Asu River Research Articles

Geophysical, hydrogeological and laboratory assessment of groundwater quality and its health implication in some urban communities in cross river state

The electrical resistivity technique which involved the Schlumberger depth sounding method, electrical resistivity tomography and geochemical analyses of water samples collected from boreholes were used to investigate the quality of groundwater in some urban communities in Cross River State, also the health implication of the said groundwater was also investigated. Forty nine electrical resistivity data were collected, modeled, and interpreted after calibration with lithologic logs. Ten electrical resistivity tomography data was were also collected, modeled and interpreted. Forty nine borehole water samples were collected and analyzed to determine anion, cation concentrations and some physical and chemical parameters, such as water colour, temperature, total dissolved solids, and electrical conductivity. The results show that the lithostratigraphy of the study area is composed of sands, sandstones (fractured, consolidated and loosed), siltstones, shales (compacted and fractured) of the Asu River Group, Eze-Aku Formation which comprises the aquifer units, and the Nkporo Shale Formation. The aquifer conduits are known to be rich in silicate minerals, and the groundwater samples in some locations show a significant amount of Ca2+, Mg2+, and Na+. These cations balanced the consumption of H+ during the hydrolytic alteration of silicate minerals. The geochemical analysis of groundwater samples revealed dominant calcium–magnesium–carbonate– bicarbonate water faces. The groundwater quality was observed to be influenced by the interaction of some geologic processes but was classified to be good to excellent, indicating its suitability for domestic and irrigation purposes.

Analysis of Joints Patterns in Albian to Santonian Strata on the Eastern Flank of the Abakaliki Anticlinorium: Implications on Paleostress Conditions and Fluid Flow Properties in an Unconventional Petroleum System

An analysis of joint patterns were carried out on multiple exposures in Albian to Turonian strata belonging to the Abakaliki Formation (Asu River Group) and the Eze-Aku Formation (Eze-Aku Group) on the eastern flank of the Abakaliki Anticlinorium of the Southern Benue Trough. The analysis was carried out using FracPaQ a MATLAB based toolbox for quantification of fracture patterns. The tool was used to calculate fracture density, and intensity of the traces; to quantify scaling distributions, and to determine dilation tendencies, slip tendencies, and to quantify connectivity, and fluid flow directions. Analysis show the presence of two major joint systems: A Major Cross-Fold Joint (CF-J) system -orthogonal to the regional fold axes- consisting of the CF-J1 set trending NW/SE (315±5°), and a subordinate Longitudinal Joint System (L-J) -subparallel to the fold axes- consisting of a NE-SW L-j1 set, an ENE-WSW (60°±5°) L-j2 set, and an E-W trending L-j3 set. Fracture patterns show intensity and density ranging from 11.2395- 53.3443 m-1 and 85.2747- 629.5928 m-2 respectively. Joints in the NE-SW show high dilation and low slip tendencies given a NW-SE directed maximum principal horizontal stress σH stress field. The units of the Abakaliki Formation show better connectivity and lower permeability anisotropy as both fracture systems are well developed in those units. These joints, having formed in the period leading up to the Santonian inversion would have been ideal conduits for migration and flow of hydrocarbon and mineral fluids. The Cross-Fold System precedes the folding episode in the Santonian period and is likely a result of overpressure conditions due to disequilibrium compaction in the Albian- Turonian strata in an initial compressive regional tectonic stress field. The Longitudinal System formed later and is related to the outer-arc flexure of the folded units taking advantage of the nascent cleavage structures in the folded shale units.

Ecological Impact and Human Health Risk Assessment of Pumpkin and Spinach Cultivated Around Non-Mining Axes of Ebonyi State

The study evaluated human health risks associated with the consumption of pumpkin and spinach cultivated around non-mining areas of the Asu River Group. Eighteen samples were collected and analyzed for As, Pb, and Cd, obtaining fifty-four results. The samples were washed with deionized water, air-dried and oven dries at 105°C for 48 hours, and analyzed using Varian (USA) Atomic Absorption Spectrophotometer. The concentration of Pb, As, and Cd in the vegetable trend follows; Ebonyi south (ES)<Ebonyi central (EC)<Ebonyi north (EN); EN<ES<EC and ES<EC<EN respectively. The Cd, As, and Pb contents were below WHO/FAO, (2007) and EU, (2006) specific limits. The daily intake of metals (DIM), health risk index (HRI), and targeted health quotient (THQ) were computed. The DIM of Pb, As, and Cd was below their respective oral reference dose (RfD) of 0.004, 0.003, and 0.001mg/kg/day. Pb, As, and Cd HRI values for adults, teenagers, and children are in the following order Adult<Teenagers<Children for all samples across the study area. The Pb abundance follows ES<EN<EC in both pumpkin and spinach, and Cd follows EN<EC<EN and EN<ES<EC for pumpkin and spinach respectively. Arsenic HRI in order of EN<EC<EN and EN< ES<EC for pumpkin and spinach respectively. On average, the HRI of Pb, As, and Cd ranges from 0.00312 to 0.0663, 0.00411 to 0.238, and 0.009 to 0.331 mg/kg/bw/day for the vegetables. The HRI and THQ for adults and teenagers were all <1 for As, and Pb while Cd THQ>1 in pumpkin from ES.

Hydrochemical Evaluation of Groundwater Resources in Ngbo Areas, Ebonyi State, Southeast Nigeria.

The hydrochemical evaluation of groundwater resources of Ngbo Area have been carried out covering parts of Ohaukwu and Ebonyi LGAs of Ebonyi State. The area lies between latitudes 6025’N and 6030’N, and longitudes 8000’E and 8005’E. Geologically, the area is underlain by highly consolidated dark-grey and fissile- brown shales, limestone and mudstones belonging to the Albian Asu River Group. Ten (10) groundwater samples were collected for analysis using Standard sampling procedures. The result which was compared with the World Health Organization and Nigerian Standard shows that the mean concentration of the physical parameters such as pH (6.92), total dissolved solid (15.56), electrical conductivity (15.56), and total hardness (1.0mg/l) of the groundwater of the area are fresh (due to TDS < 1000 mg/l at temperature range of 270C to 300C), dominantly alkaline, moderately hard in some locations such as locations 7 (Umuezaka Ngbo), 9 (Hill Top Pri. Sch., Amoffia Ngbo) and 10 (Ndiulo Umusoke Amoffia Ngbo), possibly due to bicarbonate (HCO3–) concentrations of 340mg/l, 279mg/l, and 335mg/l, and were within the permissible limits for drinking, domestic, industrial and agricultural purposes. High concentration of chloride ions in some of the samples was indicated. This could be attributed to the presence of igneous rocks and the leaching of sewage effluents down to the groundwater system. The dominant order of cations and anions chemistry for most of the analyzed groundwater samples is Ca2+>Mg2+>Na+>K+ and Cl–>HCO3– >SO42-> and NO3– respectively. This is a reflection of high carbonates in the rocks. Proper sewage disposal should be upheld in the area.

Potential petroleum prospects in the middle Benue trough, central Nigeria: Inferences from integrated applications of geological, geophysical and geochemical studies

The Middle Benue Trough (MBT) is the least well-known of the three major sub-divisions of the Benue Trough (BT) and therefore poorly understood geologically. This paper presents preliminary results of an integrated geological, aeromagnetic, gravity and geochemical studies carried out as a first step approach to petroleum exploration in the central portion (MBT) of the Benue Trough, Nigeria, so as to be able to; 1. Appraise the regional geologic setting of the MBT with a view to understanding the stratigraphy and its oil generation characteristics; 2. Determine the basin configuration and sediment thicknesses and; 3. identify and delineate “leads” or prospect areas for further detailed exploration that could lead to significant commercial discoveries of hydrocarbon in the MBT. Results have revealed the existence of petroleum systems in the MBT with the interbedded shales of the Bima and Yolde formations at the upper portions and the shales of the Asu River Group, Awe, Ezeaku and Agwu formations corresponding to the potential source rocks. The main local potential reservoir rocks are the Bima Sandstones and sandstones of the Yolde Formation coupled with the interbedded arkosic sandstones of the Awe and Keana Formations, while potential regional seals are the shales of Pindiga Formation and the arkosic sandstones overlying the shales of the Asu River Group and the basal shales of the Ezeaku formation and the upper shales horizon of the Agwu formation. Geophysical studies (Aeromagnetic/gravity survey) revealed the variability of the surface to Basement depths within the Middle Benue Trough ranging from 3 – 6 km with the deepest portions of up to 8.2 km towards the Northeastern portion of the MBT. The thick sediment piles coupled with the favorable petroleum systems, provide the conditions necessary for hydrocarbon generation, migration and accumulation. The prominent lineament structure is the NE-SW directional Keana anticline which extends along a strike for more than 100 Km from the south of Makurdi to Zurak in the northern portion. Trans tensional and trans compressional fault systems in the basin have given rise to sub-surface and extensive lineament structures systems which could either constitute major structural traps or pathways for fluid (hydrocarbon) flow. The analysis of a wide range of geochemical data from the MBT revealed TOC values ranging from 0.43 to 3.90wt% for shales/coaly shales and 14.78–79.10wt% for shaly coal/coal facies embedded in the Agwu formation with Tmax values corresponding to immature to mature stages of thermal maturation. Their petroleum potential in terms of HI values ranges from 14 to 267mgHC/gTOC in shale/coaly shale facies and 36–157mgHC/gTOC in shaly coal/coal facies, corresponding to the predominance of type III (gas-prone) in addition to type II (oil and gas-prone) organic matter suggestive of having both oil and gas generating potential. The recent discovery of significant quantity of oil (+gas) in the well Kolmani River-1 in the Gongola Sub-basin, is in strong support of its occurrence in the MBT. The paper has recommended selected prospect areas favorable for further detail hydrocarbon exploration.

Application of ground magnetics and geoelectrical methods in delineating sulphide deposit in oshiri area, southeastern nigeria

The Asu River Group Shale in the Oshiri area was evaluated using ground magnetic and geoelectrical methods within existing mine. Some exploration programs in the area have resulted to failure due to the fact that project managers have not fully understood the use and importance of geophysics in enhancing the search for mineral deposits. The aim of the study was to delineate the sulphide deposits using ground magnetics and geoelectrical methods. Result of the ground magnetic survey delineated some shallow tectonic structures like fractures and faults which are capable of hosting metallic sulphide deposits. The residual magnetic intensity of the study area indicates very low magnetic field intensities around the central and southern portions of the study area. These low values indicate absence of magnetite in the near surface materials as suggested by previous studies in the area, but could be referred to as zones with shallow tectonic structures which could be faults and/or fractures capable of housing sulphide deposits. The ore-bearing veins within the sedimentary rocks have susceptibilities of ≤ -1.8 nT. The low, negative residual susceptibility zone in the southeastern portion of the study area was targeted for the induced polarization IP and electrical resistivity tomography. Four traverses of induced polarization IP and resistivity surveys were carried out with all the profile lines were in the NE-SW direction. Isolated chargeable bodies with values greater than 340msec and a correspondingly low resistivity values (10Ωm-50Ωm), were encountered across some of these profiles. This zone may represent zones with sulphide mineralization. These identified chargeable bodies occur at approximate depth and width range of between 25-30m and 50-70m respectively. The 1D stratigraphic models reveal an average thickness estimate of 11.0m. Using scalar geometric approach, an estimate of 103,513.75tonnes was obtained, representing a relatively economically viable quantity and a worthy target for investors.

Geochemical studies of shales from the Asu River Group, Lower Benue Trough: Implications for provenance and paleo-environment reconstruction

Combined use of trace elements, rare earth elements (REEs) with hydrogen (δH) and oxygen (δ18O) stable isotope composition to elucidate origin and paleo-environment-conditions and reconstruction is a contemporary trend in the field of geochemistry. Geochemical investigations were carried out on the shale deposit from five wells within the Asu River Group Formation, exposed at Ikwo, Lower Benue Trough (LBT). Results of trace elements for the shale deposits examined showed averages of Co (19.10 ppm), Th (16.50 ppm), Zn (103.73 ppm), Sr (203.71 ppm) and Zr (292.80 ppm) compared to PAAS and UCC. Observed negative Eu anomalies, enriched LREEs and depleted HREEs patterns have shown that the shales are from rocks of continental origin. This is provided by Al/(Al + Fe + Mn) with a value > 0.2. Plots of Zr/Sc vs Th/Sc, La/Th vs. Hf and Cr/V vs. Y/Ni indicated felsic igneous rock precursors for the shale samples. C-parameter, ratios of Rb/Sr and Sr/Cu signify paleo-climatic conditions of semi-humid to arid, Ba/Al showed low paleo-productivity of the basin during shale deposition, largely within the freshwater setting according to the ratio of Sr/Ba. V/(V + Ni), U/Th, Ni/Co ratios and Ce/Ce∗ anomalies have revealed an oxic depositional environment with Fe/Ti > 20 suggesting hydrothermal activity. The temperature of formation (120 °C–∼195 °C) coupled with δ18O (+17 to + 23‰) and δH (−46.90 to −38.80‰) is consistent with materials of sedimentary origin from chemically weathered felsic precursors under humid climatic conditions with an influence of hydrothermal activity.

Pedological Properties and Classification of Soils Underlain by Asu River Group Parent Materials in Ohaozara, Southeastern Nigeria

Pedological Properties and Classification of Soils Underlain by Asu River Group Parent Materials in Ohaozara, Southeastern Nigeria

A scalar-geometric approach for the probable estimation of the reserve of some Pb-Zn deposits in Ameri, southeastern Nigeria

The Cretaceous sedimentary sequence of the Asu River Group in Ameri, southeastern Nigeria play host to lead-zinc ore deposits in irregular mineralized veins of non-uniform geometry. Two deposits (designated DEPOSIT A and DEPOSIT B) were economically assessed using an integrated approach. This was performed by employing a geometry-based classical scheme involving the mathematical relationship between the three cardinal variables of ore reserve estimation namely: surface area, thickness and density. Firstly, detailed and extensive geological mapping was carried out to establish the geological attribute of the mineral deposits. Since reserve estimation extends beyond exposed faces, spontaneous potential traverse, vertical electrical sounding and horizontal profiling, being orthogonal to the trend of the enclosing veins were used to characterize the existing sub-surface stratification and create forward models that revealed the concealed ore geometry (limiting depth, lateral extents and thickness variations). Subsequent to delineation, the depth to the top of the target ore lodes was obtained by implementing the Peter's half slope technique on self-potential curves. Thickness values of the ore bodies of interest were applied in three numerical classical integration techniques, i.e. Trapezoidal, Simpson's and Simpson's third-eight rule, for volume estimation. To overcome the non-uniqueness problem of DC resistivity data interpretation, the available drilling data was applied. Samples retrieved from each lode were subjected to mass and volume analysis using the CS200 electronic balance and water displacement technique, to determine the average density of each lode. Results from 2D subsurface resistivity sections showed the lead-zinc deposits as zones of low resistivity in a background of high resistivity. The 1D stratigraphic models reveal a mean thickness estimate of 11.85 m and 10.50 m for DEPOSITs' A and B, respectively. Sample densities correlate well with the average density of pure galena. Applying the scalar-geometric rule, a combined estimate of 10,778.95tonnes was obtained, representing a relatively economically viable quantity worthy of medium scale extraction.

Morphometric analysis of lower Enyong creek basin in South Eastern Nigeria; its implications for applied studies

The drainage basin analysis is important in any hydrological investigation such as study of hydrologic processes, management of wetlands, flood, erosion and landslides susceptibility studies, assessment of groundwater potential and groundwater management. Also, existing theories and models such as the laws of drainage composition can be verified. In the light of the foregoing, the present paper describes the drainage characteristics of the lower Enyong Creek, which is underlain by varying geologic formations. viz; Asu River Formations e.g the Abakiliki Anticlinorium to the recent alluvium in the south It involved detailed map-based quantitative analyses of two 4th order sub-catchments in the study area. The drainage pattern is mainly dendritic type. It is observed that the drainage density value is low which indicates the basin is highly permeable subsoil and thick vegetative cover. The elongation ratio value reveals that the basin is strongly elongated and stream abstraction process constrained by heterogeneous geologic materials. This study would help the local people to utilize the resources for sustainable development of the basin area.

A Comparative Study of Groundwater between Geological Groups of Southern Benue Trough, Nigeria Using Modelling Approach

Groundwater studies were carried out between two geological groups to evaluate factors that influences groundwater geochemistry. To achieve this, 30 groundwater samples were collected. Parameters such as pH, Electrical Conductivity (Ec), Total Dissolved Solids (TDS), Total Hardness (TH), and hydrochemical characteristics (Na2+, K+ , Ca2+, Mg2+, HCO3¯, NO3¯, Cl¯, CO23¯, and SO42¯) of groundwater were determined. Findings revealed that the pH value for Asu River Group ranges from 5.3 to 7.5, and that of Eze Aku Group ranges from 4.1 to 7.9. It was observed that areas around the mines had low pH values. Analyzed results that were obtained were interpreted using various hydrogeochemical models. Parson plots reflected that groundwater within the two geological groups fell within Ca˗Mg˗SO4 and Ca˗Mg˗Cl. Results from End˗member plots showed that 96% of groundwater samples analyzed were categorized under carbonate weathering, 4% fell silicate weathering. Gibbs plots revealed that interactions between groundwater and surrounding host rocks are mostly the main processes responsible for chemical characteristics of groundwater, Diamond field plots suggested that groundwater within the study were categorized to be high in Ca + Mg & SO4 + Cl, the plot of Ca2+/(HCO3¯+SO42¯) against Na+/Cl¯ revealed that groundwater was considered to be within the natural state for the two group. The plot of TDS against TH showed that groundwater is classified as soft freshwater. The study revealed there was no significant difference between factors that influence groundwater within the two geological.

Seasonal variation in abundance and diversity of zooplankton in Asu River, Ebonyi state, Nigeria

The Physicochemical variables and Zooplankton of Asu River, Ebonyi State, Nigeria were studied monthly between October 2013 and June 2014 which covered the wet and dry seasons. The study was carried out monthly in two selected sites by collecting water samples for physiochemical analysis and zooplankton identification. Shannon-Weiner diversity and Margalef's indices were used to determine the zooplankton composition. Investigation on the physiochemical variables showed that water temperature, dissolved oxygen, total dissolved solids, pH, conductivity and carbon (iv) oxide all recorded maximum values in the dry season. The present result also showed that the river is not seriously polluted. However, only carbon (iv) oxide and nitrate varied significantly between seasons (p < 0.05). Forty two (42) zooplankton species comprising Rotifera (7 families; 23 species), Copepoda (2 families; 8 species) and Cladoceran (6 families; 11 species) were identified. Rotifera spp. were numerically dominant and the most diverse group but the crustacean, Thermocyclops oithonoides dominated the total zooplankton biomass during the study. Species abundance showed inverse relationship with species richness, Shannon-Weiner diversity and Evenness. Zooplankton abundance was at its peak in the dry season while species richness, Shannon- Weiner diversity and evenness increased from dry season to wet season.

Parametric and Non-Parametric Suitability Evaluations of Rice Soils of Asu River Group Parent Materials in Ohaozara, Nigeria

The study was carried out in Ohaozara Southern Ebonyi State in Southeastern Nigeria. Study area was identified in a rice soil of about 120 hectares used for FGN/IFAD Value Chain Development program (VCDP). Three profile pits were dug on a transect line of about 100 – 200m apart for suitability evaluation study. The aim of the study was to use parametric and non – parametric suitability evaluation to study the rice soils under Asu River Group parent material. Parametric method is where each limiting characteristic was rated using information provided on factor ratings of land use requirements for wetland ricetable. In Nonparametric method, pedons were placed in suitability classes by matching their land characteristics with the agronomic requirements of rice. The index of productivity (IP) (actual and potential) was calculated using the equation: IP= A x √(B/100 x C/100 x D/100xE/100). Suitability evaluation results show that climate, soil physical conditions and wetness were optimum S1(95%) and moderately suitable S2(85%) while,fertility and toxicity parameters made the soil marginally suitable S3(60%). Parametric and non – parametric suitability evaluation revealed that the soils were mostly marginally suitable both potentially and currently. Major limitations of the investigated soils bother on fertility and Al toxicity.

Integrated geophysical study for mapping Pb–Zn sulfide deposits in Asu River Group shales in Nkpuma-Ekwoku, Abakaliki area, southeastern Nigeria

Integrated geophysical study for mapping Pb–Zn sulfide deposits in Asu River Group shales in Nkpuma-Ekwoku, Abakaliki area, southeastern Nigeria

A scalar-geometric approach for the probable estimation of the reserve of some Pb-Zn deposits in Ameri, southeastern Nigeria

The Cretaceous sedimentary sequence of the Asu River Group in Ameri, southeastern Nigeria play host to lead-zinc ore deposits in irregular mineralized veins of non-uniform geometry. Two deposits (designated DEPOSIT A and DEPOSIT B) were economically assessed using an integrated approach. This was performed by employing a geometry-based classical scheme involving the mathematical relationship between the three cardinal variables of ore reserve estimation namely: surface area, thickness and density. Firstly, detailed and extensive geological mapping was carried out to establish the geological attribute of the mineral deposits. Since reserve estimation extends beyond exposed faces, spontaneous potential traverse, vertical electrical sounding and horizontal profiling, being orthogonal to the trend of the enclosing veins were used to characterize the existing sub-surface stratification and create forward models that revealed the concealed ore geometry (limiting depth, lateral extents and thickness variations). Subsequent to delineation, the depth to the top of the target ore lodes was obtained by implementing the Peter's half slope technique on self-potential curves. Thickness values of the ore bodies of interest were applied in three numerical classical integration techniques, i.e. Trapezoidal, Simpson's and Simpson's third-eight rule, for volume estimation. To overcome the non-uniqueness problem of DC resistivity data interpretation, the available drilling data was applied. Samples retrieved from each lode were subjected to mass and volume analysis using the CS200 electronic balance and water displacement technique, to determine the average density of each lode. Results from 2D subsurface resistivity sections showed the lead-zinc deposits as zones of low resistivity in a background of high resistivity. The 1D stratigraphic models reveal a mean thickness estimate of 11.85 m and 10.50 m for DEPOSITs' A and B, respectively. Sample densities correlate well with the average density of pure galena. Applying the scalar-geometric rule, a combined estimate of 10,778.95tonnes was obtained, representing a relatively economically viable quantity worthy of medium scale extraction.

Chemical Characteristics and Assessment of Groundwater Quality Between Two Geological Group of the Lower Benue Trough ,Nigeria

Hydrochemical studies was carried out within two geological groups of the Albian to Turonian in age to evaluate factors that influences hydrochemistry of groundwater. To achieve this, 30 groundwater samples were collected. Parameters such as pH, Electrical Conductivity (Ec), Total Dissolved Solids (TDS), Total Hardness (TH) and hydrochemical characteristics (Na2+, K+, Ca2+, Mg2+, HCO3¯, NO3¯, Cl¯, CO23¯ and SO42¯) of groundwater were determined. Findings revealed that pH value for Asu River Group ranges from 5.3 to 7.5, and that of Eze Aku Group ranges from 4.1 to 7.9. It was observed that areas around the mines had low pH value. Analyzed results that was obtained were interpreted using various hydrogeochemical models. Parson plots showed that groundwater within the two geological groups fell within Ca˗Mg˗SO4 and Ca˗Mg˗Cl. Results from End˗member plots revealed that 96 % groundwater samples analyzed were categorize under carbonate weathering, 4 % fell under silicate weathering. Deductions from Gibbs revealed that interactions between groundwater and surrounding host rocks is the major processes responsible for chemical characteristics of groundwater, Diamond field plots further suggested that groundwater from the two geological group were categorized to be high in Ca + Mg &amp; SO4 + Cl, plot of Ca2+/(HCO3¯ + SO42¯) against Na+/Cl¯ revealed that groundwater were considered to be within natural state for the two group. Plot of TDS against TH showed that groundwater was classified to be soft fresh water. The study revealed there was no significant difference between factors that influences groundwater within the two geological group.

Stability analyses of dams using multidisciplinary geoscience approach for water reservoir safety: case of Mpu Damsite, Southeastern Nigeria

Geological, hydrological, and geotechnical conditions affected water reservoir safety at the studied damsite. Geophysical and hydrogeological surveys were integrated with hardness test, geological strength index (GSI), rock mass rating (RMR), and shear and compressive strength analyses of bedrocks. Fresh bedrocks were identified at minimum depth of about 10 m with resistivities ranging from 1670 to 4539 Ohm m for the respective argillaceous Ezeaku Group and indurate Asu River shales; both depicted 54 and 47.5 of RMR consecutively. Further results showed very blocky and slightly weathered bedrock, uniaxial compressive strength (UCS) ≥ 20 MPa, mean point load index of 9.3 MPa, and allowable bearing capacity (qal) ˃ 21 MPa. The bedrock qualities were certified fair for bearing dam loads, hence, signified competence as stable bearing surfaces, but devastated due to exposure to oxidation processes introduced by seepages through clay/siltstone that overlies bedrocks as composite layer. Then, uplift pressure (Pu) was initiated, resulting in failure modes. Predictably, occurrence of critical exit gradient and eventual general failure is envisaged due to vigorous leakage into the foundation zone from settling tail water portion. Panaceas should include Pu ˂˂ Dw (dam weight), grouting the leakage zones with concretes of UCS ≈ 20 MPa, and piling into deep foundations.

Effect of organic amendment on properties and nutrient loss of soils of selected parent material

Soils of Southeastern Nigeria like those of other humid tropical countries are prone to leaching due to high rainfall resulting in low fertility, nutrient status, and crop yield. Evaluating the effects of selected organic amendments on retention of nutrients in soils is of major concern and formed the purpose of the study. Soil samples were collected from Asu River Group, (ARG), Bende Ameki Group (BAG), Coastal Plain Sand (CPS) and Falsebedded Sand Stone (FBS) which were the four respective parent materials studied. Three replicates of 10 kg of prepared samples from each parent material were bagged and thereafter applied with 10 tons ha-1 each of poultry (PD) and goat droppings (PD, GD). The thoroughly mixed combinations laid in a completely randomized design (CRD) were allowed to blend for three months after which, samples were collected from each bag and analyzed. The remaining amended soils were subjected to a rainfall simulation which enabled the collection of sediment yield which was also analyzed to determine the nutrients in them. Generated soil data were analyzed with analyses of variance (ANOVA). Means were separated using the least significant difference (LSD) at 5% probability level. The result showed that soil organic carbon increased from 15.80 – 17.70, 6.90 - 14.20, 7.10 – 13.90 and 11.39 - 17.50 gkg-1 in ARG, BAG, CPS and FBS respectively before and after amendment and later decreased to 10.8, 11.30, 6.70, and 8.30 g kg-1 in the sediment yield following simulation. Similarly, there were significant losses of about 23.52, 60.85; 60.00 and 47.20 % of total nitrogen to detached soils in the respective lithologies. Total nitrogen and available phosphorus losses in the soils followed the order: CPS > FBS > BAG > ARG and FBS > CPS > BAG > ARG respectively.

Impact of heavy metals dispersion on water supplies around Oshiri and Ishiagu mine districts of Southern Benue Trough, Nigeria

The study area is underlain by igneous intrusives and shales of the Asu River Group (Albian) in the southern Benue Trough, Nigeria. The massive mining operations in the Oshiri–Ishiagu mining axis have necessitated investigation of effects of mining works on water resources in the adjoining areas. Assessment of water resources around the study area was carried out to ascertain concentrations of trace elements/heavy metals using atomic absorption spectrophotometer. Results revealed some chemical pollutants with ranges of the concentration values (in mg/l) as thus: Cd (0.18–4.37), Pb (0.06–10.11), Zn (0.13–7.11), Ni (0.02–1.21), Mn (0.04–1.16), Fe (0.03–2.04) and Cr (0.02–0.48) in surface water regime, as well as Cd (0.02–2.00), Pb (0.16–3.18), Zn (0.13–5.16), Ni (0.01–1.54), Mn (0.01–2.17), Fe (0.01–2.50) and Cr (0.01–0.28) in groundwater system. Except Mn and Ni which showed higher contamination in groundwater than in the surface water representative samples, other pollutants exhibited higher amount of contamination and metal pollution indices in surface water resources. Principal component analysis showed that pollution of water resources is controlled by mining of Pb–Zn loads as indicated in principal component (PC1) through loading of Pb, Zn and Fe as eigen values. Excess loading of SO42− in PC2 and PC3 signified that ions were released by dissolution process via breaking down (weathering) of the sulfide-associated ore. Dispersion of the ionic plumes was meteorologically aided, possibly by run-off and leaching; hence, the eigen of HCO3 at − 0.49 in PC4. Strong association of these elements in Pearson correlation confirmed the anthropogenic-induced dissolutions and geogenic-aggravated dispersions. So, deterioration of water resources by mine drainage hampers potable water supply across the studied areas and may have affected the adjacent regions.

Analysis of aeromagnetic data: Application to Early-Late Cretaceous events in parts of Lower Benue trough, Southern Nigeria

The study of the sedimentary sequence in parts of the Nigerian lower Benue trough has been carried out to understand the sedimentary thickness and its structural framework using high resolution aeromagnetic gridded data. It represents background investigation for targeting new mineralization zones and probable locations for detailed petroleum system analysis in the study area. The first order vertical derivative and the horizontal gradient magnitude of the reduced to the magnetic equator anomaly map were derived while edge detection techniques such as analytic signal, tilt derivative and horizontal derivative of tilt were implemented. Quantitative interpretations such as three dimensional Euler deconvolution, spectral analysis, and Source Parameter Imaging were applied to the residual magnetic intensity anomaly map. The results obtained show the Abakaliki Albian Asu River Group, the Caniacian Awgu shale and the Agala / Amasiri sandstones of Agubala and Ngbo to be severely intruded by rocks suspected to be basic or ultrabasic plutonic rocks. The basement topography, the sedimentary thickness of about 3800 m characterized by moderate volcanic intrusions, and the presence of a prominent anticlinorium for hydrocarbons preservation in Okpoto and environs call for a detailed petroleum system analysis. Structures hosting Lead-Zinc-Copper mineralization were identified in Ishieke, Ekeriegwe, Ugbuloke, and Abakaliki during an onsite mapping of notable structures. The mineralized structures in the areas are generally of dual origins − hydrothermal and volcanic. The hydrothermal minerals are connected to lineament intersections and occur as veins and veinlets in sedimentary rocks and feldspars while volcanic related ones occur as grains and with gangues in volcanic rocks.