ST
Maître de Conférences
Scientific activity
Researcher profile
Faculty researcher at the University of Yaoundé I. Grade: Maître de Conférences.
Scientific publications
Ashukem Ethel Nkongho, Bokanda Ekoko Eric, Bisse Salomon Betrant, Philip Fralick, Belinga Belinga Cédric, Daniel Florent Akono and 1 more
Journal of African Earth Sciences
Bisse Salomon Bertrant, Bokanda Ekoko Eric, Florence Njinto Kwankam, Ashukem Ethel Nkongho, Nfor Ngwakfu Shannon, Adama Amaya and 1 more
Solid Earth Sciences
The studied travertine deposits have been analysed using sedimentology, petrography and geochronology to evaluate their resurgence variation, Neotectonic reconstruction, hydrothermal/paleohydrology, and tectonic influence for their precipitation. These deposits display a dome structure with milimetric layers containing some dicotyledonous leaf prints mainly of angiospermic plants class and animal traces. Traces of gastropods fossil and imprinted plant leaves are seen scattered all over the samples. Microscopically, the travertine reveal laminae characterising a long spike-like dendritic millimetric crystals. The spike-like structure composed of crystals calcite enclosing putative microbial filaments which are longitudinal within some places, micrite partially filling inter-crystalline voids. The petrographic characteristics of the travertine corroborated with isotopic analyses, reveals processes such temperature variation, degassing variation, fluctuations of the physico-chemical fluid and dissolution as controlling factors to the formation of the different carbonates textures. Four units representing different sample points discloses ages of 19.839 ± 4.8 ka, 50.3645 ± 9.4 ka b2k, 2.00 ± 1.8ka b2k and 5.77 ± 1.7ka b2k. Conclusions drew from the study suggest that, (1) a forest vegetation type testifying to a humid climate prevailed at the time of the travertine precipitation, (2) there were repeated reactivation of fault systems as well as episodic high hydraulic head in the aquifers underlined by U-series dating that showthe presence of different spring systems generations in the travertine deposits (3) three phases of travertinization were disclose: first phase (Upper Pleistocene, ca 50 ka b2k), marked by significant and regular rainfall leading precipitation of massive travertine deposits, second phase (Between 50 ka b2k and 19 ka b2k), marked periodicity of rainfall forming laminated travertine, third phase (beginning of the Holocene between 5.77 ± 1.7ka b2k and 2.00 ± 1.8ka b2k), marked by obstruction of the main canal of circulation inducing a possible change of exsurgence forming new deposits recorded at the base of the dome (4) the travertine precipitation was influence by hydrothermal system and recent extensional tectonic activities owing to the presence of saline springs.
Akono Daniel Florent, Samba Assomo Philippe, Lucas Bouba, Belinga Belinga Cédric, Onana Enama Léandre, Ekomane Emile
Environmental Geochemistry and Health
Belinga Belinga Cédric, Bisse Salomon Bertrant, Amaya Adama, Bokanda Ekoko Eric, Akono Daniel Florent, Ashukem Ethel Nkongho and 1 more
Arabian Journal of Geosciences
Ikose Franklin Barake, Bisse Salomon Bertrant, Bokanda Ekoko Eric, Philip Fraclick, Munira Afroz, Ashukem Ethel Nkongho and 1 more
Arabian Journal of Geosciences
Akono Daniel Florent, Bokanda Ekoko Eric, Bisse Salomon Bertrant, Belinga Belinga Cédric, Menanga Tokouet Renaud, Tonye Marie-Diane and 6 more
Heliyon
The Ebolowa Municipal Lake (EML) (South Cameroon) in order to identify the early diagenesis processes taking place in the lake and the factors influencing them. To this end, 21 samples were collected. In situ, hydrogen potential, redox potential, conductivity, dissolved oxygen content, and turbidity were measured. In the laboratory, the samples were subjected to mineralogical analysis by X-ray diffraction, geochemical analysis by X-ray fluorescence and ICP-MS, and statistical analysis. The coefficient of variation (Qi) was calculated from the geochemical data. In the water column, OD > 2 mg/L, pH > 7 and Eh < 0 mV. In sediments: pH < 7, Eh values are lower. The contents of 2.08 ≤ TOC ≤ 12.65%. The mineralogical procession consists of quartz, kaolinite, gibbsite, goethite, and siderite. The latter is only present in the EML. The sediments are dominated by SiO 2 (60.44–89.47%), Al 2 O 3 (6.55–18.17%), and Fe 2 O 3 (1.15–6.21%). The Qi values range from 0.73 to 2.31. The Mn/Fe ratio values are below 0.40. Qi > 1 for Al, Fe, Mn, Mg, K, Na, P, Ni, Co, Zn, Pb, Cd, Cu, Ba, and V, and Qi < 1 for Si; Qi = 1 for Ca. The hierarchical cluster analysis shows two groups: the first one includes the samples from the central and western parts, while the second one includes those from the eastern and southern parts of the lake. The water column is subject to oxic conditions, while the sediments are anoxic. The rapid consumption of oxygen is due to organic mineralization, which is the main diagenesis observed in the lake. This phenomenon is more accentuated in the western part of the lake.
Ashukem Ethel Nkongho, Bisse Salomon Betrant, Philip Fralick, Bokanda Ekoko Eric, Ngo Maih Bahoya Marie Priscille, Tsamnye Justin-Junior and 4 more
Arabian Journal of Geosciences
Bokanda Ekoko Eric, Philip Fralick, Bisse Salomon Betrant, Ashukem Ethel Nkongho, Belinga Belinga Cédric, Bokanda Frankline Besonge and 3 more
Solid Earth Sciences
The shales of the Mamfe basin were geochemically analyzed to determine their paleosalinity and hydrothermal characteristics which existed at the time of their deposition. Elemental ratios such as boron/gallium (B/Ga), strontium/barium (Sr/Ba), and total sulphur/total organic carbon (S/TOC) and TOC/S were applied for paleosalinity reconstruction. The shales of the Mamfe basin show B/Ga is <3, Sr/Ba <0.2, and S/TOC is <0.1 and TOC/S >6 the values of the elemental ratio show that the Mamfe shales were deposited in a freshwater environment. For hydrothermal activities ratio, Sc/Cr was used and Binary diagrams TOC vs P and Co/Zn vs TOC were constructed to discriminate between normal water, mixed and hydrothermal influence. The Sc/Cr ratio was greater than 0.14 indicating that the shales in the Mamfe basin were deposited in a normal water environment with no influence from hydrothermal processes. The binary discriminant diagram of TOC vs P and Co/Zn vs TOC shows that all the shales were not influenced by any hydrothermal processes during the time of their deposition.
Ondoua Oyono Joseph Sadrac, Ekomane Emile, Ipan Antoinette Solange, Edima Yana Roland William, Bidjo Emvoutou Géry Christian, Bitom Dieudonné
Journal of Geosciences and Geomatics
The aim of the present study is to characterize a weathering mantle developed on pelitic rock in the tropical forest region precisely in Mintom (South East Cameroun). This characterization include morphology, physico-chemical and mineralogic analyses. The region is characterize by a hot and wet climate consisting of four seasons of inequal length and intensity. The average temperature is about 24°C and the mean rainfall is about 1633mm/years. The rocks in the area consist of limestone, dolomites and pelites. Fieldwork consist of landscape analysis, geologic prospection and soil profile description. Mineralogical and physico-chemical was carried out on various samples in the laboratory. Morphological results show that the studied profile has a general brownish yellow aspect, with a thickness of about 6m and a silty-clayey texture. Five horizons can be distinguished from top to bottom: a humiferous horizon, a loose yellow set, a yellow horizon bearing quartz fragments and large indurated blocks, a saprolite consisting of a fine and coarse saprolite possessing some pelite relics of variable sizes and a deep red colour just like that of the parent rock. The parent rock is a massive pelite with a reddish colour when wet and a violet colour when dry. It has a powdery feel. Analytically, the soils have an acidic pH (4,0 to 4,2), a high organic matter content (4,8%), a C/N ratio of about 6,76, a cationic exchange capacity of 7,64meq/100g with a saturation rate S/T of about 7. Particle size distribution shows that the silty fraction is dominant (59%), followed by the clayey fraction (30%). The main minerals are kaolinite, quartz, smectites, calcites, dolomites, goethite and hematite.
Bokanda Ekoko Eric, Njilah Isaac Konfor, Ekomane Emile, Philip Fralick, Bisse Salomon Betrant, Tata Cathryn Ntoboh
Solid Earth Sciences
Bokanda Ekoko Eric, Ekomane Emile, Njilah Isaac Konfor, Philip Fralick, Bisse Salomon Betrant, Tata Cathryn Ntoboh
Solid Earth Sciences
The shales of the Mamfe basin, West Africa, were studied using inorganic geochemical analysis to investigate the origin of the organic matter, environment of its deposition, paleoproductivity and organic matter preservation, organic matter maturity and petroleum potential. Shale samples from sites 1-7 have V/Ni ratios of: 2.9, 2.36, 3.14, 2.94, 3.04, 1.76 and 2.23 respectively. The V/Ni values of samples from sites 1,2,4, and 7 indicate a mixed terrestrial and marine organic matter origin, while shales from the other three sites have values close to those that represent mixed marine-terrestrial organic matter. Ni/Co, V/Cr and U/Th ratios of the black shales are <3, <2, and <0.75 respectively, indicating organic matter deposition in an oxic environment. The Ba/Al ratios of the studied shales average 64 while the P/Ti ratio averages 1.84 indicating a moderate to high paleoproductivity. The moderate to high paleoproductivity and rapid sedimentation influence the preservation of organic matter in the Mamfe shales. The shales have K/Rb ratios, ranging between 425 and 640, enrichment of LREE over HREE, MREE over HREE, positive Gd, Eu and negative Ce anomalies. These results indicate that the organic matter found in the shales is not yet at the level of maturity to produce petroleum, but may became good petroleum source rocks in the near future.
Bokanda Ekoko Eric, Ekomane Emile, Eyong John Takem, Njilah Isaac Konfor, Ashukem Ethel Nkongho, Bisong Rita Ndige and 1 more
Journal of Geological Research
This paper aims to investigate the genesis of clastic dykes and soft-sediment deformation structures in the Mamfe Basin, South West-Region, Cameroon. Results from this study portray the following: (1) The clastic dykes are extrusive and were generated from preexisting soft-sediments that penetrate fissures caused by seismic activity. It can be concluded that clastic dykes originate from seismic shacking, probably induced by volcanic-tectonic activity and magmatic dykes that cut across the Precambrian and Cretaceous formations of the Mamfe Basin. (2) The soft-sediment deformation structures (flexures, sheared foliations, anticlinal folds, load casts, and flame structures) are likely triggered by seismic shocks. The inferred influence of seismic activity results from rifting and rapid subsidence of basin-fill during the Cretaceous. Some of these soft-sediment deformation structures (SSDS) are induced by fluidization and liquefaction triggered by rapid sedimentation within tectonically active settings, as well as density variations illustrated by local occurrence of load casts with weak lateral extensions. (3) The synsedimentary features (joints, faults, filled fractures) are related to local stress triggered by gravitational sliding, because the fractures were filled by unconsolidated clastic materials.
Ekomane Emile, Bomolomo Michelle Vanessa, Zo’o Zame Philémon, Bisse Salomon Bertrant, Angtouzou Waya
International Journal of Multidisciplinary Research and Development
Nzesseu Nandjou Valentino, Bineli Betsi Thierry, Belinga Belinga Cédric, Ekomane Emile, Kelepile Tebogo
Journal of African Earth Sciences
Manga Owona Gaspard William, Moïse Bessong, Mioumndè Arthur Paterne, Mbesse Cécile Olive, Bapowa Laouna Carole, Kusi Micheline Michelle-Alexia Ngum and 3 more
Journal of African Earth Sciences
Bisse Salomon Betrant, Bokanda Ekoko Eric, Florence Njinto Nkwankam, Ashukem Ethel Nkongho, Nanfa Tefak Fatoumata Maelle, Yugyè Jules Alex and 4 more
Heliyon
The present study focused on evaluating the contribution of both organic and inorganic component to the chemistry of Cretaceous black shales in the Mamfe basin, Sw Cameroon by performing inductively couple plasma spectrometry analyses with the data analysed using multivariate statistical analyses. The shales are classified as calcite enriched (Ca/Mg > 1) and calcite depleted (Ca/Mg < 1). Major elements such as K, Ti, and Al shows significant correlations (>0.71) among themselves and negative correlations with total organic carbon (TOC), total organic nitrogen (TON) and total organic sulphur (TOS) indicating that they were control mainly by inorganic factors. The positive correlation between phosphorus (P) and TOC, TOS, TON maybe due to absorption by organic fraction into the lattice of the shales. Selected both biophilic (Ba, Co, Ni, and Sc) and terrigenous (Zr) trace elements were correlated amongst themselves and with organic components. Zr show negative correlation (−0.36) with organic components and correlates negligibly with Co, and Ni (0.04, 0.16) indicating these elements were derived from organic matter with exception to Ba and Sc which shows positive correlation with Zr (0.77) and negatively correlated with TOS (−0.34, −0.13), carbon (−0.25, −0.17) and TON (−0.17, −0.06). The enrichment of light rare elements over heavy rare earth elements positive europium anomaly on PAAS normalise diagrams and an insignificant to negative correlation with TOC, TOS, and TON indicating their derivation from mainly an inorganic factor. Statistical analyses by hierarchical classification ascending (HCA) and principal component analyses (PCA) confirms solely an inorganic contribution to the chemistry of the studied black shales in the Basin. The positive correlations portray by some elements with organic components maybe due to their absorption by organic fractions into their lattice. Further indirect/direct methods such as sequential extraction and FTIR is required throw light on the origin of the chemistry of black shales in the Mamfe basin.
Bokanda Ekoko Eric, Mary Ewokolo Molua Mbua Etutu, Florence Njinto Kwankam, Bisse Salomon Betrant, Ashukem Ethel Nkongho, Bokanda Frankline Besonge and 4 more
Scientific African
This study is focused on assessing the contamination levels of heavy metal elements (Cu, Cd, Cr, Ni, and Zn) in black metalliferous shales of the Mamfe basin in South Western Cameroon and identifying the possible pollution sources. Forty (40) black shale samples collected from seven outcrops from different sites in the Mamfe basin were subjected to geochemical analysis by inductively coupled plasma-mass spectrometry (ICP-MS). The results obtained from these analyses were used to calculate the contamination factor (CF), geo-accumulation index (Igeo), and Pollution Load Index (PLI). Person's correlation coefficient was applied in this work to assess the metals origin. The values of heavy metals in the shales were compared with experimental values of TEL (Threshold Effects Level), PEL (Probable Effects Level), ERL (Effects Range Low), and ERM (Effects Range Medium) to assess the long-term adverse biota effect if the shales weathers and release the hosted heavy metals. The average heavy metal concentrations in the studied shales were 35 mg/kg, 89 mg/kg, 0.24 mg/kg, 82 mg/kg and 37.3 mg/kg for Cu, Zn, Cd, Cr and Ni respectively with some above the threshold values of United State Environment Protection Authority (USEPA), average shale (ASV), toxicity reference values (TRV) and Indian River system (IRS). The shales are poorly to moderately enriched in heavy metals which may cause a long-term effect on the surrounding soils and waters after degradation. The heavy metal values of the studied shales compared with the experimental results of TEL, PEL, ERL, and ERM indicate that a little adverse biota effect of Ni, Cu and Cr to the ecosystem after degradation of the studied shales. The geo-accumulation index ranged between 0 and 0.06 indicating that the black Mamfe shales are uncontaminated to moderately contaminated and may have adverse effects on the freshwater ecology and surrounding soils. The pollution load index (between 0.0 to 0.05) and contamination factor (0.18-1.84) indicate that the shales have a low level of contamination and their long-term degradation and weathering will have a limited effect on the soils and water ecosystems. The positive correlation between Cu, and Zn, suggest the same source of contamination input. The positive correlation between Zn, Cu, Cr, and Ni indicates a natural origin of these elements in the shales. A rapid weathering/degradation of large quantity of theses shales may increase the concentration of heavy metals in the surrounding rivers and soils in the near future.
Belinga Belinga Cédric, Ekomane Emile, Bineli Betsi Thierry, Ngo Bandong Patricienne Marie Carly, Ashukem Ethel Nkongho, Bokanda Ekoko Eric and 4 more
Journal of African Earth Sciences
Bokanda Ekoko Eric, Ekomane Emile, Kenfack Nguemo Gatien Romuald, Njilah Konfor Isaac, Ashukem Nkongho Ethel, Paul Tématio and 4 more
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.
Bokanda Ekoko Eric, Philip Fralick, Ekomane Emile, Njilah Isaac Konfor, Bisse Salomon Betrant, Akono Daniel Florent and 1 more
Journal of African Earth Sciences
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