Grain Size and Heavy Mineral Analyses of Two Boreholes in Recent to Miocene Aquifer in Benin Formation

Abstract

Recent studies have revealed that groundwater contamination is dependent on the porosity and permeability of the overlying and underlying bed rocks and the mineral composition of the aquifer geometry with respect to depth. This study became important due to several reports on groundwater contamination and in order to understand the mineral composition and the grain sizes of the aquifer in the study areas. Two boreholes were drilled 4.2km apart; one at Okabere and the other at Evbuabogun community both in Ikpoba-Okha Local Government Area of Edo State. The communities have been merged with the capital city as a result of urbanization and population growth. Grain size and heavy mineral analyses were carried out on the soil samples collected from the boreholes at an interval of 15ft. The results obtained indicate that the heavy minerals in Okabere borehole is dominated by Zircon, Tourmaline, Rutile, Biotite and Garnet while Evbuababegun borehole is mainly of Zircon, Kyanite, Rutile, Staurolite, Garnet and Tourmaline which indicate that the sediments were of igneous and metamorphic origin. Grain size analysis of both wells show that mean, inclusive standard deviation, skewness and kurtosis generally indicates very coarse sand to medium sand; very well sorted to moderately sorted and very platykurtic in nature. The foregoing revealed that the aquifer geometry of the study areas is unconfined and vulnerable to contamination. It is recommended that groundwater quality assessment study should be carried out in order to determine the potability of the groundwater bodies.

Litho-stratigraphic and hydrogeological evaluation of groundwater system in parts of Benin Metropolis, Benin City Nigeria: The key to groundwater sustainability

“…From the map, groundwater flow from north-west to south-east as indicated by the arrows on the groundwater flow map. (Omorogieva, 2016) The SWL observed in the study areas correspond with earlier work of Akujieze and Oteze (2007) which put the SWL in Benin on an average of 60m.…”

“…The aquifer becomes shallower towards Okhuahe indicating proximity to sea water level (SWL). Omorogieva et al, (2016); Isikhuemen and Omorogieva (2015a); Iyasele and Idiata (2012) demonstrated that shallow aquifers are subject to contamination especially when it lacks seal materials as clay to protect the groundwater. Consequently, shallow aquifer particularly those close to anthropogenic activities have often been reported with poor water quality.…”

“…Consequently, shallow aquifer particularly those close to anthropogenic activities have often been reported with poor water quality. Imasuen et al, (2016) observed that sediments in some parts of Benin are porous and highly permeable and therefore make the groundwater vulnerable to contamination. This observation was not in contradiction to the current study especial in Okhuahe and Ikhueniro axis of the study.…”

“…Omorogieva et al, (2016); Akujieze and Oteze (2007) observed that some aquifer are shallow and subject to groundwater contamination especially in areas of high anthropogenic activities were there is no clay materials acting as seal to the infiltrating contaminants while Onyeobi and Akujieze (2014) reported that soil and sediments have a role to play in groundwater contamination. Imasuen et al, (2016) observed that sediments within Benin metropolis is of Miocene to Recent in age and are rich in accessary minerals like Tomaline, Zircon, Kynite, Rutile, Staurolite and Garrnet which indicate that the parents material is igneous and metamorphic origin. It was observed that in that report that the grain size is coarse to medium sand very well sorted to moderately sort.…”

“…The current study is aimed at characterizing the lithology of the soil by drilling boreholes randomly across the study areas; determine the static water level and groundwater flow direction. The study is highly significant because Omorogieva et al, (2016); reported that some aquifer in some parts of the study area are shallow and consequently impacted with the contaminants contained in the percolating leachates from a nearby dumpsite within the locales. The study will be valuable to local drillers and government in making policy gear towards environmental sustainability and groundwater protection for sustainable development.…”