Sedimentological and palynostratigraphical modeling of sediments penetrated by KW field wells, onshore western Niger Delta Basin, Nigeria.

Sedimentological and palynostratigraphical studies were performed on 189 ditch-cutting samples composited at 50 ft intervals from four well sections located in KW field, onshore western Niger Delta Basin, Nigeria, using sieving and visual microscopic observations, hydrochloric and hydrofluoric acids digestion methods to determine their lithological character and palynologic content of the sedimentary successions. The basis of these data is to interpret the lithofacies and biostratigraphy, establish the age of the strata, establish the palynological zones and infer the environments of deposition. Five lithofacies delineated based on the sedimentological study were very coarse sand, coarse to fine sand, shaly sand, muddy sand, and sandy to silty shale. The age of the sedimentary successions ranges from Early Miocene to Pliocene based on the bio-assemblages of these key species. The Early Miocene age is characterized by the occurrence of Magnastriatites howardi, Psilatricolporites triangularis, Praedapollis africanus, Pachydermites diederixi, Spirosyncoilpites spiralis, Praedapollis flexibility, Racemonocolpites hians, Verrutricolporites rotundiporus, Verrutricolporites microporus, and Psilatricolporites divisus. The Middle Miocene age is characterized by the FAD of Crassoretitriletes vanraadshooveni, the occurrence of Belskipollis elegans, in association with Striatricolporites catatumbus, Verrutricolporites rotundiporus, Verrutricolporites microporus, Crassoretitriletes vanraadshooveni, Racemonocolpites hians, Retibrevitricolpites obodoensis, and Retibrevitricolpites protrudens. The Late Miocene age is characterized by the occurrence of Multiareolites formosus, Cyperaceaepollis sp., Stereiosporites sp., Peregrinipollis nigericus, Gemmamonoporites sp. (Cleistopholis patens), Laevigatosporites sp., Verrutricolporites sp., Nymphaeapollis clarus, and Verrutricolporites usmensis. The Pliocene age is characterized by the basal occurrence of Retistephenocolpites gracilis in association with Nymphaeapollis clarus, Cyperaceaepollis sp., Laevigatosporites sp., Verrutricolporites sp., and Crassoretitriletes vanraadshooveni. The boundary between the Early Miocene and Middle Miocene from the studied oil well sections is marked by the first appearance datum (FAD) and numerical maximum occurrence of Striatricolporites catatumbus and Belskipollis elegans and FAD of Crassoretitrilettes vanraadshooveni. The boundary between the Middle and late Miocene is defined by the LAD of Verrutricolporites rotundiporus, the quantitative top and numerical maximum occurrence of Racemonocolpites hians, and the numerical maximum occurrence of Zonocostites ramonae. The boundary between the late Miocene and the Early Pliocene is marked by the first appearance datum (FAD) and the numerical maximum occurrence of Retistephenocolpites gracilis, the numerical maximum occurrence of Echiperiporites icacinoides, and the highest abundance of Monoporites annulatus. Four palynozones PAZ-1, PAZ-2, PAZ-3, and PAZ-4, and ten sub-zones were erected. Finally, Fluvial-coastal to shallow marine environments of deposition were inferred for the sedimentary successions using sedimentological study, nature of organic matter, and association of key environmentally-sensitive biomarker species.

Appraising the risk level of physicochemical and bacteriological twin contaminants of water resources in part of the western Niger Delta region.

This study was carried out to assess the physicochemical and bacteriological contaminants of surface, shallow well and municipal borehole waters in part of the western Niger Delta as a way of safeguarding public health against waterborne diseases. A total of 72 water samples collected from the study area were analysed and their results show that the pH average value ranges from 6.2 in the dry to 8.5 in the rainy seasons for surface water, 6.6 and 8.3 for shallow well water and 6.5 to 8.4 for borehole water. The turbidity in surface water varies from 8.1 to 26.2 Formazin Attenuation Unit (FAU), 0.3 to 2.9 FAU in shallow well water and 0.4 to 4.8 FAU in borehole water. Electrical conductivity (EC) value varies from 1010 to 1840 µs/cm for surface water, 201 to 950 µs/cm for shallow well water and 670 to 1650 µs/cm for borehole water. Total dissolved solids range from 0.1 to 2.6 mg/l in surface water, 0.2 to 4.1 mg/l in shallow well water and 0.3 to 4.4 mg/l in borehole water. The value of the total hardness ranges from 44 to 120 mg in surface water, 46 to 96 mg in shallow well water and 70 to 130 mg in borehole water. The nitrate value ranges from 1.1 to 10.6 mg in surface water, 3.0 to 8.4 mg in shallow well water and 3.7 to 9.6 mg in borehole water. The value of sulphate content varies from 4.6 to 38.5 mg in surface water, 6.2 to 34.8 mg in shallow well water and 5.7 to 55.7 mg in borehole water. The value of phosphate concentrations in surface water varies from 1.0 to 9.0 mg, 0.7 to 3.4 mg in shallow well water and 1.0 to 4.7 mg in borehole water. The bacteriological analysis using the membrane filtration technique revealed the presence of faecal bacteria and total coliform counts. The presence of the analysed twin contaminants in the studied water resources reduced their water quality. The physicochemical and bacteriological data were subjected to statistical and correlation tests. It was concluded that their concentration levels were independent of intra-seasonal changes. The likely natural and artificial sources of contaminants are run-offs from fertilized lands, septic tanks, industrial discharges, sewage and waste disposal, algae blooms and erosion from natural deposits. The inherent risk is water-related diseases such as waterborne diseases, water-washed diseases, water-based diseases and diseases transmitted by water-related insect vectors. Water resources should be protected through proper sanitation systems, limiting of up-stream discharges, maintenance of wellheads, boiling and municipal water treatment plants. Educational advice should be given to the inhabitants on the dangers posed by continuous drinking of contaminated water. These measures will prevent disease outbreak and public health burden in the area.

Granulometric and pebble morphometric applications to Benin Flank sediments in western Anambra Basin, Nigeria: proxies for paleoenvironmental reconstruction.

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.