Obudu Plateau Research Articles

Geoinformatics and Analytic Hierarchy Process (AHP) in modelling groundwater potential in Obudu Plateau, Southeastern Nigeria Bamenda Massif

Geoinformatics and Analytic Hierarchy Process (AHP) in modelling groundwater potential in Obudu Plateau, Southeastern Nigeria Bamenda Massif

Application of the enhanced horizontal gradient amplitude (EHGA) filter in mapping of geological structures involving magnetic data in southeast Nigeria

Lineament detector and depth estimation method involving modern aeromagnetic data were employed to study parts of the Obudu Plateau and Lower Benue Trough (southeast Nigeria) with the aim of mapping thermo-tectonic geologic structures and estimating sediment thicknesses. In this investigation, the enhanced horizontal gradient amplitude (EHGA) (applied to both simulated and real data) and tilt depth approaches were operated. The simulated magnetic model employing the EHGA detector generated sharp and properly defined edges of magnetic bodies with the capacity to place peaks over source borders. The tilt depth technique showed thin and thick sedimentations that vary from ∼ 500 to ∼ 1000 m and ∼ 1500 to ∼ 2500 m, respectively. The observed geologic structures trend mainly in the NW and NE, as well as minor NS directions. These structures, generated by the Younger Mesozoic Granitic intrusions of calc alkaline ring complexes, and the Santonian Abakaliki Anticlinorium serve as paths for super enriched hydrothermal fluids migration and deposition. The applied methods can be used to decipher the geologic structures in alike zones around the world.

Implications of tectonic anomalies from potential field data in some parts of Southeast Nigeria

Tectonic structures controlling mineralization in some parts of Southeast Nigeria were evaluated using airborne potential field data. High- and low-frequency filters and depth determination tools were adopted to evaluate short- and long-wavelength anomalies, resolve the spatial spreading of igneous intrusions, depths to geologic sources and basin topography. The high-frequency results exhibited high concentration of short-wavelength anomalies in the Obudu Plateau and Ikom–Mamfe Rift. The underlying main tectonics of the area elucidated by the low-frequency results caused the widespread occurrences of short-wavelength geologic structures that are revealed by the high-frequency maps. The study area is characterized by comparatively thin (~ 13.0 to < 3000 m) sedimentation. The observed thin thickness is as a result of the massive Precambrian basement outcrops in some locations in the Obudu Plateau and the proliferation of igneous intrusions within this part of the Lower Benue Trough. The 2-D models showed the undulating nature of the underlying basin topography, the location of intrusions, domal structures and related normal faults. The locations and neighbourhood of intrusions and/or short-wavelength structures are viable sites for lead–zinc–barite, brine and metallogenic minerals.

Structural and lithological interpretation of aero-geophysical data in parts of the Lower Benue Trough and Obudu Plateau, southeast Nigeria

High resolution airborne magnetic and radiometric data were used to map probable sites for polymetallic-magmatic hydrothermal deposits in the study area. The first and second vertical derivatives, horizontal gradient, analytic signal and tilt angle derivative were used to enhance magnetic data in order to determine the location of short wavelength anomalies, magnetic sources and geologic boundaries. Also, to understand and detect radiometric anomalies controlling mineralization in host rocks, enhancement operations involving potassium (K), equivalent thorium (Th), equivalent uranium (U) concentrations and ternary imageries were carried out. All these operations enabled the delineation of responses associated with mineralization, lithology and geologic structures. Generally, lineaments trend in the NE-SW, NNE-SSW, NW-SE and E-W directions, and serve as potential pathway for hydrothermal fluid migration and mineralization. Radiometric anomalies from spectrometric imageries are caused by felsic minerals, hydrothermal rock alterations, widespread shales, residual clay, oxides and accessory minerals that constitute regolith of the area. The coincident high magnetic and potassium intensities sites in Anambra Bain (AB), Abakaliki Anticlinorium (AA), Ikom-Mamfe Rift (IMR) and Obudu Plateau (OP) are probable sites for polymetallic-magmatic hydrothermal deposits. Generally, the joint magnetic and radiometric results were able to establish link between lithology, geologic structures and hydrothermal alteration patterns.

Provenance and tectonic settings of the Eze-Aku Sandstone (Turonian) in Awajir and adjoining areas, Southern Benue Trough, Nigeria: evidence from petrography and geochemistry

Eighteen representative samples for petrographic (6) and geochemical (12) studies were collected from the Turonian (Eze-Aku Formation) sandstones outcropping within Awajir and adjoining areas in the northern section of the Southern Benue Trough. Sandstones of different textural variety underlie the study area: fine-, medium- and coarse-grain sandstones facies. Field study revealed an overall coarsening upward succession, ripple bedding surfaces, cross-stratification and bioturbation, which suggest prevalence of a shallow shelf with relict shoreline environmental settings. Petrographic study show that the sandstones are subarkosic to arkosic and deposited in a humid to semi-humid paleoclimatic condition. Polygenic (mixed) provenance source is inferred for the sandstones and the insignificant presence of sedimentary rock fragments in the framework constituents suggests the Precambrian Basement complex of southern Nigeria as the most likely source area. This result is consistent with trace element ratios such as Cr/Zr (< 0.6) and Cr/Th (0.3–15.7) as well as La/YbN versus CeN diagram which points all the sandstone facies to an intermediate Igneous provenance, unambiguously ruling out the chances of mafic igneous rocks being present in the source terrain. The most probable provenance for the sandstones is the continental Basement complex rocks of Obudu plateau and Oban massifs. The study showed that there was a mild influence of diagenetic alteration on the sandstone facies after deposition in an active continental margin-continental island arc setting.

Geoelectrical Resistivity and Geological Characterization of Hydrostructures for Groundwater Resource Appraisal in the Obudu Plateau, Southeastern Nigeria

Electrical resistivity tomography (ERT) and vertical electrical sounding (VES) techniques were employed to assess the hydrogeological structures and groundwater potential of the Obudu Basement Complex. The Wenner electrode configuration was used to acquire the ERT data along 4 profiles, while the Schlumberger configuration was employed in the VES investigation, where 30 locations were occupied during the data acquisition campaign. Results show that rock distribution is predominantly the granite gneiss series that are considerably weathered in several locations especially within the western portion of the study area. Three potential hydrogeological scenarios were identified from three of the ERT profiles. These include the regolith-, doleritic- and kaolin-induced groundwater conduits. Within the central segment of the study area, transtensional stress regimes traceable to the neo-Proterozoic syn-orogenic event were observed to have resulted in the establishment of some regional fault systems. Over time, several episodes of minor tectonic events have resulted in cataclastic deformation of the gneissic rocks, creating pathways for groundwater circulation. Additionally, it was observed that dolerite intrusion in some locations cataclastically deformed the host rock resulting in syn-emplacement fractures that can create pathways for groundwater to flow. Saprolite units and locations within major fault lines were inferred to have moderate to good groundwater potential due to their large width and the presence of multiple interconnected fractures as inferred from the pseudo-sections and lineament map. More so, streams and rivers within these areas can infiltrate through the pathways created by the faults, hence increasing groundwater circulation within the conduits.

Preliminary review of the geology of the hornblende biotite gneisses of Obudu Plateau Southeastern Nigeria

The Obudu Plateau, southeastern Nigeria is dominantly underlain by gneissose rocks with migmatitic characteristics, one of which is the hornblende-biotite gneiss. The gneisses are banded with quartz and plagioclase as the major minerals in the leucosome while hornblende and biotite occur in the palaeosome. Geochemically, the rocks are enriched in silica and alumina with an average of 71.6wt% and 14wt% respectively. Geochemical plots indicate that they are calc-alkaline to tholeiitic in character and derived from protholiths of igneous origin with minor sedimentary input.KEYWORDS: Obudu Plateau, migmatitic gneiss, calc-alkaline

Composition, provenance and tectonic setting of Eze-Aku Sandstone facies in the Afikpo Synclinorium, Southern Benue Trough, Nigeria

Field study, petrographic and major element geochemical composition of the Eze-Aku Sandstone facies outcropping in the Afikpo Synclinorium, southeastern Nigeria, were utilized in this study. The aim is to interpret the provenance and tectonic setting for sandstones in the sedimentary basin. Field observation shows alternating sequence of parallel sandstone ridges trending NE-SW and shales which represent the low-lying plains in the area. Four major sandstone facies were identified: massive conglomeritic sandstone facies, laminated sandstone facies, bioturbated sandstone facies and cross-bedded sandstone facies. Ternary plots for framework elements (quartz, feldspar and rock fragments) from petrography of the sandstones indicate the sandstones as arkosic and subarkosic arenites. Tectonic setting discrimination diagrams plotted based on major element oxides revealed continental block provenance dominantly in a passive continental margin. Petrographic and geochemical results indicate large amounts of detritus were derived principally from plutonic igneous rocks with minor contribution from metamorphic source region, probably from Obudu Plateau, Oban and Cameroon Massifs.

Preliminary investigation of pegmatites in Obudu Area, Southeastern Nigeria, using stream sediments geochemistry

Stream sediments of Obudu Plateau were investigated with a view to elucidating their geochemical features, mineralization potentials and element concentrations. Stream sediment samples were collected from Southern Obudu Plateau area and analyzed for 22 elements, comprising major and trace elements, using Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). The data obtained were statistically treated. Ba, Sr, Nb, Co, Pb, Ta and Na show moderate to high concentrations, when compared with threshold values of these elements. The concentrations of these elements in sediments of Southern Obudu show low mineralization potentials of pegmatites of the Obudu Plateau. The elements in Obudu stream sediments show perfect, strong, moderate and weak correlations among themselves, indicative of variations in their mobility.

Geochemical Pattern and the Evolution of the Mafic Rocks of Southwest Obudu Plateau, Bamenda Massif, Nigeria

Geochemical Pattern and the Evolution of the Mafic Rocks of Southwest Obudu Plateau, Bamenda Massif, Nigeria

The chemical composition and industrial quality of Barite mineralization in Calabar flank, Oban Massif, Mamfe embayment and Obudu Plateau, southeastern Nigeria

Barite occurrences in the Calabar Flank, Oban massif, Mamfe Embayment and Obudu Plateau of Southeastern Nigeria have been sampled and analyzed for the purpose of assessing their chemical composition and industrial quality. Barite occurrences were observed mostly along faults and unconformities marking the boundaries between the Precambrian basement rocks of Oban and Obudu massifs and the Cretaceous sediments of the Calabar Flank and Mamfe embayment. Occurrences were also observed within the sediments. The chemical data show that BaSO 4 , SiO 2 and TiO 2 are the major chemical species of the barite. The Ba and SO 4 content vary between 53.62 – 56.10 wt% and 27.57 – 39.35 wt% respectively across the sampled areas. The specific gravity is 4.45 and this combined with high BaSO 4 (approximately 94 wt%) shows that the mineralization is of high industrial quality and compares favourably with the Azara barite deposits of the Benue Trough. The quality of the barite meets American Petroleum institute (API) requirements for use as drilling mud.

The effects of forest land use and fragmentation on White-throated Mountain Babblers &lt;i&gt;Kupeornis gilberti&lt;/i&gt; a globally threatened bird species on the Obudu Plateau, southeast Nigeria

The effects of forest land use and fragmentation on White-throated Mountain Babblers &lt;i&gt;Kupeornis gilberti&lt;/i&gt; a globally threatened bird species on the Obudu Plateau, southeast Nigeria

Breeding phenology and moult of the endemic Bannerman's Weaver Ploceus bannermani

The breeding phenology and moult cycle of the vulnerable and range-restricted Bannerman's Weaver Ploceus bannermani was studied on the Obudu Plateau in the eastern region of Nigeria. The peak breeding season was between August and October; a major cause of breeding failure was egg predation by children. The estimated start date of moult for the average bird was 21 August (SD 39.2 d), with 95% of birds starting moult between 11 June and 30 October, estimated duration of moult was 159 d (SD 7.1 d), and the estimated end date of moult was 27 February. Our results indicate there is an overlap between breeding and moult.

Geochemistry of Schists of Northwest Obudu Plateau, Southeastern Nigeria

Precambrian, highly foliated, fine – medium grained schists, which comprise migmatitic schist (MS), quartz mica schist (QMS), biotite mica schist (BMS) and hornblende biotite schist (HBS) constitute important lithological unit in Northwest Obudu Plateau. The schists are associated with gneisses, amphibolites and metaquartzites, and variously intruded by granites, pegmatites and quartzo-feldspathic veins. Sedimentary rocks, which are mostly Cretaceous sandstones, flank the western margin of the study area. Modal analysis shows that all the schists are enriched in quartz, plagioclase (An32), biotite and garnet, except the HBS which is relatively depleted in quartz but highly enriched in biotite (25 vol. %) and hornblende (55 vol. %). Sillimanite and epidote occur in accessory amounts. The co-existence of quartz- plagioclase (An32)- garnet-biotite- muscovite- sillimanite in the MS assemblage indicates that the Schists are derivatives of metamorphism of pelitic and mafic rocks, which had attained the uppermost amphibolite facies grade. Geochemically, the schists are enriched in Si02, which ranges from 60.11 wt % in the HBS, rising to 62.94 wt % in the BMS and 66.58 wt % in the QMS, with average of 64.56 wt %. The high SiO2 content points to a probable effect of an intruding granitic magma on the Pan – African schists. The Al2O3, Fe2O3, MgO, CaO and alkalies are relatively moderate to high. The samples are quartz normative, have high molecular value of Al2O3 &gt; {CaO + Na2O + K2O}. Plots in chemical discrimination diagrams confirm the peraluminous characteristics of the schist and suggest pelitic rock protolith except for the HBS.Keywords: Petrochemistry, Obudu Plateau, Protolith, Metapelite, Precambrian, Uppermost Amphibolite Facies

Petrologic and Structural Features of Basement Rocks of Parts of Mukuru Area, Southeastern Nigeria

Field investigations in the western part of Mukuru area indicate intense structural imprints and high HT/HP metamorphism, and some magmatism. The rock units in the area include migmatitic gneisses, granulites, amphibolites, schists, charnockites, epidiorites and granites. The charnockites which are common in the shear zone and boundary areas appear to mark the end of magmatism. However, relicts of magmatic rocks mapped at Ubong Community in the study area suggest earlier magmatism. The metamorphic rocks are strongly deformed in a N-S to NE-SW direction with ghost structures, pinch and swell structures, ptygmatic veins, showing evidence of extensional tectonics. No visible contact relationship between the migmatitic gneisses and schists was observed. Diagnostic metamorphic structures like fine banding/layering of alternating dark- and light-coloured layers are conspicuous in gneisses and some amphibolites while schistosity and deep weathering are present in schists. The geodynamic features prevalent in Mukuru area are deformation and metamorphism. They indicate a possible petrogenetic link to southern Obudu Plateau in the north, western Cameroon in the east than Bansara in the west.

Single zircon evaporation ages: Evidence for the Mesoproterozoic crust in the southeastern Nigerian basement complex

The Ukwortung area of the Obudu Plateau exposes high-grade metamorphic rocks of upper amphibolite to granulite facies. Zircon grains from three locations of Southwest Obudu Plateau were dated by the Pb-Pb dating method. This single zircon radiometric dating method confirms the occurrence of Mesoproterozoic crust in the southeastern Nigeria basement complex. The pyroxene gneiss (granulite facies) sample from Biereberi near Ukpe yielded a mean age of 2061.4±0.4 Ma, suggesting the presence of Paleoproterozoic crust. The combined 207Pb/206Pb ratios from the garnet-biotite gneiss in the area gave a mean age of 1794.4±0.4 Ma. This further confirms the presence of Paleoproterozoic crustal components within the Obudu Plateau. The Mesoproterozoic (1548.8±0.5 Ma) and Neoproterozoic (619.8±0.9 Ma) ages were obtained from two populations of zircon grains from the leucogranite in Okordem, Southwest Obudu. These “signatures” collaborate the occurrence of Mesoproterozoic ages in the Afar region and Cameroon basements along with the southeastern Nigerian basement complex, constituting the major portion of the West Central African mobile belt. The zircon age of 1794.4±0.4 Ma may probably be the maximum depositional age of the meta-sediment (garnet-biotite gneiss) and the age of 1548.8±0.5 Ma may be interpreted as the time of emplacement of the granitoid. The Neoproterozoic age (619.8±0.9 Ma) probably records the metamorphic event that was prevalent during the Pan-African period and thus affected the area.

The stopover behaviour of the Garden Warbler Sylvia borin in Obudu, southeast Nigeria

The Garden Warbler breeds in the Palaearctic and migrates to sub-Saharan Africa for the non-breeding season. We studied its passage, body mass and moult at the Obudu Plateau in southeast Nigeria in October–December 2005 and December 2007–January 2008. In Nigeria, Garden Warblers in the Guinea savanna have been shown to increase body mass in October–November, preparing for migration to wintering sites further south. They begin to arrive at Obudu from mid-October and the numbers gradually increase with time; median date of passage was 3 December. This influx is clearly different from that which has been recorded for other sites in West Africa. The patterns in wing length and size-corrected body mass of individuals suggest a difference in the migration time of individuals of different sizes in the two years. Average fuel loads were lower at Obudu than has been reported in Central Nigeria. This, and the capture of moulting individuals, suggests that Garden Warblers may not embark on a longer journey southwards in mid winter, and possibly may even winter at Obudu.

A New Puddle Frog (Phrynobatrachidae: Phrynobatrachus) from the Obudu Plateau In Eastern Nigeria

A new species of puddle frog (Phrynobatrachus) is described from the Obudu Plateau in Cross River State of eastern Nigeria. The new species is distinguished from Phrynobatrachus species that are either closely related or occur in Nigeria or nearby countries by the combination of its larger body size (larger than the closely related P. chukuchuku, P. danko, P. manengoubensis, and P. werneri) and more extensive degree of development of male traits such as the nuptial pad and gular spines. The new species is also distinguished by a pale or white line along the anterior edge of the supratympanic skin ridge. A molecular phylogenetic analysis reveals that this morphologically distinct taxon is conspecific with a juvenile specimen from the Obudu Plateau previously referred to as P. werneri, and that this new species forms a clade with three other small species from the mountains of Cameroon and Nigeria (P. danko, P. werneri, and P. manengoubensis). The description of this species adds to the diversity of amphibian species of the Obudu Plateau, many of which have disjunct distributions with other populations located in the mountains of neighboring Cameroon.

Petrology and major element geochemistry of high-K peraluminous granites in southeast Obudu plateau, southeastern Nigeria

Petrology and major element geochemistry of high-K peraluminous granites in southeast Obudu plateau, southeastern Nigeria

Chemical characteristics of ground water from parts of the Basement Complex of Oban massif &amp; Obudu plateau, SE Nigeria.

Groundwater samples from 29 boreholes in the Basement areas of Obudu and Oban in Cross Rivers State have been analyzed for their major, minor and trace element constituents and some physical characteristics. The results are evaluated with a view to determining its quality and potability. The Ca2+, Mg2+, − 3 NO , 2− 4 SO and Cl– concentration levels of 0.8 – 69.2mg/l, 0.8 – 22mg/l, 0.02 – 1.7mg/l, 0.3 – 22mg/l and 0.3 – 22mg/l respectively, for the water samples are lower than the WHO recommended highest desirable levels of 75, 50 and 200mg/l respectively. Total Iron and Mn2+ concentration are 0.02 – 1.6 and 0 – 0.66mg/l respectively. All the water samples, with the exception of some from Okodi and Sankwala for total Iron and Anineje for Mn2+ have their concentration levels below the WHO maximum permissible levels of 1.0mg/l and 0.5mg/l. The total hardness (as CaCO3) concentration levels of 10 – 220mg/l are in most cases higher than the WHO maximum permissible levels (of 500mg/l). The pH (5. 0 – 7.5) with the exception of those obtained from Sankwala, fall within the maximum permissible levels of 6.5 – 9.2 units. Generally, these chemical characteristics compare well with those of the groundwater from other basement areas but differ in many respects from those from sedimentary terrains. The water is of good quality and therefore potable. Keywords: Basement area, concentration level, permissible levels, potable.