Earth Science

Extensive field and site investigations were conducted to assess and evaluate the situation in the presently exploited quarries of cement raw materials in Yemen. These quarries have several geological complications represented mainly by high elevations, steep slopes, rugged topography, heterogeneity in bed thickness, lithologic composition and quality, presence of igneous sills and dykes, intensive fracturing and jointing and abundance of karstification features. Moreover, the processes of quarrying and related operations have several negative environmental impacts the most important of which are soil failure, overburden and land sliding, toppling and rock falls (which result in considerable mass wasting) and emission of dust and noise. Generally, quarrying operations are more hazardous in quarries of gypsum and basement rocks than in those of carbonates and volcanics. Furthermore, the quarries have problems related to the conservation of natural resources. These are represented primarily by the excavation of the valuable agricultural and reclaimed lands and improper exploitation of the cement raw materials and the fresh and underground waters the reserves of which decreased drastically. To deal with the above-mentioned problems, a number of recommendations are outlined. They comprise mitigation measures which must be strictly implemented. Also, it is of almost importance to conduct prospecting for new occurrences of the presently exploited cement raw materials and their possible substitutes as well as additional groundwater resources.

Major ion geochemistry was used to characterize the chemical composition of the groundwater in the Accra Plains and to understand its geochemical evolution. Sodium and chloride were the dominant ions in the groundwater. The TDS values increase south eastwards through the central part of the Plains towards the coast. Three hydrochemicsl facies which evolves from Na-Mg-Ca-Cl-HCO3 to Na-Ca-Cl was identified using the Piper diagram and Chadha proposed rectangular plot. The R-mode factor analysis result show that three factors account for 83.65% of the total variance in the hydrochemistry. Interpretation of the hydrochemical data suggested that mineral (silicate) weathering, cation-exchange and reverse ion–exchange control the chemical composition of the groundwater. The thermodynamic plots indicate that the groundwater is in equilibrium with kaolinite and montmorillonite minerals. The saturation index also indicated that about 47% of the groundwater samples were oversaturated with respect to calcite and dolomite.

Geoelectrical sounding technique has been used to determine the groundwater potential zones in Anambra state, Nigeria. The study area is underlain by four main geological formations. A total of four hundred and fifty-two (452) vertical electrical sounding (VES) was acquired over one hundred (100) locations, employing the Schlumberger array configurations. Static water level (SWL) and yield of the aquiferous layer at various observation points were determined by pumping test fifty (50) borehole sites. The depth, thickness, lateral extent and resistivity of aquiferous horizon were determined by the electrical survey. Aquifer hydraulic properties were inferred using the empirical relationships. Interpreted VES data show predominance of A and K curve type, indicating dry overburden, underlain by wet/saturated horizon. Comparisons of geoelectric sections and borehole logs in a SW-NE direction show fairly good match, while correlation of geoelectric sections along SW-NE direction show variation in depth for the suspected aquiferous horizon. 2D maps of resistivity, depth, thickness, transverse resistance, longitudinal conductance, coefficient of anisotropy, aquifer transmissivity and hydraulic conductivity were constructed. High values of estimated aquifer transmissivity predominate, thus suggesting thick and prolific aquiferous zone. Groundwater flow direction is variable in the study area. Two potential groundwater zones were identified based on aquifer transmissivity potentials, interplay of apparent resistivity, thickness and coefficient of anisotropy. They are the moderate and high potential zones. The various contour maps and the groundwater potential zones map will serve as a useful guide for groundwater exploration and development in the study area. The developed physical transforms can be adapted to other areas with similar geologic setting.

The concentration and distribution of heavy metals (Cd, Pb, Cr, As, Ni, Zn, Fe and Cu) lead, in soils of Warri and environs were examined using Atomic Absorption Spectrophotometer, in the rainy and dry seasons. A total of forty-eight soil samples were collected from parks, commercial areas, main roadside, from residential areas, and from industrial areas, as well as from control sites. The range of mean heavy metal concentrations during the rainy season were: Pb: >0.01 – 0.21mg/kg, Cd: >0.01 – 0.01, Cr: >0.01 - 2.61, As: >0.01, Ni: >0.01 – 0.17, Cu: >0.01 – 7.21, Fe: 0.44 – 1348.66, and Zn: >0.01 – 21.12. The range of mean heavy metal concentrations during the dry season were: Pb: >0.01 – 1.11mg/kg, Cd: >0.01 – 5.92, Cr: >0.05 – 6.12, As: 0.001- 0.01, Ni: >0.01 – 0.34, Cu: >0.01 – 8.12, Fe: 0.87 – 1451.02, and Zn: >0.01 – 19.58.The mean concentrations of heavy metals obtained in all the soil samples in the study area showed an increasing order of As>Cd>Pb>Ni>Cr>Zn>Cu>Fe in both rainy and dry season. The concentrations of heavy metals studied in soil of all sites in dry season were slightly higher than those in the rainy season. Hierarchical cluster analysis (HCA) was employed in order to further ascertain the sources of heavy metal in soils of the study area, and it revealed that the heavy metals in all the sampled media had a common origin and were associated with anthropogenic activities in the study area. Pearson’s correlation of heavy metals in the samples showed strong relationships among metals suggesting a similar distribution pattern and a combination of natural and anthropogenic sources. Spatial distribution maps of the study area showed that patterns of heavy metals were associated with several factors which include industrial activities such as gas flaring, high traffic density, and the geology of the study area. While measured concentrations are within international limits, there is cause for concern since metal concentrations in the sediment and surface water samples were elevated near some indusrial areas. Therefore, regular monitoring of the soils is essential to prevent excessive build-up of the toxic heavy metals in the soils and water resources of the study area.

A palynological study of forty ditch-cutting samples from CHEV-2 well drilled offshore in the Niger Delta showed that the sediments were mainly deposited during the Miocene age. Palynological assemblage was dominated by pollen and spores with rare occurrence of dinoflagellate cysts. The stratigraphic ranges of Retitricolporites irregularis, Psilatricolporites crassus, Echitritricolporites spinosus, Zonocostites ramonae, Foveotricolporites crassiexius, Monoporites annulatus, Psilatricolporites operculatus, Multiareolites formosus, Podocarpus milanjianus and some other marker species were used to demarcate five informal palynogical zones in the study area.

This work employs geoelectrical method to evaluate the resistivity of subsurface materials, characterize the aquifer hydraulic properties and delineate potential groundwater zones at Mpu town and its environs, Enugu state, Nigeria. Mpu lies within latitudes 050 57’ 0’’ and 060 02’ 0’’ N and longitude 0070 40’ 0’’ and 0070 45’ 0’’E with area extent of 55.37square km. The study area is underlain by Awgu Shale, with its lateral arenaceous facie; Owelli Sandstone outcropping north of Oduma. Fifteen (15) vertical electrical soundings (VES) were carried out within the study area, using the Schlumberger electrode configuration. Interpreted VES data shows predominance of Q and H curve type, indicating a fractured – clay/shale subsurface. Georesistivity layers show a clay/shale - sandy shale - dry shale - fractured shale sequence. Contour maps of resistivity, thickness, overburden depth, transverse resistance, longitudinal conductance, aquifer transmissivity and hydraulic conductivity were constructed. Computed aquifer transmissivity show trends with good signals and recorded transmissivity value of 135m2/day. Thus, indicating moderate yield. Low yield areas correspond to high hydraulic conductivity zone. Low and moderate groundwater potential zones were delineated. Comparisons of georesistivity sections and various contour maps show fairly good match in analysis. The study will serve as a useful guide for groundwater development in the study area.

The activity concentrations of natural occurring radionuclides, uranium (²³⁸U), thorium (²³²Th), radium (²²⁶Ra) and potassium (⁴⁰K) were measured in geological samples collected from the Accra Plains using a high resolution hyper pure germanium (HPGe) detector. Their radiological parameters were also calculated. ²³⁸U concentration was found to vary from below detection limit to 363.5 Bq/kg. Activity concentration of ²³²Th varied from below detection limit to 370.41 Bq/kg. The activity concentration of ²²⁶Ra ranged from 4.04 Bq/kg to 295.01Bq/kg, whereas, the ⁴⁰K activity concentration varied from 145 Bq/kg to 2274.3 Bq/kg. The absorbed dose rates varied from 18.27 to 479.26 nGy/h. The annual external effective dose rates ranged from 0.02 to 0.51 mSv/y. The radium equivalent activity (Raeq) varied from 29.15 to 986.42 Bq/kg. Value of external hazard index (Hex) varied from 0.11 to 2.66. Good correlations existed between ²³²Th and ²²⁶Ra activity concentrations and the total activity concentration. The Th/U ratios obtained indicated metasomatic activity of the analyzed radionuclides. The gamma ray radiation hazards due to the radionuclides increased with depth. 

In this paper, to see the climate change on monsoon variability, the analysis of aerosol concentration, Global and surface air temperature over central Indian region and South West (SW) Monsoon season rainfall (June-September) variability have been study. For the study different set of data have been consider. The trend analysis of aerosol concentration and rainfall over different regions of India has been carried out for recent period 1981 to 2002. The analysis reveals that there is decreasing trend in aerosols concentrations and decreasing trend in West central monsoon rainfall goes hand in hand. To see the temperature effect in pre-monsoon months on monsoon variability the Principal component Analysis (PCA) technique is used. By using PCA the monthly temperature gradient series have been prepared. For analysis, the grid (1°*1°) point surface air temperature data taken from the Climate Research Unit (CRU) at the University of East Anglia is used. The analysis is carried out for 105 years 1901-2006. From the analysis it seen that the North South surface air temperature gradient in month of May over the central India can be useful for seasonal prediction of monsoon rainfall over the North East India. To see the global warming effect on rainfall, the analysis of global surface air temperature 125 (1880-2004) years of data have been used. It is found that during warming or cooling episodes, there is a general below-normal rainfall activity over almost all the homogeneous regions expects the CNEI and NEI.

Though major earthquake of large magnitude has not occurred in Nigeria from previous records, however, the incessant earth tremor currently being experienced within the central northern Nigeria basement complex whose cause is yet to be ascertained calls for concern. Hence, the need for site seismological evaluation and characterization becomes paramount before putting up structures. The aim of this research therefore is to carry out a detail seismic survey of the site under investigation, and determine among other factors, the velocity distribution, the overburden thickness, depth to aquifer, depth to weathered and fresh basement, which will be used to infer and evaluate the nature of Geological Hazards, Seismic shaking hazard, surface fault rupture hazard, ground lurching, liquefaction Hazard, water inundation and shrink swell potential of near-surface soil of the site. The results of the investigation revealed that the seismic wave velocity registered a general increase of velocity with depth, with velocity range of 990 m/s to 3340 m/s. The velocity distribution gave an indication that the site is majorly characterized by hard rocks which are of low elevation thereby ruling out the possibility of landslide in the event of seismic shaking from a remote earthquake. The seismic survey did not detect any obvious fracture or fault that will constitute geological hazard by acting as pathway for contaminant to move into the underground water, or that could engender major earthquake that will cause surface fault rupture hazard. The investigation also reveals that the soil is not predominantly loose sand and the groundwater is restricted to isolated aquifers, therefore the structure sited within this site will not heave or lurch in the event of any shaking because, the possibility of soil liquefaction is ruled out. It was also observed that since the near surface material is not predominantly clay but laterite, therefore the swell potential of the near surface soil will be infinitesimally small. The geological hazard analysis have revealed that the site under investigation is not prone to any geological hazards that could be induced by earthquake, faults, elevation depth to aquifer, and nature of soil.

A total of 60 composited ditch cutting samples from Koda-1 and Mar-1 wells from onshore and offshore areas of the western Niger Delta Basin were processed and analysed for the lithological, microfauna and microflora contents. Based on the microfaunal analysis, one informal planktonic foraminiferal namely Orbulina universa zone which corresponds to the N9 zone (Middle Miocene) and one informal benthonic biozone Amphistegina radiata zone with Bolivina striatula, Spiroloculina antilarum, Quinqueloculina stelligera and Bulimina elongata sub zones were established for Koda–1 well. An informal planktonic foraminiferal named Globorotalia margaritae zone which corresponds to N17-N19 (Late Miocene–Early Pliocene) was established for Mar-1 well while one informal benthonic biozone Cibicides refulgens zone with Lagena cantenulata, Quinqueloculina costata, Nonionina orbicularis and Planulina wuellerstorfi sub zones were established. The recovered benthonic foraminiferal assemblages and other microfauna accessories indicated that the sediments of the two wells were deposited in marginal to coastal marine (inner neritic, inner to middle neritic and middle neritic) environments. The paleotemperature of the sea was warm with normal salinity, based on the presence of tropical marine indicator species of Orbulina universa.