Sedimentary Terrain Research Articles

Radiotoxicity and groundwater quality for drinking in a multi-layered saline sedimentary terrain of Keana, Central Benue trough, Nigeria

Radiotoxicity and groundwater quality for drinking in a multi-layered saline sedimentary terrain of Keana, Central Benue trough, Nigeria

Assessing the Prediction Accuracy of Frequency Ratio, Weight of Evidence, Shannon Entropy, and Information Value Methods for Landslide Susceptibility in the Siwalik Hills of Nepal

The main objective of this study is to assess the prediction and success rate based on bivariate frequency ratio (FR), weight of evidence (WoE), Shannon entropy (SE), and information value (IV) models for landslide susceptibility in the sedimentary terrain of Nepal Himalaya, as the area is facing threat for sustainable development as well as sustainable resource management. This study also seeks to evaluate the causative factors for landslide susceptibility. Initially, a landslide inventory map was created, consisting of 1158 polygons. These polygons were randomly divided into two sets, with a ratio of 70% for training and 30% for testing data. The multicollinearity approach was evaluated to assess the relevance of selected conditioning variables and their inclusion in the model construction process. The area under the curve (AUC) and other arithmetic evaluation methods were employed to validate and compare the outcomes of the models. In comparison, the predictive accuracy of the FR model surpasses that of the IV and SE models. The success rates, ranked in descending order, are as follows: WoE (79.9%), FR (75.3%), IV (74.4%), and SE (73.2%). Similarly, the success rates of four distinct models, namely WoE, FR, IV, and SE, are 85%, 78.75%, 78.57%, and 77.2%, correspondingly. All models have an accuracy and prediction rate exceeding 70%, making them suitable for assessing landslide susceptibility in the Siwalik Hills of Nepal. Nevertheless, the weight of evidence model provides more precise outcomes than other models. This study is expected to provide important information for road and settlement sustainability in the study area.

Interpretation of aeromagnetic and remote sensing data of Auchi and Idah sheets of the Benin-arm Anambra basin: Implication of mineral resources

Abstract The need for mineral resources for economic development is key in both developing and developed countries. However, miners usually resort to random excavation of mineral deposits without proper investigation to identify structures of interest in target areas. This usually leads to land depletion and abandonment. The aim of this study is to assess the mineral potential in part of the Benin-arm of the Anambra basin by investigating the geophysical characteristics of the area using remote sensing and aeromagnetic data. Surface and subsurface regional structures, including faults and zones of mineralisation, were mapped by integrating aeromagnetic and remote sensing data. The mineral bearing zones that show high prospects of mineral deposits in the region were identified. The rose diagram revealed that the surface lineaments are aligned in the NW–SE, N–S, NE–SW, E–W, NNE–SSW, ENE–WSW, and ESE–WNW directions. The orientations of the subsurface lineaments are aligned mostly in the NE–SW, N–S, and E–W directions. The magnetic intensity ranged between −431.38 and 399.82 nT, while reduction-to-pole magnetic intensity ranged from –416 to 664.45 nT. The first vertical derivative showed magnetic intensity which ranged from –0.5863 to 0.9060 nT/km2. The total horizontal derivative magnetic intensity ranged from –0.00031 to 0.762691 nT/km2, while the analytic signal showed magnetic intensity ranging from 14.0664 to 394,607.3438 nT/cm2. The windowed Euler deconvolution depth to magnetic source showed depth range of <20 to 2,000 m. Many of the features delineated in the study area were characterised by shallow magnetic source depths (<500 m); this is a common characteristic of basement complex terrains. Deeper magnetic source depths (>1,000 m) were observed in the sedimentary terrain. Mineral exploration should be focused in areas with high lineament concentration, as lineaments are potential conduits for economic minerals deposition.

Metallogenesis of the Cu-Ni sulfide type mineralization in the Bounhas vein deposit (Eastern Anti-Atlas, Morocco): Insights from ore mineral paragenesis and fluid phases

The Moroccan Anti-Atlas hosts numerous precious metal (Au, Ag, Co, PGE...) and base metal (Cu, Pb, Zn...) mineralizations that are developed in various geological and geodynamic contexts. Some of these mineralizations, such as copper and nickel, are known in the form of deposits at the scale of the Anti-Atlas and are the subject of mining development and exploitation. This is the case of the Bounhas deposit, which is located in the southern part of the Eastern Anti-Atlas, 50 km SE of the city of Alnif. It is characterized by Cu, Ni, Pb and Zn mineralizations, which are essentially hosted in sedimentary terrains of a sandstone-pelitic nature of the upper formation of the second Bani group (Upper Ordovician). These terrains are affected by brittle deformations that have developed faults that host the lenticular vein mineralization in an E-W direction. The arrangement and textural relationships between the mineral phases of the Bounhas deposit have allowed to distinguish two distinct mineralizing events: (i) a primary hydrothermal event subdivided into 3 metalliferous episodes the first, with Fe, characterized essentially by pyrite mineralization in a carbonate gangue (ankerite and siderite); the second with Cu, Ni, As ± Zn ± Pb, precipitates most of the arsenopyrite, sphalerite I, galena I, gersdorffite and chalcopyrite mineralization in a quartz gangue; and the third, with Pb, Zn, and Ba, places galena II and sphalerite II in a barytic gangue. A late supergene alteration event, characterized by the appearance of minerals typical of cementation, sulfation, carbonation and oxidation zones (covellite, native copper, anglesite, malachite, azurite and iron oxides). Moreover, the study of the fluid inclusions associated with the Cu, Ni, As ± Pb ± Zn mineralization from the Bounhas deposit reveals the presence of two types of fluids: (i) a hypersaline fluid, characterized by a salinity varying between 25 and 30 wt% NaCl eq and a homogenization temperature: Th = 200 to 240 °C. This fluid would be responsible for the development of the copper-nickel-arsenic mineralization of this deposit and (ii) a late medium saline fluid (12 to 15 wt% NaCl eq) and a homogenization temperature Th = 80 °C to 120 °C, to which would be attributed the development of the Pb and Zn mineralization of this deposit.

Effects of Soil Resistivity Variation with Depth on Crop Yield in a Typical Sedimentary Terrain: A Geophysical Method Application in Agricultural Practice

Accurate knowledge of soil fertility is required to promote global food security for life sustenance. Literatures have shown that electrical resistivity method is effective for agricultural site selection without passing through the rigor of soil test. However, the factor responsible for inconsistence in resistivity signature with soil fertility from one place to another, effect of soil texture and depth variation on crop yield are the questions this work geared at providing answers. Ten Vertical Electrical Sounding (VES) were done across the study area using Schlumberger array. Res1Dinvers was used for the inversion model, using Least Square method. Twenty soil samples were obtained in the VES points, two samples per point. One samples each at first and second layer. Result of the resistivity showed that areas with high-excellent crop yield have resistivity signature above 500 Ωm while areas with low yield are characterized by values less than 500 Ωm. In both areas of low and high-excellent crop yield, the result of geochemical analysis indicated that Nitrogen, phosphate, and Potassium varied as 59-61%, 43-54mg/kg and 49-51mg/kg, respectively except for organic matter content that was above 3.8% in the first layer have high-excellent yield while low yield soil showed less than 3.8% in their first layer and even if the second layer’s organic matter is above 3.8%. This study has shown that organic matter has significant effect on soil resistivity signature than others soil nutrients (Phosphate, Potassium and Nitrogen). The study shows that soil’s first layer (0-0.3m) is the most suitable depth good for soil minerals occurrence for optimum agricultural output, soil texture affect soil fertility and geological terrain is responsible for resistivity signature inconsistency with soil fertility.

Petrography and Clay Mineral Variations Across the Cretaceous/Paleogene (K/Pg) Boundary, Sulaimani, Kurdistan Region, Iraq

The Cretaceous/Paleogene (K/Pg) boundary marks the global extinction of many life forms, this boundary around Sulaimani city coincides with the boundary between Tanjero and Kolosh formations. These two units are flysch deposits of the Zagros Foreland Basin. This study focuses on petrography and clay mineralogy variations between these two units. Petrographic study, X-Ray Diffraction analysis, and Scanning Electron Microscope analysis were conducted on samples from different lithologies. The petrographic study of fine-grain lithologies shows that they are mainly wackestone without variation across the boundary. Sandstone petrography shows variation in framework components by increasing quartz, feldspar, and igneous fragments while argillaceous, carbonates, chert, and chalcedony fragments are decreased from Tanjero to Kolosh formations. Obtained results from XRD and SEM show that the clay mineral assemblage is dominated by corrensite (regularly interstratified chlorite/smectite) with discrete chlorite, smectite and traces of illite. The existence of these clay assemblage suggests that corrensite is the diagenetic product of smectite as it is an intermediate stage of smectite chloritization. Enrichment of precursor smectite and high content of unstable grains in sandstones across the K/Pg boundary is the result of low-intensity weathering in arid and seasonal climates of the source area. The smaller size of detrital smectite than other clay minerals is behind its enrichment in the deep marine basin for both Tanjero and Kolosh formations. Sandstone enrichment with sedimentary fragments in both formations related to uplifted sedimentary terrain in its hinterland, while variation across the boundary indicates gradual uplift of Zagros ophiolite zone in the early Paleogene.

Integrated hydrogeophysical and GIS based demarcation of groundwater potential and vulnerability zones in a hard rock and sedimentary terrain of Southern India

This research has identified the groundwater potential and vulnerability zones in Tiruchirappalli district of Tamil Nadu, India. The Schlumberger electrode array has been used to conduct vertical electrical sounding (VES) at 95 sites with a maximum electrode spacing of 150 m. The study area comprises of hard rock and sedimentary formations. Geographical Information System (GIS) has been used to integrate the geoelectrical data and to prepare spatial variation maps for various parameters. Finally, groundwater potential and vulnerability zones have been demarcated, and these outputs have been validated using water level and nitrate data, respectively. The Dar-Zarrouk parameters such as longitudinal conductance (S), transverse unit resistance (T), and aquifer anisotropy (λ) have been used along with the spatial variation of resistivity and aquifer thickness to find out groundwater potential areas with the support of GIS. The thickness of topsoil, weathered zone and fractured zone are not uniform in the research area. Top soil plus weathered zone acts as a water table (phreatic) aquifer, which extends up to 38 m from the surface. Fractured zone extends up to 45 m, which acts as a kind of confined/semi-confined aquifer. Open and bore wells have been constructed to tap groundwater from the unconfined (water table) and confined/semi-confined aquifers, respectively. High to very high groundwater potential areas are associated with low resistivity, high thickness, low longitudinal conductance, high transverse unit resistance and high aquifer anisotropy areas. Very high groundwater potential areas are mostly confined to flood plain (alluvium) deposits in the central portion of the study area. High potential areas are noticed in the northern part, whereas low potential areas are noticed in the southern part. The areas with high longitudinal conductance indicate low permeable zones with less possibility of external pollution. Since agriculture is an important activity in the study region, this work will be useful to provide water supply for irrigation as well as for domestic needs.

Subsurface depleting aquifers in the sedimentary terrain of Quetta Valley in Balochistan: a review

Subsurface depleting aquifers in the sedimentary terrain of Quetta Valley in Balochistan: a review

Quality and hydrochemical assessment of groundwater in geological transition zones: a case study from N.E. Nigeria.

Sustainable management of groundwater resources in geological transition zones (GTZ) is essential due to their complex geology, increasing population, industrialization, and climate change. Groundwater quality monitoring and assessment represent a viable panacea to this problem. Therefore, there is a great need to investigate groundwater resources in terms of their chemistry and pollution to ascertain their quality and implement robust pollution abatement strategies. This study focused on the characterization of groundwater in a typical geological transition zone in northeastern Nigeria. Eighty-seven (87) groundwater samples were collected from dug wells and boreholes during the 2017 dry season. pH, conductivity, and total dissolved solids (TDS) were measured in situ using a multiparameter probe, while major cations and anions were measured using atomic absorption spectrometry and ion chromatography, respectively. Data were analyzed using descriptive statistics, principal component analysis (PCA), water quality index, and standard hydrochemical plots. TDS ranged between 95 and 1154 mg L-1 in basement terrains and between 49 and 1105 in sedimentary areas. pH ranged between 6.8 and 7.7 mg L-1 in basement terrains and between 5.0 and 6.5 in sedimentary areas, suggesting a moderately acidic to alkaline low mineralized groundwater. Calcium (2.6-128.0 mg L-1) was the dominant cation in the basement areas, suggesting silicate weathering/dissolution, while sodium (1.9-106.0 mg L-1) dominated the sedimentary zones due to base exchange reactions. The PCA analysis suggests that mineral dissolution (mostly silicate weathering) controls the hydrochemistry of the basement aquifers, while ion exchange and albite weathering, with some influence of anthropogenic factor, control the sedimentary aquifers. The water quality index revealed that the basement setting was predominated by poor to unsuitable groundwater, while the sedimentary terrain was characterized by potable groundwater. The dominant hydrochemical facie in the basement areas was Ca2+-(Mg2+)-HCO3- characteristic of recharge meteoric water. The Na+- (K+)-HCO3- facie characterized the sedimentary zones, indicative of cation exchange reactions, while the mixed water facie typifies the geological contact zones. The shallow nature of the basement groundwaters makes them more susceptible to geogenic and anthropogenic pollution compared to the sandstone aquifers. However, the basement aquifers have better irrigation indices (Kelly ratio and soluble sodium percent) as compared to the sandstone aquifers, which exhibit poor Kelly ratios (< 1) and soluble sodium percent (> 50) ratings. Results from the study clearly highlight the poor-unsuitable groundwater quality in parts of the studied GTZ and can be very instrumental to the policymakers in implementing sustainable water treatment strategies and cleaner production technologies in GTZ to forestall the incidence of water-related diseases.

Analysis of high-resolution airborne-magnetic data for hydrocarbon generation and preservation potential evaluation of Yola sub-basins, northern Benue Trough, northeastern Nigeria

High-resolution airborne-magnetic data acquired over the Yola extension of the northern Benue Trough, northeastern Nigeria, were analyzed to delineate rock distribution, define basement geometry, determine sedimentary thicknesses, and highlight structural framework among others for the hydrocarbon prospect evaluation of sub-basins in the extension. Filtered and refined magnetic intensity data were subjected to Analytic Signal, Horizontal and Vertical Tilt Derivatives and Euler deconvolution depth weighting analyses to enhance various geological features requisite for petroleum prospect evaluation. Sedimentary rock units flanked the northeast and south widely occur in the central part with volcanic rock intrusions delineated within the sedimentary terrain. Extracted lineaments (less than 5 km and up to 45 km) were observed to dominantly follow the established Benue Trough and Yola sub-basin evolutionary trend along the NE–SW and ESE–WNW directions, respectively. Three prominent sub-basins with sedimentary thicknesses in excess of 3 km and width of more than 60 km, separated by basement highs of mostly volcanic intrusions origin, were identified. The occurrence of relatively thick and extensive sub-basins which are underlain by structurally active basement rocks suggests relatively high geothermal gradient for generation of hydrocarbon from organic matter rich source rocks while the generated oil and gas are preserved within intra-sedimentary structural traps created when the basement fractures were reactivated.

Alcoves as Havens From a Harsh Martian Environment

AbstractFuture missions to Mars will undoubtedly be directed toward sedimentary terrains in search for evidence of past life and geologic history. Astronauts will need to find shelter from harsh surface conditions. Natural underground voids provide a readily adaptable habitat for crews to shelter from radiation. Naturally formed caves would be desirable habitat sites, but thick deposits of limestone or other soluble rocks in which karst topography would form have not been identified by current observations. Alcoves, arched recess in steep escarpments, should be widely distributed across the planet and provide an adaptable shelter for astronauts operating on the surface of Mars. Alcoves provide a more stable thermal environment, a reduced radiation environment, shielding from macro‐ and micro‐meteorite impacts, and protection from atmospheric disturbances.

Effects of Soil Resistivity Variation with Depth on Crop Yield in a Typical Sedimentary Terrain, Igieduma-Edo State, Nigeria: A Geophysical Method Application in Agricultural Practice

Accurate knowledge of soil fertility is required to promote global food security for life sustenance. Literatures have shown that electrical resistivity method is effective for agricultural site selection without passing through the rigor of soil test. However, the factor responsible for inconsistence in resistivity signature with soil fertility from one place to another, effect of soil texture and depth variation on crop yield are the questions this work geared at providing answers. Ten Vertical Electrical Sounding (VES) were conducted across the study area using Schlumberger array. Res1Dinvers was used for the inversion model, using Least Square method. Twenty soil samples were obtained in the VES points, two samples per point. One sample each at first and second layer. Result of the apparent resistivity showed that areas with high-excellent crop yield have resistivity signature above 500 Ωm while areas with low yield are characterized by values less than 500 Ωm. In both areas of low and high-excellent crop yield, the result of geochemical analysis indicated that Nitrogen, phosphate, and Potassium varied as 59-61%, 43-54mg/kg and 49-51mg/kg, respectively except for organic matter content that was above 3.8% in the first layer have high-excellent yield while low yield soil showed less than 3.8% in their first layer and even if the second layer’s organic matter is above 3.8%. This study has shown that organic matter has significant effect on soil resistivity signature than others soil nutrients (Phosphate, Potassium and Nitrogen). The study shows that soil’s first layer (0-0.3m) is the most suitable depth conducive for soil minerals occurrence for optimum agricultural output.

Multivariate interrelatedness of geotechnical and petrophysical properties towards developing near-surface lithology clusters in a sedimentary terrain

The study reports the approach of interrelating geotechnical and petrophysical parameters to develop near-surface lithology clusters in a sedimentary terrain. Field-based and laboratory-based geophysical, geotechnical, and petrophysical measurements were carried out with a view to finding correlations among related parameters, grouping the parameters into depth clusters, and determining trend correlations between field-acquired and laboratory-obtained parameters. Four agglomerate hierarchical cluster signatures were identified at depth 0–30 cm, three at 30–60 cm, and five at 0–90 cm. Principal component 1 retained 74% of data variation and differentiated the petrophysical parameters according to Poisson’s ratio (v) and velocity ratio (Vp/Vs). Principal component 2 explained another 14% of variability in the original responses and separated parameters based on elastic modulus (E) and clay fraction (C). Degree of correlation of Vp/Vs with porosity (Φ), sand fraction (S), C, unconfined compressive strength (U), and California bearing ratio (R) followed order Φ > S > C, and U > R. Trend correlation of shear velocity at 1 m showed good agreement (R2 = 0.992) between field and laboratory data with an amplification factor of 4.13 separating the corresponding values. Lithology determined from soil analysis agreed with that inferred from measured electrical resistivity while geotechnical, petrophysical, and geophysical spatial analysis supported site lithology configuration patterns. Thus, multivariate association of geotechnical and petrophysical parameters exhibited potentials for rapid and exploratory near-surface lithology mapping even at a regional scale.

A New Insight into the Structural Framework of a Crystalline Formation and the Adjoining Sedimentary Terrain in Parts of the Precambrian Basement Complex of Nigeria

A New Insight into the Structural Framework of a Crystalline Formation and the Adjoining Sedimentary Terrain in Parts of the Precambrian Basement Complex of Nigeria

Factors controlling gully morphology on the quartzite ridges of Ibadan, Nigeria

Gullying processes on sedimentary terrains have received significant attention from researchers while such processes are often overlooked in Basement Complex areas because of their perceived resistance to denudation. In an attempt to address this deficiency, we evaluated the nature and variation in gully morphology on a Basement Complex. Three gully systems on prominent quartzite ridges of Ibadan, Southwestern Nigeria were examined: Mokola, Mapo, and Eleyele quartzite ridges. Slope angles of gullied areas were recorded along with observations on slope convexity/concavity and vegetation cover. Gully morphological characteristics of length, width, depth and depth of gully head were measured in the field, and were used to calculate width/depth ratios and gully sinuosity, shape, and volume. Gully bank soil was sampled at a depth of 0–30 cm and 23 samples were analyzed for particle size composition, pH, Electrical Conductivity (EC), Organic Matter (OM), Sodium Adsorption Ratio (SAR) and Exchangeable Sodium Percentage (ESP) using standard laboratory techniques. These parameters showed considerable variation within and between sites. The mainly reddish indurated layer of the channel beds was predominantly composed of sandy clay and gully banks exhibited significant evidence of piping and tunneling. Our study showed that SAR (r = 0.794) and ESP (r = 0.867) were positively correlated with gully cross-sectional area, and SAR and ESP show positive relationships with total gully volume (an indicator of soil loss) ofr = 0.661 andr = 0.758 respectively. The relationship between gully volume and maximum depth reveals a Durbin-Watson value of 2.67 where R°2 = 0.826. The dominant factors of gully development on the ridges were identified as topography (slope shape and angle), soil properties (SAR and ESP), and land use/ human activities (urban growth). This study has identified the need to quantify the impact of lineaments on gully morphology dynamics on Basement Complex terrains.

Empirical relationship of p-wave velocity, depth and shear strength parameters of remoulded geological materials from a sedimentary terrain in North-eastern Nigeria

Empirical relationship of p-wave velocity, depth and shear strength parameters of remoulded geological materials from a sedimentary terrain in North-eastern Nigeria

Analysis of high-resolution aeromagnetic (HRAM) data of geological transition zones of southeastern part of Bauchi, N.E Nigeria

The study investigated the subsurface tectonic framework and structural disposition of the basement/sedimentary transition zone in the southeastern part of Bauchi, Northeastern Nigeria, to delineate the basal and lateral contacts and unravel some of the hydrogeological and engineering challenges in such areas. The method deployed involved analysis of high-resolution aeromagnetic (HRAM) data, through the application of several filtering techniques. The transformation techniques applied include reduction to pole, second vertical derivative techniques analytic signal, and Euler deconvolution. Euler depths result range of 1 to 200 m coincides with region where basement rocks outcrop on the surface while depth range between 0 and −800 m correspond to sedimentary terrain (Kerri-Kerri Fm.) or part of the area where the basement rocks are overlain by thick overburden sediments. The 2-D depth model around the transition zone showed high variability as it ranged from 0 to -500 m owing to the presence of basement highs and depressions. The basement highs are usually characterized by impermeable rocks with poor aquifer characteristics and are responsible for the failure of boreholes in these zones. The basement depressions, however, constitute good groundwater prospects depending on the hydrological properties of the sedimentary infill. The general orientation of lineaments in the area revealed NW-SE, NE-SW, and ENE-WSW, with minor N-S and E-W trends, suggesting a pan-African origin. The occurrence of lineaments in parts of the contact zones also contributes to the groundwater prospects. The erratic bedrock relief exhibited by the study area is also detrimental to foundation of pavement structures as it undermines their durability. Therefore, a detailed site investigation is crucial in such geological contact zones prior to the erection of structures. Additionally, vertical electrical soundings are recommended before borehole drilling to ascertain the suitability of these hydrogeologically complex zones.

Groundwater quality assessments around acassava processing mill on the sedimentary terrain of Ilaro, South-western Nigeria

Groundwater quality assessments were carried out around a cassava processing mill within the Ilaro metropolis, South-western Nigeria using a hydro-chemical approach. Nineteen samples were obtained from proximate water wells which serve as sources of water for drinking, domestic, and irrigation activities. Twenty physicochemical parameters were analyzed, and the results were compared with the permissible limits of the world health organization (WHO) for drinking water. The pH values of the groundwater samples range between 4.60 and 7.65 which were not within the permissible limit and suggest the presence of contaminants in the water samples. The concentrations of electrical conductivity (EC), total dissolved solids (TDS), and total hardness (TH) in the groundwater samples were 100% compliance, while Hydrogen cyanide (HCN) concentrations in the groundwater samples were 0% compliance with standard permissible limit by WHO. All the Anions (Cl−, HCO3−, NO3−, SO42−) in the groundwater samples were 100% compliance except CO32-which is 79% compliance, and cations (Ca2+, Mg2+, Na+ and K+) concentrations were 100% compliance with the standard permissible limits. The concentrations of Fe, Cd, Mn, Pb, Zn, Cu in the samples were 0%, 0%, 31%, 36%, 100%, 100% in compliance respectively with standard permissible limits. The groundwater quality index (GWQI) and contamination index (CI) of the groundwater samples ranges from 527.24 to 699.16 and 24.03 to 38.80 respectively. The values of GWQI and CI of the groundwater samples were 0% compliance with recommended standard permissible limit for drinking and domestic purposes. The samples also showed moderate to high tendencies of aggressively corroding metals. The samples were unsuitable for irrigation and the concentrations of HCO3− and CO32− influenced the suitability of the samples. Strong direct relations exist between carbonate and electrical conductivity indicating freshwater status.

Analysis of aeromagnetic filtering techniques in locating the primary target in sedimentary terrain: A review

Abstract This article analyzes some aeromagnetic filtering techniques for mitigating deceptive geophysical conceptions that may result in a distorted range of geological information from aeromagnetic data. The implication of using the aeromagnetic method, data processing, and enhancement to distinguish sediment-produced anomalies was considered. Two methods to locate buried faults in aeromagnetic data were compared: Edge and fault detection were considered using the magnetic contrast and horizontal gradient methods, whereas rapid depth estimation was considered using the Euler deconvolution method and Signum method. The general challenge to find the magnetic anomaly depth and delineate edges relies on geophysical filtering techniques discussed in order to maintain its geological relevance. The magnetic-contrast layer model signatures help clarify the existence of intra-sedimentary faults. The horizontal gradient approach relative to other derivative methods has better noise stability and fast adaptation to grids without modifying parameters. However, the Signum transform (ST) approach offers a more special solution in depth estimation than the Euler’s deconvolution approach whose solution relies on the required choice of default shape parameters and windows. The Euler deconvolution procedure may not be able to detect structures found by the ST approach and vice versa. As a result, these techniques may be used in conjunction with one another during analysis, as complementary interpretation tools. This review will however aid in the analysis of information used as a criterion for determining faults using various analytical techniques like ST or Euler deconvolution.

Deep groundwater recharge mechanism in the sedimentary and crystalline terrains of Sri Lanka: A study based on environmental isotope and chemical signatures

Springs discharge groundwater that travels along flow paths of different spatial and time domains. In many instances, it is difficult to describe its involved groundwater movement, availability as well as geochemical evolution due to its hidden nature. The present study has assessed the deep groundwater in the form of thermal and non-thermal springs in the Palavi and Vanathavillu basins of sedimentary terrain as well as the Southern, Eastern, and Eastern-North Central lowlands of the crystalline terrain of Sri Lanka, using isotope and geochemical approaches. The results revealed that cation exchange in the sedimentary aquifers, whereas rock-water interaction in hard rock and fairly deep aquifers, are the important factors that control the groundwater chemistry. Artesian wells in the sedimentary terrain are mainly recharged by meteoric water, moving through fractured basement rocks at elevations from 100 to 200m above sea level, and have a long residence time. Despite its proximity to the West coast, the data acquired do not indicate that there is seawater mixing. Mixing of percolated water through an unconsolidated geological matrix appears to promote an increase in the salinity of groundwater. Non-mixed, non-evaporated, and young groundwater with a recharge elevation of more than 1000 m above mean sea level can be found in the Southern lowlands of the crystalline terrain. In the Eastern North Central lowlands, groundwater is lowland originated, fast replanished and significantly mixed with evaporated surface water. Thermal waters do not contain tritium and therefore are older than 50 years and have deeply percolated. Artesian water in the Eastern region is high altitude originated and intensely rock-water interacted. Some hot springs in the same area emerging through weathered overburden have water significantly mixed with recent precipitation. Thermal springs that emerge through quartzite bedrock have a non-mixed, non-evaporated, and less rock-water interacted nature. Both thermal and non-thermal water with artesian conditions have clearly indicated that they originate from a common recharge source but with different flow paths, penetration depths, and travel distances, resulting in different chemical characteristics. Non-thermal springs are recharged by recent precipitation and have percolated only to shallow depths.