Benue Trough Research Articles

The BIOSTRATIGRAPHY AND PALEOENVIRONMENTAL ANALYSIS OF THE YOLDE FORMATION, NORTHERN BENUE TROUGH, NIGERIA

This research is an attempt to investigate the micropaleontology of the Yolde Formation with the view to determine the age and paleoenvironments of the formation. The Yolde Formation, a key stratigraphic unit within the Benue Trough, provides insights into the Cretaceous paleoenvironments of the region. A total of ten samples were examined using a light microscope. Samples two and six exhibited the greatest taxonomic diversity, each containing 13 different taxa, while the other samples showed a range of 1 to 11 taxa. The benthic taxa Marssonella, Ammobaculites agulutinans, and Plectina were found to be prevalent throughout the composite section. Certain taxa, such as Marssonella Verneuilinoides Sp., Gyroidinoides sp., and Textularia subhauriiw, each constituted approximately 30% of the benthic assemblage. Common benthic indicators identified in the Yolde Formation include Marssonella, Verneuilinoides Sp., Ammobaculites agulutinans, Plectina cenomana Sp., Tritaxia tricarinata, Gyroidinoides Sp., Heterohelix Sp. etc. The presence of Bulbobaculite Sp. and Gavelinella Sp. in the Yolde Formation indicates that this formation dates to the Cenomanian age. This dating is supported by the identification of other foraminifera such as Marssonella, Verneuilinoides sp., Ammobaculites agulutinans, Plectina cenomana sp., Tritaxia tricarinata, Gyroidinoides sp., Heterohelix sp., etc. These benthic foraminifera are linked to low-oxygen paleoenvironments that reached the seabed. The presence of Ammobaculites Spp., Tritaxia tricarinata, and Gyroidinoides Sp. suggests anoxic conditions. Consequently, the paleoenvironments represented by the benthic foraminifera and the lithofacies reflects a paleoenvironments ranging from inner neritic to middle neritic zones within lower shoreface to upper shoreface.

Structural and Geochemical Characterization of Baryte Mineralization in Liji Area, Northern Benue Trough, Northeastern, Nigeria

Structural and Geochemical Characterization of Baryte Mineralization in Liji Area, Northern Benue Trough, Northeastern, Nigeria

An integration of hydrochemical data and stable isotopes in groundwater evaluation in Ngboejogu, Southern Benue Trough, Nigeria

An integration of hydrochemical data and stable isotopes in groundwater evaluation in Ngboejogu, Southern Benue Trough, Nigeria

Tectonic reevaluation of West Cameroon domain: Insights from high-resolution gravity models and advanced edge detection methods

The West Cameroon region, characterized by a diverse geomorphology of highlands and plains resulting from tectonic processes across different geological ages, has been extensively explored for natural resources. Recognizing the significance of its tectonic and magmatic features associated with seismic and volcanic activity, this study focuses on geodynamic investigations of the Cameroon Volcanic Line (CVL). Despite previous efforts, detailed structural geophysical studies of the West Cameroon domain have proven inconclusive, prompting a comprehensive structural reinterpretation. Utilizing the high-resolution SGG-UGM-2 satellite gravity model and innovative processing techniques, including the horizontal gradient of a modified tilt (HGSTDR), the balanced horizontal gradient (BHG), the tilt of the horizontal gradient (TAHG), the improvised horizontal gradient tilt angle (impTAHG), and the Tilt Depth method, our research aims to enhance the interpretational quality of tectonic lineaments. By separating regional and residual anomalies in the Bouguer gravity map and applying a combination of filters to delineate geological units, the BHG filter emerges as a robust tool that highlights subsurface edges without generating false features. This approach unveils previously undetected NNW-SSE-oriented lineaments, confirming the presence of deep fractures and faults in Bafoussam, Nkongsamba, and along the Benue Trough, corroborated by newly discovered NNW-SSW trending lineaments. The study suggests that the region’s topography is overcompensated by deep mountain roots and compressive tectonism. Digitizing the BHG filter produces a structural map, revealing predominant NE trends in identified geological margins, including NNE-SSW, N-S, NW-SE, E-W, and NE-SW directions. Geological contacts between granite and high-grade gneiss are indicated by NNW-SSE and NNE-SSW trending lineaments along the Benue Trough. These results contribute significantly to the understanding of the tectonic setting of the West Cameroon Domain.

Coal chemistry, utilization potential, and coalbed methane (CBM) assessment of some coal deposits in Central Benue Trough, north-central Nigeria

Coalbed methane (CBM), a current global legislative priority for climate change mitigation, is an unconventional and eco-friendly clean source of energy that is considered a veritable alternative to conventional fossil fuels. Despite its overwhelming advantages, CBM evaluation studies of Nigerian coals have received little or no attention. To bridge the gap in knowledge, we have for the first time in Jangwa-Shankodi and Lafia-Obi, described the potential of harnessing CBM for its gainful utilization in Nigeria using some coal deposits in its north-central region as a case study. The gas contents of the coals were determined empirically by taking account of their ultimate and proximate properties. Other coal parameters such as fuel ratio and vitrinite reflectance (Ro (%)) have also been computed and discussed. Proximate analyses of the studied coal samples show moisture contents that vary between 2.28 and 2.56%, whereas, volatile matter yield is placed in the range of 29.98–30.34%. Ash yield ranges from 7.83 to 8.64%. Fixed carbon content varies from 55.97 to 56.30%. Variation in fuel ratio shows a restricted range from 1.72 to 1.87. All the coal samples were found to be low in sulphur (< 1%) with H/C ratios that vary from 0.072 (LAF 2, 3 and 4) to 0.086 (JSK 3). Moreover, the coals were found to be of medium-volatile bituminous rank, with gas contents that range from 12.65 to 13.20 cc/g. In the current study, kerogen lies in the Type IV zone, which suggests the generation of methane gas by the studied coal samples. Also the estimated range of vitrinite reflectance (Ro) which varies between 1.073% and 1.086% indicates thermogenic gas expulsion in the coals. There is a noticeable increase in gas content with coal maturity and depth. These values are indicative of good quality coals that show antecedents for CBM production. However, considering that this work is a pilot study, we recommend that core drilling be employed in obtaining insitu measurements of the coal gas contents and thus, verify these empirical estimates. Also, detailed laboratory study on pore structure (and its distribution) and adsorption isotherm curve are recommended to better understand the coal reservoir properties and hence, consolidate the present study.

Diagenesis and reservoir quality evolution of estuarine sandstones: Insights from the Cenomanian-Turonian Yolde Formation, northern Benue Trough, NE Nigeria

Estuarine sandstones often exhibit complex diagenetic pathways due to the interaction of fluvial and shallow marine processes, resulting in significant reservoir heterogeneities. The Yolde Formation is an important petroleum reservoir in the Northern Benue Trough, NE Nigeria. However, diagenetic and reservoir quality evolution of the formation are still poorly understood. This study utilizes thin-section petrography, XRD, SEM, and fluid inclusion microthermometry to analyse the composition, diagenesis, and reservoir quality of the sandstones. Results show that the sandstones are mainly arkose and subarkose in composition; they are generally well-sorted and vary in grain size from very fine-to coarse-grained. Three diagenetic stages are identified: early, middle, and late. The early stage includes feldspar dissolution, formation of kaolinite, development of clay coating, and mechanical compaction. The middle stage comprises the formation of authigenic chlorite and Fe-oxide cements. The late-stage diagenesis involves illitization of kaolinite, formation of dickite, albitization of K-feldspar, and precipitation of quartz overgrowths. The diagenetic evolution of the sandstones was strongly controlled by their compositional makeup. The feldspathic nature of the sandstones resulted in the formation of kaolinite, illite, and quartz overgrowths, through feldspar dissolution and silica supply. The inner and middle estuarine facies have inhibited the development of quartz overgrowths due to well-developed clay coatings, whereas the outer estuarine facies were well-cemented by quartz overgrowths due to lack of clay coatings. Illitic clay coatings were found to be effective in preventing quartz cementation. Fluid inclusion analysis reveals that the formation temperatures of the quartz overgrowths range from 98 °C to 135.5 °C, corresponding to burial depths ranging between 2.3 and 3.5 km. These findings would provide useful insights that would reduce the risks of exploration of the sandstones and also supplies potential input data for forward diagenetic modelling of their subsurface equivalents in similar depositional settings elsewhere.

Paleoenvironmental factors controlling organic-rich formations deposition in the Babouri-Figuil Basin (Northern Cameroon)

The Babouri-Figuil Basin is an intracratonic basin (half-graben) in northern Cameroon that is genetically connected to the Benue Trough from Nigeria, and is an area of interest in terms of petroleum prospectivity. Recent studies highlighted the presence of organic-rich formations in the basin. However, none of these works have identified factors that governed the accumulation of organic matter (OM) in the sediments. The main objective of this work is the characterization of these formations through palynofacies and organic geochemical techniques (total organic carbon - TOC, total sulfur, insoluble residue and biomarkers), in order to determine the organic facies, their depositional environments and the main drivers for organic enrichment in the basin. The current study reveals that black shale and massive claystone lithologies constitute the main organic-rich formations in the basin, with TOC reaching up to 26.08 wt%, being characterized by a dominance of bacterially-derived amorphous OM. Palynofacies and biomarker data revealed that these formations are positively associated with anoxic conditions and a partly highly saline and stratified lake water column. The deposition of organic-rich formations in the Babouri-Figuil Basin was mainly controlled by restriction conditions which developed in connection with the regional tectonic framework. The Lower Cretaceous rifting episode in the West and Central African Rift System (WCARS) basins led to the formation of accommodation space, a reduction in water levels, and the development of anoxic conditions within the basin, facilitating the deposition of organic-rich formations. Therefore, the organic enrichment of the Babouri-Figuil Basin has been predominantly controlled by its tectonic evolution, particularly during the syn-rift phase. This phase created favorable conditions for the deposition and preservation of OM, including the establishment of anoxic conditions. Additionally, the paleoclimate (arid conditions), the development of bacterial biomass, and the basin's paleogeography all played a significant role in this process. The organic-rich formations of the Babouri-Figuil Basin show characteristics of prospective petroleum source rocks (high organic content, high proportion of oil-prone kerogen, significant thickness and lateral extension). The combination of organic-rich formations with sandstone deposits above and extensive claystone/shale deposits on top can indicate the presence of an oil play in the basin. A detailed study with broader sampling is needed to investigate thoroughly the variation of organic facies and the influence of paleoenvironmental factors that control the deposition of thick source rock intervals.

Facies distribution, paleoenvironment and hydrocarbon potential of Kanawa Member of Pindiga Formation, Gongola Basin, Northern Benue Trough, Nigeria

The Gongola sub-basin is a frontier inland sedimentary basin consisting of Cretaceous to Tertiary sediments, believed to have been deposited in continental to coastal shallow marine complex. The Kanawa Member of Pindiga Formation is a sequence of limestone and shale. Sedimentology, facies analysis, biostratigraphy, thermal maturity assessment and kerogen typing were conducted on these strata to determine the facies, facies associations, facies successions, paleoenvironment, age, and hydrocarbon generation potential. The studied sequences are of Turonian–Santonian age, deposited due to a major transgression of the basal part of the Pindiga Formation. The shale-limestone series of the Kanawa Member is interpreted as lagoon-to-shallow marine deposits of a carbonate ramp depositional system. The sediments consist of mainly wackestone and packstone facies and shallow marine foraminiferal, suggesting that the Kanawa Member was deposited under low-energy condition. The presence of Ammobaculites subcretacea, Haplophragmoides bauchensis, Haplophragmoides pindigensis, Haplophragmoides excavata, Ammobaulites pindigensis, Ammobaculites bauchensis, Ammobaculites gombensis, Ammobaculites benuensis Ammoastuta nigeriana, Reophax guineana and Miliammina pindigensis foraminiferal assemblages, indicating Late Cretaceous age. Hydrocarbon potential is interpreted to be gas prone although, minor oil could be expected. These correspond to temperature range (TAI values) of 60 to 75 indicating thermally matured for both oil and gas generation.

Insights into Afikpo Synclinorium structures: Subsurface analysis and intrusion outlining from airborne magnetic data

The airborne magnetic data over Afikpo Synclinorium were used to highlight subsurface structures and establish the orientations of tectonic features and their influence on the hydrocarbon play of the area. The characteristic trends of the lineaments were achieved through the center for exploration targeting of grid data analysis. The results of the TMI, residual magnetic field, first vertical, horizontal derivative, Analytic signal, and Tilt angle derivative classified the area into regions of high magnetic intensity observed around the northeastern, southwestern, and central portions of the study area. These areas characterized by anomalous signatures of short magnetic wavelengths delineate shallow magnetic sources. Conversely, regions with medium to low magnetic intensities are characterized by long magnetic wavelengths which indicates deep-seated magnetic source(s) and prospect for hydrocarbon (if other play concepts are emplace); due the thick sediment cover at the southern portion of the area (around, southern part of Nguzu, Ohafia, Biakpan, Abriba and Bende areas). The sediment thickness decreases towards north, west, North-east and north-west (dominated by Benue Trough deposit). Depth to the anomaly sources is of two categories, namely, shallow <1.0 km (dominated by NE trending structures) and deep ≥2.5 km. Ground-truthing confirmed the anomalous zone of high magnetic sources in the northeastern and central regions as Tertiary related tectonic-magmatic intrusion. The most prominent intrusion cuts across Amangwu Edda in Afikpo South through Amaeta-Oziza to Cross River State in a fissure form. This intrusion occurrence conformed to the high magnetic signature identified as a dolerite sill within the Afikpo Sub-basin. It stretches over 16 km in length with an average width of about 1.2 km, having its widest part in the northern parts of Mata Hospital Afikpo. The subsurface topographic model indicated that no fewer than 50% of the study area is characterized by sporadically distributed intrusive rocks. The result revealed several structural lineaments with high lineament density at the northcentral corner of the area trending NE-SW with fault lines (slip fault) perpendicular to it, offsetting the Akpoha, Ibii, Amasiri. and Ozara-ukwu ridges. The major drainage systems across the area followed major structural trends perpendicular to the identified major lineaments, passing through the major regional structural displacement pattern of the Basin. The emplacement of these intrusions might have impacted the hydrocarbon potential of the basin.

Bioavailability and environmental implications of major and trace metals in manihot esculenta (cassava) grown on shaly and calcareous soils in parts of southern benue trough, nigeria.

bioavailability and environmental implications of major and trace metals in manihot esculenta (cassava) grown on shaly and calcareous soils in parts of southern benue trough, nigeria.

Radiotoxicity and groundwater quality for drinking in a multi-layered saline sedimentary terrain of Keana, Central Benue trough, Nigeria

Radiotoxicity and groundwater quality for drinking in a multi-layered saline sedimentary terrain of Keana, Central Benue trough, Nigeria

Palynostratigraphy and Paleoenvironment of Afikpo Well_3, Afikpo Syncline, Nigeria

The Afikpo Syncline constitutes the western segment of the southern part of the Benue Trough. The syncline orients in the northeast-southwest direction and unconformably overlies the pre-Santonian strata of the Benue Trough. This study investigates the sediments of Afikpo Well_3, drilled within the syncline, identifies its different palynozones, and interprets their paleoenvironments of deposition. Forty-two ditch-cutting samples recovered from the well at a 150 ft interval consist of mudstones, calcareous mudstones, carbonaceous shales, and calcareous shales. These samples were subjected to palynological analysis following the conventional acid maceration technique. A total of 637 palynomorph counts were recovered. These comprise 316 pollen grains, which make up 49.61%; 129 spores, which make up 20.25%; 9 fungi spores, which make up 1.41%; 17 microforaminifera wall linings, which make up 2.67%; and 166 dinoflagellate cysts, which make up 26.06%. Two palynozones were identified within the well. These include zone AF-01 (Monocolpites marginatus assemblage zone), which ranges from depths of 1500–1320 ft and is Campanian in age; and zone AF-2 (Dinogymnium sp. assemblage zone), which extends from depths of 50 ft–1320 ft and dates back to the Maastrichtian period. Based on the predominance of palmae pollen, together with the subordinate occurrence of dinoflagellate cysts, and the fair representations of spores (Cyathidite minor), the environment of deposition of the sediments ranges from a nearshore brackish water to a shallow marine environment. The shallow environment is further confirmed by the frequent occurrence of microforaminifera wall lining and the dominance of the peridinoid dinoflagellate cysts over the gonyaulacinoids.

Implications to basin evolution from the interpretation of superficial and buried geological features from remote sensing and magnetic data sets, Lower and Middle Benue Trough, Nigeria

The Lower and Middle Benue Trough is an intra-continental rifted basin with most rocks concealed by thick sediments and vegetation. Geological field mapping is very difficult resulting in high uncertainties. Remote sensing and geophysical techniques can assist in refining lithological boundaries and detecting buried geological features such as intrusive bodies, which can be very useful in interpreting the structural history of a basin. The main aim of our study is to re-process and interpret aeromagnetic and multispectral satellite datasets to understand the evolution of the Benue Trough. We used high-resolution aeromagnetic data and, Landsat 8 and ASTER data sets to interpret surface and near-surface lithologies, particularly igneous bodies, within the Benue Trough, Nigeria, with the aim of better constraining the basin evolution in time and space. A matched bandpass filter was applied to the aeromagnetic data to separate shallow/near-surface (residual) anomalies from deep (regional) anomalies. The result of the residual anomaly was further filtered by derivative-based filters to delineate surface/near-surface igneous bodies. The satellite remote sensing datasets were processed and enhanced, and diagnostic mineral spectral signatures related to geology were interpreted. A spectral angle mapping (SAM) supervised classification was used to map various lithologies and their boundaries. The delineated igneous bodies (volcanic rocks, plugs, dykes, bosses, and sills) are concentrated along the SE margin of the Trough where they intruded along a major NE-SW trend; but changes in the intrusion style are interpreted to relate to specific stages in the basin history. We suggest that the initial magma emplacement was controlled by structures mostly along the SE margin of an asymmetric basin, but the rifting locus later migrated towards the centre of the present basin.

GIS-based multi-criteria decision models for barite exploration in Nigeria’s Benue Trough

Spatial predictive mapping using geographic information system (GIS) is considered an invaluable tool for reconnaissance-scale exploration of mineral resources. In this study, geospatial data on geophysics, remote sensing, and structural and lithological attributes were systematically integrated to prospect barite potential zones within the Mid-Nigerian Benue Trough (MBT). Correlation attribute evaluation was used to establish the relationship between mineral deposit occurrences and geospatial data, while data integration was implemented using the Multi-Objective Optimization by Ratio Analysis (MOORA), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), and Additive Ratio Assessment (ARAS) multi-criteria models. Here we show that the correlation attribute evaluation suggests that barite occurrences displayed a strong correlation with spatial data on lineament density, ferric iron alteration, and potassium to thorium (K/Th) ratio, whereas a weak correlation was observed with spatial data on the first vertical derivative (FVD), proximity to the host rock, and ferrous iron alteration. Here we report that the quantitative estimation of predictive models indicated that very high predictive zones for barite occurrences accounted for 19% of all the models. The accuracy assessment using Receiver Operating Characteristic (ROC)/Area Under the Curve (AUC) showed prediction levels above 78% for all models. The effectiveness of the spatial application of multi-criteria decision models makes them a reliable tool for barite exploration within the Mid-Nigerian Benue Trough (MBT) and other geologically similar environments.

Lithological and Structural Characterization of parts of the Lower Benue Trough, Southeast Nigeria, Using Radiometric and Aeromagnetic Data

Lithological and Structural Characterization of parts of the Lower Benue Trough, Southeast Nigeria, Using Radiometric and Aeromagnetic Data

Provenance and paleoenvironmental studies of Bima and Dukul Formations in the Yola Basin, Northern Benue Trough, Nigeria.

Sedimentological studies of some areas located within latitudes 11035’E &amp; 12000’E, and longitudes 9014’N &amp; 9025’N were undertaken to delineate the surface lithologies of the Yola sub-basin, in the Northern Benue Trough. Field observations of the surficial deposits at Mayolope, Taana, Kpasam and Bille revealed that they are Bima Formation while the ones in Abare are Dukul Formation. Paleoenvironmental studies based on the characteristics of lithofacies of these exposed sections and laboratory assessments of some selected samples showed that the Bima Formation was deposited in a continental setting while the Dukul Formation was deposited in a low-energy marine setting. Petrographic studies of framework components showed that the samples of the Bima Formation were predominated by quartz minerals, leading to their identifications as sandstones and classifications as quartzarenites while the samples of the Dukul Formation were limestones and were classified as bioclastic packstones. Heavy mineral compositions of the sandstones revealed their provenance; Zircon and Tourmaline with a combined amount of 60.1% suggested igneous and low-grade metamorphic rocks while rutile and staurolite with a total amount of 27.7% indicated contributions from high-grade metamorphic rocks.

Assessing gully erosion susceptibility dynamics using information value and hazard index methods: A case study of Agulu-Nanka watershed, Southeast Nigeria

Gully erosion is one of the major causes of land degradation leading to the loss of productive lands globally. The Benue Trough in Nigeria is plagued with the problem of gully erosion, with a myriad of natural and anthropogenic factors considered as contributory factors. In this study, quantitative and qualitative methods were combined to evaluate gully susceptibility in the Agulu-Nanka watershed located in the lower part of Benue Trough between 2000 and 2018. Landsat 7 and 8 images, Digital Elevation Model (DEM), geological, soil, and rainfall erosivity maps were used to generate the gully erosion controlling factors including vegetation cover, lithology, soil, land use/cover, slope, curvature, aspect and rainfall erosivity. Additionally, high resolution image was used to develop gully inventory map. The information value method was used evaluate the influence of various classes of gully erosion controlling factors on gully distribution in the watershed. This enabled objective derivation of weights for the various classes of these factors. Information value analysis reveal that low percentage vegetation cover (<10 %), Ameki Group lithological unit, high slope gradient (17 − 43°) and Dystric Fluvisols soil type have the highest influence on gully erosion in the watershed. Since the information value method does not consider interrelationship between factors, the rank sum technique was used to derive factor weights based on the relationship between the factors. To develop the gully susceptibility map for the Agulu-Nanka watershed for the years 2000 and 2018, the erosion controlling factors were integrated using factor class weights derived through information value and factor weights derived through rank sum method. The analysis of gully erosion hazard maps show that approximately 48 % of the watershed was under low erosion risk over the period of 18 years. Areas under moderate, high and severe erosion risk decreased from 27.45 %, 9.45 % and 0.27 % of the watershed in year 2000, to 21.30 %, 8.41 %, and 0.20 % of the watershed respectively in 2018. On the other hand, the areas under negligible erosion risk increased from 14.69 % in year 2000, to 21.26 % of the watershed in 2018. The validation of the gully erosion susceptibility map for years 2000 and 2018 using the Receiver Operating Curve (ROC) showed ROC-AUC values of 0.81 % and 0.88 % respectively suggesting good model results. While the result of study indicates that restoration efforts through afforestation is yielding some result, the minimal reduction in the size of areas under severe and high gully erosion susceptibilities indicate that additional mitigation measures need to be combined with intensified afforestation efforts to effectively combat gully erosion in the watershed.

Groundwater Exploration Within Shallow Depths Around Distinct Litho-Petrological Contact Zones

The world’s increasing demand for freshwater has put a strain on existing reserves in recent years, necessitating further exploration of new groundwater reserves. However, geologic provinces located within the contact boundary of Sedimentary Basin-Basement Complex region are somewhat faced with the problem of shallow sediment thickness. As a result, exploring for groundwater poses a challenge as the sediment thickness might be insufficient to host productive aquifers. Hence, exploring for faults and fractures zones that are embedded on the hard rock underneath the sediment is very essential and complimentary. In this study, high resolution aeromagnetic data over a litho-petrological contact zone of the Middle Benue Trough (MBT) and the Adamawa Massif were analyzed to delineate groundwater exploration areas using a simplified qualitative and quantitative approach. Visual inspection of isolated and aggregate anomalies is performed by analyzing their shapes, dimensions, lateral extents, and discontinuities. Lineaments were then extracted from the residual magnetic map to determine faults, fractures, and joints. A two-source-depth model is indicated by the Spectral Analysis technique used to determine the thickness of the sediments in the area. The deeper source (Z1) has a thickness of 0.9 - 3.6 km, while the shallow source (Z2) has a thickness of 0.1 - 0.8 km. While in some areas the overburden thickness may be sufficient for groundwater exploration, in others it was not, as indicated by the shallow magnetic depth, Z2. Nonetheless, areas of shallow thickness but with aggregates of faults, fractures, and joints were identified as possible locations for groundwater accumulation through magnetic lineament exploration.

Lithological discrimination and mapping in part of the upper Benue Trough using Landsat 8

This study focused on evaluating the efficiency and complementarity of image enhancement techniques for lithological discrimination and mapping in the upper parts of Benue Trough using Landsat 8 data. To achieve this, image enhancement techniques such optimum index factor, band ratio, principal component analysis, and minimum noise fraction were applied on Landsat 8 OLI data covering parts of the Upper Benue Trough. False colour composites (FCC) were created from three most informative derivatives of these image enhancements. The FCCs were compared in terms of their capability to differentiate different lithological units in the study area by comparing the FCCs with existing geological map. The results show that the FCC created from band ratios provided the highest amount of information, while those created based on optimum index factor provided the least amount of information with respect to lithological discrimination. Additionally, it was observed that the FCCs created from the derivatives of band ratio, principal component analysis and minimum noise fraction provide complementarity. Thus, the three FCCs from these three enhancement methods were fused into a single image, which further aided lithological discrimination. By combining the outputs from three image enhancement techniques, most of the sedimentary and crystalline rocks in the study area were successfully delineated. The method adopted in this study particularly the fusion of outputs from band ratio, principal component analysis and minimum noise fraction represents a novel approach that is suitable for lithological mapping in remote areas, particularly arid and semi-arid terrains with considerable rock exposure.

Microfacies and mineralogical analyses of the late cretaceous carbonate rocks from The Central Benue Trough, Nigeria

The Cretaceous limestone facies from Yandev section in the central Benue Trough, Nigeria constitutes parts of the potential reservoirs and sources rocks for petroleum prospects in the basin. The central Benue Trough is the least studied basin among its contemporaries due to lack of subsurface data. Detailed mineralogical, facies analysis and diagenesis of these carbonate rocks in the basin have not received significant study. The aim of this study was to employed multifaceted methodology such as sedimentological, facies analysis petrographic and geochemical approaches which was lacking in previous research in the trough. The sedimentological analysis was done to evaluate fabrics grain sizes, and lithology types. For petrographic analysis, thin sections were prepared and examined under a petrographic microscope and categorized according to Dunham's classification. Geochemical analysis involved X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscope - energy dispersive X-ray spectroscopy (SEM-EDX) techniques to unveil mineralogical, oxide, and elemental compositions. The sedimentological results revealed light to dark grey medium to fine-grained limestone facies with intercalation of dark grey shales and siltstones. The XRD mineralogy data, revealed calcite (60.00 - 64.10%), quartz (14.30 - 51.00%), albite (12.30 - 19.00%), and chlorite (6.30 - 8.10%). Microfacies results revealed distinct sandy bioclastic wackstone and sparitic intraclastic packstone, as well as micritic intraclastic wackestone and sparitic bioclastic packstone. SEM images highlighted the intricate composition, including elongated structures, whites and dark spots suggesting varying conditions of deposition. Elemental analysis through EDX emphasized significant proportions of carbon, oxygen, sodium, potassium, calcium, silicon, aluminum, iron, and magnesium. Based on sedimentological, biofacies, lithofacies and geochemical evidence we infer that the carbonate sediments were mainly deposited in a shallow marine depositional environment (inner to outer neritic).