1.1.  Study Background

Even though a century of geological studies have enabled a broad understanding the geology of the Benue Trough, it was only in the latter part of the 20th century that a picture of the structural framework, within which the Benue trough evolved, began to emerge. The controversies surrounding the tectonic evolution of the Benue Trough have been largely resolved, with the overwhelming evidence leaning towards the interpretation of the so called French school of structural Geologists which sees the Benue trough as a collection of pull apart basins related to transcurrent or strike-slip movement along deep-seated  basement shear zones of Pan African origin reactivated as oceanic transform faults (Benkhelil, 1982, 1989; Guiraud, 1993). This view is supported by field evidence in the Northern Benue trough where the climate and the nature of the sedimentary units allow for classic geologic study. In the Southern Benue Trough, the fine grained nature of most of the units and the dense vegetation as a result of a wet tropical climate have hindered field studies and created a missing link in the proper explanation of the structural framework of the basin.

The Afikpo area offers a unique opportunity to study and understand the deformational processes and to determine the tectonic stresses active in the southern Benue Trough as the highly indurated nature of the sediments allow for an abundance of outcrops that is unmatched anywhere else in the region.

1.  Geographical Setting
1.1.1.     Location and Accessibility

The study area is bounded by latitudes N 5° 51´ and N 6° 03´; and longitudes E 7° 51´ and E 8° 06´ (Figure 1) and covers the areas around Afikpo town, Amaseri, Ohaozara, Akpoha and Abomege in Ebonyi State of South Eastern Nigeria. Itigidi, Ediba, Itegeve and Adadama communities in Cross River state also fall within the study area. Access to the area is through the roughly east-west Afikpo-Okigwe road which connects the Okposi-Amaseri-Amoso road at Amaseri. On the outskirts of Afikpo town, this road connects with the Northbound Abakaliki road passing through Akpoha and Abomege. The eastern side of the study area is accessible through the Abomege-Ugep road which passes crosses the Cross River at Itigidi on its way to Ugep and Calabar to the south of the study area. Other minor roads link the smaller interior villages from these major roads. The major roads are tarred while the minor roads are at best graded and may not be accessible in the peak of the rainy season.

1.1.2.     Physiography          Topography

The study area can be divided into roughly two regions, northern and southern, with different topographic styles (Figure 2). The northern region has a lower elevation on average (less than 100 m) and is characterized by ridge and swale topography. The ridges are most prominent towards the Western part of the study area around Amaseri and Ibi where they trend NE-SW. The ridge profiles are asymmetrical with a gentle south eastern dip slope and a steeper north western scarp slope. They are related to the indurated sandstones which comprise them.

Towards the eastern part of the study area the trend of the ridges gradually rotate from NE-SW to NW-SE with dip slopes facing southwest around Ameta-Oziza. In the eastern part of the study the ridges are less prominent and can be seen to be folded about a NE-SW axis from digital elevation models (Figure 2).

The southern part of the study area is has a much higher elevation (above 100 m) and is more rugged than the Northern region. These hills are dissected by the Cross River which has cut gorges with moderately steep slopes at Itigidi and Oziza.          Drainage

The Cross River is the largest river passing through the study area (Figure 1). It originates in Cameroon, where it takes it is called the Manyu River and flows southwards through the study area to the Atlantic ocean (“Cross River (Nigeria),” 2013). The Aboine River is one of the major tributaries of the Cross River. It passes through the study area from north to south where it joins the Cross River. Its path seems to be controlled by NNW-SSE lineaments. The Asu River is a West-East flowing tributary of the Aboine River. Its flow direction is controlled by the alignment of the ridges and the river path is limited to one of the large shale swales through which the river meanders and forms a wide flood plain before joining the Aboine River at Akpoha. These rivers, though perennial, show a large variation between peak flow (usually at the end of the rainy season) and ebb flow (at the end of the dry season) where they are reduced to a bare trickle. Their banks provide in the dry season, very good exposures of the shale units otherwise hidden in other locations.  Other minor smaller streams are also controlled by the ridge and swale topography giving a roughly trellis drainage pattern along with the Aboine and Asu rivers.




Reservoir quality assessment and characterization of sandstone units was carried out across the Afikpo area of the Southern Benue Trough. The study involved field investigations and laboratory studies/analyses. Field samples were subjected to Grain Size Analysis (GSA), Sand Equivalent test and Methylene Blue test. Studies revealed that the sandstones are friable, cross-bedded and show coarsening upward motif. Results from lithofacies analysis indicate seven (7) lithofacies deposited in a low to high energy environment. They are (1) Dark Gray Shale facies (Micaceous Dark Gray Shale Facies and Fossiliferous Dark Gray Shale Facies), (2) Bioturbated Sandstone Facies, (3) Wave Rippled Sandstone Facies, (4) Cross Stratified Sandstone Facies, (5) Horizontal/Laminated Sandstone Facies (6) Heterolithic Sandstone Facies, and (7) Pebbly/Conglomeritic Sandstone Facies. The Micaceous Dark Gray Shale Facies belongs to the Eze-Aku Group while other liithofacies are of the Nkporo Group. Granulometric analysis of sand samples indicates sediments that are poorly to well sorted, generally positively to very positively skewed and mesokurtic to leptokurtic. Results from bivariate plots indicates river sand deposition while multivariate plots indicate the sediments are fluvial and deposited in a shallow marine environment. Out of 18 locations sampled, 13 locations had Sand Equivalent values ranging between 90% – 99%, 4 locations had values between 80% – 89% and one location had 77%. These results indicate that a high number of the samples contained little clay because the higher the Sand Equivalent values, the cleaner the sands. The Methylene BlueF test revealed that the clays contained in the samples are not susceptible to moisture (do not swell) as they had Methylene BlueF values ranges of 1.7g/kg and 3.3g/kg. These values do not exceed the Methylene BlueF limit which is 10g/kg. Permeability results range from 35.07mD to 4112.56mD indicating moderate to excellent reservoir while porosity values indicate poor to good with value range of 7.0 – 15.7%. Regression analyses showed a good correlation between porosity and permeability with R2 (coefficient of correlation) being 74.6%. There was a weak correlation between Sand Equivalent and Methylene BlueF Tests with R2 being 39.5%. Thus, combining results derived from the various analyses, sandstones within the study area possess good reservoir qualities especially to house gas hydrocarbon.




The study area is located in the Southern Benue Trough (Fig. 1), between latitudes 5°49′N and 5°54′N, and longitudes 7°54′E and 8°00′E. Benue Trough is an intra-continental rift basin characterized by tectonic and magmatic activities that occurred during Cretaceous times. The Benue Trough was affected by Santonian tectonic activity which deformed the “Benue Trough” and inverted the main depocenter of the Abakaliki Trough and subsequently created the Anambra and Afikpo Basins to the north-west and south-east respectively (Murat, 1972; Benkhelil and Guiraud, 1980; Benkhelil, 2001). The Santonian tectonics differentiated the sedimentary successions into pre and post Santonian packages. The post-Santonian successions are Campanian – Maastrichtian in age (Reyment, 1965); they occur both in the Anambra and Afikpo Basins respectively. In the Afikpo Basin, the Campanian – Maastrichtian succession comprises the Nkporo, Mamu, Ajali and Nsukka Formations.

Sandstones within the Afikpo area occur as ridges which consist of sands that are occasionally pebbly with few heterolithic beds as well as a lot of clays/fines. These ridges form northeast-southwest-trending topographic prominences while the shales underlie the swales i.e. the depressed areas. The sandstone ridges are dry and often barren of vegetation, while the swales are swamps. The ridges show extensive and deep weathering and laterization, such that exposures of fresh rock are available only along new roadcuts, ditches/gullies, quarries and some stream channels. The ridges are asymmetrical, with their gentler, coarser flanks facing the southeast and east, while the steeper flanks face the west.


The study area lies within the Afikpo Basin and covers about 44km2. It is limited by latitudes 5°49′N and 5°54′N, and longitudes 7°54′E and 8°00′E. The area is bounded in the north by Ibii and the Cross River which runs north-to-south direction on the eastern border and is the main drainage system in the area, south by Unwana and west by Edda and Amasiri villages. The locations studied are Ndibe, Edobi village, Mac Gregor, Mgbom, Ugwuagu, Ozizza, Ngodo, Kpoghirikpo and Akpughuru (Fig. 2).

Access to the study area is through a network of roads which are main, secondary and minor roads. Some of the access routes are untared which during the rainy season are essentially not motorable thereby making geological fieldworks difficult. Others are footpaths which connect most parts of the study area. Exposures in the southern part of the study area were accessed through the Afikpo-Unwana Road, those in the northeastern part were accessed through Ndibe Beach Road, those in the north through Ngodo Road and those in the northwestern part through Afikpo-Amasiri-Abakaliki Road.




The study area is located in Nsukka Local Government Area of Enugu State Nigeria. It lies between latitudes 6° 49′ N, and 6° 50′ N, and longitudes 7° 15′ E, and 7° 21′ E respectively. The area is underlain by Nsukka Formation, which is capped by the laterites, and underlain by heterolithic Sandstone / Siltstone layers with some clays or shale at some deeper horizons.  Geophysical investigation using Electrical Resistivity and IP methods with ABEM Terameter, SAS 1000, reveal the presence of fault in one section of the area, (Profiles 1 and 2, see Fig. 13, 14a and 14b of pages, 47 and 48 respectively) which potentially serves as the conduit through which water percolates to aquifer which eventually feeds the pond throughout the seasons.  This is indicated by the interpretation of anomalous low resistivity values within this zone, which shows a downward continuity within the geo-electric section in these profiles. A shallow possible source of the water in a perched aquifer following precipitation during the wet season, serves as recharge to the deep seated aquifer.  The result of the Profile 3 shows no continuity of the fault across that point, hence no anomalous drop in the resistivity in this area.



1.1 Location and Accessibility

The study area is located within Nsukka town of Enugu State in Southeastern Nigeria. It lies within Latitudes 6° 49′ N and 6° 50′ N and Longitudes 7° 15′ E and 7° 21′ E. The area is bounded by major communities which include Nsukka town, Obimo town, and Edem town. The study area is accessible through a network of tarred and untarred roads. The major roads include Obimo road, Ogurugu–Adani road, and Barracks Junction-Obimo road via St. Cyparin Special Science School. The minor roads include Umukashi road, Odoru-Nsukka road, and Edem road. Many foot paths connect the study area to the tarred and untarred roads.





Integration of 2D geophysical methods, Electrical Resistivity Imaging (ERI) and Induced Polarization (IP) were used to study the subsurface geology and structures around Ihe pond, Nsukka in Anambra basin. The research work has delineated the geologic structures and strata responsible for the water in the pond, and determined the origin of the Pond. Three 2D resisitivity profiles of maximum spread lengths of 500, 400 and 500m were run around the pond. Horizontal profiling, using Wenner array configuration was employed in the data acquisition for both methods. Four faults designated Apo 1, 2, 3 and 4 with colour codes, blue, red, green and black and their fault zones were mapped. The faults were located at points 224, 265 and 325m on ER model line one, and at points 170, 205, 275 and 296m on ER model line two. Three lithologic units of consolidated coarse, medium grained, fine-grained sandstones and saturated zones were identified on the ER and IP Psuedosections. The ER and IP values from the three profiles range from 136 – 21559Wm and -81.0 to 240Ms respectively. The faults zone acts as water pathway to the pond. Inverse chargeability models established the faults zones, as large gradients of chargeability. Correlation of strata to known formation depicts the presence of consolidated coarse to medium grained sandstones, while known exposed fault was correlated to Apo 3 fault using coordinates readings. Analysed sample of water from the pond shows low Salinity and sulfides. Soil sample oxide content was also analysed to compliment the geology, and the result shows that Aluminum oxide (Al203), Silicon oxide (Si02), Ferrous oxide (Fe203), Zinc oxide (Zn0) and Sodium oxide (Na203) are relatively low and are in conformity with characteristics of laterite. 



Electrical Resistivity (ERI) and Induced Polarization (IP) surveys were conducted simultaneously around Ihe pond Nsukka, in Nsukka Local Government Area of Enugu State (Fig 1.1), to study the subsurface imaging of the prospective area. Electrical resistivity imaging survey was used to determine the subsurface resistivity distribution, by introducing artificial generated current DC through the rock layers mainly by the passage of ions in pore waters of the rocks (electrolytic process) (Kenrey and Brooks., 1991), the potential voltage is read through the potential electrodes at the surface. A good result is obtained if the rock is porous, as porosity is the major control of the resistivity of rocks, resistivity increases as porosity decreases.

Induced polarization (IP) is a second-order resistivity measurement that quantifies the charge storage capacity of earth materials. The technique over the past 30 years has proven to be one of the most successful geophysical methods in providing direct information in subsurface imaging about rock mineralogy especially in search for disseminated sulfides and massive sulfide mineralization. It has been demonstrated in field applications that IP has the potential to distinguish between sediments of different lithological composition (Slater and Lesmes, 2002a; Kemna et al., 2004) and of different groundwater salinity (Seara and Granda, 1987).

The ground resistivity is related to various geological parameters such as the mineral and fluid content, porosity and degree of water saturation in the rock. Electrical resistivity survey has been used for many decades in hydrogeological, mining and geotechnical investigations. More recently, it has been used for environmental surveys and mapping of geological faults.

The distribution of potential can be related theoretically to ground resistivities and their distribution for some simple cases, notably, the case of a horizontally stratified ground and the case of homogeneous masses separated by vertical planes (e.g., a vertical fault with a large throw or a vertical dike).  Mineral grains comprised of soils and rocks are essentially nonconductive, except in some exotic materials such as metallic ores. Resistivity surveys can be useful in detecting bodies of anomalous materials or in estimating the depths of bedrock surfaces.  In coarse, granular soils, the groundwater surface is generally marked by an abrupt change in water saturation and thus by a change of resistivity.  In fine-grained soils, however, there may be no such resistivity change coinciding with a piezometric surface.  IP also finds application in the study of clay minerals. It has been used, in the fields of hydrogeology (Vacquier et al., 1957), (Marshall and Madden, 1959), oil and gas field exploration (Sternberg and Oehler, 1990) and in environmental studies, such as mapping of polluted land areas (Towel et al., 1985).

The dependency of polarizability of rocks/soils upon their lithological composition and hydrogeological properties favours the application of the IP method for hydrogeological (groundwater) and engineering geologic investigations.

The usefulness of ERI and IP has necessitated integration of both mehods to delineate the geologic structures and strata responsible for the water in the pond and to determine the origin of the Pond. The study also analysed water and soil samples from the Pond and its environs for salinity, sulfide and oxides concentrations for the safety of the consumers and to compliment the goelogy of the study area. The result shows that ERI and IP is an effective tool for mapping, faults, fault zones, lithologic units and chargeability increases as salinity of the groundwater increases up to 500mg/L (Barker, 1990).


The study area around Ihe pond, Nsukka Town, in Nsukka Local Government Area of Enugu State. It is bounded by latitudes 60 49I 50.1II N – , 60 51I 20.4II N and longitutdes 70 21I 55II E, – 70 22I 33.9II E, it has an area coverage of about 1.4km2. It is accessible by motorable roads and foot-path, especially those created by the villagers to fetch water from the pond. The base map of the study area, showing the accessibility to the study location is shown in fig 1.2.


Igbozurike (1975) recognizes four vegetation zones in the eastern Nigeria; among these, the study area falls within rainforest savanna zone. The vegetaion is made up of grasses and trees, and occasinally shrubs. Grasses and shrubs covers the high land areas, while tall trees tend to be more concentrated in valleys and low lands where they form forest. The study area lies within the humid tropical rainfall belt of Nigeria. The rainfall regime in the area lasts between the months of April and October, while dry season ensues between November and March. The dry periods are characterized by very high temperatures and lower relative humidity. Temperature is high in most part of the year except during the hamattan (December- January). The month of December has low temperatures (200C) at nights and mornings, and warmer days (up to 340C). The hottest period is between February and early April. Rainfall often occurs as violent down pours accompanied by thunderstorms, heavy flooding, groundwater infiltration and percolation. The study area also shows two major types of landforms, which consist of a high relief zone with undulating residual hills, valleys and the lowland areas.




The rocks and soils underlying Lambata-Minna and Minna-Bida roads in central Nigeria were mapped with the view to determine their impact on the stability of the roads underlain by them. Vertical electrical sounding was done along the roads to determine the soil profile of the roads and statistics of the roads utilization was also done to infer if the roads are overused by vehicles. The geophysical studies revealed that the soil profiles of the two roads are composed of laterite, sand and clayey soils while the road statistics revealed that the traffic densities in the two roads are within the permissible limits. A total of 5 and 4 rock samples were collected from Lambata-Minna and Minna-Bida road respectively and each subjected to thin section, XRD and XRF analyses. The thin section and XRD were used to determine the mineralogical composition of the rocks while the XRF was used to determine the chemical composition of the rocks. Thirty five (35) and twenty eight (28) water samples respectively were collected from wells along Lambata-Minna and Minna-Bida roads and subjected to hydrochemical tests to determine the variations in the ionic concentration and physical properties of the groundwater with the underlying lithologies. A total of 47 and 60 soil samples respectively were collected along the same roads and each subjected to grain size distribution test using wet sieving to determine the soil group dominating the soil occurring on each lithologic unit. Thirty nine (39) and fifty (50) samples from the above were selected and subjected to Atterberg limit tests to determine their plasticity. Twenty two (22) and nineteen (19) samples from the above were subjected to compaction, permeability and California bearing ratio (CBR) to ascertain which of the soils are suitable for sub-grade, sub-base or base material. The field mapping, thin section and XRD results revealed that Lambata-Minna road is underlain by migmatites, gneisses, granites, marble, granodiorite and schist while Minna-Bida road is underlain by granites, migmatite, schist and sandstone. The chemical compositions of the rocks indicate they are mostly acidic rocks/protholith. The physico-chemical tests revealed that the groundwater occurring within the sandstone terrain of Minna-Bida road has the least ionic concentration and physical properties while that occurring within migmatite/schist terrain along Lambata-Minna road has the highest ionic concentration and physical properties. The grain size distribution test revealed that the soils occurring within the sandstone terrain are composed mostly of sandy soils (SW and SP) while those within the migmatite gneiss and granite terrain along Lambata-Minna road are gravely (GW and GP) soils. Permeability of the soils ranges from 4.73 x 10-4 to 9.78 x 10-3 cm/s. The compaction test revealed that the soils occurring within the sandstone terrain along Minna-Bida road has optimum moisture content (OMC) ranging from 9.4 to 18.0%. The OMC of the migmatite gneiss and granite terrain along Lambata-Minna road ranges from 18 to 27% while those within granite terrain ranges from 15 to 18%. The soaked CBR of soils within the sandstone terrain along Minna-Bida road ranges from 45 to 95% while those within the migmatite gneiss and granite terrain along Lambata-Minna road ranges from 0.9 to 70%. The unsoaked CBR of soils within the sandstone terrain along Minna-Bida road ranges from 70 to 144% while those occurring within the migmatite gneiss and granite terrain along Lambata-Minna road ranges from 5 to 70%. Results of the permeability tests revealed that permeability of the soils is generally low and does not vary with the different underlying lithologies. Grain size distribution, Atterberg limits, compaction and CBR reveal that soils underlying Minna-Bida road are generally more competent than those underlying Lambata-Minna road. The results also show that soils occurring within the sandstone terrain along Minna-Bida road are more stable than other portions of the studied roads and can satisfactorily serve as road sub-grade and sub-grade in their natural state. The consistent failure of the Lambata-Minna road portion underlain by migmatite gneiss and granite is attributed to the fact that the soils occurring within those terrains have poor geotechnical properties to serve as either sub-grade, sub-base or base material in their natural state.



1.1 Background Information

Engineering geologists and geotechnical engineers are integral parts of design team for virtually all civil engineering projects like roads and buildings that involve site characterization and geotechnical design. To understand the geologic conditions of a site for civil engineering project and their implication(s) in design criteria, a common understanding of the site geologic origin and geotechnical properties of the construction aggregates to be used in the civil engineering project is essential. Generally, the engineering geologist provides basic information for the planning of land-use and for the design, construction and maintenance of civil engineering works. Such information is needed to assess the feasibility of a proposed land-use which will in turn assist in the selection of the most appropriate type and method of construction in order to ensure the stability of the intended structure as well as aid in the performance of necessary maintenance. Engineering geological research and mapping are therefore mainly directed towards understanding the interrelationships between the geological environment and the engineering structure; the nature and the geological relationships of individual geological components; the active geodynamic processes and the possible effect(s) that can result from the changes being made.

In Nigerian highway construction, attention is mostly paid to the sampling and testing of the aggregates to be used as the base/sub-base and wearing surface of the pavements as well as those serving as sub-grade. However, irrespective of billions of Naira spent by Nigerian government on the design and construction of these roads, most of the constructed roads do not render satisfactory service. The cause of these road failures can be attributed to the neglect of the role of geologists/engineering geologists in highway design by Nigerian contractors/civil engineers. For example, in choosing the route for the highway, one of the important factors to be considered is geology (lithostratigraphy and hydrogeological conditions) of the intended route. Such information can only be confidently ascertained by a geologist/engineering geologist.

Research has shown that the stability of pavements constructed in tropical regions is controlled mostly by the geological/hydrogeological, soil, climatic and drainage conditions of the terrain as well as the design technique, type of aggregates used, construction procedure and age of pavement (Clare and Beaven, 1962; Tanner, 1963; Gidigasu, 1974, 1975, 1983; Okagbue and Uma, 1988).  Works by Weinert (1968), Farquhar (1980), Okagbue and Uma (1988) have shown that geological conditions along a highway route are important factor to the proper performance of the highway. Since roads are built on and with geologic materials (rocks and soils), a good knowledge and understanding of these materials is therefore vital for the successful construction of roads.


1.2.1 Location and Accessibility

This study was done in North-central Nigeria in the area lying between longitudes 6o01’E and 7o00′ E and latitudes 9o05I N and 9o 36ˈN (Fig. 1.1). The study was centered along Lambata – Minna Road (LM-R) and Minna – Bida Road (MB-R). The Lambata – Minna Road (LM-R) is a trunk A road constructed/maintained by the Federal government that links most of the North western state to the Federal Capital Territory. The Minna – Bida Road (MB-R) is a trunk B road constructed/maintained by the Niger State Government. The Lambata – Minna Road (LM-R) covers a linear distance of 76 km and the Minna – Bida Road (MB-R) covers a linear distance of 84 km. Some important towns along the road traversed are Bida, Mina, Kataeregi, Mingida, Guto, Pita, Lambata and Gawu.





Automobile junk markets have been observed to be one of the sources of heavy metal pollution in soil and water. The aim of this study is to assess the level of heavy metal pollution within two acclaimed biggest automobile junk markets at Obosi and Nnewi, Anambra State, Nigeria. Twenty four (24) composite soil samples including the background samples at 0-15cm and 15-30cm depths, and six (6) water samples were randomly collected. Samples were properly digested and subjected to spectroscopic analysis using Atomic Absorption Spectrometer (AAS) for trace metals, Physiochemical and Microbiological analysis. The result shows that trace metals concentration (ppm) in 0-30 cm depth are well above the background values with Ni in excess of international standard. Metal enrichment is in the order of Ni> Fe >> Zn > Cu > Mn > Pb > Cr. The pollution load index and contamination factor reveals that the soil around the automobile junk market is at various stages of pollution with heavy metals, ranging from slight contamination to severe pollution. The geoaccumulation index however suggested that the soil is not contaminated. Result also suggested that water around the automobile junk markets are not advisable for domestic uses, as a result of its heavy metal contents, acidity, high turbidity, high salinity and dissolved oxygen as well as the presence of bacteria such as coliform and e.coli which are connected to the effects of industrial waste accumulation and indiscriminate domestic waste disposal as suggested by the principal component analysis.


  • Background Study

Heavy metals are chemical elements that occur naturally and maybe toxic in high concentrations. Excess heavy metal accumulation in soils is toxic to humans and other animals. Heavy metals content of soil are of major significance because of their non degradable nature and ability to accumulate for long period of time (Gallego et al 2002, Wu and Zhang, 2010). Some of these heavy metals like Iron, Copper, Zinc, Cobalt and Manganese are essential to life but can be toxic in high doses (Adepoju-Bello et al, 2009). The environmental pollution concern rises when they are in higher concentration due to natural mineralizing processes and/or human activities. The impact of heavy metals on the environment is a concern to government and the general public (Page and Chang, 1985, Feigin et al 1991, Tiller 1992). Uncontrollable inputs of heavy metals are undesirable because once accumulated in the soil, these elements are generally very difficult to remove and potentially harmful effects that may arise in the future should not be ignored.

The concentrations of heavy metals in soils are associated with biological and geochemical cycles and are influenced by anthropogenic activities such as agricultural practices, transport, industrial activities, waste disposal respectively (Lund 1990). Overload of heavy metals ions in soil environment clearly poses a significant risk to the quality of soils, plants, natural waters and human health (Adraino, 2001). The bioavailability of metal ion in soils is influenced by the temperature, cation exchange capacity, organic matter, competition with other metal ions, composition and quality of soil (Moon et al.2000, Mapanda et al. 2005, Machender et al. 2010). Exposure to heavy metals is normally chronic (i.e over a long period of time) due to food chain transfer. Chronic problems associated with long term heavy metal exposures are: Mental lapse, Kidney problems, skin poisoning, liver problems, gastro-intestinal complications amongst others.

Some industries usually discharge their wastes into the environment with little or no treatment. The automobile industry is one of the producers of industrial pollutants into the environment (Ogbuagu and Ajiwe, 1998). Automobile junks are waste auto engines traded and transferred to developing countries. These waste or knock down engines are recycled and reused or abandoned giving rise to poor waste management.




Investigations were carried out for groundwater potentials and hydro-geochemical characteristics of the Nanka-Oko area and environs, southeastern, Nigeria. The areas are underlain by the Nanka Sands Formation. Data from 14 vertical electrical soundings were interpreted using computer aided techniques (IPI2win software). A total of 16 borehole groundwater samples, were also analyzed for their physiochemical and biological properties with the aim of assessing their characteristics and quality for domestic and agricultural purposes. The results of the interpretation of the geophysical data show that the area is characterized by variable subsurface layering ranging from six layers to eight layers.Lithologic logs, geoelectric sections and static water levels data reveal that the area is characterized by two aquifer horizons (upper and lower) and two aquifer types (confined and unconfined).Based on the estimated hydraulic conductivity, transmissivity and specific yield, two groundwater potentials zones (low and high) were defined.  Results also show that the order of magnitude of the ionic species of groundwater of the area is > Na+> Ca2+>> Cl> Mg2+>> Fe2-/3-.  Only  among the major ions (, Cl,,Ca2+,Mg2+ and Na+) shows a pronounced difference in concentrations from the two aquifer types. The chemical composition of the groundwater is controlled mainly by weathering processes with little contribution from dilution processes. Three hydro-geochemical facies were deduced from the Piper diagram namely, CaHCO3, mixed CaMgCl and CaCl2.  The geochemical data also reveal that the groundwater from the area is potable as drinking water and suitable for irrigation purposes.



1.1       General Information

The Nanka Sandstone has proven to be a prolific aquifer with intriguing hydraulic and challenging geotechnical properties. The characteristic nature of the sandstone continues to attract the interest of researchers in the fields of hydrogeology, geotechnical engineering, and environmental geology among others for obvious reasons. Dozens of works have been done on the Nanka Sandstone in recent times, but none so far has holistically treated all the challenges posed by this litho unit as each work has concentrated on a particular/peculiar challenge. In general, increased urbanization with its attendant increase in demand for potable water for domestic and agricultural purposes has increased interest in the study area. With the presence of Federal Polytechnic at Oko, and a perennial expanding Ekwuluobia Market for example, more groundwater exploration has become necessary.

Thisresearch project reports the groundwater potentialsof the Nanka Sands using vertical electrical soundings (VES), geologic logs of boreholesand hydrochemical data of the groundwater.

1.2 Objectives

The objectives of this study were to determine the groundwater potentials as well as the hydrochemical characteristics of the aquifers in the study area.

1.3       Location of the study area

The study area (Nanka-Oko and environs) lies within latitudes 6000’ and 6008’North, and longitude 7000’ and 7008’ East. Some of the towns include Nanka, Ekwuluobia, Oko, Obeledu and Agulu (Fig 1).

  • Climate And Physiography

The climate of the area is tropical with an average yearly rainfall of 1478mm, daily minimum and maximum temperatures of 220 and 330 C, respectively. Relativehumidity ranges from 60% (at dry seasons) to 90 % (at rainy seasons). Two seasons exist namely, wet season (March to October) and dry season (November to February).




Groundwater constitutes the main sources of water supply in part of lower Benue Trough (mainly Gboko area). Sustainable development and management of the resources require an understanding of its holistic characteristics. In this study, an attempt has been made to study the groundwater quantitative potential distributions, its geochemical evolution, geochemical characteristics, and quality. The methods of investigation employed included pumping tests, static water level measurement, groundwater and subsurface soil samplings. The results of the pumping tests carried out within Gboko metropolis showed that the Gboko Central has the lowest groundwater potential with transmissivity value of  8.208m2/day while Gboko Low Cost area has the highest groundwater potential with transmissivity value of 281.52m2/day. The variation in the groundwater potential is attributed to varying degree of weathering. Nitrate concentration in the studied groundwater ranged from 0mg/l (below detection limit of 0.02) to 156.85mg/l and its concentration has a negative correlation (correlation coefficient of -0.0997) with water well depth. Nitrate was also found to pollute the groundwater of the area with its contamination observed to result from both agricultural practices and wastes, and also from domestic wastes. The groundwater from the urban land use (especially the poor income earners with poor environmental sanitation) have more dissolved nitrate than those from the rural agricultural land use. The concentration of each heavy metal tested in groundwater of the area varied spatially throughout the area. Co, Fe, Pb, Ba and Mn were found to be above the stipulated WHO 2008 guideline values. The sources of heavy metals in the groundwater were found to be both geogenic origin (weathering of host rocks) and anthropogenic (agricultural wastes and practices, domestic wastes and urbanization effects). The groundwater of the area is not generally potable as 84% of the groundwater samples tested was found to have heavy metal content. Principal component analysis revealed 12 controlling processes that are affecting the hydrochemical characteristics of the groundwater. Some of these processes include weathering of host rocks REE minerals, geogenic and anthropogenic contamination, uranyl complex factor, alkaline earth metal and heavy metal factor, redox potential factor, mixed or diverse contamination sources, metallurgical material wastes factor, and arsenic contamination factor. Cluster analysis grouped the groundwater samples of the area into 16 groups with various groups falling under high or low pollution loading. The results of the rare earth elements (REEs) showed that the groundwater of the area is characterised with predominance of light rare earth elements (LREEs) formed under an oxidising condition over heavy rare earth elements (HREEs) formed under a reducing condition. Also, the groundwater of the area all showed positive Ce and Eu anomalies. The positive Ce anomaly may be attributed to oxidation of Ce3+ to Ce4+ and incorporation of Ce into Mn and Fe oxyhydroxides phases while positive Eu may be attributed to weathering of zircon rich minerals. The δ18O composition of the groundwater samples of the study area ranged from -3.14 o/oo to -28.45 o/oo, δ2H ranged from -28.45o/oo to -14.53o/oo,and the groundwater showed a general depletion in both δ18O and δ2H. Also, 85% of the groundwater of the area was formed or recharged under a cooler climate than the present day. The aquifer vulnerability GOD model classified the aquifers of the area into three zones namely, the high vulnerability, the moderate vulnerability and the low vulnerability zones. The moderate and low vulnerability zones predominate in the area. The results of the subsurface soil samples analysis revealed that the soils in the area have been polluted by As, Cd, Ag, Au, Mn, Mo, Ni, Pb, Co, Cr, Cu, Hg, Sb and V. It was observed that both geogenic sources and anthropogenic activities mainly agricultural activities and urbanization are contributing to the contamination and pollution of the soils.




Water resources, irregularly distributed in space and time, are under pressure due to the combination of both naturally occurring conditions and anthropogenic actions. The need to develop more sustainable practices for the management and efficient use of water resources as well as the need to protect the environmental ecosystems where these resources are located, has led to major shifts in awareness and public concern over the years. Economic convenience and political criteria continue to govern water resources development decisions at most local, regional, national and international levels, without taking into account environmental issues.

Population growth and rapid economic development have accelerated freshwater withdrawals. Water use shows high variability globally, both within continents and across users.

The consumptive uses of freshwater from agriculture, industry and domestic sectors place the greatest pressures on natural systems, both in quantity and quality. In many countries of the world, agriculture is by far the main user of water.  According to Food and Agriculture Organization, FAO (2013) irrigated agriculture accounts for about 70% of water withdrawals from available sources followed by industry (19%) and domestic water supply (12%). The annual freshwater withdrawals by regions for various uses are presented in Table 1.About 92% of global water uses (agriculture, industrial and municipal supply) are met by withdrawals from renewable sources, either surface water or groundwater. In many areas of scarce freshwater resources, treated brackish water and wastewater are often used to meet demand. Again, according to FAO (2013) around 20% of the total water use demand globally is from groundwater sources, and about 74% is from surface water. Groundwater is the major source for drinking water, while surface water is for irrigation, energy and industry.

The importance of groundwater is gaining recognition because this resource constitutes the predominant reservoir and strategic reserves of freshwater storage in the world. It represents 30% of the freshwater resources, and as much as 96 percent of the fraction in liquid state (WWAP, 2006; Shiklomanov and Rodda, 2003). Groundwater supplies more than 1.5 billon urban dwellers with water and it is extensively used for rural water supply. Groundwater is the predominant source (about 55%) for public water supply

Table 1: Annual freshwater withdrawal by region




Average annual internal renewable water resources (m3/capital)2000 Annual freshwater withdrawal
Per capital (m3) Agriculture (%) Industry (%) Domestic (%)
Europe 3,981 704 39 45 14
North America 21,583 1907 25 66 8
South America 34,791 518 71 11 17
Asia 3,668 627 81 9 7
Africa 5,159 307 85 6 9
SSA* 87 4 9
World 7,045 664 70 22 8

*Sub Saharan Africa; sources: UNDP et al 2000; World Bank, 2000; FAO, 1995

due to its generally higher quality than surface water (EEA, 2009). In some locations it provides a more reliable supply than surface water in the dry seasons because of its large storage capacity. Moreover, groundwater resources are cheap to obtain because of their widespread occurrence and they generally present good natural quality (Zaporezec, 2002). Groundwater is less vulnerable to anthropogenic impacts than surface water bodies, because it is naturally protected by the soil and the confining strata. However, as a result of large storage and long residence times when aquifers become polluted, contamination is persistent and difficult to reverse (Clarke et al., 1996).

Throughout the world, most countries’ practices of urban and industrial development, agriculture and mining activities have caused groundwater contamination. Water quality is influenced by both direct point sources and non-point (diffuse) pollution. Diffuse pollution from farming activities and point source pollution from sewage treatment and industrial discharge are the principal contaminant sources. Concerning agriculture, the key pollutants include pesticides and organic fertilizers. The contaminants most commonly associated with organic fertilizers are oxygen-demanding substances, ammonia, nutrients (particularly nitrogen and phosphorus), sediments, pathogens and odorous compounds. Organic fertilizer is also a potential source of salts and trace metals, and to a lesser extent, antibiotics, pesticides and hormones.




Reservoir characterization is the key to a successful oil field development program. The recovery efficiency of any reservoir is influenced by its heterogeneities; particularly the distribution of porosity and permeability. To develop a reservoir model that represents the reservoir properties we must be able to define the vertical distribution of reservoir properties “flow units” and each flow unit has its own characteristics which control fluid flow behaviour. The understanding of flow units allows us to identify preferential flow zones. This study involves the determination of the number and distribution of hydraulic units (flow units), key flow unit characteristics and qualitative interpretation of flow performance using Stratigraphic Modified Lorenz Plot (SMLP) and Flow Unit Speed (FUS) parameter in the three selected wells of “Aqua Field”, Niger-Delta, Nigeria. A total of forty-two (42) flow units were identified throughout the hydrocarbon bearing intervals of Wells B, D and E. Well B has sixteen (16) flow units with six (6) speed zones and ten (10) baffles zones. Well D has five (5) flow units delineated, with three (3) speed zones. Also a total of twenty-one (21) flow units were delineated for Well E with nine (9) flow unit speed zones; the rest being baffles. The number of flow units delineated is an indication of the extent of the reservoir heterogeneity. The dominance of the speed zones to the baffles zones in a hydrocarbon bearing interval is an important factor in the flow performance and recovery efficiency during enhanced oil recovery. These various hydrocarbon bearing intervals of “Aqua Field” are dominated by baffles and an anticipated long term production will be sustained by the baffles zones. This will be characterized by a steady to slow decline production behaviour. This study has shown that Stratigraphic Modified Lorenz Plot (SMLP) is a cost effective, quick look method of characterizing petrophysical flow units.



1.1 Background Discussion

Petroleum geologists have long recognized the need of defining quasi-geological engineering units to shape the description of reservoir zone as storage containers and reservoir conduits for fluid flow. The exploitation plan for petroleum reservoirs is based on results from production forecasts, which are obtained from detailed reservoir studies. It is important to know how much oil, gas and water exist in place and how the fluids will move through the reservoir. In particular, fluid movement is difficult in highly heterogeneous reservoirs and considerable efforts to develop a good reservoir description that adequately defines the vertical and lateral distributions of reservoir properties are needed. Primarily the porosity and permeability distributions are considered. This is better understood when reservoir heterogeneity is better defined which has profound effect on all phases of hydrocarbon recovery. The variation of reservoir properties gives rise to different hydraulic (flow) units within a lithologic formation. A flow unit is a volume of total reservoir rock within which geological and petrophysical properties that affect fluid are internally consistent and predictably different from other properties of other rock volumes (Ebanks, 1987). A given flow unit exhibits similar permeability-porosity relationship and has similar properties for fluid flow. Flow units of a reservoir are relatively easy to determine using three parameters, porosity, permeability and bed thickness to generate cumulative flow capacity and storage capacity for crossplot (Gunter et al.,1997).The vertical variation in flow and storage capacity characterized by unique slope line give rise to different flow units which are indications of key flow unit characteristics such as conduits, baffles or barrier (Rushing and Newsham,2001).The flow unit division allows fluid flow within the reservoir to be better understood and categorized in a useful manner for simulation analysis and reservoir management.

1.2 Research Aims/Objectives

The Niger-Delta Basin has numerous marginal productive or abandoned oil fields. Typically production records are non-existent which hampers further development interest. The purpose of this study is to use a quick look method of characterization when data are limited. The permeability-porosity relationship within each flow unit allows us to identify and characterize the flow units using the Gunter et al. (1997) flow unit characterization method. However, without permeability distribution, flow unit prediction is not possible. This research seeks to predict flow units using only well log data when no core data and seismic data are available for analysis. The use of the core and seismic data will aid in refinement and validation of estimated porosity-permeability values obtained from well log and also the identification of fractures, faults and other structures which contributes or limits to the fluid flow potential of a reservoir.

By following the methodology the research aims to

  • identify the number of flow units within a reservoir using well log data;
  • predict the key flow unit characteristics in each hydrocarbon bearing zone;
  • determine the distribution of flow units within the hydrocarbon bearing zones; and
  • make a qualitative flow performance interpretation using the slope of inflexion and flow unit speed parameters.

1.3 Study Area/Tools

The Aqua-field is a mature field situated in the Central Swamp I Depo-Belt of the Niger Delta area (Fig.1a & c). Three wells, namely Well – B, Well – D and Well – E, used for this study were drilled to total depths of 11930 ft, 11600ft and 13132ft respectively (Fig.1b). The dataset used for this research is  three conventional open hole well logging data which have Gamma Ray(GR),Caliper (CAL-X),Sonic transit time (ΔT),Bulk density (ρb) and Resistivity (R-ILD,R-ILS and R-MSFL), made available by Shell Petroleum Development Company (SPDC) of Nigeria.





The study area, Adudu Metalogenic Province, lies in the Benue Trough. Although no economically viable discovery of hydrocarbon has being made in the Benue trough, it remains a site that receives constant influx of people owing to the large occurrence of various economic minerals present in its sedimentary piles. Some of the minerals that have being reported in the basin include barite, galena, sphalerite, salt etc.

Records show that organized mining started in Nigeria around 1939 through the privately owned foreign companies (Channda et al., 2010). However, no mining legislation was enacted until seven years later (1946) and this was not reviewed until 1999. Although the duo (1946 and 1999 mining acts) do not make provisions for artisanal mining, major pack-up of the mining companies in the 70s left many mine workers employed without any means of sustenance and future security. This scourge opened doors for massive illegal mining in various parts of the country including the Benue trough (Channda et al., 2010).

Various age groups, regardless of gender discrimination are involved in artisan mining, and the technology used by these majorly unskilled workers are dominantly primitive. Agricultural implements such as cutlass, hoe, digger and shovel are used by these groups for digging out the overburden to grant them access to the ore body (open cast mining). Underground channeling, lotto and the use of explosives are also being used, though at a regular frequency in comparison to the open cast mining. The hoary, open cast mining, which generates large amounts of sulphide-rich tailings (Bhattacharya et. al. 2006), has a serious environmental impact on the quality of soils and surface water due to pollution (Igwe et. al., 2014).

According to Nriagu and Pacyna (1988), the metal content in soil is a product of metals originating from natural processes and human activity. It is estimated that the contribution of metals from anthropogenic sources in soil is higher than the contribution from natural ones. Anthropogenic activities such as mining and smelting of metal ores have increased the prevalence and occurrence of heavy/trace metal contaminations and pollutions at the earth’s surface. In general, mined soils are mechanically, physically, chemically and biologically deficient (Vega et al. 2006), characterized by instability and limited cohesion, with low contents of nutrients and organic matter and high levels of heavy metals (He et al. 2005). Apart from the local disturbance of the physical properties, potential toxic metals (PTMs) can cause a more widespread contamination of soil, sediments and food crops leading eventually to a loss of biodiversity and a potential health risk to inhabitants in the vicinity of the mining area (Verner and Ramsey 1996; Lee et al. 2001; Zhang et al. 2002).

The Lead-Zinc mineralization which occur in the form of veins and veinlets associated with the host rock, are localized along the Northern-Southern trending belt of slightly deformed Sedimentary Cretaceous sequences (Albian Asu River Group) that measure about 500m thick (Igwe et al., 2014). This mineralization is structurally controlled and localized in fissures, faults zones and gently dipping veins. The veins are steeply dipping and have a depth of over 150m. They vary in width from less than a meter to 20m and in length from 30m to 120m. The dominant ores in the areas were observed from the fissures and contain lodes of sphalerite (ZnS), and/or galena (PbS) in association with smaller quantities of copper.  Galena is lead-grey in colour in veins and lenses. Orazulike (1994) had reported that the three types recognized on the basis of crystal form include: fibrous, granular, and cubic galena. Fibrous galena is often found close to fault zones and the gneissic texture is as a result of shear strain association with movement on the fault. In hand specimen, galena in granular form consists of a mass of tiny granules. It typically occurs away from the fault zones. Sphalerite is opaque, dark brown in colour and is usually in intimate association with galena. Its crystals are large and tabular with some faces measuring up to 8cm across.

Metallic ores are characterized by occurrence of gangue alongside mineralization of interest. Identified gangues associated with the Pb-Zn deposits in the Benue aulacogen includes siderite (FeCO3), pyrite (FeS2), marcasite, quartz and barites with other secondary minerals such as sulphates, carbonates and oxides. Marcasite is a ubiquitous gangue mineral though much less in abundance than siderite and quartz. Chalcopyrite is a minor mineral component, occurring generally in association with siderite and galena. It is massive and structure-less in hand specimen. Siderite is massive and has beige colour when fresh. On exposure to air, it tarnishes to dark brown. The crystal faces are poorly formed suggesting deposition at relatively high temperatures. Siderite is found in the main veins, minor fractures and vein-lets. In addition to galena and sphalerite, barite deposits in the trough as well as saline groundwater are of economic importance. Although the environmental impacts of the Pb-Zn mineralization in the lower Benue trough, which is being mined in the Enyingba district has received numerous attentions from researchers (e.g. Ezeh et al.,(2007), Ezeh and Anike (2009), Igwe et al., (2014)); there is no published work that has examined the effects of mining activities in the Adudu province found by me. It is therefore the focus of this research to critically examine the potential risks associated with the harvesting of these economic minerals in stated location.

There are two mining methods carried out in the area: open cast mining and underground mining. In the open cast mining, weathered materials known as overburden are removed by excavators to gain access of the minerals (fig.1.1). In the underground mining, the overburden is not removed but shafts are dug to meet the minerals underground where they are removed and brought by conveyors (fig.1.2). In both mining methods, groundwater is constantly pumped out to access the minerals.




Used motor oil is constantly disposed indiscriminately at mechanic workshops in Nigeria without considering its impact to the soil and the environment at large. This work investigates intrinsic changes in the engineering properties of lateritic and clayey sand materials. Soil samples were collected at the depth of 30cm and were then air dried at room temperature for seventy two (72) hours. After air drying, the lateritic material was divided into five equal parts. Each of the samples was artificially contaminated with 4%, 6%, 8%, and 10% of used motor oil; the last uncontaminated portion was used as the control sample. This same procedure was carried out on the clayey sand material. These materials were kept in an air tight polythene bag for fourteen (14) days to enable the mixture to cure. Samples were subjected to mechanical analysis, specific gravity, permeability, Atterberg limits, compaction and triaxial tests. Results revealed that specific gravity of the samples decreased with increase in used motor oil from 2.66 – 2.25 in lateritic soil and 2.72 – 2.35 in clayey sandy soil, permeability also decreased with increase in the percentage of used motor oil, 2.75 – 1.85 cm/sec in lateritic soil and 1.97 – 1.70 cm/secin clayey sandy soil, maximum dry density(MDD) and shear strength of the samples also decreased with increased percentage of used motor oil in both the lateritic and clayey sand samples. This research shows that used motor oil reduces the shear strength of the soil.




Engine oil or motor oil is derived from petroleum based compounds which consists mainly of hydrogen and carbon. Thus, engine oil is a hydrocarbon compound. Used motor oil can be dispersed into the soil in four different ways: escape and loss of oil during motor operations; applications on rural roads for dust control, during asphalting with asphalt-containing waste crankcase oil, and finally, when it is placed directly on landfills or at the mechanic workshops. The release of used engine oil on soil poses a big threat to engineering structures. Apart from engineering structures, soil microbes and plants as well as contaminate groundwater resources for drinking or agriculture may also be contaminated (Hong et al, 2010). Used motor oil is a very dangerous polluting product, it contains polynuclear aromatic hydrocarbons (PAH’s) and high levels of heavy metals, PAH’s are dangerous to health because some are known to be mutagenic and carcinogenic, benzo[a]pyrene are well known for their high carcinogenicity(IRAC, 1983; Raphael 1989).

Used motor oil contaminations of soil are common wherever motor mechanic workshops are located. It has been reported that the bearing capacity of such soils is drastically reduced and made engineering structures unsuitable to run, or plant growth by reducing the availability of nutrients or by increasing toxic contents in the soil (Euchun and Braja, 2001). Mechanic workshops are seen at every point in town and developing areas (Fig. 1); some well-known mechanics have occupied a piece of land for more than 10 years. The oil from vehicles are disposed carelessly, sometimes the oil is drained from the vehicle and collected in a container and are disposed at a particular point on the land but most times released directly from the vehicle to the ground. Cases have been witnessed where individuals or even the government reclaims a piece of land that was formally used as a mechanic workshop and structures are erected on it.

The essence of this research is to examine the influence of used engine oil on the engineering properties of lateritic and clayey sand materials.

Hydrocarbon contamination will not just affect the quality of the soil but will also alter the physical properties of oil contaminated soil. This will lead to geotechnical problems related to construction or foundation structure on this oil contaminated sites (Mackenzie, 1970). This implies that care should be taken in the disposal of hydrocarbon compounds. But unfortunately, an average Nigerian do not care how the bad oil from his vehicle is being disposed, all he cares is that the oil has been drained from his vehicle to prevent damage to it (vehicle). 




An investigation was carried out on the groundwater potentials and aquifer protective capacity of Ishiagu area, southeastern Nigeria. The study area lies within the lower Benue trough of Nigeria and is underlain by the Albian Asu River Group and the Turonian Ezeaku Shales.The methodologies employed in the study include measurements of static water levels of 15 hand dug wells, pumping tests carried out on 4 boreholes and vertical electrical sounding (VES) of 20 stations. Groundwater potentials of the area was thoroughly characterizedusing aquifer parameters of hydraulic conductivity and transmissivity within unit cells.These parameters were supplemented with those determined from empirical relationships.The hydraulic conductivity and transmissivity determined from the pumping test data range from 0.6m/day to 3.04m/day and 4.86m2/day to 34.93m2/day respectively while those from empirical relationships range from 0.04m/day to 4.34m/day and 0.07m2/day to 61.69m2/day respectively.Three groundwater potential ratings were defined based on the aquifers’ hydraulic conductivity and transmissivity data; poor (45%), fairly good (35%) and good (20%). The hydraulic head map reveals two divergence and two convergence zones. The computed hydraulic heads range from 58.2m to 84.5m.Vertical electrical sounding reveals that the area is characterized by 4-, 5- and 6- subsurface geo-electric layers with the 6-layer type being the dominant type. Longitudinal unit conductance of the 20 VES stations was estimated from the layers’ resistivity and thickness data.Longitudinal unit conductance of the overburden units ranged from 0.07mhos to 2.22mhos. Based on the estimated longitudinal unit conductance, three aquifer protective capacity types were defined namely, weak (25%), moderate (40%) and good (35%). It was observed that areas of good groundwater potentials also have good aquifer protective capacity. Groundwater development should therefore be concentrated more in areas of good groundwater potential for continuous/steady supply of potable water.




The Ishiagu area lies within the lower Benue trough of Nigeria and is underlain by the Albian Asu River Group and the Turonian Ezeaku Shales. The area is also intruded in many places by Santonian intrusive rocks and mineralized in some parts by hydrothermal Pb –Zn ores. (Kogbe, 1976)

The geology of the area is not favourable for groundwater availability. With population explosion in Ishiagu town occasioned by the presence of several mining and quarrying companies such as Crushed Rock Industries Ltd., Setraco Nig. Ltd. etc, a greater need for potable water has become obvious. More so, the need to assess the protective capacity of the aquifer in the area cannot be overemphasized as there is the danger of its contamination from surface industrial effluents and pollutants emanating from mining and quarrying activities in the area.

As exploitable quantity of groundwater is expected to be available only in fractured or weathered zones of the area, surface geoelectrical method becomes very necessary to locate such areas of reasonable groundwater potential. Furthermore, knowledge of values of aquifer parameters such as hydraulic conductivity and transmissivity in the area is useful in evaluating the groundwater potential of the area.

Although the conventional way of determining the mentioned aquifer parameters has been the use of pumping test method, it has proved to be expensive, tedious and time consuming. Also various formulas available for calculating the aquifer characteristics from pumping test data analysis are valid only if various assumptions about aquifer continuity, thickness, homogeneity, isotropy, well storage and nature of fluid flow are valid under field conditions (Freeze and Cherry 1979),hence the need for a reasonable alternative.Surface geoelectric methods have proved to be a handy alternative to pumping test method in the determination of aquifer parameters (Guérin, 2005). The method is cost and time effective and is used to predict the parameters for even those areas where there are no existing wells (Ekwe et al 2006).


The objectives of this research work are to:

(1)        Determine the lithological succession and the prospective water bearing horizons in terms of resistivity, thickness and depth across the study area using vertical electrical sounding method

(2)        Evaluate hydraulic conductivity and transmissivity of aquifers in the study area using Da-Zarouk parameters from vertical electrical sounding

(3)        Compare the value of aquifer hydraulic conductivity obtained from this study with that obtained by pumping test method using statistical correlation tool.

(4)        Assess the overall groundwater potential across the study area

(5)        Assess the level of protection of aquifers in the Ishiagu area from surface pollutants(aquifer protective capacity) using Da-Zarouk parameters from vertical electrical sounding

(6)        Correlate geoelectric sections in the study area with existing borehole logs.

(7)        Determine groundwater flow direction using existing well data and elevation values.




This research work presents findings of the extent and distributions of saline zone and the hydrochemical characteristics of the groundwater of Awe, Keana and Giza areas in the Middle Benue Trough of Nigeria.Staticwater levels(swl) of hand dug wells were measured andthe results used to generate hydraulic head data and hydraulichead map. The static water levels range from 1.0m to 13.5m at Awe, 1.0m to 4.5m at Keana and 2.2m to 9.2m at Giza. The hydraulic head maps for the three areas show different patterns/directions of groundwater flow for each area. Geophysical investigations, mainly vertical electrical sounding (VES) using Schlumberger electrode configuration array were performed at 47 locations spread across the entire study areas. Results of the VES revealed that the studyareas are characterized by3, 4 and 5geo-electrical layers with 9 different curve type signatures. Also, results of the VES show that Awe area has the highest occurrence of saline zone, followed by Keana and Giza respectively. Multi-layer saline zones were observed only at Awe. Thirty (30) groundwater samples (10 each from the 3 areas) were analyzed for physiochemical parameters (rare earth elements, heavy metals, major cations and major anions).Results of hydrochemical analysis revealed five (5) hydrochemical facies namely,Ca-HCO3, NaCl, NaHCO3, Ca-Na-HCO3 and Ca-Mg-Cl facies. Principal component analysis of the hydrochemical data revealed that the groundwater chemistry of the areas is controlled by the mineralization of the host rocks, weathering of galena, uranite, felsdspathic minerals and dissolution of limestone and dolomite. The spatial distribution pattern of the rare earth elements of groundwater of the study areas showed a strong positive correlation exists between brine and the elements. Uranium, however, showed a district distribution pattern which may indicate a distinct source from the other elements. Of the three areas studied, Keana has the most potable water supply.  Awe and Giza groundwater have chloride (Cl), nitrate (NO3) and lead (Pb) contaminations.It was observed that the groundwater quality of the study areas is not only salinity dependent, but also influenced by anthropogenic activities such agricultural wastes and domestic waste released into the environment.Based on the irrigation water quality indexes employed, groundwater of the areasrange from unsuitable to suitable for irrigation purposes.




The Benue Trough of Nigeria is one of the most prominent geologic features in West Africa. It extends over a length of 800km trending NNE-SSW from the Niger Delta to the south-west of Lake Chad basin and ranges in width from 130 to 250 km (Figure 1.1).  Due to the large regional extent, studies in the Trough are often divided geographically (though arbitrarily) into upper, middle and lower regions (the approximate boundaries of these regions are given in Figure 1.1. No concrete line of subdivision can be drawn to demarcate the individual regions, but major localities (towns/settlements) that constitute the depocenters of the different regions have been well documented (Obaje et al., 1999). The depocenters of the Lower Benue Trough comprise mainly the areas around Nkalagu and Abakaliki, while those of Middle Benue Trough comprise the areas around Makurdi through Yandev, Lafia, Obi, Awe, Keana, Giza, Jangwa to Wukari. In the Upper Benue Trough, the depocenters comprise Pindiga, Gombe, Nafada, Ashaka (in the Gongolaarm) and Bambam, Tula, Jessu, Lakun and Numan in the Yola arm.

The origin of the Trough (which is still controversial in details) has long been associated with the breakup of Gondwana – the separation of Africa from South America and the opening of the South Atlantic Ocean.

Occurrences of saline groundwaters as springs, ponds or in dug wells and boreholes are common in parts of the Trough. Prominent outcrops (which commonly support local salt industries) are found in the Lower Benue Trough and Middle Benue Trough (Figure 1.2). Brine is saline or salty water, particularly a highly concentrated solution of common salt (sodium chloride). It occursnaturallyas an underground salt lake and is one of the commercially important sources of common salt in the world (Leford and Jacoby, 1983).  Thesaline groundwaters in the Lower and Middle Benue Trough are frequently associated with tectonic elements such as intrusive and mineralized veins (Uma, 1998).

The presence of brine constitutes a serious hydrogeological problem on groundwater and as noted by Adeoti et al. (2010), saltwater intrusion into aquifers has become a major concern in most of the areas around brine fields as it constitutes the commonest of all the pollutants in freshwater.Therefore, understanding the point of saline intrusion is essential for the management of groundwater in such areas.Awe, Keana and Giza brine fields in Awe and Keana Local Government Areas (LGAs) of Nasarawa State are some of the brine fields located within the Middle Benue Trough.

According to Offodile (1983), the saline ponds in the areas appear to originate from underground brine issuing from the western flanks of Keana anticline and perhaps also from the interbedded shale of fractured sandstone of Awe Formation and feeding the Awe and the other brine fields in the Middle Benue Trough.