Detailed fieldwork in parts of the Benin (Dahomey) Basin SW, Nigeria has allowed the recognition of sedimentary successions deposited in different continental depositional environments interpreted as fluvial sedimenta...Detailed fieldwork in parts of the Benin (Dahomey) Basin SW, Nigeria has allowed the recognition of sedimentary successions deposited in different continental depositional environments interpreted as fluvial sedimentation characterised by abandoned channels and subaerial exposure features. The lithofacies recognised are: conglomerates, debris flow deposits, very coarse grained sandstone, ferruginous cross bedded sandstone, siltstone, shale/clay and massive sand. The lithofacies were interpreted in terms of sequence stratigraphic elements with the recognition of sequence boundaries characterised by distinct facies dislocations and subaerial exposures. Four depositional sequences (DS I to DS IV) were identified. Depositional sequences (DS I) exhibited a complete regressive–transgressive cycle comprising LST, TST and HST, while DS II to DS IV were incomplete comprising of sediments interpreted as LST deposits. On the basis of the depositional facies and sequence stratigraphic elements, the sediments in the area of study are interpreted as predominantly of Ilaro Formation while fewer exposures are sediments of the Coastal Plain Sands/ Benin Formation. This observation suggests a re-interpretation of the Tertiary sedimentary successions, which hitherto recognised all the sediments in the area of study as Coastal Plain Sands.展开更多
In this paper, a collection of statistical correlation methods is used in the study of aquifer potentials in Abia State of south-eastern Nigeria. The Physiology, geomorphology and hydrogeology of the area are first pr...In this paper, a collection of statistical correlation methods is used in the study of aquifer potentials in Abia State of south-eastern Nigeria. The Physiology, geomorphology and hydrogeology of the area are first presented. Sixty-six Vertical Electrical Sounding (VES) data sets are used to determine the aquifer. Demographic studies are then carried out in 220 communities in order to determine the relationship between population size on one hand and a unit draw-down of wells due to groundwater abstraction on the other. The relationship between geological Formation, aquifer potentials and depth of boreholes are then calculated using Pearson’s correlation matrix. Results show that the mean population of persons appears to be higher in Bende-Ameki Formation (of Eocene-Oligocene age) and the late Tetiary-Early Quaternary Coastal Plain Sands, than in the Cretaceous shale Formation of Asata Nkporo. The mean population of persons sitting on these Formations is 31,200, 18,370 and 5400 respectively. Furthermore, it is observed that a population increase of about 50 persons in a community in Abia State is accompanied by a unit volume (1 m3) draw-down of wells due to groundwater abstraction. It is therefore concluded that population size is positively correlated with groundwater abstraction, aquifer potentials and geological Formation favouring aquifer in Abia State.展开更多
文摘Detailed fieldwork in parts of the Benin (Dahomey) Basin SW, Nigeria has allowed the recognition of sedimentary successions deposited in different continental depositional environments interpreted as fluvial sedimentation characterised by abandoned channels and subaerial exposure features. The lithofacies recognised are: conglomerates, debris flow deposits, very coarse grained sandstone, ferruginous cross bedded sandstone, siltstone, shale/clay and massive sand. The lithofacies were interpreted in terms of sequence stratigraphic elements with the recognition of sequence boundaries characterised by distinct facies dislocations and subaerial exposures. Four depositional sequences (DS I to DS IV) were identified. Depositional sequences (DS I) exhibited a complete regressive–transgressive cycle comprising LST, TST and HST, while DS II to DS IV were incomplete comprising of sediments interpreted as LST deposits. On the basis of the depositional facies and sequence stratigraphic elements, the sediments in the area of study are interpreted as predominantly of Ilaro Formation while fewer exposures are sediments of the Coastal Plain Sands/ Benin Formation. This observation suggests a re-interpretation of the Tertiary sedimentary successions, which hitherto recognised all the sediments in the area of study as Coastal Plain Sands.
文摘In this paper, a collection of statistical correlation methods is used in the study of aquifer potentials in Abia State of south-eastern Nigeria. The Physiology, geomorphology and hydrogeology of the area are first presented. Sixty-six Vertical Electrical Sounding (VES) data sets are used to determine the aquifer. Demographic studies are then carried out in 220 communities in order to determine the relationship between population size on one hand and a unit draw-down of wells due to groundwater abstraction on the other. The relationship between geological Formation, aquifer potentials and depth of boreholes are then calculated using Pearson’s correlation matrix. Results show that the mean population of persons appears to be higher in Bende-Ameki Formation (of Eocene-Oligocene age) and the late Tetiary-Early Quaternary Coastal Plain Sands, than in the Cretaceous shale Formation of Asata Nkporo. The mean population of persons sitting on these Formations is 31,200, 18,370 and 5400 respectively. Furthermore, it is observed that a population increase of about 50 persons in a community in Abia State is accompanied by a unit volume (1 m3) draw-down of wells due to groundwater abstraction. It is therefore concluded that population size is positively correlated with groundwater abstraction, aquifer potentials and geological Formation favouring aquifer in Abia State.
