the top. Their mineralogy consists of quartz and clay minerals with small amounts of mica, rutile, anatase and feldspars. Tectonic discrimination diagrams and plots of K2O/Na2O vs. SiO2, and TiO2 versus Zr, intermediate sedimentary provenance, within active continental margins in a collisional setting. The A–CN–K ternary diagram points to a high degree of chemical weathering of the source area. The increased plagioclase index of alteration (PIA) values point to a high leaching of plagioclase feldspars during source weathering and transport. The chemical index of alteration (CIA) and the chemical index of weathering (CIW) values for the studied samples suggest a highly intensive chemical weathering in a humid warm climate. The strong chemical weathering of the source rocks is revealed by the presence of kaolinite, goethite and gibbsite. The Moloundou swamp sediments are tectonically in an active setting, derived from mixed acid to intermediate magmatic and metamorphic source rocks.
Christel Sobdjou Kemteu, Abakar Mahamat, François Bidzang Ndong, Mero Yannah, Gabriel Ngueutchoua, Simon Ngos
International journal of innovation and applied studies
Many research studies have been done in the Mungo-River valley, they were mostly concerning the genesis and stratification of outcrops, but not really their petrology (description and classification). According to those reasons, this article is going to increase the petrology’s understanding of Mungo-River’s cretaceous outcrops, in Douala sub-basin. So, the studies have been done on Moundeck village’s outcrops and near the railway bridge on the Mungo-River. In fact, the studies were concerning the description of eight outcrops; the classification of their facies and the interpretation of their genesis. The description of outcrops has showed that they are constituted of positive and negative sequences. The thin sections have permitted to classify the facies described as litharenites and lithic arkoses, which are friable rocks. The genesis of Mungo-River’s outcrops could be understood according to two approaches. On the one hand, the sedimentary structures such as intercrossed and oblique stratifications observed on outcrops signify that, the sedimentation had been taken place in a fluvio-deltaic environment. On the other hand, the positive and negative sequences delimited on described outcrops, testify the influence of sedimentary cycles (transgression and regression) within the depositing environment.
Gabriel Ngueutchoua, John Takem Eyong, Armel Zacharie Ekoa Bessa, Zita Bih Azanji Agheenwi, Alain Emane Maschouer, Christel Sobdjou Kemteu et 4 autre(s)
Journal of African Earth Sciences
Bokanda Ekoko Eric, Ekomane Emile, Kenfack Nguemo Gatien Romuald, Njilah Konfor Isaac, Ashukem Nkongho Ethel, Paul Tématio et 4 autre(s)
Heliyon
Petrography, heavy mineral and trace element geochemistry have been used to unravel the tectonic setting, source area lithology, diagenesis and paleoclimate conditions of the Mamfe sandstones. Quartz exists as monocrystalline (79%), and polycrystalline grains (21%). Orthoclase and microcline are the most dominant feldspars in the rocks. Heavy minerals such as zircon, tourmaline, kyanite, augite, garnets, hornblende, epidotes, diopside, muscovites, biotites, and opaque minerals were disclosed by the samples after bromoform separation. These sandstones are mineralogically and texturally immature and have been classified as arkose on the basis of the QFR diagram. QtFL plot indicates derivation mainly from a transitional continental region of continental block provenance with trace elements geochemical data pointing to a felsic source. The felsic sources are related to the Precambrian granitic/gneissic rocks which formed the basement and margins of the basin. The bivariant log-log Qt/F+R and Qp/F+R plot and the nature of quartz grains of the studied sandstone specimens indicate a semi-humid climatic condition prevailed at the time of deposition in a fluvial environment. The sandstones display deformation of mica, cementation, replacement, and albitization with some having an imprinted reddish brown color indicating a redoxmorphic, locomorphic and phyllomorphic diagenetic stages associated to early, burial and uplift diagenetic processes.
John Takem Eyong, Gabriel Ngueutchoua, Moïse Bessong, Victor J. Hell, Bokanda Ekoko Eric, Paul B. Wignall et 1 autre(s)
Journal of African Earth Sciences
Alexandrine N’nanga, Ngos Simon, Gabriel Ngueutchoua
Journal of African Earth Sciences
Nguo Sylvestre Kanouo, Gabriel Ngueutchoua, Arnaud Patrice Kouske, Rose Fouateu Yongué, A. S. Venkatesh
Minerals
Trace element concentrations and U–Pb ages were obtained using Laser Ablation Split Stream Method from the core of 115 zircon grains from the western Meiganga gold placer deposit. The data was used to characterize zircon, to understand the history of crystallization and to locate source rocks within the local and regional geological settings. Zircon trace element geochemistry was used to distinguish between magmatic and metamorphic affinity. The magmatic zircons have characteristics compatible with their probable origin from granitoid, syenite, tonalite, charnockite and mafic to ultramafic rocks. The metamorphic zircons composition is compatible with growth from anatectic melts and by sub-solidus crystallization in equilibrium with garnet. The zircon ages reveal Archean, Paleoproterozoic, Mesoproterozic, and Neoproterozoic events with the principal source could mainly belong to Paleoproterozoic magmatic lineage. Some of the Paleoproterozoic magmatic zircons were probably sourced from two mica granite found within the local geology, whereas the remaining zircons have features indicating source rocks within the Congo Craton. We suggest that the geologic history of these zircons is related to crustal-scale magmatic and/or tectono-metamorphic events, possibly linked to Eburnean and Pan-African orogeny.
P. L. Kenfack, Pierre Ricard Njiké Ngaha, Georges Emmanuel Ekodeck, Gabriel Ngueutchoua
International Journal of Geosciences
The aim of this research work was to report a facies analysis of the N’Kappa formation, identified the clay minerals present in those facies and evaluate their oil potential. For that to be done, Lithostratigraphic descriptions were performed on three natural outcrops chosen in three different localities of the northern border of Douala sedimentary basin. Ten shaly samples were then collected on those outcrops and submit to X ray diffraction and Rock-Eval pyrolysis. Lithologically, the N’Kappa formation is made up of dark to grey shales and fine to coarse sandtones. The mineralogic content of the shales is made up of Kaolinite, dickite, low quartz and vaterite. Those shaly facies present high amount of immature organic matter (average TOC content around 2%). The petroleum potential is fair to poor (average S2 for all the samples around 3.33 mg HC/g of rock) though some samples (M1 and M2) presenting a good petroleum potential up to 6.62 kg HC/t of rock and 6.44 kg HC/t of rock respectively. They have undergone a low degree of diagenesis (early to burying diagenesis). This is evidenced by the predominance of kaolinite and dickite, low quartz and vaterite which are minerals stable at low temperature.
Joseph Bertrand Iboum Kissaaka, Marie Joseph Ntamak-Nida, Gabriel Ngueutchoua, François Mvondo Owono, P. G. Fowe Kuetche, Sylvie Bourquin
The present study is based on an approach including offshore seismic data and outcrops to better understand the tectonic evolution of the Kribi-Campo sub-basin. Tectonic markers recognized (normal and reverse faults, listric faults, fractures, drag folds, anticlines, grabens, slump and divergent structure) confirm the existence of syn-rift extensional and compressive phases. Two structural regions were recognized on the seismic lines: the western and eastern depocentres. Within both depocentres, the syn- rift succession is bounded above by the J erosive unconformity, which marks the end of the rifting in the Kribi-Campo sub-basin. In the Campo outcrops, the major active faults in the syn-rift deposit are those having a N000-020°E, N160-180°E, N80-110°E trend. Structures such as normal faults are connected to extensional syn-rift. Reverse faults and folds are indicative of a compressive episode, which is placed in the Lower Cretaceous (105-95 Ma). These faults and tectonic activity indicate that the Campo outcrops belong to the transitional or ending rifting phase.
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