Patti Formation Research Articles

Micropaleontology and inorganic geochemical studies of the Campanian-maastricthian shale sediments in the Anambra and southern Bida basins Nigeria: Implication for provenance and paleoenvironment

The Micropaleontology and Inorganic Geochemical analysis were carried out on the shales of Enugu and Patti Formations (Anambra and Southern Bida Basins) deposited during the Campanian-Maastrichtian time interval to evaluate the connectivity of the paleo-sea depositional environment and sediments source. The method of analysis employed includes field sampling of two exposed sections of the formations and laboratories analyses which includes foraminiferal studies, Xray Fluorescence spectrometry (XRF) and Xray diffraction analysis (XRD). 30 selected shale samples were used for these analyses. The lithologic sections presented shows similarities in the reconstructed visible layers of sediment by the exposed sections in the two formations. The foraminiferal analysis revealed abundance of Benthic species depicting a shallow marine environment for the deposition of the sediments. The Benthic species recovered includes, Ammobaculite coprolithiformis, Ammobaculites exiguus, Ammobaculites strathearnensis, Ammobaculoides parvus, Ammomarginulina cf. A. curvature, Bolivina afra, Eponides sp, Haplophragmoides bauchensis, Haplophragmoides bausa, Haplophragmoides saheliense, Lenticulina cultrataspecies, Miliammina petila, Nonionella robusta, Praebulimina bantu, Textularia hockleyensis and Textularia parvula. The XRF analysis results of the selected shale samples of the two formations revealed SiO2 as the dominant oxide (Average Enugu-87.06 wt % and Patti-62.42 wt %). The Al2O3/TiO2 ratios in the two formations suggests that source rocks of these formations are likely to be transitioning from mafic to intermediate rock composition. Plot of SiO2/Zr display positive correlation in the shale of the Patti Formation to indicate lack of biogenic silica while showing negative correlation in that of Enugu Formation suggesting favorable environment for biotic life. Also, the plots of TiO2/Zr and TiO2/Al2O3 described both formations as intermediate rock composition for provenance. The plot of V/Ni revealed both formations as marine anoxic paleoenvironments. The Xray diffraction analysis reveals abundance of quartz and small amount of accessory minerals like goethite, kaolinite, smectite, mica, anatase, siderite and calcite.

Outcrops as windows to petroleum systems: Insights from the southern Bida Basin, Nigeria

The study assessed petroleum systems in the southern Bida Basin, Nigeria, focusing on the Cretaceous sediments. Reservoirs comprise Lokoja and Patti Formation sandstones, while shales, claystone, and siltstone serve as source rocks and stratigraphic traps/seals. Detailed studies delineating the key elements of the petroleum systems in the basin have not been conducted due to a lack of subsurface data. The goal of the current study was to use field observations, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and geochemical and geomechanical data to evaluate key components of petroleum systems in the southern Bida Basin. The results presented in this investigation are intended to attain specific objectives, especially those lacking in the basin's study sections. Petrophysical analysis revealed that the Lokoja Sandstone has porosity of 37%–39.5% and moderate permeability of 23.22–42.29 mD. The Patti Formation sandstone reservoirs exhibited high porosity (38%–42%) and moderate to good permeability (31.54–66.48 mD), suggesting good potential reservoirs. SEM results revealed intragranular pores and micro-fractures in the Patti Shale, whereas the sandstone reservoirs in the Lokoja and Patti formations displayed fractures, facilitating hydrocarbon migration. Quartz was the dominant mineral in the sandstone units of both formations. XRD analysis revealed that brittle and clay minerals influenced the microstructure of Patti Shale. Geochemical analysis indicated promising petroleum potential in the Patti Shale, with a total organic carbon (TOC) content of 1.87 wt%, free hydrocarbon from kerogen (S1) of 0.41 mg/g, hydrogen index (HI) of 0.75 mg HC/g TOC, and production index (PI) of 0.17. The Patti and Lokoja formations' shale, claystone, and siltstone exhibited sealing potential, with a plasticity index of 24–35 and coefficient permeability of 2.8 × 10−4- 3.6 × 10−4 cm/s. Field studies, XRD, geochemical data, and geomechanical index values have confirmed the key components of the petroleum system, which in turn facilitate hydrocarbon generation, migration, accumulation, and entrapment in the basin.

Application of Vertical Electrical Sounding (VES) for the Determination of Water-Bearing Zone in Karaworo, Lokoja Kogi State, Nigeria

The importance of water in our various communities and the difficulties faced so far to get good and clean water for both domestic consumption and industrial purposes can never be overemphasized. For these purposes to be accomplished, it is necessary to survey the area of study to know more about the geology of the area, which is characterized by the Lokoja Formation, Patti Formation, and Agbaja Ironstone and the possible reasons why there is a lack of water in the area. The geoelectric survey was conducted at Karaworo with the objective of determining the sedimentary formation's geoelectrical features and analyzing the potential of the groundwater in the study area. The most frequently used type of array for Vertical Electrical Sounding (VES) is the Schlumberger array, which needs a lot of space at both ends to yield deeper subsurface information. The Schlumberger configuration was used for data acquisition. About fifteen (15) VES points were acquired at different locations within the study area. For the different VES positions, the maximum AB/2 is within 100m to 180m. Partial curve matching was used to determine the layer parameters as part of the quantitative interpretation of the VES curves. The IP2WIN software was used in the final data analysis. The depth sounding interpretation revealed subsurface layers which comprises of topsoil/clay with a resistivity range between 1.42 ohm-m to 81.0ohm-m and a thickness of 0.253 m to 70.4 m, lateritic clay with a resistivity range between 01.06ohm-m to 1730 ohm-m and a thickness of 0.236 m to 19.2 m, siltstone with resistivity range between 0.423 ohm-m to 5069 ohm-m and a thickness of 4.09 m to 28 m and sandstone with resistivity range between 0.664 ohm-m to 137 ohm-m with the thickness at infinity. Sandstone constituted the aquiferous zone. In conclusion, different types of curves which include HA-type, H-type, KH-type, QH-type and HAK-type characterize the area and hence it is suggested that boreholes be placed in low resistivity zones and considerable depth and thickness as revealed in VES 4 and VES 8 but those with low resistivity without considerable depth, for example, VES 2, VES 5, VES 6, VES 7, etc. can be developed into a hand dug well.

Revised stratigraphic sequence and type sections of the Southern Bida Basin, Nigeria

A reassessment of the stratigraphy of the Southern Bida Basin has been attempted among various disagreements. For this work, field geological mapping and stratigraphic descriptions of exposed lithologic types on outcrop sections were used. Section-by-section descriptions of important outcrops based on field observations aided in identifying lithologic units and delineating the boundaries of the sub-basin's three formations (Lokoja, Ahoko, and Agbaja). The type sections for formations in the sub-basin were not properly erected, so Jones (1958) type section has been supplemented by a more comprehensive hypostratotype, and the name Patti Formation, which is considered a misnomer in this context, has been replaced with Ahoko Formation proposed by Rahaman et al. (2019). Ahoko village is the type locality. The Agbaja Plateau, where the Agbaja Formation is best exposed, has been presented as the lectostratotype for the formation, while the revised stratigraphic succession of the Lokoja region shows the Lokoja Formation directly encompassing the Paleozoic Basement terrain, with the Maastrichtian Agbaja and Ahoko Formations (former Patti) overlying it sequentially.

Empirical modelling of geotechnical strength based on index properties: a case of patti formation, southern bida basin, nigeria

The strength properties of geo-materials are paramount to the stability or otherwise of civil engineering structures. However, the determination of some of these properties such as California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) is costly and time-consuming. This necessitates the generation of models that can quickly predict the strength properties from cost-effective and less time-consuming index properties of the same geo-materials. In this study, an attempt has been made to predict the CBR and UCS values from Atterberg limit tests for sediments derived from Patti Formation, Southern Bida Basin, Nigeria. The tests were performed following appropriate codes of the British Standard Method for testing materials. Both linear and polynomial fitting models were employed for regression analysis between the index and strength parameters. The results showed that Liquid Limit (LL), Plastic Limit (PL), and Shrinkage Limit (SL) are strongly correlated with UCS and CBR, having R2 ranging from 0.8-0.91. The equations can be used to quickly predict UCS and CBR in areas with similar geology. Similar studies are recommended in other parts of the country to aid the regional evolution of models for rapid strength characterization of geo-materials.

Facies, textural and geochemical evaluation of the post-Santonian sandstones in the Bida basin, Nigeria: Implications for control on hydrocarbon sandstone reservoir characteristics and paleoenvironments

Using a combination of field observations, textural analysis, scanning electron microscopy (SEM), mineralogical X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and thin-section analysis, the hydrocarbon and paleoenvironmental characteristics of the Cretaceous sandstones of the southern Bida Basin, Nigeria, were evaluated. SEM data were used to display the mineral morphology, degree of cementation and presence of clay minerals on the grain surfaces and their pores on both sandstones of the Patti and Lokoja formations. The lithofacies analyses revealed three distinct facies associations. The XRD data showed that for the Lokoja and Patti sandstone reservoirs contained quartz from 49 to 67% and 43–68%, respectively. The XRF data also showed that both formations' sandstone reservoirs have a high percentage of silicon and low aluminum content. The grain size study showed that the Lokoja sandstone reservoirs include medium-coarse sandstone (−0.63 to 1.30 ф) that are poorly-moderately sorted (0.72–1.82 ф). In contrast, the Patti Formation is primarily made up of fine-medium sandstones at investigated outcrops, which typically display reasonably good to poor sorting (0.70–2.53 ф). The skewness of the sandstone reservoirs ranged from fine to coarse, and their kurtosis ranged from very platykurtic to leptokurtic. The research area's predominant depositional environments include shoreface/foreshore, estuary mudflat, and estuarine delta with fluvial interference, according to an analysis that combined sedimentary facies and textural data. This demonstrates that the sandstones from the two units have moderate quality prospective hydrocarbon reservoirs based on their physical and chemical characteristics.

Source Area Weathering and Tectonic History Inferred from the Geochemistry of the Maastrichtian Sandstone from Patti Formation, Southern Bida Basin, North Central Nigeria

Sandstones sampled from Patti Formation, Southern Bida Basin, were studied geochemically using Inductively Coupled Plasma Atomic Emission Spectrophotometer (ICP-AES) and an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique to evaluate their weathering and tectonic setting as well as to deduce the paleo-climatic conditions that existed during their deposition. Geochemically, SiO2 range from 73.9% to 86.2%, Al2O3 (6.7%~17.1%), Fe2O3 (1.1%~1.9%), K2O (0.1%~0.7%) while MgO, CaO, Na2O, P2O5, MnO and TiO2 were <1%. Enriched in Ba (Av. 622.94), Sr (Av. 153.63), Rb (Av. 55.08) and Zr (Av. 51.86) relatively similar in composition to UCC. High SiO2 but low other major oxides signify high mobility during processes of weathering. This was confirmed by high value (>80%) for indices like chemical index of alteration, chemical index of weathering, plagioclase index of alteration, mineralogical index of alteration and relatively lower values for weathering index of parker, recently used alpha indices (αAl E) of sodium (326.17αΑl Na<344.40), magnesium (100.54αΑl mg<398.55), calcium (12.07αΑl Ca<198.99), potassium (4.43αΑl K<64.33), strontium (0.84αΑl E<21.40), barium (0.45 αΑl Ba<10.52) and rubidium (0.0008αΑl Rb<0.06), supported by AI2O3-(CaO*+Na2O)-K2O and CIA vs. SiO2 plots that imply intense weathering in the source area. The obtained high CIA values (>80) indicates a steady-state of weathering under a warm/humid climate as confirmed by the SiO2 vs. Al2O3+ K2O + Na2O plot. High average SiO2 (75.41wt%) with K2O/Na2O ratio >1 (15.63), low Fe2O3 (1.27wt %), Al2O3 (15.82wt%) and TiO2 (0.46) suggest passive margin tectonic setting. This is supported by enriched ΣREE (209.64 ppm), ΣLREE (195.78), LREE/HREE (27.78) and negative Eu/Eu* (0.68), plots of log (K2O/Na2O) vs. SiO2 and SiO2/Al2O3 vs. K2O/Na2O. Major elements discriminant-function multi-dimensional diagram, DF1 (arcrift-col) vs. DF2 (arc-rift-col), for high-silica sediments revealed a continental rift tectonic setting. Thus, the Patti Formation sandstone underwent a high degree of weathering under a humid climatic condition within a continental rift tectonic setting.

Sedimentary facies and textural characteristics of Cretaceous sandstones in the southern Bida Basin, Nigeria: Implication for reservoir potential and depositional environment

A study of sedimentary facies, mineral and textural characteristics of sections of conglomerates/pebbles and sandstone facies found within the Lokoja and Patti Formations in southern Bida Basin, Nigeria, is carried out to evaluate the paleo-environment and reservoir quality of the sandstones of the formations through field observations and textural and mineralogical (using X-Ray Diffractogram) analyses. Nine lithofacies are identified and grouped into three main facies associations. These sedimentary facies suggest deposition in both foreshore and estuaries. The mineral analysis (XRD) shows that the quartz content in sandstone facies of the Lokoja Formation ranges between 49% and 67%, and that of the Patti Sandstone between 43% and 56%, indicating a quartz dominance. The granulometric studies reveal that the Lokoja Formation comprises coarse-to medium-grained (−0.63 to 1.30 φ) sandstone with moderate-poor sorting of 0.72–1.82 φ. On the other hand, medium to fine-grained sandstones dominate the Patti Formation, which is averagely poorly sorted (1.29–1.54 φ). The sandstones are coarsely skewed to finely skewed, with the kurtosis ranging from very platykurtic to leptokurtic. Morphological results of the pebbles from both Lokoja and Patti Formations indicate that the study areas are mainly characterized by the interplay of both wave and fluvial processes, which suggests that the environment of deposition of sandstone facies is predominantly of the fluvial to the shallow marine environment with the indication of tidal influence.Integrating sedimentary facies and textural results suggests subtidal sand ridge/foreshore, estuarine mudflat, and estuarine delta environments with fluvial influences. Evidence from the textural and mineral characteristics indicate that the sandstone facies of the Lokoja and Patti Formations are fairly matured and can act as potential hydrocarbon reservoirs in the formations. The facies, XRD mineral, and textural results have revealed potential hydrocarbon reservoir areas and paleo-depositional features of the Lokoja and Patti Formations.

X- Ray Diffraction Studies of Patti Claystone Member of the Campano-Maastrichtian Patti Formation, Southern Bida Basin, North Central Nigeria

X-ray diffraction and field studies were carried out on the Patti Clay Member of the Patti Formation in the southern Bida Basin. The studies involved field collection of samples and XRD laboratory analysis of clay samples in order to determine the dominant clay type, subordinate associated minerals, geologic processes and paleoenvironment of deposition. Field study involved standard litho-description by noting textural properties, facies type, fossil presence, structure and diagenetic effect. Laboratory XRD analysis procedure included sample grinding, XRD recording condition, selection and measurement of reference minerals, quantification of clay minerals using XRD processing software, XPert-Highscore Plus to generate results indicating clay mineral type and other minerals peaks. Lithostratigraphic section is dominated by the alternation of sandstone and claystone layers. The sedimentary structures are planar parallel and cross bedding in nature. The sandstone at Ahoko and along Lokoja-Abuja highway is characterized by liesegang ring and bioturbation structures. XRD results indicated that the Patti Clay Members are dominated by kaolinite with subordinate illite, montmorillonite and zincite in rare cases. The clay members were suggested to be deposited by moderate to low energy of transportation, moderate to low rate of deposition through prograding mechanism in a marginal marine setting. The kaolinite clay was formed by meteoric water reaction with the shallow-seated clay members through leaching of K+, Na+ and silica ions with resultant kaolinite stable at adequate pH that was not acidic.

Mineralogical studies of the Maastrichtian Gerinya Claystone of the Patti Formation, southern Bida Basin, Nigeria: Implication for industrial application

Abstract The mineralogical compositions of the Gerinya claystone, Patti Formation, Southern Bida Basin, Nigeria, were investigated to infer their sedimentological process and industrial application. Mineralogical analysis of the claystone was carried out using the X-ray diffraction (XRD) method. The diffractogram peaks aided the identification of the clay and non-clay minerals in the study area. The XRD showed kaolinite as the major clay mineral with compositions ranging from 10.8 - 67.6 wt%. The non-clay minerals were quartz, anatase, diopside, goethite, hematite, rutile, muscovite and micro-cline. Among the non-clay minerals, quartz had the highest percentage mineralogical composition of 21.2 to 83.4 wt%. The mineral assemblage is typical of a hot and humid climate where chemical alteration and hydrolysis of silicate minerals are severe. The sediments are of mafic and felsic crystalline rocks origin. The sediments are of low energy floodplain/interchannel depositional environment. The Gerinya claystone vary from low to high porosity and very low to low permeability. The claystone can be used as clay liners and as raw material for ceramic production. The application of the claystones in fertiliser production will require some processing. The clay-stone can be used for haemorrhage control in the pharmacological/medical sector. Although, the ingestion of the clay-stones could lead to dental damage and possible perforation of the sigmoid colon in the gastrointestinal tract.

Geochemical evaluation of Campanian-Maastritchian clay-shale sediments of Patti formation, Southern Bida and Mamu Formation, northern Anambra basins

Two basins (Southern Bida and Northern Anambra Basins) were investigated to deduce weathering, paleooxygenation, provenance, depositional environment and tectonic setting, as well as to establish a relationship between the two basins. The obtained high values of calculated weathering indices such as Chemical index of alteration (CIA > 90), Chemical Index of Weathering (CIW > 90), Plagioclase Index of Alteration (PIA > 90) and the Al2O3-(CaO + Na2O)-K2O ternary relationship for the clay – shale sediments from both basins indicate intense weathering in the source area. Important geochemical ratios such as V/Cr, Cu/Zn, Ni/Co, (Cu+Mo)/Zn, revealed predominantly oxic conditions for the clay – shale sediments from both basins, although, a more reducing or an anoxic condition cannot be ruled out for the clay – shale sediments from the Southern Bida basin due to high ratios of U/Th (1.93-5.67) and Cu/Zn (0.19-5.00). In addition, the Sr/Ba ratios (0.16–3.50) for the clay-shales from the Southern Bida basin indicated an alternated marine and continental paleo-depositional settings and only continental setting (Sr/Ba ratios = 0.22 – 0.50) for the Northern Anambra basin. The Th/Sc, La/Sc, Th/Co and the LREE/HREE ratios showed a derivation of the shale and clay deposits from similar felsic-rich source rock while the log of (K2O/Na2O) vs SiO2, revealed a Passive Margin tectonic setting for the two Basins. There is insignificant differences between the geochemical classifications, weathering, source rock/provenance and tectonic settings of clay-shale sediments of both sedimentary basins, however, there exist slight disparity in their salinity conditions and redox settings.
 Keywords: Geochemistry, Clay-shale, Provenance, Tectonic Setting, Northern Anambra and Southern Bida Basins

Genesis and paleoenvironmental analysis of the ironstone facies of the Maastrichtian Patti Formation, Bida Basin, Nigeria

The recently constructed Lokoja-Abuja highway and a quarry which cut through the Patti Formation, provided opportunity for the field study and sampling of the exposed ironstone interbeds within the carbonaceous shales and clays in Ahoko-Idu axis of the southern Bida Basin, Nigeria. The origin and paleoenvironmental significance of the ferruginous intervals were examined in this paper. Investigation reveals that the ferruginous bands occur as three lithofacies comprising of laminated, bioturbated and spheroidal concretionary facies. The primary components and depositional features of the host shales (detrital minerals, wood and herbaceous fragments, laminations) are largely preserved in the ironstones indicating compositional similarity and therefore a diagenetic origin for the ironstones. Results of XRD reveal substantial amount of siderite and illite but minor amounts of kaolinite, hematite, calcite and magnetite. Major elements such as Fe2O3, SiO2, Al2O3, CaO, MgO and P2O5 range from 41.50 to 54.60%, 6.10–23.30%, 3.64–7.00%, 1.40–13.60%, 0.30–1.20% and 0.10–8.80% respectively. The current data is suggestive that kaolinite was diagenetically replaced by siderite at early stage of burial in a reducing environment. Migrating pore water, probably enriched with alkali metals like Ca and Mg, sourced from sea water in the depositional basin and abundance of organic matter in the primary sediments are interpreted to be part of the factors responsible for the siderite precipitation. Both the host shale and the ferruginous beds contain significant amount of MgO, CaO, relics of dissolved bioclasts and body fossils. The geochemical proxies combined with the presence of magnesian siderite in the ironstones indicate that the host shales were deposited in marine environment with occasional freshwater influence. The study concludes that the ironstones are marine to non-marine, sideritic and diagenetic. The laminated and fossiliferous ironstone facies was deposited at the peak of marine transgression during the Upper Cretaceous time and represents maximum flooding surface. Shallowing up and regression into fresh water swamp condition was marked by the occurrence of freshwater sideritic ironstone.

The response to the rebuttal on the revised stratigraphy of the Bida Basin, Nigeria: New observations.

The late Cretaceous Bida Basin lithostratigraphy was carried out in order to establish a correlation between the northern (Bida area) and the southern part (Lokoja area) of the basin. The detailed fieldwork carried out over four years involved field description and mapping of outcrops in the entire basin. The study showed that the basin is underlain by mainly continental sedimentary rocks with minor occurrence of marginal/shallow marine to freshwater flood-plain deposits. The basin fill is characterised mostly by several cycles of amalgamated and/or stacked alluvial fans of the Bida/Lokoja Formation directly overlying the Basement Complex. The study revealed that the Lokoja/Bida Sandstone is overlain directly by the oolitic/pisolitic ironstone of the Agbaja/Sakpe Formations, which, in turn, is succeeded by fine to medium grained, grey and white sandstones, siltstones, grey clays, carbonaceous silts and shales, and ubiquitous concretionary ironstone bands of the Patti/Enagi Formation. Given the current detailed investigation, this study suggests that contrary to the rebuttal published, the Agbaja Ironstone is not the youngest formation in the basin. This study further revealed that the sequence of rocks and fossils used to define the Patti Formation and its probable age do not exist on Mount Patti in Lokoja, rather they are found along excavated road sections, quarries and boreholes around the Ahoko Village. Based on the detailed field work and sedimentological investigations, this study hereby proposes that the name ‘Patti Formation’ be changed to ‘Ahoko Formation’.

Geotechnical and Mineralogical Appraisal of Shale and Claystone Facies of the Maastrichtian Patti Formation, Bida Basin, Nigeria

The need for construction materials in the rapidly developing areas around Federal Capital Territory, Abuja, Nigeria cannot be overemphasized and this study was undertaken in line with this need. The study area, located about 60km from Abuja, is underlain predominantly by shales and claystones of the Patti Formation. These argillaceous rocks may offer locally sourced construction material if they meet certain specifications, however to date, there has not been a geotechnical study of these rocks. The geotechnical properties and the mineralogy of the shale and claystone were investigated to evaluate their suitability for civil engineering works. Particle size distribution, Atterberg limits and X-ray diffraction analyses were performed on fifteen shale and claystone samples collected from three localities (along an approximately 25km transect) for determination of their geotechnical properties and mineralogical composition. Mineralogical data obtained show the samples are dominated by kaolinite with minor amount of montmorillonite. Quartz and minor amounts of microcline, rutile and anatase dominate the non-clay mineral fraction. Particle size data indicate high proportion of fines and they are well graded. The Atterberg limits indicate that the samples have average values of liquid limit of 51%, plastic limit of 23%, plasticity index of 29% and shrinkage limit of 13%. These indicate they are of medium compressibility, low to medium shrink/swell potential, marginal expansive rating and low permeability. High bulk specific gravity (average of 2.61) suggests the samples are inorganic and this is supported by the consistency limits values. Generally, the results indicate the shale and claystone can be useful as stabilizing materials in civil engineering works. In addition, the marginally expansive nature of the shale and claystone, low permeability and intermediate to high plasticity may make them suitable as road subgrade.Keywords— activity, Bida Basin, Gerinya, Kaolinite, plasticity, Patti Formation

Organic geochemical and palynological studies of the Maastrichtian source rock intervals in Bida Basin, Nigeria: implications for hydrocarbon prospectivity

The Patti Formation which consists of sandstone and shale offers the best potential source beds in the Bida Basin. This inland basin is one of the basins currently being tested for hydrocarbon prospectivity in Nigeria. Fresh samples of shale from Agbaja borehole, Ahoko quarry and Geheku road cut were analysed using organic geochemical and palynological techniques to unravel their age, paleoecology, palynofacies and source bed hydrocarbon potential. Palynological data suggest Maastrichtian age for the sediments based on the abundance of microfloral assemblage; Retidiporites magdalenensis, Echitriporites trianguliformis and Buttinia andreevi. Dinocysts belonging to the Spiniferites, Deflandrea and Dinogymnium genera from some of the analysed intervals are indicative of freshwater swamp and normal sea conditions. Palynological evidence further suggests mangrove paleovegetation and humid climate. Relatively high total organic carbon TOC (0.77–8.95 wt%) was obtained for the shales which implies substantial concentration of organic matter in the source beds. Hydrocarbon source rock potential ranges from 0.19 to 0.70 mgHC/g.rock except for a certain source rock interval in the Agbaja borehole with high yield of 25.18 mgHC/g.rock. This interval also presents exceptionally high HI of 274 mgHC/g.TOC and moderate amount of amorphous organic matter. The data suggests that in spite of the favourable organic matter quantity, the thermal maturity is low as indicated by vitrinite reflectance and Tmax (0.46 to 0.48 Ro% and 413 to 475 °C, respectively). The hydrocarbon extracts show abundance of odd number alkanes C27–C33, low sterane/hopane ratio and Pr/Ph > 2. We conclude that the source rocks were terrestrially derived under oxic condition and dominated by type III kerogen. Type II organic matter with oil and gas potential is a possibility in Agbaja area of Bida Basin. Thermal maturity is low and little, or no hydrocarbon has been generated from the source rocks.

A revised stratigraphy of the Bida Basin, Nigeria by Rahaman et al., (2019) [J. Afr. Earth Sci., 151, 67–81]: A rebuttal

This paper revisits the revised stratigraphy of the Bida Basin by Rahaman et al. (2019). We rebut their errors and misconceptions in proposing the Ahoko Shale as a formation and their assertion that it is younger than the Agbaja Ironstone Formation. Field evidence and palynological and geochemical data are provided in support of the widely accepted stratigraphic framework of the basin. The distinct sedimentological and petrographic features of the sandstone facies of the Lokoja (e.g., unidirectional cross stratification and compositional immaturity) and Patti (e.g. clay drapes, herringbone cross beddings and mineralogical maturity) formations discussed herein also support their different origins and depositional processes, and indicate that it is illogical and unacceptable to lump the sandstones together as Lokoja Formation. In view of the data provided, the elevation of the Ahoko Shale to a formation by Rahaman et al. (2019) is conjectural because their revision lacks field and analytical evidence.

Heavy Mineral Distribution in the Lokoja and Patti Formations, Southern Bida Basin, Nigeria: Implications for Provenance, Maturity and Transport History

Abstract Heavy mineral component of 13 samples from the Lokoja and Patti Formations, Bida Basin have been studied for their textural characteristics, compositional abundance, maturity and provenance determinations. The suite of heavy minerals encountered is classified as opaque and non-opaque constituents. The non-opaque components include zircon, tourmaline, rutile, garnet, staurolite, epidote, kyanite, titanite, lawsonite, cassiterite, sillimanite, hornblende, hypersthene and andalusite. The assemblage is generally dominated by zircon and tourmaline in the two formations. The constituent heavy minerals identified are dominated by ultra-stable and stable classes, whereas the ZTR indices indicate mineralogical immaturity coupled with textural immaturity of the constituent grains. This suggests the possible dominance of chemical weathering of the source rock. The suites of minerals recovered have been linked to both metamorphic and non-metamorphic crystalline rock origins.

Updates on the Geology and Potential Petroleum System of the Bida Basin in Central Nigeria

The Bida Basin is one of Nigeria’s inland frontier basins. The conventional stratigraphy of the Bida Basin has the Bida Formation at the base in the northern sector, followed successively upward by the Sakpe, Enagi, and Batati Formations. In the southern sector, the Lokoja Formation is at the base, followed by the Patti Formation and ending with the Agbaja Formation at the top. Detailed field mapping carried out in this study has not identified the Batati Formation at the previously assigned Type Locality at Batati village. A new formational name of “Pattishabakolo Formation” has been proposed. The Patti Formation is also not mappable at the previously assigned Type Locality of the Mount Patti in Lokoja but mappable at Gegu, Ahoko and midway on the Agbaja Plateau. A new Type Locality at Ahoko has been proposed. Sediment thicknesses in the Bida Basin are shallower at the margin and generally deepen towards the centresuch that the central portions constitute the most prospective areas. Geophysical aeromagnetic interpretation has assisted in the interpretation of the geology of the basin. Organic geochemical studies show that the Kudu Shale in the Northern Bida Basin equivalent to the Ahoko Shale in the Southern Bida Basin constitutes the source rocks in the potential petroleum system. With averages for source rock thickness of 40m, area of basin of 45,000km2, TOC of 9.0wt%, and HI of 220mgHC/gTOC, charge modeling indicates 623 million barrels of oil equivalent extractable hydrocarbons in the Bida Basin, at current knowledge and if the appropriate maturity has been attained at deeper sections. The Bida/Lokoja Formation sandstones as well as the well sorted sandstones in the Enagi Formation constitute potential reservoirs in the basin. Regional seals are provided by the clayey members of the Enagi and Batati Formations. Potential traps are both structural and stratigraphical.

Evaluation of aquifer hydraulic characteristics using geoelectrical sounding, pumping and laboratory tests: A case study of Lokoja and Patti Formations, Southern Bida Basin, Nigeria

AbstractThe hydraulic characteristics of aquifers in Lokoja and Patti Formations were investigated using combination of vertical electrical sounding (VES), pumping and laboratory tests. A total of 20 VES (10 each in areas underlain by Lokoja and Patti Formations) were carried out at different locations with 5 pumping tests around VES stations in order to determine the geoelectric layers, thickness, depths to water table and groundwater potential of the area. 21 samples extracted fromaquiferous units of surface outcrops were also subjected to laboratory constant head and falling head permeameter tests in order to determine hydraulic conductivity (K) values using the Darcy’s law of liquid flow. The results of VES for areas underlain by Lokoja and Patti Formations revealed 4-5 geo-electrical layers. The depths to water table vary from 5.91-40.8 m. Thickness values are within the range of 7.37-27.3 m for aquiferous units of Lokoja Formation, and 10.8-20.1 m for the Patti Formation. The results of aquifer characteristics using Dar-Zarrouk Parameter gave hydraulic conductivity (K) values between 1.92-91.7 m/day and 2.15-31.8 m/day for aquifers of Lokoja and Patti Formations respectively. Transmissivity (T) values of the aquiferous units of Lokoja Formation fall within 24.97-2117 m2/day, while those of Patti Formation vary from 27.9-456.91 m2/day. There is a strong correlation between the values of measured and calculated hydraulic conductivity and transmissivity between measured and calculated transmissivity for the five wells (R2 = 0.99 and 0.92, respectively). Based on the results obtained and interpretations proffered, aquiferous units in both formations are capable of yielding optimum groundwater for private consumption and partly to small communities, and to some extent can supply water for great regional use. It is suggested that similar study should be carried out in other sedimentary basins where to aid regional planning and management of groundwater resource.

Geochemical assessment of claystone deposits from the Patti Formation, Southern Bida Basin, Nigeria

Abstract Geochemical studies of claystone deposits from the Patti Formation in the southern Bida Basin, north-Central Nigeria, were carried out on representative samples to determine the basin’s depositional conditions, provenance and tectonic setting. The localities within the study area included Gegu, Ahoko, Ahoko-Etigi, Omu and Idu. Semi-quantitative phase analysis using the Rietveld method and X-ray powder diffraction data revealed that the claystone samples had prominent kaolinite with other constituents such as quartz, illite–muscovite, K-feldspar, pyrite, marcasite, anatase, rutile and gorceixite. Enrichment of Al2O3, Ba, Th, Sr, Cr and La suggests that these elements are primarily controlled by the dominant clay minerals. Geochemical parameters such as U, U/Th, Ni/Co, V/Cr and Cu/Zn ratios strongly implied that these claystones were deposited in an oxidising environment. Provenance deducing ratios for felsic, mafic and basic igneous rocks were compared. Al2O3/TiO2 ratio suggested intermediate to felsic rocks as the probable source rocks for the claystone samples; however, Y/Ni, Cr/V, La/Sc and Th/Sc ratios suggested a felsic progenitor. The tectonic discrimination diagram showed that the samples’ plot was within the region specified for passive margin-type tectonic setting.