NE-SW Direction Research Articles

Depositional model, facies analysis and reservoir quality in a wave-modified clastic lacustrine system: The early cretaceous Tongbomiao formation of the Tanan Depression, Tamtsag Basin, Mongolia

The Tanan Depression has experienced multi-phase tectonic movements and formed various types of reservoirs, which has brought some difficulties to proper oil exploration. This study aims to characterize the depositional facies and petrophysical properties of clastic reservoirs in the Tanan Depression and to determine the most prolific areas for exploration based on the analyses of core samples, thin sections, logging data, petrophysical properties, seismic profiles, and paleontological data. A wind-wave controlling sedimentary model and seven primary depositional facies, namely: 1) alluvial fan; 2) braided delta plain; 3) braided delta front; 4) wave-modified fan-delta front; 5) shoreface; 6) storm deposits; and 7) sublacustrine fan, were revealed in this study. The predominant wind direction during the deposition of the upper Tongbomiao Formation was from the southeast (SE), and the resulting wave-modified sandbodies mainly extended along the paleoshore line of the lake in a NE-SW direction. Facies of weakly-to not-modified depositional settings (alluvial fan, braided channel, braided delta front, and sublacustrine fan) were mainly characterized by high matrix content, poor grain sorting, and poor maturity. Conversely, facies related to wave-dominated depositional settings (wave-modified fan delta front, shoreface and storm deposits) are characterized by low matrix content, higher grain sorting, and higher maturity. A positive correlation between reservoir quality and wave-modified intensity of sandstones is evidenced in the study area. Sandbodies that have experienced wave modification, early carbonate cementation, and dissolution served as the main reservoirs for oil accumulation. Therefore, future oil exploration in the Tanan Depression should focus on clastic sedimentary bodies reworked by waves. Moreover, the facies distribution model and high-quality reservoirs forming mechanism in the Tanan Depression could provide a significant reference for oil exploration and development in other similar basins.

Interpreting the magnetic signatures and radiometric indicators within Kogi State, Nigeria for economic resources

The mineral and geothermal potentials of part of Kogi State was investigated through the interpretation of aeromagnetic and radiometric data of the study area. The analysis targeted bridging the gap of insufficient geophysical information of sub-crustal resources that could be of economic value within the area of study. Vertical derivatives, analytical signal and spectral depth analysis were used for the interpretation of the aeromagnetic data while the concentration and ternary images of the three radiogenic elements were used for the interpretation of the radiometric data. The result of first vertical derivative was helpful in delineating mineral potent lineaments labelled F1 to F8. The lineaments were seen trending E-W and NE-SW direction. A principal fault line F6 tends to separate the regions of sediments to the south-east and basement geologic formations to the south-western regions. Result of the analytical signal amplitude revealed regions with shallow intrusive magnetic rocks having high amplitudes ranging from 0.152 to 0.557 nT/m, while regions with magnetic rock intruding into sedimentary formations at greater depths, have medium to low amplitudes ranging from 0.014 to 0.136 nT/m. Regions delineated to be altered through hydrothermal process coincided with areas of major magnetic lineaments. The lineaments which could be fractures, faults or shear zones usually serve as conduits for mineral deposits during hydrothermal process. Result of potassium_thorium ratio map showed evidence of hydrothermal alteration in the NW and SW regions of study area. These regions of alterations also corresponds to regions where major lineaments were mapped and thus represent regions with significant potency for mineralisation. Result of spectral depth analysis on the aeromagnetic data showed that peak values of geothermal gradient and Heat flow were 27°C/km and 68 mW/m2 respectively, the values were recorded at the North-eastern part of study area, at the lower end of Koton-Karfe and part of Lokoja where the shallowest Curie point depth of 24 km also occurred. The estimated values of heat flow falls below the range of 80 to 100 mW/m2 recommended as threshold for a good source of geothermal energy, hence the region will not be prospectively good for a cost effective geothermal energy exploration. In order to assess the heat production within the study area due to activities of radioelements, a comparative analysis of the concentration of the three radiogenic elements was carried out. A relatively high radiogenic heat production (RHP) value of 3.4 μW/m3 was recorded at the North-western region indicating high occurrence of radioactivity within the granitic rocks. The (RHP) value of 3.4 μW/m3 is slightly below 4.0 μW/m3 which is a recommended value for a good source of geothermal energy.

Contribution to the seismic microzonation of Lisbon based on the integration of geological, geophysical, and geotechnical data

Lisbon has been affected by several moderate to strong earthquakes that caused considerable damage and produced significant economic and social impacts (e.g., the November 1st, 1755, earthquake). Studies on the potential damage due to a seismic event have been done considering Lisbon's moderate to high seismic hazard, but the seismic site effects have not yet been investigated at the city scale. The local ground conditions can locally modify the characteristics of surface seismic motion.Based on a multidisciplinary dataset composed of surface geology, a geotechnical database, and a geophysical database that compiles all the available geophysical tests carried out in Lisbon, an integrated approach to seismic ground characterisation was performed.A regression analysis of the shear-wave velocity values compiled in the geophysical database was done for each geological unit. The peak frequency distribution in the city, assessed from the ambient vibration measurements, showed a pattern in peak frequency variation. It decreases from the oldest to the most recent geological formations that outcrop in the SW-NE direction. Three zones based on peak frequency value distribution were proposed.An estimation of the impedance contrast depths was computed through two processes, considering the previous results: (i) the shallower contrast depth was assessed through a sharp variation of NSPT values available in the geotechnical database, and (ii) the deeper contrast depth was estimated based on geology data and deep borehole information. The results showed that for the upper ∼100 m of depth, a consistent relationship between the contrasts identified through different data was obtained, even if uncertainty increased with depth.

Analysis of gravity data for extracting structural features of the northern region of the Central Indian Ridge

In this study, structural lineaments and fracture zones of the northern region of the Central Indian Ridge have been determined using gravity data from XGM2019e_2159 global gravity model. In this scope, firstly, the edge detection performances of the gradient amplitude of the tilt angle (THDR), theta map (TM), improved local phase (ILP), and improved logistic (IL) methods have been evaluated on synthetic examples. The results show that the IL method effectively avoids false edges and produces high-resolution edges. Then, the methods are applied to the gravity anomaly of the northern region of the Central Indian Ridge. It has been determined that the most prominent structural lineaments observed over the region are in the NE-SW and NW-SE directions. These trends match reasonably with the significant trends of the Tilt depth solutions that show a depth range of 2.2 km to 7 km for different geological structures. In addition, the obtained results are compatible with the known fracture zones of the study area. The findings help us to improve our understanding of the structure and tectonic framework of the study region.

Faulting and Lithological Features in Vegetation Distribution: A Remote Sensing Asisted Case Study from SE Turkey

In this study, the effect of lithological and tectonic parameters on vegetation density was investigated. In this context, two faults and their immediate surroundings in an area whose bedrock is flysch and limestone in the southeast of Turkey (south of Lake Van) were chosen as the sampling area. In the research area, generally, the extensional tectonic regime in NE-SW direction has developed many normal faults and these faults have gained oblique character in places. The aforementioned faults not only controlled the tectonic-morpho dynamics and geomorphic character of the research area, but also controlled the texture of the vegetative cover. For the target purpose of the study, field studies were carried out and remote sensing techniques were applied. GIS and remote sensing outputs (NDVI, lineament, lithological map) and field findings were compared. As a result, it was determined that there were significant relationships between vegetation density in the sampling area, fault lines and lithological features

Assessment of catchment scale groundwater-surface water interaction in a non-perennial river system, Heuningnes catchment, South Africa

A significant proportion of the world's river networks are non-perennial rivers that are characterized by segments of dry, standing, and flowing water. However, the role of groundwater and the controlling elements governing the flow processes in these rivers is not widely documented. In this study, aquifer-river interaction was assessed using a combo of geological, hydrological, environmental stable isotope, and hydrochemical data in the Heuningnes catchment, South Africa. Results showed the depth to groundwater levels ranging from 3 to 10 m below ground level and aquifer transmissivity values of 0.17 to 1.74 m2/day. The analytical data indicated that Na-Cl type water dominates most groundwater and river water samples. Environmental stable isotope data of river samples in upstream areas showed depleted δ18O (-4.3 to -5.12 ‰) and δ2H (-22.9 to -19.3 ‰) signatures similar to the groundwater data, indicating a continuous influx of groundwater into the river water. Conversely, high evaporative enrichment of δ18O (1.13 to 7.08 ‰) and δ2H (38.8 to 7.5 ‰) were evident in downstream river samples. It is evident from the local geological structures that the fault in the north-eastern part of the study area passing Boskloof most likely acts as a conduit to groundwater flow in the NE-SW direction thereby supplying water to upstream river flow, while the Bredasdorpberge fault likely impedes groundwater flow resulting in hydraulic discontinuity between upstream and downstream areas. Relatively low conductive formation coupled with an average hydraulic gradient of 8.4 × 10−4 suggests a slow flow rate resulting in less flushing and high salinization of groundwater in downstream areas. The results underscore the significance of using various data sets in understanding groundwater-river interaction thereby providing a relevant water management platform for managing non-perennial river systems in water-stressed regions. Overall, the study provides important insights into the need for maintaining moderately high groundwater levels in shallow and local groundwater systems for sustaining the ecological integrity of non-perennial rivers.

Large variations of crustal thickness across the Taiwan orogeny constrained by Moho-refraction recorded by the Formosa Array

The Taiwan orogenic belt is formed by the strong convergence between the Philippine Sea Plate and the Eurasian Plate. The detailed mountain building process is still under debated largely due to the poor constraint of deep crustal structures, particularly the geometry at the Moho-depth. Here the Moho-refracted P waves are identified from the seismic data recorded by a dense seismic array (Formosa Array) in northern Taiwan. Although the refracted seismic energy is often weak at each individual station, the waveform similarity recorded at the nearby stations provides a reliable constraint for estimating the apparent velocity recorded by the dense seismic array. The forward modeling of the observed Moho-refracted P waves shows a larger crustal thickness (~ 52 km) beneath the Backbone Ranges than beneath the adjacent Hsuehshan Ranges (~ 36 km). Such a result is not only confirming the Moho variations along a few of the NW-SE profiles from the previous studies, but also showing the strong Moho variation is well extended along the NE-SW direction. The large change in the crustal thickness across the Taiwan orogeny strongly indicate that the orogenic deformation in Taiwan might extend beyond the shallow crust, possibly involving in the deep crust and upper mantle. The Taiwan orogeny may not be reaching to the isostatic equilibrium yet.

Characteristics of azimuthal anisotropy in SE Tibetan plateau and its relationship with the background of block structure

The southeastern Tibetan Plateau, which includes the Tibetan Plateau, Yangtze Block, and Cathaysia Block, is geotectonically situated in the compound part of the Tethys-Himalayan tectonic domain and the Peninsular Pacific tectonic domain. It is one of the critical regions for studying the scientific problems of plateau material lateral escape, lithosphere deformation, geotectonic properties of blocks, and deep dynamics. In this study, we use ambient noise data recorded by 401 broadband stations to obtain high-resolution short-period (T = 4–32 s) Rayleigh wave azimuthally anisotropic phase velocity maps. These could provide fresh clues for an in-depth understanding of the crust-mantle velocity structure, deformation mechanism, and geotectonic evolution in the southeastern Tibetan Plateau. Within the Simao block, the strikes of the faults and the orientations of the principal compressive stress of the stress field both generally coincide with the fast-wave polarization direction (FPD). The FPD near the Lancangjiang fault zone in the west is in the NE-SW direction, near the Wuliangshan fault zone in the center is near the NS direction, and near the Red River fault zone in the east is the NW-SE direction. We estimate that the compressive stress in the southwest direction of the Tibetan Plateau material has a controlling effect on the crustal deformation of the Simao block, which is likewise blocked by the Lincang granite belt, resulting in strong tectonic deformation. The FPD of the crust in the middle Red River fault zone is NS direction, significantly different from the fault strike. Combining with the seismic activity and GPS results, the depth of 8 km below the surface of the middle Red River fault is completely locked, and we conclude that the anisotropy of the upper crust of the middle part of the Red River fault zone is related to the action of the regional tectonic stress field. Taking into account geochemical and thermochemical results, we speculate that the complex tectonic stress at the junction of the blocks leads to prominent regional characteristics of the FPDs of azimuthal anisotropy in the crust, suggesting that the Shizong-Mile fault zone may be the western boundary between the Yangtze block and the Cathaysia block.

Structurally-controlled Gold Mineralization in the Southern Zuru Schist Belt NW Nigeria: Application of Remote Sensing and Geophysical Methods

A significant number of gold occurrences are hosted by hydrothermal alteration zones in the Zuru Schist Belt, Northwestern Nigeria. The aim of this study is to identify the spatial correlation between faults, sheared, hydrothermally altered zones, and gold mineralized areas using geophysical and remote sensing data. The main structural trends of the schist belt as interpreted from the application of total gradient amplitude and local wavenumber techniques on the aeromagnetic data are in the E-W and NE-SW directions. These trends align with the locations of gold mineralization and key pathfinders such as faults in the Anka-Yauri-Iseyin shear zone. In the radiometric data, magnetic faults occurred in areas with elevated potassium enrichment within the Anka-Yauri-Iseyin shear zone and present evidence for structurally controlled hydrothermal processes. The mapped Anka-Yauri-Iseyin shear zone from the aeromagnetic data further coincides with morphological features such as ridges, valleys, and highlands, signifying that the shear zone is represented by topographical linear indicators. Importantly, the integrated approach and results presented in this work show that the Southern Zuru Schist Belt is fragmented by a NE-SW oriented AYI shear complex. Faults and hydrothermally altered zones in the AYI shear complex are new target areas for direct exploration of gold in the study area.

Extensional structures of the Nan′an Basin in the rifting tip of the South China Sea: Implication for tectonic evolution of the southwestern continental margin

Nanan Basin is a giant hydrocarbon basin, but its tectonic division scheme and associated fault systems has not been well understood. Based on newly acquired seismic data from the southwestern margin of the South China Sea, this study analysed the structural units, tectonic feature and geodynamics of the sedimentary basin. The new data suggests that the Nanan Basin is a rift basin oriented in the NE-SW direction, rather than a pull-apart basin induced by strike-slip faults along the western margin. The basin is a continuation of the rifts in the southwest South China Sea since the Late Cretaceous. It continued rifting until the middle Miocene, even though oceanic crust occurred in the southwest subbasin. However, it had no transfer surface at the end of spreading, where it was characterized by a late middle Miocene unconformity (reflector T3). The Nanan Basin can be divided into eight structural units by a series of NE-striking faults. This study provides evidences to confirm the relative importance and interplay between regional strike-slips and orthogonal displacement during basin development and deformation. The NE-SW-striking dominant rift basin indicates that the geodynamic drivers of tectonic evolution in the western margin of the South China Sea did not have a large strike-slip mechanism. Therefore, we conclude that a large strike-slip fault system did not exist in the western margin of the South China Sea.

EFFECTS OF HEAVY METALS, CONTAINED IN FLOTATION TAILINGS, ON PLANTS USED IN REVEGETATION

During the processing of precious and base metal ores from the Baia Mare mining area, which contained Au, Ag, Cu, Pb and Zn, large amounts of flotation tailings resulted, which were deposited in the Bozânta tailings management facility, located between Săsar and Bozânta Mare villages, 4 km west of Baia Mare. Due to the presence of minerals containing metal sulphides (mainly pyrite), the acid rock drainage (ARD) has become very active, catalysed by iron- and sulphur-oxidizing bacteria, which naturally occur at these sites. Decreasing the surface of the pond as a result of evaporation, combined with the increase of the beach surface and the absence of any protection at the embankment ridge, led to the entrainment of the tailings by wind at considerable distances. They often end up in neighbouring settlements, especially in the two mentioned villages, as a result of prevailing winds from the NE-SW direction. The purpose of the research was to test the resistance of some plant species (Sinapis alba L. – white mustard; Trifolium pratense L. – red clover and Lolium perenne L. – ray grass) to the conditions generated by the tailings on the surface of the depot, in order to create a vegetation cover with a role in diminishing tailings discharges in the adjacent areas. There were tested the effects of the industrial eluate (acid mine water, pH 4.3), obtained from the tailings pond, over seed germination parameters: germination capacity (GC); germinative energy (GE) and relative seed germination (RG). The results of the tests pointed out that the least affected was white mustard: GC – 95.3%; the differences in the values obtained in the control samples and the GE test – 5.3%; the results for RG – 99.3%, confirm that the white mustard seeds were the least influenced by the industrial eluate, followed by ray grass and red clover. In the tests for plant growth on the tailings pond, 5 experimental variants were used: a) soil (S); b) flotation tailings (T); c) mixture of flotation tailings and soil (T+S); d) mixture of flotation tailings and organo-zeolitic material (T+OZ); e) mixture of flotation tailings, organo-zeolitic material and soil (T+OZ+S). It is recommended to use the T+OZ+S mixture on the pond surface and sowing with Sinapis alba and Trifolium pratense. For both species, double seed sowing is recommended.

Insights into the late Cenozoic structural deformation and tectonic stress field of the Qiabuqia region, Gonghe Basin, northeastern Qinghai–Tibetan Plateau

In addition to overall uplift of the Qiabuqia region during the Late Cenozoic, three deformation stages can be identified in the northeastern Qinghai–Tibet Plateau. Specifically, these deformation stages were recognized in areas east of the Gonghe Basin that surrounds Waliguan Mountain and include: 1) Late Miocene to Late Pliocene deformation—dominated by thrust napping with dextral strike-slipping; 2) Early Pleistocene to late middle period of Pleistocene deformation—fault structures were dominated by the dextral strike-slipping with thrust napping; and 3) end of Late Pleistocene to Middle Holocene deformation—thrust napping slowed down and finally braked, while the shallow surface began to loosen and extend at Qiabuqia region’s rear-edge. DR4 borehole drilling data indicate that the Xiangshuihe Formation’s buried depth is ∼1,000 m. The Xianshuihe Formation’s top section is characterized by normal fault–type (NF) tectonic stress, while the maximum principal tectonic stress (σ1) is perpendicular and the minimum principal tectonic stress (σ3) is horizontal. In contrast, the deep basement is characterized by thrust fault (TF) and strike-slip (SS) tectonic stress, while the σ1 is in the NE-SW direction, ranging from 20.1° to 75.3° with an average of 40.0°. Based on the aforementioned observations, it can be inferred that there are three sets of hidden faults in the basement of the Qiabuqia region: 1) the NW–NNW trending compressional–torsional faults; 2) the NE trending tensional–torsional faults; and 3) the NWW trending compressional–torsional faults. The findings in this study can potentially offer a robust geological basis for exploring and utilizing hot, dry rock resources within the Gonghe Basin.

Delineating the main structural outlines and the petrophysical properties of the Albian-upper Cretaceous Reservoirs using seismic and well log data, Shushan Basin, north Western Desert, Egypt

This study concerns with delineating and analyzing the subsurface structural setting of Khalda Oil Field at Shushan Basin as a key factor for evaluating the petrophysical properties and the deliverability of the Bahariya Formation. Shushan Basin is considered one of the most prospective basins in the Western Desert. The oil is trapped within a gentle seismically defined anticline that contains a series of coastal sandstone reservoirs interbedded with a neritic and tidal flat mudstone and a few carbonate interbeds of the Albian-Cenomanian Bahariya Formation forming multiple oil-bearing sandstone reservoirs. A set of borehole logging and seismic data were available, tied, processed, and mapped to delineate the predominant structures in the study area. Results show the implication of the NW–SE, NE–SW, and E–W gravity faulting on the Bahariya and the overlying Abu Roash formations. This set of gravity faults is attributed to the Mesozoic tensional stresses. The depth structure contour maps on the upper surfaces of the Lower and Upper Bahariya members reveal the presence of some NE–SW gravity faults that dissected the Khalda Field into some slightly tilted blocks, shallowing in depth to the south as deepening to the north. Besides, the study area has been affected later in the Jurassic by E–W gravity faults during the Atlantic Ocean opening. This faulting trend was changed later into the NE–SW direction as a result of the movement of North Africa against Laurasia. The petrophysical analysis indicated that the Lower Bahariya sandstone reservoir has a good reservoir quality (16 ≤ ∅ ≤ 25%, 53 ≤ Sw ≤ 59%, 6.0 ≤ Vsh ≤ 32.2%, and good net-pay thickness 18.0–38.0 ft). It is revealed that the drilled wells penetrating the crest of the anticline are prospective while that located in the anticline flanks are water-bearing recommending exploration away from the anticline flanks. By applying this workflow, it is possible to explore for the similar subsurface hydrocarbons-bearing sequences in the Western Desert and North Africa in future exploitation plans.

MESOZOIC DELTAIC SYSTEM AND SEQUENCE STRATIGRAPHIC MODEL OF THE LOWER JURASSIC DATTA FORMATION ALONG THE WESTERN SALT RANGE, PAKISTAN

In this research, the Early Jurassic Datta Formation from three outcrop sections of the western Salt Range has been extensively studied to elucidate facies architecture, sedimentary features, diagenetic features, sequence stratigraphy, and depositional model. Datta Formation is well exposed with massive thickness in the western Salt Range and the Trans Indus Ranges, while tapering in the central Salt Range further eastward, it dies out. Its mainly dominated by variegated sandstone, siltstone, shale, fire clays, laterites, and carbonates. Seven lithofacies has been identified and interpreted in the Datta Formation, i.e., (i). Fluvial Meandering Lithofacies (JDL-01), (ii). Braided Fluvial Lithofacies (JDL-02), (iii). Lateritic Lithofacies (JDL-03), (iv). Flood Plain Lithofacies (JDL-04), (v). Siliciclastic Lagoon Lithofacies (JDL-05), (vi). Carbonates dominant Lagoon Lithofacies (JDL-06), (vii). Swamps related Deltaic Lithofacies (JDL-07). Sequence stratigraphic analysis is primarily based on recognizing sequence surfaces, finning-coarsening upward trends, and types of facies. Two transgressive-regressive cycles are identified in the south-eastern section (Kassan Nala and Kaowali sections), while four sequences are identified in the Nammal Gorge section. These sequences are started with the underlying sequence boundary of LST and ended with the sequence bounding surface after HST. Datta Formation is possibly deposited in fluvial to deltaic environments in the study area, revealing a prograding delta with a shoreline oriented in the SW-NE direction and the siliciclastic detritus fed the fluvial system running over the Indian cratonic basement in the direction of N-NW. The lower part of the formation is deposited in fluvial settings, probably in the incised valley. The point bar sequences result from meandering channel facies and show association with overlying flood plain/overbank facies. Moreover, the lagoonal facies mainly covered the upper part of the formation and displayed mixed lithologies of delta plain to delta front setting. However, the repetition of these lithofacies in the study area at several points indicates the recurrence of depositional phases. The carbonaceous shales and coal streaks are evident by the presence of swamp or marshy lands. These conditions meet the criteria of deltaic settings. Furthermore, several laterites and fire clay horizons are also argue periodic sub-aerial exposure of the depositional area. Thus it is concluded that the depositional area lies in a fluvial to deltaic setting with major distributary channels and their flood plain in the adjoining delta plain to delta front part.

Mapping and Petro-Structural Study of the Geological Formations of the Alépé Region (South-East of Côte d’Ivoire)

This study focuses on the petrographic and structural characteristics of the geological formations of the Alépé region in the Comoé basin. The petrographic characterization allows us to retain that the study area abounds in a variety of lithologies: amphibole metagranite, metadiorite, amphibolite and metagrauwacke. The lineament map attests that the study area was affected by polyphase tectonics (ductile and brittle), all these deformations have NW-SE to NNW-SSE; NW-ESE to NW-SE; ENE-OSW and NE-SW directions. Coupled geochemical data show that the protoliths of the studied rocks evolve between granites and gabbros that are weakly to moderately be altered. They would originate from continental crust and mantle and would be emplaced in collision contex.

Thermostructural Evaluation of the Muriaé Watershed (Rio de Janeiro portion).

The hydrological basins can be considered sources of relevant information about the evolution of the Earth's crust since the relief forms that define the hydrographic channels are the resultant of the interaction between tectonics, pedogenics, intemperics and thermals processes. The geothermal field of Muriaé watershed was evaluated using eight (8) thermal logs and twenty-two (22) geochemical logs. The structural lineaments evidenced on the surface were interpreted jointly with the identification of sixty-five (65) magnetic lineaments from airborne magnetic data interpretation. The depths of these structures were range from the surface up to 4.5 km. The interpreted data allowed identification of regional tectonics features in the NE-SW direction, where the identified magnetic lineaments show a spatial correlation with accentuated topographic structures. The differences in the depths of the magnetic bodies found in conjunction with the heat flow distribution, evidence two distinct thermostructural zones: A1 (east part) presenting heat flow values within the average (approximately 60$\frac{mW.

Influence of Infiltrations on the Recharge of the Nkoabang Aquifer Located in the Center Region, Cameroon

Due to the limited reach of the drinking-water delivery network, Yaoundé’s surrounding communities (such as Nkoabang) rely on well water, boreholes, and springs. This study conducted a Thornthwaite water-balance analysis in the watershed in order to understand its hydrology capability and investigated the influence of the flows and infiltrations on the recharge of the aquifer of Nkoabang (Centre Region, Cameroon). The methodology of this work consisted of updating the rainfall and temperature data of the Mvan meteorological station in Yaoundé to carry out the hydrological and water balances of the Nkoabang aquifer and performing the piezometric monitoring of seven wells and one spring in the dry season and the rainy season. The average rainfall height for the period between 1951–2017 was 1577 ± 222 mm, while the monthly temperatures ranged from 22.8 (July) to 25.4 °C (February) for an average of 24.1 °C ± 0.8 °C. The average interannual infiltration was 137 mm, corresponding to an infiltration coefficient of 8.68%. The value of the piezometric levering varies between 706 and 718 m for an average of 711.76 m during the dry season. It fluctuates between 706 and 719 m during the rainy season for an average of 712.95 ± 4.09 m. Irrespective of the season, the highest and lowest values are those of P6 and P3, respectively. Piezometric level values vary little from one season to another but are higher in the rainy season than in the dry season. Wells in the study area generally show small variations in piezometric level amplitude, ranging from 0.4 to 3.3 m with an average of 1.19 ± 1 m. The analysis of the piezometric map of the Nkoabang aquifer shows a flow in the NE-SW direction; storage areas south of the study areas and the water supply area in the peaks and NE of Nkoabang. The daily indicative flow rates of the spring (S) are 0.15 m3 (dry season), which can supply in the dry and rainy seasons 36 to 46 people, respectively, based on a ratio of 0.1 m3 per day per habitant.

Investigation of Groundwater Potential Using Geological, Hydrogeological and Geophysical Methods in Federal University of Technology, Minna, Bosso Campus, North Central, Nigeria

Groundwater exploration and extraction in challenging hard rock formations with inherent heterogeneity is addressed comprehensively in this study through geological, hydrogeological, and geophysical investigations. Hydrogeological studies assess existing borehole recharge rates and provide an overarching groundwater potential assessment. A 1D Vertical Electrical Sounding (VES) survey, employing the Schlumberger method, acquires sounding data analyzed with WINRESIST software to extract groundwater controlling parameters, revealing distinct geoelectric layers and illuminating groundwater and aquifer system structural control. Geological mapping, employing detailed topographical data, revealed the prevalence of granitic rocks exhibiting quartz vein and joint intrusions, primarily oriented in the NE-SW direction. These geoelectric layers encompassed the topsoil, weathered/fractured granite, and fresh granite, each characterized by apparent resistivity values ranging from 14 Ωm to 572 Ωm, 10.0 Ωm to 408 Ωm, and 1468 Ωm to 19,031 Ωm, accompanied by varying thicknesses. Further insights were gained from isopach and resistivity maps at depths of 10 m and 30 m, identifying areas with low apparent resistivity values and substantial overburden. These findings pinpointed zones with potentially high groundwater potential, particularly in the northeastern and southeastern regions. Additionally, the results from the weathered layer analysis aligned with the isopach and resistivity outcomes. Hydraulic conductivity measurements, falling within the range of 7.00 × 10–5 m/s to 4.31 × 10–4 m/s, confirmed the subsurface materials' capacity to transmit water. Moisture content ranged from 12% to 20%, while infiltration rates varied from 2.675 × 10–4 L/s to 1.259 × 10–5 L/s. Yield test results from three borehole locations yielded production rates ranging from 56.52 m3/day to 364.26 m3/day, although other boreholes returned indeterminate results. Based on the groundwater potential classification, 25% of the area demonstrated high potential, 45% moderate potential, and 30% low potential. Accordingly, the recommendation is to prioritize well or borehole drilling in high-potential areas to ensure optimal water supply management.

Engineering Geology and Slope Stability of West Pit Coal Mine of PT. Tawabu Mineral Resource, East Kalimantan, Indonesia

The research area was located in the west pit of the open pit coal mine of PT. Tawabu Mineral Resource (TMR) which is located in Bengalon District, East Kutai Regency, East Kalimantan Province, Indonesia. The research was driven by several landslides that occurred in the research area, but the engineering geological conditions and stability of the remaining slopes have not been evaluated. The objectives of this study were to better understand the engineering geological conditions and stability of the research area. The engineering geological conditions (i.e., geomorphology, rock and soil, geological structure, and groundwater conditions) were evaluated by photogrametric analyses, field observations, and analyses of borehole logs and laboratory test results. The slope stability analyses were firstly carried out by conducting back stability analyses of failed slope on the northern lowwall slope segment. The shear strength parameters obtained from the back analyses were then used for forward stability analyses of the remaining 10 lowwall and highwall slopes. The slope stability analyses involved deterministic and probabilistic analyses, under static and dynamic using the limit equilibrium method (LEM). The results showed that the research area and the surrounding consisted of two geomorphological units, namely the alluvial plain and structural hills. Rocks in the study area consisted of claystone, sandstone, and coal with a general layer strike direction of N59°E – N63°E with a dip of 19°-26°. These rocks were grouped into two lithological units, namely the alternating of claystone and sandstone unit and alternating of sandstone and claystone unit. The geological structures were identified on the highwall, from west to east namely major sinistral shear fault with a relative direction of NNE-SSW, two minor sinistral shear faults with a relative direction of NE-SW, and a major dextral shear fault with a relative direction of NW-SE. These geological structures were interpreted as being formed by the folding process. The groundwater level was estimated at a level of -45 m to 20 m. The slope stability analyses showed that only the East HW-4 slope, which was located on the east highwall, was unstable. It is recommended to optimize the slope by either lowering the groundwater elevation by 4 m from the actual level or by reducing the angle the overall slope to 31°.

Vertical Electrical Sounding (VES) Technique to Map Potential Aquifers of the Guigou Plain (Middle Atlas, Morocco): Hydrogeological Implications

Vertical electrical sounding (VES) as a geoelectrical method has proven its effectiveness throughout the history of groundwater geophysical investigation. In this sense, VES was carried out 47 in the study area with the aim of determining the geometry and limits of Quaternary basaltic aquifer formations and, above all, the location of electrical discontinuities in the area located in the north of Morocco, between the center of Almis Guigou and the city of Timahdite. This area is experiencing an overexploitation of the groundwater due to excessive pumping and the development of intensive agriculture activities, resulting in a continuous decrease in piezometric levels. The processing of the diagrams by WINSEV software showed the presence of an electrically resistant surface level, attributed to basaltic formations, of the Quaternary age, whose thicknesses reach at least 150 m to the SW of the area. This level is superimposed on a moderately conductive horizon which, according to local geology, corresponds to Pliocene marl and limestone alternations. The correlation of VES interpretation models allowed us to elaborate thematic maps and geoelectrical sections which illustrate the vertical and lateral extension of the basaltic reservoir as well as its thickness, which decreases in general from the south-west to the north-east; however, the main electrical discontinuities also correspond to faults and fractures, and they show a NE–SW direction sub-parallel to the major accidents of the Middle Atlas. A prospectivity map of the local aquifer was generated, coinciding with regional fault lines and confirmed by the alignment of very good flowing water boreholes. This geophysical study by electrical sounding shed light on the geometry and extension of the aquifer and opened avenues to draw further conclusions on its physical and hydrodynamic characteristics, as well as to optimize the future siting of groundwater exploitation boreholes through the elaboration of the local aquifer prospectivity map.