Assessment of groundwater potential using geophysical data: a case study in parts of Cross River State, south-eastern Nigeria

Abstract

Groundwater potential of some parts of Cross River State, Nigeria, was assessed involving vertical electrical sounding (VES) and high-resolution aeromagnetic methods (HRAM). The VES and HRAM dataset were used to delineate the hydro-lithostratigraphic units and map the spatial distributions of geologic structures, respectively. The electro-stratigraphic sections revealed the various hydro-lithostratigraphic units composed of fractured/weathered crystalline basement, sandstones, siltstones, sandy shales, and highly baked and fractured shales occurring at different depths. Generally, the unsaturated top layer is composed of shales, marl, clay, silt, gravel and lateritic materials with resistivity ranging from ~ 3.0 to ~ 550 Ω m. This layer is underlain by various aquifer units like sandstones, siltstones, fractured shales and limestone/marl, and fractured/weathered basement occurring at different depths (~ 30 to ≤ 100 m) as revealed by the electro-stratigraphic sections obtained in the study area. In the Calabar Flank (CF), Oban Massif (OM) and Ikom-Mamfe Embayment (IME), the apparent resistivity for these hydro-lithostratigraphic units varied between ~ 8.50 and ~ 59.50 Ω m, ~ 120.2 and ~ 1562.6 Ω m and ~ 30.8 and ~ 277.2 Ω m, respectively. The enhanced total magnetic intensity maps and source parameter imaging result showed that the OM and IME are characterized by high concentration of short-wavelength anomalies, while the CF is dominated by relatively undisturbed thick sedimentation (~ 6217 m). HRAM results show that such areas are predominated by geologic structures like faults, fractures, fissure, dyke swamps, etc. caused by tectonics. Such geologic structures create secondary porosity and enhance permeability. From all the results obtained, OM and IME represent areas with moderate groundwater potential. The CF dominated by argillites with no significant tectonic activity is observed to have low groundwater potential.

Implications of tectonic anomalies from potential field data in some parts of Southeast Nigeria

“…11 and 12) areas respectively. These geologic structures related to the Santonian Abakaliki Anticlinorium (Ekwok et al, 2020a) and Quaternary-Recent Cameroun Volcanic Line (Akpan et al, 2014) caused extensive uplifts, faulting, fracturing and baking of sedimentary series (Ekwok et al, 2020b;Arinze et al, 2019;Oha et al, 2016) in these locations and adjoining areas. Fig.…”

“…The intensity, localization, features of hydrothermal mineralization plus the direction and character of groundwater migration are controlled by faults, fractures, fissures etc. (Ekwok et al, 2020a;Ekwok et al, 2020b). The enhanced use of geologic concepts and geophysical investigations in a completely integrated programs have been successful in the determination of buried geologic structures and location of new mineral deposits (Woakes et al, 1987).…”

“…Gravity anomalies can reveal the subsurface form of igneous intrusions (Bott et al, 1958), locate sedimentary basins, and provide important information on mechanisms of basin formation (Kearey et al, 2002). However, it can also be employed in engineering and archaeological investigations (Kearey et al, 2002), hydrogeological search (Ekwok et al, 2020b;Van Overmeeren 1975) and as a follow-up technique applied on a targets well-defined by electromagnetic and magnetic anomalies in joint base-metal explorations (Telford et al, 1990). This investigation seeks for magnetic and gravity anomalies from variations related to the mineralized regions and/or some certain geologic location of mineralization.…”

Depth Estimation of Sedimentary Sections and Basement Rocks in the Bornu Basin, Northeast Nigeria Using High-Resolution Airborne Magnetic Data

“…The 10th generation Inte national Geomagnetic Reference Field (IGRF) version 4.0 was applied by FAS on the com piled dataset to remove IGRF. In magnetic data reduction practice, IGRF, which is easil available and universally accepted, provides consistency in data reduction procedure [60 Processed and corrected high-resolution aero-magnetic data are very appropriate for min eral evaluation programs, basin framework, hydrocarbon, and hydrogeological explora tions, and delineation of the regional geologic boundary [26,[61][62][63][64][65][66][67]. The airborne magnet data employed in this investigation were corrected and processed to a total magnetic in tensity map (Figure 3) which were gridded, saved, and displayed in Oasis Montaj Geoso in colour raster format.…”

Groundwater Potentiality Assessment of Ain Sefra Region in Upper Wadi Namous Basin, Algeria Using Integrated Geospatial Approaches

“…There have been numerous uses of RS and GIS in groundwater quality investigation in latest decades. Some researchers, such as Gogu, Hallet [16], Hodlur, Prakash [17], Jaiswal, Mukherjee [18], Das and Pardeshi [19], Das, Pal [20], and Ekwok, Akpan [21] have used GIS to determinate potential zones of groundwater, while Sreedevi and Subrahmanyam [22] likewise relied exclusively on remotely sensed data to identify prospective locations of groundwater. Moreover, numerous scholars such as Fashae, Tijani [15], Bhuvaneswaran, Ganesh [23], Jasmin and Mallikarjuna [24], Shah and Lone [25], and Bhunia [26] have used GIS and remote sensing techniques together to identify potential areas of groundwater.…”