North Cameroon Research Articles

Physicochemical Potential of Balanites aegyptiaca Seed Kernel Oil from Northern Cameroon for Biodiesel valorization

This research work reports the physicochemical potentialities of Balanites aegyptiaca kernel oil for biodiesel valorization. Balanites seed was sampling from Pitoa, Maroua and Moutourwa localities located from North Cameroon and the kernel oil was extracted using Soxhlet apparatus. The physicochemical and the free fatty acid composition of kernel oils was determined. Among the three samples, those of Pitoa shows the higher oil yield (56.6 %). All the Refractive index of these oils were ranged in ASTM and their kinematic viscosities were small compared to the EN ISO 3104 standard. The Acid values measured were all less than EN 14104 standard and the iodine values were in accordance with EN 14111 standard, whereas, the saponification value for the samples of Maroua (139.5 ± 0.07) was higher than those of Pitoa (123.6 ± 0.04) and Moutourwa (131.5 ± 0.06) and the Peroxide values measured were lower than 10 meq/Kg. Unsaturated fatty acids were higher for the sample of Maroua (78.8 %) than those of Moutourwa (76.9%) and Pitoa (77.7 %). This research work indicate that B.aegyptiaca kernel oil obtainable from North Cameroon as higher yield (50.7-56.6%). The kernel oil shows good physicochemical properties and fatty acids profile which can be valorised as a feedstock for the production of biodiesel.
 Place and Duration of Study: School of Chemical Engineering and Minerals Industries - Department of Chemical Engineering, University of Ngaoundere – Cameroon
 work takes place between October 2020 and Jun 2021.

Optimization of the photovoltaic systems on the North Cameroon interconnected electrical grid

Optimization of the photovoltaic systems on the North Cameroon interconnected electrical grid

Groundwater prospecting using remote sensing and geoelectrical methods in the North Cameroon (Central Africa) metamorphic formations

Remote sensing imagery and geoelectrical surveys used in this study help to evaluate the groundwater potentiality in the metamorphic formations of the North Cameroon. The methodology of the work is then mainly based on the extraction and identification of lineaments or fracture zones which acts as the passageway for groundwater. Manual and automatic extraction technics applied on the Landsat-8 images made it possible to find sixty one (61) lineaments. The main directions of these lineaments are N-S and N22°E (NNE-SSW) and the secondary directions are N10°E, NE-SW, then W-E to N100°E. According to the lineament density map, high density values are located at the centre and at the western part of the study area. The lineament density contrasts show the level of fracturing in the area. This fracturing is also evidenced by the geoelectrical survey. Indeed, results of the electrical resistivity profiling and 2D electrical imaging around or near lineaments, reveal the existence of fractures and shear zones characterized by the conductive discontinuities in the electrical current responses. Usually, the discontinuities sus-evocated above form potential groundwater targets. So, based on the combined results from remote sensing and geoelectrical method, the present study thus demonstrates the effectiveness of using this approach for assessing the availability of potential groundwater zones in the metamorphic formations. However, methods used in this study should be supported by the drill hole methods for the validity of results.

Efficacy and Induction Resistance of Neem Extract and Mancozeb 80 Wp on Physoderma Brown Spot and Physoderma Stalk Rot Diseases of Corn (Zea mays) caused by Physoderma Maydis in Far North Cameroon

Corn (Zea mays) is one of the most widely spread cereals in the world. However, in the Far North Region of Cameroon, the incidence of some maize diseases progress because of farming practices and climate change (rainfall). This work aims to evaluate effect and resistance stimulation of neem extract and Mancozeb fungicide on Brown Spot (PBS) and Stalk Rot (PSR) diseases of corn due to Physoderma maydis in field condition. The experimental design was a two-factor split-plot. The treatments were a combination of Control (T), Mancozeb (Mz) at the concentration of 6g/L and aqueous extract of neem seeds (AENS) at the concentration of 50g/L with CMS 9015 and CMS 8704 varieties. Incidence, severity, rainfall, Area Under Disease Progress Curve (AUIPC, AUSiPC) were recorded. Phenol and protein rates, enzymatic activity of Polyphenol oxidase (PPO), peroxidase (POX) and glucanase were carried out. Stalk length and yield were evaluated. Incidence and severity of Physoderma Brown Spot (PBS) and Physoderma Stalk Rot (PSR) increased with time and environmental conditions (rainfall). The highest disease incidence was observed in the control treatments with both diseases, 52.39 and 37.67 % respectively for Brown Spot and Stalk Rot in CMS8704 variety and lower with AENS, 13.5 and 36.01%. AENS reduced PBS incidence and severity by 23.1 and 19.9 %, respectively and Mz by 9.3 and 18.1 %. The AUIPC and AUSiPC of PBS and PSR remained lower with AENS treatment during the growing season and higher with the other treatments. The highest phenol and proteins rates (8.81 and 25.1 mg/g/FM) were recorded for the AENS treatment in CMS9015 and CMS8704 variety, respectively. Enzymatic activity was more enhanced in CMS8704 variety with AENS. 4.22 A470/min/g, 1.55 A470/min/g and 1.15 µmole/min /g were recorded respectively for PPO, POX, and Glucane activities. Stalk length was higher in AENS and Mancozeb treatments with variety CMS8704 (125.13 and 123 cm respectively). A yield increase of 7.44% was obtained in the AENS treatment. The combination or not of aqueous neem extract and CMS8704 could be used in the integrated control of PBS and PSR of maize

Optimal integration of photovoltaic power into the electricity network using Slime mould algorithms: Application to the interconnected grid in North Cameroon

This document proposes a method for determining the optimal point of integration of PV Generated into the electricity grid. The Slime mould optimization algorithm ( SMOA) is applied to determine the best node in the case of one and two injection points. The problem has been modelled as an optimization problem where the objective is to minimize joule losses and the main constraint is to regulate the voltage at each point. The proposed method was implemented in MATLAB and applied in the nodes of the IEEE networks 33 and 69 and the north interconnected grid (NIG) of north Cameroon. The results allowed us to determine the optimal points of the NIG allowing us to inject with less losses. Comparison of the results obtained with other algorithms showed that the SMOA has the best reduction in power losses and a good improvement in the voltage profile.

Extraction and analysis of structural lineaments from Mokolo area, North Cameroon, using DEM and remote sensing images, and their influence on drainage morphometric

Extraction and analysis of structural lineaments from Mokolo area, North Cameroon, using DEM and remote sensing images, and their influence on drainage morphometric

Tuberculosis in goats in Benoue area of North Cameroon: Prevalence, diagnostic performance of intradermal tuberculin skin test and zoonotic risk factors

Tuberculosis (TB) due to Mycobacterium bovis is a wasting disease of animals with severe public health significance. Though widely diagnosed in cattle and the performance of Tuberculin Skin Test (TST) at different cut-off points compared in various environmental conditions, there is dearth of information with respect to TB in goats in Cameroon. This study estimated the prevalence of bovine TB in goats in Benuoe area of Cameroon, based on the performance of TST against detection of tuberculous-like lesions and acid-fast bacilli as gold tests. The study detected goat TB based on tuberculous-like lesions (27.87%), acid-fast bacilli (3.29%); and bovine TB positive reactions (12.28%, 95%CI: 9.19–15.95), (8.95%, 95%CI: 6.31–12.23) and (5.37%, 95%CI: 3.36–8.09) at Single intradermal cervical tuberculin (SICT) ≥2.5mm, ≥3mm, and ≥4mm and (2.30%, 95%CI: 1.06–4.32), (1.79%, 95%CI: 0.72–3.65) and (1.02%, 95%CI: 0.28– 2.60) at Single intradermal comparative cervical tuberculin (SICCT) ≥2mm, ≥3mm, and ≥4mm cut-off points, respectively. SICT and SICCT sensitivity (11.76%) against detection of tuberculous-like lesions was significantly lower [p<0.05] with slight agreements [Kappa=0.161] compared to sensitivity (100%) and perfect agreements [Kappa=1.00] against detection of acid-fast bacilli at these cut-offs. The Bayesian model revealed a goat TB prevalence of 18.41% (95%CI: 11.73–27.00) using SICT and 4.28 (95%CI: 1.26–8.60) using SICCT with the performance characteristic being higher for SICT than SICCT at ≥2mm cut-off. However, two-graph ROC (TG-ROC) analysis revealed that the optimal goat TB diagnosis with SICCT was at ≥2mm cut-off point. Many goat handlers were aware of health hazards of zoonotic TB but ignorant about goat TB and its possible zoonotic transmission to humans. The study reports the first comparative tuberculin skin test of goats in Benoue area of North-Cameroon and confirmed that zoonotic TB is a neglected health and production problem of goats in Cameroon that needs further investigated.

Structural interpretation of gravity data in Garoua, North Cameroon

Structural interpretation of gravity data in Garoua, North Cameroon

Democratization, Social Renegotiations and the Hegemony of the Rey Bouba Lamidate over the Population of Slavish Mboum Origin in Question in the District of Touboro (North Cameroon)

This article analyzes the effects of democratization on power relations between the Rey-Bouba lamidate and the population of slavish Mboum origin in the district of Touboro (North Cameroon). The analysis of the challenges of its political participation (conventional and unconventional) leads to the study of its political activism in a context of diversification of the partisan offer. It also involves entering the profiles of political elites, from their rank and their associative movement. Based on the theory of coloniality of power and collected empirical data, democratization seems to be a favorable framework for social renegotiations between the lamidate of Rey-bouba and the population of the slavish Mboum origin.

Re-use in road construction of a Karal-type clay-rich soil from North Cameroon after a lime/cement mixed treatment using two different limes

Swelling clays characterized by their shrinkage and swelling phenomenon are known to be the main cause of cracking of paved roads. So, the road construction on swelling soils require knowledge and specific techniques, including the chemical stabilization with lime or cement addition. This technique favors the sustainable development by avoiding waste production especially soils. Indeed a maximum reuse of materials located in the building project area allows reaching the "zero loan, zero deposit" objective.In this paper, the efficiency of mixed treatment with lime and cement was tested on swelling karal-type soils collected at Pitoa in the North Cameroon region. The soil samples were characterized by applying microstructural and geotechnical tests (XRD, SEM, Particle Size Analysis, Atterberg Limits, Modified Proctor, CBR test, and Unconfined Compressive Strength (UCS)). The results showed that the mixed treatment of karal soils using a 2% of hydrated lime mixed with CaO or a 3% of low carbonated hydrated lime and 3, 5 or 7% of cement, reduced drastically the soil volume variation under water content change and improved the soil physico-mechanical properties. Finally, soils after treatment reached the minimum characteristics required for recovery in road construction.

Comparison of Terrestrial Gravity and EGM 2008 Data on Extracted Lineaments: A Case Study of the Adamawa Massif, North Cameroon

A structural study on the Adamawa Massif highlights the major structures (faults) of the shear zone as well as the igneous intrusion near Mayo Baleo. Through this study, a comparison on the use of gravity data from the EGM 2008 and terrestrial models was carried out on the basis of gridded gradient data obtained by applying the MAGMAP filtering algorithm on the Oasis Montaj software system. Using the gradients has an advantage in that they contain much information especially on geological structures. The resulting maxima have strong density contrasts, enabling them to be used as tools in explaining geological contacts. Gravimetric lineaments marked by the geometry of the peaks (elongated shape) and the igneous intrusion corresponding to the circular peak were detected on the horizontal gradient maps. Reconciliation with the geology, the slope map and satellite images justifies the presence of the Djohong-Ngaoundal-Dir-Tibati, Tibati-Banyo and Tignere-Banyo lineaments which indicate the underlying Foumban (extension), Tibati and Tchollire-Banyo faults respectively, comprising the shear system residing in the massif underlain by a gneiss-migmatite bedrock. The limitation on the use of gravity data from the EGM 2008 model is manifested through the Djohong lineament correlating with the large mylonitized feature trending NE-SW, defined as a steep relief (27° to 60°), separating the Mbere basin from the upper unit with about 358 m in height difference. This terrain is a small area of relief with morphological units adapted as in the case of the mountainous areas of the West to the use of gravity data from the EGM2008. The other lineaments that are part of the shear zone fault system are not elucidated because they correspond to deep mega structures that the EGM 2008 model resolution cannot attain at depth. The use of this model is suitable for studies of superficial structures which are associated with huge formations such as the volcanic dome of Mayo Baleo, an intrusion of young trachytes with steep slopes (27° to 60°) at an altitude of 2419 m.

The issue of the performance of industries in Northern Cameroon: an analysis of the role of key players

In accordance with the strategic orientations of the Cameroonian government, industrialization is a fundamental process for the much sought-after emergence. This desire of the public authorities to make Cameroon an industrialized country is questionable, given the glaring delay that its northern part is registering in terms of industry. While this part of the country abounds in the natural and human potentialities necessary for the development of the sector of transformation of raw materials into manufactured products, it is less industrialized than the southern part of the country. In fact, the life expectancy of an industry is particularly short in North Cameroon. This situation is worrying both for the State, for local and national economic operators, but also for a young, dynamic, and increasingly qualified workforce. This reflection aims to better understand the foundations of the performance, both good and less good, of industries in North Cameroon, a region that has many strengths and where the demand for manufactured goods is constantly increasing. The methodological approach consisted of the use of data resulting from a critical reading of scientific productions in the field and a careful collection of field data. The results thus obtained sufficiently illustrate that the conditions particularly essential for the flourishing of any manufacturing company are lacking in the local industry. For the northern industry too, sustainable performance depends first of all on the opportunities to be seized by its promoter (s), then on human capital and the equipment invested and finally on the management which includes the raw material supply system, their processing and marketing of manufactured products.

Study of Digital Surface Data for Soils and Flood Risk Areas Mapping in Sudano-Sahelian Zone (Mayo-Danay Division, Far North Cameroon)

In general, living close to a river is advantage, but there is always of flooding risk, that recurrence in recent decades provokes serious material damage and loss of life. Thus, in order to protect environmental health, economic viability and human activity zones of Mayo-Danay, a careful study of components of natural environment, mainly soil, has proved essential. Clearly, use of GIS in management of natural disasters is most relevant method, designed on integration, Multicriteria Analysis (MCA) and spatial data. Thus, Digital Elevation Model is obtained by manual digitization of contour lines, in order to define the large pedological sets on which wells have been opened, profiles described, soil samples taken and analyzed in laboratory. Main results reveal that soils are sandy to clayey, with neutral and basic pH (7 to 8), high CEC and low organic matter. While, quartz is predominant, associated with smectites, illites, feldspars and iron oxyhydroxides. Updated soil map shows five soil units (1) vertisols with hydromorphic characters (26%), (2) tropical ferruginous soils (32%), (3) less evolved hydromorphic soils (15%), (4) halomorphic vertic soils (9%), and (5) hydromorphic vertic soils (18%). It is an excellent tool for work and research, that responds to agronomic and development problems. It is therefore an excellent tool for work and research, which responds to agronomic and development problems. The multi-criteria spatial analysis establishes hazard and vulnerability, crossing of which gives of flood risk areas map, according to hazard level, very high (12%), high (16%), moderate (14%), low (30%) and very low (28%) risks. For this purpose, it emerges that rainfall is relatively low (700 mm/year), but falls very abruptly during short periods, at high intensity with flows exceeding the infiltration capacities. Morphology of low-slope "yayrés" (280 m) (2‰) is bordered by high landscape (500 to 1400 m) that prevent flow of many rivers that converge into plain. Sandy soils dominated by quartz favor fast rising in water table, while very clayey soils governed by 2/1 clayey (smectites) whose behavior induce waterproofing and intense surface runoff that generate flooding. Evidently, land use change leads to transformation of natural spaces into agricultural and urban environments, which makes soils more compact and impermeable, favorable to flooding. Keywords Soil; Flood risks; Mapping; Mayo-Danay Division; Spatial data DOI: https://doi.org/10.23953/cloud.ijarsg.501

Effect of Aqueous Neem Extract on Development of Pestalotia heterocornis Agent of Pestalotia Leaf Blight of Cashew in Far North Cameroon

Cashew (Anacardium occidentale L.) trees are threatened by my many fungal diseases, among which pestaliotiopsis occupies an important place in terms of damage created in Cameroon. The aim of the present study is to evaluate the effects of aqueous extract of neem seed (AENS) on the development of Pestalotia heterocornis, the causative agent of pestalotiopsis of cashew. Isolates of P. heterocornis were obtained from diseased cashew leaves collected in the orchads. The concentrations of AENS were C1 = 500 μg/ml, C2 = 50 μg/ml and C3 = 5 μg/ml. Mancozeb 80 WP (Mz) was used as positive control. Effect of Mancobeb 80WP on the growth and spore germination of isolates were performed. The effect of AENS on the plants was evaluated in vivo. Four (4) isolates of P. heterocornis were used. AENS C1 concentration reduced the growth of all isolates. The percentage of inhibition was ranged from 45 to 90 % with the other concentrations. AENS did not inhibited spore germination (0.0 %). But Mz totally inhibited conidia germination of all isolates. In vivo, AENS protected plants against P. heterocornis. AENS can be integrated in management of cashew plants against P. heterocornis.

Brown Spot and Stalk Rot Diseases of Maize (Zea Mays) and Susceptibility of Two Varieties to Physoderma Maydis in Far North Cameroon

Corn (Zea mays L.) is one of the most widely grown cereals in the world. However, in Cameroon, particularly in the Far North Region, yields remain low because of diseases increasing due to farming practices and climate change. This work aimed to characterize Brown Spot and Stalk Rot of corn and evaluate the susceptibility of two maize varieties to Physoderma maydis in field conditions. Two maize varieties, CMS9015, and CMS8704 were evaluated in a randomized block design. Disease symptoms were observed and described using identification keys. Microscopic characteristics of pathogens were performed using a microscope. Incidence, severity, and areas under disease curve progress (AUIPC and AUSiPC) were calculated. Brown spot occurred 3 or 4 weeks after sowing (WAS) at the growing stage in CMS8704 variety first, and stalk rot 7 WAS. Brown spot appeared in leaves and is characterized by oval yellowish spots in the leaf blade and brownish spots in the midrid. Stalk rot infects stem nodes and is characterized by brownish spots, leading to the broken stem. The incidence of brown spot increased with time and environmental conditions (rainfall). The highest incidence of Physoderma Brown Spot was recorded with CMS8704 variety 53.06 % against 51.72 % with CMS9015. Severity was respectively 54.40 % and 47.12 % with CMS8704 and CMS9015. The incidence and severity of stalk rot were almost identical in both varieties. AUIPC of PBS and PSR was higher in CMS9015 than in CMS 8704, 63 DAS. PBS and PSR infect maize production, and both varieties are susceptible to P. maydis.

Impacts of refugees and climate change on agricultural yields in the Sahelian zone of Minawao, Cameroon

The village of Minawao in the Far North of Cameroon is located in the Sudano-Sahelian zone where the population lives mainly from agriculture. Since the installation of refugees from the Boko Haram conflicts, the village of Minawao and its neighbouring villages have experienced a decline in their agricultural yields. In order to know the different impacts of refugees and climate change on agricultural yields, a survey was conducted among the heads of households of refugees and natives; and another was carried out in the transport and agriculture delegations of Mayo-Tsanaga. The data was analysed using XLSTAT software. The result shows that agricultural yield loss was highly reported by refugees in Minawao village (55.45%) and about 570 t/ha of agricultural production is lost annually. Agricultural losses observed in Gawar (530 t/ha) and Zamay (510 t/ha) are also considerable. High temperatures were reported by people in Minawao (98.59%), Sabongari (99.62%) and Zamay (99.62%). The highest rainfall peaks are recorded in 2015 (1236 mm), 2000 (1281 mm) and 2019 (1370 mm). For temperatures, high values were observed in 1989 (28.4°C), 1990 (27°C), 2001 (27.7°C), 2011 (28.8°C) and 2018 (27.4°C). The variations in precipitation and temperature are not proportional. This climate change, combined with the settlement of refugees, is causing the greatest disruption to the agricultural activities of the people of Minawao and its surroundings. The main impact observed is the decrease in agricultural production. This impact causes food scarcity in these villages whose populations live mainly from agriculture. Therefore, participatory management is urgently needed to restore the soil around the refugee camp.

Clayey soils from Boulgou (North Cameroon): geotechnical, mineralogical, chemical characteristics and properties of their fired products

In this study, clayey soils are characterized as backfill and potential fusible raw materials for engineering. Geotechnical tests (particle size distribution, Atterberg limits, densities) and chemico-mineralogical analyses (X-ray fluorescence, X-ray diffraction and Fourier transform infrared) were carried out on samples collected from field in the locality of Boulgou (North Cameroon) followed by the determination of mechanical properties of fired bricks (850–1200 °C). The excavations carried out have revealed a thick layer of clayey soils (~ 2 to 2.5 m) over a sandy layer. This clay formation presents some stratifications with limited influence variation in terms of mineralogy. Mean grain size distribution is dominated by sand (62–80%), clay (12–25%) and silt (6–9%). It corresponds to silty–clayey soils regarding their methylene blue values (3.3–5.6), with low plastic (13–22%) to high plastic (33%) characteristics. They are classified by USCS as clayey sand/silty clay, while one sample is a poorly graded sand (SP). Clay minerals observed are kaolinite (6–12%), montmorillonite (2–6%) and illite (8–10%). Those parameters associated with their fine nature and high compressibility make them suitable engineering applications for backfill material and barriers. From chemical analyses, relatively high contents in alkali and alkaline earth elements (~ 4 to 6%) to be used as potential fusible raw materials for fired bricks or gres ceramics were revealed. Bricks characteristics are varied: linear shrinkage (0.3 to 9%), bulk density (1.8 to 2.3 g/cm3), water absorption (19.7 to 1.3%) and flexural strength (0.3 to 17.4 MPa). Overall, the requirement for fired brick (< 20%) is met up by the water absorption values. As from 1050 °C, these soils are made suitable for brick-making with good characteristics (metallic sound, good cohesion and flexural strength).

Factors affecting the commercialization of food legumes in North Cameroon

The study focused on factors affecting the commercialization of food legumes-cowpeas (Vigna unguiculata), bambara groundnuts(Vignasubterranea), groundnuts (Arachis hypogaea) and soybeans (Glycine max) in two departments (Benouéand Mayo-Louti) of the North Region of Cameroon. Qualitative and quantitative methods were used to collect data. Qualitative methods involved focus group discussions and direct observations. A structured interview guide was administered in major peri-urban and urban markets to get supportive quantitative data. The respondents were selected using purposive sampling technique. A content analysis was conducted and quantitative data was analyzed with the aid of XLSTAT 2007 software and Excel. A cross-section of the age and gender population was involved in the marketing of food legumes. Women constituted more than 80% in the retail sector on peri-urban markets. The study found that 100% of the vendors had never got any form of training on business management before engaging into the sector. Socio-cultural factors were determinant factors that impacted negatively in promoting an entrepreneurial culture among women. The marginalization of women, the restriction of land ownership by traditional tenure and poor distribution of land for agriculture were some of the main constraints faced by women. The impediments of women’s empowerment include their lack of access to the decision-making process, low participation in local governance and limited access to technology inputs and credit. Traditional practices forbid women and girls to have or manage large amounts of money. Such restrictions have serious consequences on agricultural production. Instead of exploiting the productive capacity of women at all levels, including food production and transformation, some of the traditions simply stifle their potential energies. In addition to socio-cultural factors, major bottlenecks faced in the production and commercialisation of food legumes includes social structural and institutional, agronomic, natural(biotic and abiotic stress)and climatic factors. Development of intervention strategies through exogenous innovation techniques might act as an incentive for smallholder farmers to invest more of their land and energy in cultivation of food legumes. More attention should be focused on market research and development with crop improvement programmes that are economically profitable, if food legumes are to continue making a greater contribution to the household income, nutrition and sustainable development in North Cameroon.

Mechanisms of sedimentation in lacustrine environment of Babouri-Figuil and Mayo Oulo-Lere basins deposits (North Cameroon) during the Southern Atlantic opening: sedimentary structures and geochemistry constraints

Sedimentary structures are very useful to characterize sedimentation environments. In this study, sedimentary structures are documented in the Lower Cretaceous Babouri-Figuil and Mayo Oulo-Lere intracontinental Basins whose genesis is linked to the opening of the Southern Atlantic Ocean. Geochemical data is also presented with the aim to discriminate the paleoenvironment. Field investigations and facies analyses revealed synsedimentary and postsedimentary structures related or not to tectonic. Synsedimentary structures not affected by tectonic are lamination or bedding (rhythmic), graded bedding, cross-stratification, loads casts, channels, and ripple marks. Those affected by tectonic are convolute bedding, slump (Slump sensus stricto and olistolith). Desiccation cracks and print marks are postsedimentary structures not related to tectonic; others are stratigraphic unconformity, oblique bedding, clastic injection, and volcanic veins. The bottom of the sequence in the two basins is fluvio-lacustrine deposits with oblique stratification and global positive graded bedding; sometimes there is alternation of positive and negative graded beddings related to progressive variation of energy of sedimentation from high to low and low to high. The intermediate level is lacustrine dominated by lamination or bedding that characterizes a calm sedimentation environment marked by regular seasonal fluctuation. The ripple marks, desiccation cracks, and dinosaur footprints indicate the emersion period, and their fossilization indicates slow phases of sedimentation. Channels and load casts correspond to a rapid sedimentation phase. Seismic shocks at time break the fragile stability of deposited materials causing gravitational flows of the sublacustrine avalanche type and give olistolith and convolute bedding to slumps. The clastic or chemical injections and volcanic veins are related to brittle tectonic that affects consolidated deposits. From the geochemical data, the high accumulation of LREE (average: 142.93 ppm) over HREE (average: 13.10 ppm); La/La* generally 2) and the slight to very slight negative Ce/Ce* (0.87–0.99) suggest the nonmarine deposition, and the Y/Ho ratios (< 45) and ratios indicate river condition or transportation. The Sr/Ba ratios, ranging from 0.55 to 6.41, suggest a freshwater environment with fluctuant salinity and sometimes hypersaline (Hypersaline Lake). Thus the synsedimentary structures were essentially formed in lacustrine milieu, and some structures such as graded bedding and cross-stratification affecting the basal deposit indicate a fluviatile to fluvio-lacustrine environment.

Accès aux financements externes et pérennité de la très petite entreprise: quelle évidence en temps de crise sécuritaire?

The Far North of Cameroon has been weakened since 2014 by recurring attacks and suicide bombings orchestrated by the Islamic sect ‘Boko-Haram’. This article aims to analyse the moderating effect of this security crisis on the relationship between access to external financing by VSBs in their start-up phase and their sustainability. The data needed to conduct the study were collected, with a questionnaire, from 229 promoters of VSBs created between 2014 and 2018 and still operating in the Far North region of Cameroon. These data were then analysed using the logistic regression model. The results demonstrate a positive effect of access to external financing during the start-up phase of the VSB on its sustainability. However, it appears that the frequency of Boko-Haram attacks and the restrictive measures adopted by the government (border closures and curfews) are not conducive to the external financing of the VSB, let alone its sustainability. This result shows that the intensification of the security crisis experienced by all micro-entrepreneurs, combined with the challenges specific to their activity, has thus undermined the confidence they place in the future prospects of their business.