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Sphericity-form diagram of Sneed and Folk (1958), Sphericity-form plots of mean indices of the-3.5,-4.0,-4.5,-5.0-5.5 phi size classes for the five locations studied.
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The Benin Formation is well exposed along the Atamiri River, which traverses Uli town, in the Niger Delta Basin of Southeastern Nigeria. Lithologic sections were measured, described and sampled so as to decipher the paleodepositional environment, using an integration of lithofacies data, pebble morphology, grain size and paleocurrent analysis. The...
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Context 1
... ± 1.489, which is above the -1.5 minimum value required for pebbles formed in fluvial environments. Sneed and Folk [22] and Els [5] reported a significant decrease in sphericity of quartz pebbles with increasing size. The sphericity values listed in Table 4B -F, too appear to be following this pattern. Plots on the sphericity form diagram of [22] (Fig. 6) for the -3.5, -4.0. - 4.5, -5.0 and -5.5 phi size classes for the five locations studied indicate that the larger pebbles are generally more bladed than the smaller ones (Fig. 6).In summary, the study of form indices has shown that pebbles from the Benin Formation were shaped in the fluvial setting. The Sphericity form plots also ...
Context 2
... quartz pebbles with increasing size. The sphericity values listed in Table 4B -F, too appear to be following this pattern. Plots on the sphericity form diagram of [22] (Fig. 6) for the -3.5, -4.0. - 4.5, -5.0 and -5.5 phi size classes for the five locations studied indicate that the larger pebbles are generally more bladed than the smaller ones (Fig. 6).In summary, the study of form indices has shown that pebbles from the Benin Formation were shaped in the fluvial setting. The Sphericity form plots also indicate that sphericity decreases with increasing size. ...
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The East Asian monsoon is generally regarded to have initiated at the transition from the Late Oligocene to the Early Miocene. However, little is known about this process because of a lack of continuous strata across the boundary between the Late Oligocene and the Early Miocene in Asia. Based on previous drilling (core HZ-1) in the Miocene sediment...
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... En principio, se verifica a los conglomerados entre dos estratos de areniscas conglomerádicas. Esto se interpreta como alternancias de energías de sedimentación, con bancos de depósitos fluviales representados por las areniscas conglomerádicas (Odumodu, 2014) y sedimentos de alto flujo en sistemas fluviales entrelazados que depositaron a las capas de los conglomerados (González y Bartel, 1999). ...
Se ha reconocido la presencia de exposiciones de rocas del Paleozoico Inferior a orillas
del Río Paraguay, en la zona de Angostura. Las litologías observadas son conglomerados y areniscas conglomerádicas intercaladas entre sí, y se ajustan a las descripciones de la Formación Paraguari. En el presente trabajo se destacan estos afloramientros como una manifestación muy occidental de esta unidad geológica, en relación a los reportados anteriormente en otras localidades de Paraguay.
... Moreso, [8] studied the sandstone deposits of Ameki Formation, exposed in the northeastern part of Akwa Ibom State, and discovered from the granulometric analysis, that the deposits are moderate to poorly sorted, suggestive of fluvial origin. A paleogeographic model for the sandstone member of the Imo Shale was developed by [9] , which portrayed the sands to be texturally mature, fine to coarse-grained with characteristic large-scale cross-stratification. Grain size and textural analysis of sandstone packages of Benin Formation, exposed along Atamiri River showed that the sandstones were deposited in a fluvial depositional environment [10] . Pebble morphometric studies of Nanka Formation by [5] showed that the bivariate plots are indicative of reworked pebbles deposited by fluvial processes, and the form indices diagram which connotes bladed, compact-bladed, and platy, is diagnostic of river action. ...
... Studies from the pebble morphometric analyses of the pebbly sandstone of Ameki Formation by [8] showed that they were deposited in a fluvial environment. A pebble form studies of the pebbles from Benin Formation, exposed along Atamiri River by [10] , revealed that they were deposited in a fluvial environment. This present study is aimed at carrying out a detailed outcrop mapping and integrating the data obtained from granulometric and pebble morphometric analyses to better delineate the lithologic units and understand the paleodepositional environment that resulted in the deposition of the sediment packages. ...
Geological mapping and outcrop studies were carried out around the Uzuakoli-Ahaba axis located in Abia State, Southeastern Nigeria. The aim was to better understand the underlying lithologies and lithostratigraphic units. Detailed sedimentological logging was integrated with granulometric and pebble morphometric analyses in determining the paleodepositional environment of the sediment packages in the study area. Five lithologic units namely sandstone, shale, siltstone, heteroliths, and mudrock were identified within the study area. These lithologic units were exposed within four lithostratigraphic units that underlie the study area namely; the Imo Formation, Ameki Formation, Ajali Formation, and Nsukka Formation. Results from the granulometric analysis of six sandstone samples reveal that the mean size value is indicative of medium-grained to coarse-grained sandstone and suggestive of intermediate to high energy setting. Standard deviation and kurtosis suggest that the sediments are moderately sorted to poorly sorted. Log probability plots, bivariate and multivariate plots reveal fluvial to shallow marine environment. Results from the bivariate plots and Sphericity-Form diagram of pebble morphometry suggest that the pebbles were deposited in a beach dominated environment. Overall, based on the integration of the various plots, it can be concluded that the rock units were deposited in a fluctuating environment ranging from shallow marine to fluvial environment.
... The Ogwashi-Asaba Formation underlies the Benin Formation (Reyment, 1965, Study area Nwajide, 2013). The Benin Formation (Miocene to Recent) progrades unto the surface of the Anambra Basin (Odumodu, 2014). In these study four boreholes return-samples were systematically logged against depth. ...
Water is essential for human consumption and usage. The people of Igbariam-Achalla areas are yet to get access to 50liters of potable water daily. The area under study is underlain by the Imo Formation. The formation in the mapped area consists of thick series of clay shale interstepped with thin sand bodies and limestone lenses as revealed by borehole lithologs. Borehole drillings to depths of 350-530 meters within and around the study area have not been very successful due to the shally nature of the underlying lithologies. The costs to exploit these aquifers are high and locals can hardly afford it. Water-quality analysis results for the surface waters indicate the pH values to be 5.3 to 6.6. Turbidity values ranges from 2.9 to 5.9 mg/l, conductivity values obtained ranges from 180-300 µs/cm while total dissolved solids ranged between 120 to 160 mg/l. Chemical analysis of calcium determined is between 11.2 to 14.3 mg/l, sodium is from 6.3 to 13.6 mg/l and magnesium from 1.3 to 1.6 mg/l. The bicarbonate ion ranges from 20.3 to 83.6 mg/l while sulfate concentrations are 3.4 to 6.0 mg/l. No phosphorus or nitrate ions were detected from any of the sample. Microbial analysis results were positive for fecal and total coliform counts probably due to human and livestock pollution of the surface waters. The Physiochemical analyses present results that do conform to standards established by W.H.O and S.O.N for drinking water quality. A calcium-bicarbonate water type which is fresh and soft classifies the hydrogeochemical facies of the surface water found within the area. Alternative water supply sources are sought for. Hand-dug wells have been put in places but are yet to meet the water demand of the people. Rainfall harvesting has been proposed as an alternative source of water supply. Rainfall harvesting systems (surface and subsurface reservoir) which when properly constructed and maintained will address the water supply problem facing the people.
... In terms of morphometric characteristics of granule-sized sedimentary grains, the initial shape of the particles as they were liberated from their parent rock and the antecedent properties of the depositing medium determine their final geometry. Hence, they yield invaluable information about the energy conditions and the environment of deposition [36][37][38][39][40]. Essien et al. [6] endorsed the different unweathered quartz pebbles encountered in the South-East Nigeria to interpret the paleodepositional environment of the deposit. ...
Pebble morphometry of unbroken quartz pebbles collected from the basal section of Awi Formation exposed around Ewen area, southeastern Nigeria was studied for paleoenvironmental reconstruction. Paleoenvironmental analysis refers to the study or use of ancient geological materials (rocks) to infer the depositional environment or setting within which they were deposited. Pebble morphometric analysis has aided the determination of paleoenvironment during the deposition of Awi Formation. The depositional processes responsible for shaping the pebbles and the environment that prevailed during past geological times was characterised. This involved the measurement of the three orthogonal axes (long, intermediate and short), determination of their corresponding roundness, flatness indices and elongation indices for no less than 200 pebbles. The pebbles were selected from 20 points across four exposed sections of the Awi Formation around Ewen village. The roundness was determined using the standard roundness chart. The results show that the pebbles are sub-rounded to sub-angular and predominantly compact-bladed. The mean values for the following morphometric parameters: Flatness index, elongation ratio, maximum projection sphericity index and oblate-prolate (OP) index are 0.57, 0.78, 0.74 and 15.65 respectively. These values are in agreement with those of modern fluvial pebbles. This result was integrated with the deductions from bivariate plots of roundness against elongation ratio and sphericity against OP index, and they all inferred the deposition of the conglomeratic sandstones in a fluvial setting with subordinate transitional setting. Fluviatile process with some overlapping littoral influence has been shown to be responsible for the variation in clast morphology of the paraconglomerates (matrix-supported) of Awi Formation. Integrating all observations viz; the sediment stratification and grading style (fining upwards successions) and the dominant unidirectional nature of the crudely imbricate pebbles, a typical fluvial setting is inferred. It is possible that the jointing, faulting, sheeting and/or exfoliation of the rocks of the Oban Massif, which is believed to be the principal source of the sediments (provenance), also accounts for the abundance of vein quartz in the area which was eventually adapted for this study. Within sedimentary settings as this one with paraconglomerates associated with high energy flux during deposition and other typical channel lag deposits are locations of good economic deposits (placer deposits) and in some cases hydrocarbon accumulation. Therefore, besides the significance for pebble morphometry in deciphering paleoenvironments, it also gives clues for potential sites of ore bodies and/or characteristics of some targets for hydrocarbon pools. There are obviously several methods for paleoenvironmental reconstruction using sediments as earlier mentioned, grain morphology is one. However, care must be taken when reconstructing paleoenvironment because the shape of grains is a result of so many other factors and for effective utilisation, a careful study and integration of all other parameters are recommended.
... The Imo Formation, Ameki Group (Nanka Formation) and Ogwashi-Asaba and Benin Formations were deposited into the basin during Tertiary period [21][22][23][24][25]. The Benin Formation progrades unto the surface of Anambra Basin (Table 1) [26]. ...
... The Imo Formation, Ameki Group (Nanka Formation) and Ogwashi-Asaba and Benin Formations were deposited into the basin during Tertiary period [21][22][23][24][25]. The Benin Formation progrades unto the surface of Anambra Basin [26] (Table 1). ...
Lignite is the lowest rank of coal; its deposits found within the Paleogene Anambra Basin are Tertiary in age. They occur within the uppermost stratum of the Eocene Ameki Group, the Oligocene Ogwashi-Asaba Formation and the basal part of the Miocene Benin Formation. Energy is considered as one of the fundamental resources for industrialization. The current situation in Anambra State is that energy demand is greater than energy supply; this forms the basis of this research. Lignite can play an important role for power generation in Anambra State as a domestic resource that will be proximally available. Anambra State is enriched with substantial lignite deposits, but these deposits are currently under fire attack, which if not tackled will result in total loss of the deposits and unimaginable geologic hazards. The lignite seam fires were examined; the causes and possible solutions were documented. Strategies for sustainable exploitation and harnessment of this resource were also enumerated, which when properly implemented will solve the energy problem facing the State, thereby enhancing its socioeconomic status and also create opportunities for investments, employment and national development.
Keywords: Lignite seam fire; Paleogene Anambra Basin Ogwashi-
Asaba Formation; Anambra State; Power generation; National
development; Spontaneous combustion; Sustainable exploitation
... The Ameki Group is overlain by the Oligocene Ogwashi-Asaba Formation [1]. The Benin Formation (Miocene to Recent) prograde unto the surface of the Anambra Basin [17]. ...
The Eocene–Oligocene sand facies is well exposed around Osumenyi and Ukpor areas in the Anambra Basin of southeastern Nigeria. Outcrop sections were located, measured, described in detail and sampled so as to decipher the paleoenvironment of deposition, using an integration of sedimentary facies and grain size analyses. The sedimentary facies study suggests that the Eocene–Oligocene age in this area consist mainly of three facies association; sandstone, lignite and clay facies. The fine-grained sandstone sub-facies is indicative of shoreface, the medium grained sandstone sub-facies is indicative of estuarine, while the coarse-grained sandstone sub-facies suggests a fluvial environment. The lignite facies indicate a continental origin (swamp environment) while
the clay facies are interpreted as fluvially intercepted shallow marine environment. Results of grain-size analysis for the Eocene–Oligocene age show that the sands are medium grained, moderately to poorly sorted, very negatively to positively skewed and very
platykurtic to very leptokurtic. Bivariate plots of mean size against standard deviation and skewness against standard deviation support a fluvially dominated shallow marine environment with tidal crosscuts. Result of multivariate functions showed a fluvially
intercepted shallow marine environment. This study is significant in providing evidence for the reservoir potentials and aquifer characteristics of the Eocene – Oligocene sand facies for petroleum accumulation and prolific water bearing units within the basin.
Keywords: Eocene–Oligocene sand facies; Anambra Basin; Paleoenvironment; Grainsize analysis; Reservoir potentials; Petroleum accumulation
... The Ameki Group is overlain by the Oligocene Ogwashi-Asaba Formation [16]. The Benin Formation (Miocene to Recent) progrades unto the surface of the Anambra Basin [17]. ...
The Maastrichtian - Danian age is well exposed around the Owerre-Ezukala area in the Anambra Basin of southeastern
Nigeria. Two geologic units were encountered in the study area; Maastrichtian Ajali Formation and Danian Nsukka Formation.
Outcrop sections were located, measured and described in detail following standard field methods. Pebble beds were
sampled to evaluate their form indices which served as signatures of the paleoenvironment of deposition. The research
methodologies were standard methods used in pebble morphological analysis. A total of one hundred and thirty pebbles were
collected from three localities (Olo, Owerre–Ezukala and Ubaha). The following parameters were evaluated; Flatness Index
(FI), Oblate-Prolate Index (OPI), Pebble form and Maximum Projection Sphericity (MPS). The mean values of FI, OPI and
MPS (44.7%, -0.066, and 0.789 respectively), are suggestive of a fluvially agitated shallow marine environment (estuarine).
Bivariate scatter plots of FI versus MPS and MPS versus OPI suggest fluvio-estuarine environment. Plots made on sphericity-
form diagram suggest a transitional setting (probably fluvial to estuarine). The sedimentary facies analysis supports a fluvio-
estuarine setting for the Maastrichtian – Danian age.
Keywords:
Maastrichtian-Danian age; Anambra Basin; Ajali
Formation; Nsukka Formation; Pebble morphological analysis
... The second set of sediments (Mamu Formation, Ajali Sandstone and Nsukka Formation) was deposited during the Maastrichtian times (Murat, 1972;Kogbe, 1976;Nwajide, 1980;Agagu, Fayose and Petters, 1985). The third sequence were deposited during the Paleogene and Neogene times consisting of the Paleocene Imo Formation, Eocene Ameki Group comprising of Ameki Formation, Nanka Sands and Nsugbe Formation, Oligocene Ogwashi-Asaba Formation and the prograding Miocene Benin Formation (Nwajide, 2013;Odumodu, 2014). ...
Water is vital to life, ensures human survival and societal development. Its overdraft and harnessing can affect the environment adversely. This study evaluates the water resources and geotechnical properties of soils in Uga area, southeastern Nigeria. The study area lies in the rainforest zone where rainfall is extreme and thus boasts of high water resources potential. Comprehensive data are lacking for effective water planning purposes. This research work contributes to existing data on the water resources potentials of Uga and environs. Surface waters (Obiada River and Agwura Stream), springs (Nwagene, Obizi and Ogbei Springs) abound in the area. Nanka Sands which is a prolific water-bearing unit defines the underlying geology of the area. Flow rates of surface waters are high due to annual precipitation of 2500mm a year. Springs are clear. Nwangene Spring has a flow rate of 0.39 m/sec while Obizi spring has a flow rate of 0.04 m/sec. Borehole depth at Nanka and Oko is 380 meters and 314 meters respectively while static water level is 42 meters and 69 meters respectively. Huge sand deposits abound in the area. This research work highlighted the geotechnical properties of soils from the area. Cobble, pebble and gravel sized grains are absent. CBR values ranged from 30% to 35%. Highest MDD gave a value of 1-824gcm-3 with an OMC of 11%. The lowest MDD recorded a value of 1.622gcm-3 with an OMC of 8%. LI test conducted on one of the samples yielded a value of 16%. PL and PI tests gave zero values for all the samples. The geotechnical results implied that soils from the area are excellent to good reserves for sub-grade and sub-base materials respectively.
... Empty cells indicate that as not all the same parameters were analyzed for all samples. characzeristics Litty et al. (2017): river sands F. Ch. Odumodu (2014): pebbles from fluvial environments Panwar et al. (2017): river sediments from pre-, post-and monsoon periods ...
The particle size, shape, surface texture and composition of aeolian and fluvial sedimentary samples were analyzed and compared using optical microscope-based automatized image analysis, in order to suggest indicators that could discriminate these two modes of transport on Mars. The principal goal is to assess if such indicators – established on Earth – could be used on Mars thereby aiding interpretations on the origin of sediments analysed by the ExoMars 2020 rover during its mission. Wind and water transported sand from, respectively, the Sahara Desert and the Maros river bar in Hungary were investigated and treated as mainly aeolian and fluvial end-members. In addition, two Mars-analogue aeolian and fluvial basaltic sediments from Iceland were analysed similarly. Our analyses demonstrated that useful parameters for the distinction of aeolian and fluvial transport included the degree of sorting, the grain diameter/perimeter ratio, the circularity (reflecting the sphericity of the grains) and convexity (showing roughness of the grains) of particles. Mature aeolian sands are always well-sorted with high diameter/perimeter ratios since they are dominated by rounded grains. Differences were observed in both surface textures and the range of mineral compositions, wherein the aeolian samples reflect a more mature state. Separation of the two Icelandic samples with different origins was less straightforward due to both shorter transport distances and the fact that the fluvial sample was made of scoria, although the intermixing of grains with a probable aeolian origin could be also determined. The characteristics of grain size and shape parameters are potential indicators allowing the separation of the two transport modes, and their determination is shown to be feasible based on high resolution Close-UP Imager (CLUPI) observations. Nonetheless, knowledge of the geological context – for instance sedimentary facies, layering, sorting of the sediments and grain shape – is a requirement for proper interpretations. These sedimentary features could be party determined by MaMISS, CLUPI and PanCam observations. Differences between aeolian and fluvial grains are expected to be more pronounced on Mars than on Earth due to the episodic and likely short-term subaqueous transport, as opposed to the long-term activity of wind. However, future interpretations of the ExoMars 2020 rover images of martian sedimentary grains will be hampered by the limited knowledge of fluvial/aeolian transport on Mars. Based on our results, future research should focus on determining the dominant transport mode of any sediment and the degree of grain mixing, which strongly based on the transport mode.
... During sampling, deformed pebbles with distinct fresh breaks, flatness or clear primary elongation as well as those that show lithologic inhomogeneity were removed to ensure that the shapes obtained are true reflection of the environmental impact on the grains. The method of measurement was based on that described by Sneed and Folk (1958), adopted by Lutig (1962), Sames (1966), Dobkins and Folk (1970), Stratten (1974), Nwajide and Hoque (1982), Okoro (2012), and Odumodu (2014). ...
... Several workers have shown and proved that pebble morphometric parameters are very useful indicators in paleoenvironmental interpretations (Sneed and Folk 1958;Lutig 1962;Sames 1966;Dobkins and Folk 1970;Stratten 1974;Barrett 1980;Els 1988;Illenberger and Reddering 1993;Okoro et al. 2012b;Odumodu 2013 and2014). Dobkins and Folk (1970) carefully studied the pebbles shaped by fluvial (river) and marine (beach) process in Tahiti -Niu and concluded that pebble suites with mean MPSI of ≤ 0.65 indicates a beach process, while those > 0.65 indicate fluvial process. ...
Integrated granulometric and pebble morphometric study of Late Cretaceous rocks of the Benin Flank, Nigeria, were used to delineate depositional process and environment of the rocks in the study area. Granulometric analysis reveals that the sandstones of the Lokoja Bassange Formation have an average graphic mean (Mz) of 0.59Φ (coarse grains), inclusive graphic standard deviation (δi) of 1.36Φ (poorly sorted), graphic kurtosis (Ka) of 1.12Φ (leptokurtic), and inclusive graphic skewness (Ski) of − 0.14Φ (stongly coarse skewed). The sandstones for the Mamu Formation have an average Mz of 1.42Φ (medium grains), inclusive graphic standard deviation (δi) of 0.74Φ (moderately sorted), graphic kurtosis (Ka) of 1.43Φ (leptokurtic), and inclusive graphic skewness (Ski) of 0.02Φ (nearly symetrical). The sandstones for the Ajali Formation have an average Mz of 1.23Φ (medium grains), inclusive graphic standard deviation (δi) of 1.21Φ (poorly sorted), graphic kurtosis (Ka) of 1.46Φ (leptokurtic), and inclusive graphic skewness (Ski) of − 0.17Φ (nearly symetrical). Pebble morphometric analysis of the larger grains reveals that the mean values of elongation ratio (ER) = 0.69, coefficient of flatness (FI) = 54.90%, oblate–prolate index (OPI) = 3.34, the maximum projection sphericity index (MPSI) = 0.75, form = 0.67, and roundness (ρ) = 36.28% for the Lokoja Bassange Formation; ER = 0.76, FI = 37.07%, OPI = −3.20, the MPSI = 0.53, form = 0.38, and ρ = 52.93% for the Mamu Formation; and ER = 0.72, FI = 47.44%, OPI = 1.12, the MPSI = 0.67, form = 0.54 and ρ = 42.68% for the Ajali Formation. The integration of the various granulometric and pebble morphometric data, different bivariate and ternary plots indicate fluvial environment for the Lokoja Bassange Formation, dominantly shallow marine environment for the Mamu Formation and fluvial – shallow marine environment for the Ajali Formation. This study shows that the Benin Flank, western Anambra Basin has a depositional setting radiating between fluvial and shallow marine environments.
