scholarly journals Occurrence of some campanian-maastrichtian organic-walled microfossils from Enugu Shale, Anambra Basin, Southeastern nigeria: Implications for age and paleoenvironments

2021 ◽  
Vol 19 (1) ◽  
pp. 133-143
Author(s):  
Okechukwu Nicodemus Ikegwuonu ◽  
Osita Igwebuike Chiaghanam ◽  
Nnamdi Enock Nwakoby ◽  
Emmanuel Ude Aniwetalu ◽  
Kingsley Chukwuebuka Chiadikobi
Keyword(s):  
Conventional Method ◽  
Brackish Water ◽  
Laboratory Examination ◽  
Tree Fern ◽  
Southeastern Nigeria ◽  
Field Mapping ◽  
Anambra Basin ◽  
Environmental Value ◽  
Equable Climate ◽  
Depositional Setting

Detailed geological field mapping and sampling of the Enugu Formation in the Anambra Basin has been carried out in order to re-examine the age of sediments and reconstruct their paleoenvironments of deposition. A total of ten (10) outcrop samples of shale were subjected  to palynological laboratory examination, using conventional method of acid demineralization and maceration techniques for recovering acid-insoluble organic-walled microfossils from sediments. Two main lithological units were distinguished: - carbonaceous fissile shale and siltstone. A late Campanian - Earliest Maastrichtian age was assigned based on index palynomorphs marker taxa Longapertites   marginatus (overwhelming abundance), Monocolpites marginatus, Zlivisporis blanensis, and Echitriporites trianguliformis. The age designation was strengthened by the occurrence of a well-known stratigraphic age-diagnostic organic-walled microplankton Coronifera tubulosa, Senegalinium spp. and Andalusiella polymorpha. Palynomorphs of environmental value include Cyathidites minor, (a tree fern of wet, forested, tropical to temperate regions, usually most developed in mountainous / highland terrains under moist and equable climate); Spinizonocolpites baculatus/echinatus, Longapertites marginatus, Mauritidites crassibaculatus and Moncolpites marginatus, which are palm pollen that inhabit similar brackish water as the mangrove. A non-marine to marginal marine depositional setting has therefore been proposed for the Enugu Formation.

scholarly journals Geochemical Appraisal of the Mamu Shales Exposed around Igodor in the Benin Flank of the Anambra Basin, Nigeria

2020 ◽  
Vol 24 (3) ◽  
pp. 489-493
Author(s):  
M.E. Okiotor ◽  
E.J. Ighodaro
Keyword(s):  
Inductively Coupled Plasma ◽  
Mineralogical Composition ◽  
Field Studies ◽  
X Ray Diffraction ◽  
Inductively Coupled ◽  
Anambra Basin ◽  
Icp Ms ◽  
Edo State ◽  
Depositional Setting ◽  
Representative Samples

The Auchi area of Edo state which lies within the Benin flank of the Anambra Basin host shaly sediment exposures that have been classified by  previous researches as units of the Mamu Formation. This study evaluated samples of this sediment from Igodor near Auchi for its geochemical and  mineralogical properties, and intereted its, depositional environment and geotectonic setting. In order to achieve this, field studies were  carried out and representative samples obtained for Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) analyses of major oxides, trace and rare earth elements. X-Ray Diffraction analysis was also carried out to determine the mineralogical composition. Some of the minerals determined were Aragonite and galena. Binary plots, triplots and elemental ratio plots including SiO2/, Al2O3, Th/Sc, Th/Co and La/Sc , Th-Sc-Zr, and the abundance of Cr, Ni were employed to determine the provenance. The concentration of detrital indicators such as SiO2, Al2O3 and TiO2, with averages of 51.95, 25.34 and 1.39 respectively, indicate high detrital influx into the Benin Flank of the Anambra basin. SiO2/Al2O3 ratios of 1.80-2.20, indicate that the shales were made up of pure kaolinite. The Ni and Cr abundance indicated a mafic and felsic provenance for the sediments, however, Th/Sc, Th/Co and La/Sc ratios show that the provenance was predominantly felsic, while the Th-Sc-Zr triplot shows that the depositional setting was passive.

scholarly journals Use of Geochemical Fossils as Indicators of Thermal Maturation: An Example from the Anambra Basin, Southeastern Nigeria

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Olumuyiwa Adedotun Odundun
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Land Plant ◽  
Source Rocks ◽  
Chemical Compositions ◽  
Organic Input ◽  
Southeastern Nigeria ◽  
Anambra Basin ◽  
Subsurface Sediments ◽  
Geochemical Studies

Organic geochemical studies and fossil molecules distribution results have been employed in characterizing subsurface sediments from some sections of Anambra Basin, southeastern Nigeria. The total organic carbon (TOC) and soluble organic matter (SOM) are in the range of 1.61 to 69.51 wt% and 250.1 to 4095.2 ppm, respectively, implying that the source rocks are moderately to fairly rich in organic matter. Based on data of the paper, the organic matter is interpreted as Type III (gas prone) with little oil. The geochemical fossils and chemical compositions suggest immature to marginally mature status for the sediments, with methyl phenanthrene index (MPI-1) and methyl dibenzothiopene ratio (MDR) showing ranges of 0.14–0.76 and 0.99–4.21, respectively. The abundance of 1,2,5-TMN (Trimethyl naphthalene) in the sediments suggests a significant land plant contribution to the organic matter. The pristane/phytane ratio values of 7.2–8.9 also point to terrestrial organic input under oxic conditions. However, the presence of C27 to C29 steranes and diasteranes indicates mixed sources—marine and terrigenous—with prospects to generate both oil and gas.

scholarly journals Geology and Geotechnical Investigations of the Anambra Basin, Southeastern Nigeria: Implication for Gully Erosion Hazards

2021 ◽  
Author(s):  
Azuka Ocheli ◽  
Ovie Benjamin Ogbe ◽  
Godwin Okumagbe Aigbadon
Keyword(s):  
Mean Value ◽  
Gully Erosion ◽  
Plasticity Index ◽  
Sand Content ◽  
Southeastern Nigeria ◽  
Average Value ◽  
Compaction Test ◽  
Silt Content ◽  
Anambra Basin ◽  
Geotechnical Investigations

Abstract BackgroundGeologic and geotechnical conditions of soils where Nanka and Ajali Formations outcropped in Anambra Basin, Southeastern Nigeria were investigated and accessed. This was done using detailed mapping and mechanical soil laboratory tests to unravel the genesis and continued expansion of gully erosion in the study areas. ResultsField study revealed that gully erosions are more pronounced in the study area with poor vegetation cover and a high degree of slope steepness. Grain size analysis revealed that the soils of the Nanka Formation have an average sand content value of 90.90% (sandy) and silt content value of 3.0% (low fine portions). The plasticity index of the fine portions indicates that the soils are weak plastic, with a mean value of 5.29%. The soils have an average cohesion value of 0.30kg/cm2 indicating a very weak cohesion. The soils are highly permeable; with an average value of 2.67x10-3 cm/sec. The compaction test further revealed that the soils are loosely compacted. The soils for the Ajali Formation have an average sand content value of 95.10% (sandy) and silt content value of 1.43% (low fine portions). The plasticity index of the fine portions indicates that the soils are weak plastic, with a mean value of 2.70%. The soils have an average cohesion value of 0.30kg/cm2 indicating a very weak cohesion. The soils are highly permeable; with an average value of 2.70x10-3 cm/sec. The compaction test revealed that the soils are loosely compacted.ConclusionsAfter field surveys and laboratory analyses, it was found that the gully erosions have been developing respectively on steep slopes and non-vegetated areas, and their genesis facilitated by the cohesionless and very permeable nature of the sandy formations. Following those key findings, it was proposed many practices (agronomic and engineering mainly) that can help mitigate the formations as well as the expansion of this very damaging hazard type. The potential implications of these gully erosion include damaging of buildings, residential houses, bridges and roads, loss of farmland and vegetation, isolation of villages and towns, increased migration of inhabitants as well as degradation of agricultural fertile land.

Geochemical Characteristics of the Campano-Maastrictian Sediments of the Anambra Basin, Southeastern Nigeria - Implication For Provenance, Paleodepositional Environment, Maturity and Tectonic Setting

2021 ◽  
Author(s):  
Michael Edirin Okiotor ◽  
EDeh Desiree Ogueh
Keyword(s):  
Inductively Coupled Plasma ◽  
Tectonic Setting ◽  
Passive Margin ◽  
Source Rocks ◽  
Sediment Provenance ◽  
Southeastern Nigeria ◽  
Inductively Coupled ◽  
Anambra Basin ◽  
Plasma Mass Spectrometry ◽  
Chemical Index Of Alteration

Abstract The present study investigates the Anambra Basin shales to determine the provenance and maturity of the sediments using standard geochemical techniques. Twelve (12) representative samples recovered from shale sequences of The Mamu Formation and Nkporo Group of The Anambra Basin were studied to determine the sediment provenance, paleoenvironment, diagenetic conditions, maturity as well as the tectonic setting. To consider in detail and establish the inherent constituents of the Major minerals, Trace and Rare Earth elements, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses techniques was employed. The detrital minerals determined are Al2O3 (18.27% and 21.16%), TiO2 (1.73% and 1.63%) and Fe2O3 (2.78% \ and 2.85%), for Nkporo Group and Mamu Formation respectively. The enrichment of SiO2, Al2O3 and TiO2 (1.14, 1.94, 3.67 respectively) supported by Chemical Index of Alteration (CIA) of 93.54 & 39.55 and Rb/Sr ratio of 0.57 & 0.40, indicate that the Anambra Basin sediments are matured. TiO2/AL2O3 binary plots, Th/Co Vs La/Sc crossplots, Th-Sc-Zr triplots and Cr, Ni concentration suggest mixed provenance of felsic to mafic source rocks for these sediments. From the log (K2O/Na2O) Vs SiO2 crossplots, a passive margin tectonic setting was determined for these sediments.

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