Terrain Conductivity Research Articles

Impacts of Terrain Conductivity Survey for Groundwater Investigation in a Typical Sedimentary Formation; A Case Study of Itori, South-West Nigeria

A geophysical investigation for groundwater development involving conductivity measurement using Electromagnetic profiling was conducted to locate fractured and fissured zones and associated groundwater containing media at Itori communities, Southwestern Nigeria. The area is underlain by the typical sedimentary rocks of South-West, Nigeria with the local geology predominantly clay, shale, clay sand, limestone and Sandstone. Measurements of the ground conductivity were carried out with Geonics EM 34-3 along 5 traverses whose profile lengths varied between 160 and 200 m. Intensive geophysical fieldworks were performed utilizing Frequency Domain Electromagnetic Method (FDEM) using Geonics-EM-34 to determine the vertical and lateral variations of subsurface conductivity probing depths of 20 m, 40 m and 60 m. The EM data were acquired at 500 m intervals along 10 profiles. The Vertical Dipole Moment in the first layer exhibited the highest true conductivity and lowest true conductivity of 42.65 mS/m and 29.1 mS/m for EMITO1 and EMITO2 respectively and the corresponding Horizontal Dipole Moment exhibited the highest true conductivity of 36.0 mS/m and 25.41 mS/m for EMITO1 alongside EMITO2 and EMITO8 respectively while the Vertical Dipole Moment in the second layer exhibited the highest true conductivity of 45.62 mS/m and lowest true conductivity of 34.76 mS/m for EMITO1 and EMITO8 respectively and the corresponding Horizontal Dipole Moment exhibited the highest true conductivity of 44.0 mS/m and lowest true conductivity of 36.3 mS/m for EMITO3 and EMITO8 respectively. The qualitative interpretation of EM results identified areas of hydrogeologic importance and forms a predictive and suggestive basis for Vertical Electrical Sounding (VES) investigation; points of positive EM anomalies were considered as priority area for electrical resistivity sounding and prospective groundwater development, since they suggest lithological variations within the unconsolidated overburden and/or water–filled fissures in the bedrock. The identified major geological interfaces were suspected to be of weathered zones

Joint Electromagnetic-Terrain Conductivity and DC-Resistivity Survey for Bedrock and Groundwater Characterization at the New Al-Obour City, Egypt

A multi-spacing electromagnetic–terrain conductivity survey profile and vertical electrical resistivity soundings were carried out at New Al-Obour City, Northeastern Cairo. The chief purpose of this survey was to characterize the bedrock, and groundwater occurrence, and hence to image both the surface and subsurface structures. The water is used mainly to meet the demands of the agricultural sector in the area. Accordingly, a set of sixteen Multi Spacing Electromagnetic Terrian Conductivity profiles and 11 vertical electrical soundings were done from September 2018 to March 2019. The data sets were transformed–inverted comprehensively with regard to stitched one-dimensional (1D) electrical resistivity smoothed-earth models. These sets were used efficiently in the interpretation of the geologic sequence of bedrock through successive conductive anomalies and electrically resistive. Remarkably, the obtained subsurface electrical resistivity structures are coincident with the mapped field geologic faults. The current study proved that a comprehensive Multi Spacing Electromagnetic Terrian Conductivity and vertical electrical sounding resistivity survey could help optimize geotechnical exploratory work. The results of the interpretation of geoelectrical data indicate that the elevation of the top of the groundwater aquifer ranges from 60-70 m above sea level.

Integration of EM techniques for mapping buried historical harbours: a case study from the archaeological site of Tell el-Rub'a, Egypt

AbstractThis study focuses on the integrated application of the frequency-domain terrain conductivity (TC) and transient electromagnetic (TEM) methods to map an ancient riverine harbour (port) at the Egyptian archaeological site of Tell el-Rub'a (prehistoric Mendes). Fifty-one TC profiles were measured using six EM frequencies and 16 TEM soundings were performed at the selected site. The apparent conductivity maps derived from the TC survey enabled defining the lateral extension of the harbour basin and its edges to penetration depths ranging between 12 and 30 m. The vertical extension of the harbour basin was determined using the TEM inversion. Three layers were defined: the topsoil, the conductive silty clay infill and the resistive sand bedrock. The bedrock is found at depths ranging from 19 to 31 m. The TC and TEM results were combined to form a 3D image of the harbour basin. This study confirms the existence of Mendes harbour and demonstrates the effectiveness of the TC and TEM methods for such archaeological studies.

Geophysical and hydrophysical evaluation of groundwater around the Igbenre Ekotedo dumpsite Ota, Southwest Nigeria, using correlation and regression analysis

A study involving geophysical survey and groundwater analysis was carried out at the Igbenre Ekotedo dumpsite in Ota, Southwest Nigeria. The aim was to monitor and track the depth of leachate contamination around the dumpsite. A proposed simple multiple linear regression (MLR) model of groundwater total dissolved solids (TDS) was also developed. This was achieved by correlating the observed TDS of groundwater samples collected within and around the vicinity of the dumpsites with multiple terrain conductivity data derived from a geophysical method. The results of the electrical resistivity tomography (ERT) obtained along four profile lines in August 2014, and a time-lapse survey in December 2015 delineated leachate plumes as low-resistivity zones ranging between 0.54 and 12.5 Ω m around the dumpsite, with good correlation between the wet and dry season models. The results also showed that leachate from the decomposed refuse materials has polluted the subsurface under the dumpsite from the surface to a depth of about 45 m, and by extension contaminating groundwater aquifer around the area. Results from the electromagnetic (EM-34) experiment and groundwater TDS parameters from seven (7) boreholes around the vicinity of the EM profiles showed a strong positive correlation. Therefore, a simple multiple linear regression (MLR) TDS model that relates the TDS data obtained from boreholes to the geophysical parameters obtained from the EM-34 data (HD 20, HD 40, and VD 40) was developed for the purpose of efficient groundwater resources monitoring and management around the dumpsite and their communities. The predictive power of the developed MLR TDS model was also apprised to determine the feasibility of using the TDS model to predict and estimate groundwater TDS around the study area. The developed TDS model can be reliably deployed for groundwater TDS estimation and monitoring around the study area where there are no boreholes, but with only terrain conductivity data. However, where there are borehole and hand-dug wells, terrain conductivity data around the area alone can be applied to the model to determine TDS concentration in groundwater, thus reducing the time and cost of determining and monitoring both parameters independently.

Imaging contamination surrounding a wastewater dumpsite using 2 terrain conductivity meters

Terrain conductivity meters are effective tools for imaging shallow groundwater and soil contamination; however, the capability of different meters as well as the comparability of their results is a controversial issue. We used the EMP-400 Profiler and EM-31 terrain conductivity meters to investigate the soil and groundwater contamination around a wastewater lake in Wadi Uranah, western Saudi Arabia. Both devices are used simultaneously to collect apparent conductivity data along 19 profiles with a total length of 40 kilometers and the collected data are subjected to similar processing routines and plotting parameters. The results show that despite differences in the absolute conductivity values acquired by both meters, they produce significantly comparable subsurface images of apparent conductivity distribution. The results also show that each meter has a set of advantages and disadvantages. The EMP-400 Profiler is lighter, smaller, and easier to handle and operate in field and has the capability to operate at 3 different frequencies, yielding images at variable depth slices. On the other hand, subsurface apparent conductivity images provided by the EM-31 show apparent conductivity images with more details those of the EMP-400 Profiler. The apparent conductivity maps, collected by both meters, confirm that the flow and accumulation of contaminants in the area are structurally controlled and trending the northeast-southwest direction.

Modeling groundwater total dissolved solid from derived electromagnetic data using multiple linear regression analysis: a case study of groundwater contamination

The high concentration of total dissolved solids (TDS) and other physicochemical parameters in groundwater around dumpsites have been used to implicate contamination from decomposed waste materials. A simple multiple linear regression (MLR) TDS model that integrates the TDS data derived from boreholes and hand-dug wells to the geophysical parameters obtained from the frequency-domain electromagnetic (EM) data was developed in this research. This is with a view to efficiently monitor groundwater resources and exploration around the Olusosun dumpsite and its communities. With the aid of the MLR equation, the observed TDS concentration of water samples collected from boreholes and hand-dug wells, and the corresponding estimated ground conductivity data in the vertical dipole mode (VD 40) and horizontal dipole modes (HD 40 and HD 20), obtained from geophysical surveys were regressed in Microsoft Excel software to generate a MLR TDS model. The integrity of the derived TDS model was appraised to examine the possibility of deploying it to investigate the TDS content of groundwater around the study area. The EM data and the resistivity models obtained around the study area confirmed contamination going on around the dumpsite. The developed TDS model can be put to use with high confidence, for groundwater TDS prediction around the study area where there are only terrain conductivity data but with no boreholes parameters. Also, terrain conductivity data alone can be applied to the model to predict the concentration of TDS in groundwater where there are no boreholes and hand-dug wells, therefore reducing the cost and time of determining and monitoring both parameters independently. With the aid of the ArcGIS software, the TDS model was used to generate TDS estimate map for the area. The knowledge of the TDS variability in such a map could give a clue about the integrity of the underground water around the site.

Radiometric and electromagnetic investigations of the Olushosun dumpsite Lagos, Southwest, Nigeria

Abstract The Olushosun dumpsite is one of the largest dumpsites in Nigeria, and variety of waste materials are often deposited on the dumpsite. Therefore, radiometric and electromagnetic (EM) investigation of the dumpsite was embarked upon to assess the radioactive status and the extent of leachate contamination. A well calibrated portable radiometric spectrometer nuclear radiation monitoring metre (Model BG0-Super-SPEC RS 230) and the Geonics EM 34 measuring instruments were used to achieve this objective. The mean activity concentration of 40K measured along all the profile lines ranged from 0.22% to 1.19% (68.86–372.47 Bq/kg), while that of 238U and 232Th ranged from 0.88 ppm to 2.02 ppm (10.87–24.95 Bq/kg) and from 4.87 ppm to 15.61 ppm (19.65–63.38 Bq/kg) respectively. The results of the radiation dose rate measurement showed that the overall mean absorbed dose rate measured in the study area were comparable to those reported around some cities in Nigeria. The radiation level along some points on the profile lines, even though high, did not exceed the safe limit of 70 μSvyr−1 as recommended by UNESCO on effect of Atomic Radiation. This implies that the inhabitants around this area are not exposed to radiological risk, and the dumpsite when reclaimed in future, could be used for the construction of buildings without any form of restrictions. However, continuous exposure to these radiations may have long term consequences on human health. Results from the EM data set along traverses on the dumpsite show that the subsurface is characterised by high conductivity (60–680 mS/m) up to a depth of 60 m. The high terrain conductivity signature here may be attributed to leached contaminats migrating into the subsurface and contaminating shallow aquifers. The descriptive statistical analysis of the measured EM data sets showed higher level of correlation among parameters measured along control lines outside of the dumpsite. Generally, correlation between the entire EM data on the dumpsite was poor, but reasonably better for the control data. This could be attributed to the heterogeneous properties of waste materials deposited on the dumpsite.

Understanding fracture distribution and its relation to knickpoint evolution in the Rio Icacos watershed (Luquillo Critical Zone Observatory, Puerto Rico) using landscape‐scale hydrogeophysics

AbstractThe Rio Icacos watershed in the Luquillo Mountains (Puerto Rico) is unique due to its extremely rapid weathering rates. The watershed is incised into a quartz diorite that has developed a large knickzone defining the river profile. Regolith thickness within the watershed generally decreases from 20 to 30 m at the ridges to several meters in the quartz diorite‐dominated valley to tens of centimeters near the major river knickpoint, as determined from previous studies. Above the knickzone, we observe spheroidal corestones, but below this weathering is much less apparent. Measured erosion rates from previous studies are also high in the knickzone compared with upper elevations within the river profile. A suite of near‐surface geophysical methods (i.e. ground penetrating radar and terrain conductivity) capable of fast data acquisition in rugged landscapes, was deployed at kilometer scales to characterize critical zone structure. Concentrations of chaotic ground penetrating radar (GPR) reflections and diffraction hyperbolas with low electrical conductivity were observed in vertical zones that outcrop at the land surface as areas of intense fracturing and spheroidally weathered corestones. The width of these fractured and weathered zones showed an increase with proximity to the knickpoint, and was attributed to dilation of these sub‐vertical fractures near the knickpoint, as postulated theoretically by a stress model calculated for the topographic variability across the knickzone in the Rio Icacos, and that shows a release of compressive stress near the knickpoint. We hypothesize that erosion rates increase in the knickzone because of this inferred dilation of fractures. Specifically, opened fractures could enhance access of water and in turn promote spalling, erosion, and spheroidal weathering. This study shows that ground‐based hydrogeophysical methods used at the landscape‐scale (traditionally applied at smaller scales) can be used to explore critical zone architecture at the scales needed to explain the extreme variability in erosion rates across river profiles. © 2018 John Wiley & Sons, Ltd.

Origin and hydrogeological setting of saline groundwater discharges to the Athabasca River: Geochemical and isotopic characterization of the hyporheic zone

Identifying impacts of oil sands development on aquatic ecosystems requires understanding of the natural background water quality. In the Athabasca Oil Sands Region of Alberta this is challenging because the Athabasca River is incised directly into bitumen saturated sands of the McMurray Formation, and other saline Cretaceous and Devonian formations. This study compares the geochemical and isotopic composition of porewater sampled from the alluvial sediment beneath the Athabasca River with regional groundwater data to identify the geological origin of these saline groundwaters, and improve characterization of natural background sources of solutes entering the Athabasca River. Terrain conductivity surveys conducted along the Athabasca River were used to identify areas with evidence of saline groundwater discharge. Porewater samples were obtained from the alluvial sediment using drive point piezometers installed between 1 and 3 m below the water-sediment interface and were analyzed for δ18O, δ2H, δ34SSO4, δ18OSO4, 87Sr/86Sr, δ13C-DIC, δ13C-DOC, 3H, and 14C. The porewater in the alluvial sediment showed variable degrees of mixing with the overlying Athabasca River water, but the geochemical and isotopic composition in zones 1, 3 and 5 are consistent with discharge of saline groundwater from Cretaceous or Devonian units. The low percentages of modern carbon, and δ18O, δ2H, δ34SSO4, δ18OSO4, and 87Sr/86Sr signatures in the deepest porewater samples from Zones 1, 3 and 5 indicate glaciogenic water with high total dissolved solids originating from Devonian sourced solutes. Theses saline groundwater discharge zones occur where higher horizontal hydraulic gradients coincide with areas of higher salinity in the adjacent Cretaceous and Devonian aquifers, and areas with vertical connectivity with underlying Devonian aquifers. The results of this study demonstrate the influence of groundwater-surface water interactions and saline bedrock formation water discharge to water quality along some reaches of the Athabasca River which need to be considered in monitoring and water management strategies.

Use of electromagnetic–terrain conductivity and DC–resistivity profiling techniques for bedrock characterization at the 15th-of-May City extension, Cairo, Egypt

A joint multi-spacing electromagnetic–terrain conductivity meter and DC–resistivity horizontal profiling survey was conducted at the anticipated eastern extensional area of the 15th-of-May City, southeastern Cairo, Egypt. The main objective of the survey was to highlight the applicability, efficiency, and reliability of utilizing such non-invasive surface techniques in a field like geologic mapping, and hence to image both the vertical and lateral electrical resistivity structures of the subsurface bedrock. Consequently, a total of reliable 6 multi-spacing electromagnetic–terrain conductivity meter and 7 DC–resistivity horizontal profiles were carried out between August 2016 and February 2017. All data sets were transformed–inverted extensively and consistently in terms of two-dimensional (2D) electrical resistivity smoothed-earth models. They could be used effectively and inexpensively to interpret the area's bedrock geologic sequence using the encountered consecutive electrically resistive and conductive anomalies. Notably, the encountered subsurface electrical resistivity structures, below all surveying profiles, are correlated well with the mapped geological faults in the field. They even could provide a useful understanding of their faulting fashion. Absolute resistivity values were not necessarily diagnostic, but their vertical and lateral variations could provide more diagnostic information about the layer lateral extensions and thicknesses, and hence suggested reliable geo-electric earth models. The study demonstrated that a detailed multi-spacing electromagnetic–terrain conductivity meter and DC–resistivity horizontal profiling survey can help design an optimal geotechnical investigative program, not only for the whole eastern extensional area of the 15th-of-May City, but also for the other new urban communities within the Egyptian desert.

Near-surface geophysical surveys at the Duport gold deposit, Ontario, Canada: Relating airborne responses to small-scale geologic features

Near-surface geophysical measurements using magnetometer, magnetic susceptibility, terrain conductivity, and time-domain electromagnetic instruments were made at the shear-hosted Duport gold deposit on Cameron Island in Shoal Lake, western Ontario, Canada, to help relate airborne total magnetic intensity (TMI) and helicopter electromagnetic survey data to small-scale geologic features. The magnetic airborne response provides a weak indication of a narrow anomaly within the Duport deformation zone, and the airborne electromagnetic response provides an indication of enhanced conductivity in the northwest of Cameron Island. In contrast, surface magnetic responses are dominated by the narrow 10,000–15,000 nT magnetic anomaly of a talc-chlorite-dolomite schistose basalt unit, a feature barely visible in the airborne TMI data. This geologic unit hosts the veins containing gold mineralization, so the surface TMI data provide a valuable response for delineating the corresponding rocks. Modeling of the TMI data indicates that the unit has a susceptibility of up to 0.7 SI and a corresponding magnetite content of up to 20%. The TMI data also reveal along-strike variations in the magnetic anomaly providing information on the component of ultramafic rocks in the protolith of the unit. The surface geophysical data allow the enhanced conductivity in the northwest part of Cameron Island to be attributed to several narrow sulfidized zones containing up to 10% pyrrhotite. Additional conductive and positively magnetized zones are associated with concentrations of 5%–10% of magnetite. The near-surface geophysics at the Duport deposit provided a rapid and inexpensive method for defining the magnetic and electrical properties of the geologic units at the site and for defining the exact location, width, and internal structure of features observed in the airborne geophysical data. Availability of magnetic susceptibility measurements from a single drill core enhanced the accuracy of the interpretations and the ability to relate the near-surface geophysical responses to geologic features.

Rolling ball algorithm as a multitask filter for terrain conductivity measurements

Portable frequency domain electromagnetic devices, commonly known as terrain conductivity meters, have become increasingly popular in recent years, especially in locating underground utilities. Data collected using these devices, however, usually suffer from major problems such as complexity and interference of apparent conductivity anomalies, near edge local spikes, and fading of conductivity contrast between a utility and the surrounding soil. This study presents the experience of adopting the rolling ball algorithm, originally designed to remove background from medical images, to treat these major problems in terrain conductivity measurements. Applying the proposed procedure to data collected using different terrain conductivity meters at different locations and conditions proves the capability of the rolling ball algorithm to treat these data both efficiently and quickly.

Integrated geophysical and physicochemical assessment of Olushosun sanitary landfill site, southwest Nigeria

An integrated surface geophysical and physicochemical study involving 2-D electrical resistivity imaging (terrain conductivity measurement using EM34-3) complimented with measurement of some physical parameters was conducted at Olushosun sanitary landfill site in Lagos metropolis, southwestern Nigeria, with the aim of investigating the lateral extent and depth of the possible subsurface leachate contamination plumes (electrically conductive anomalies) within the area. Fourteen 2-D resistivity imaging lines were investigated with a maximum spread length of 249 m per line. The result of the resistivity imaging delineated the contaminant plume as low-resistivity zones (0.24–36 Ωm) to a maximum depth of 59 m. The electrical resistivity tomography (ERT) lines were projected to produce stacked block models of the site which show southeast flow pattern of the leachate and, possibly, the groundwater flow direction. Eleven electromagnetic (EM) profiles were established with a maximum spread length of 150 m per profile using both the vertical and horizontal dipole configurations to measure terrain conductivity of the study area; 10, 20, and 40 m coil separations were deployed for the measurement. Qualitative interpretation of the EM34-3 data reveals high conductivity range of values (30–264 mmho/m) within the dumpsite as compared to conductivity values ranging between 4 and 26 mmho/m for the control site. It delineated the vertical extent of the contaminated zones up to a maximum depth of about 30 m (horizontal dipole configuration) and a maximum depth of about 60 m (vertical dipole configuration). Physicochemical analysis of the water samples taken from wells and boreholes within the precinct of the dumpsite reveal an elevation in concentrations of total dissolved solid (TDS) (range of 513–2,000 mg/l) and electrical conductivity (EC) (range of 1,019–3,999 μS/m) in wells 4, 7, 10, 11, 15, 16, and 19 with the values obtained moderately above the WHO standards. The pH obtained from water samples indicates high acidic content (5.34–6.85). These possibly indicate contamination of the groundwater as a result of solid waste leachate accumulation, thus complimenting the geophysical data. Leachate flow direction was generated from the increasing concentration of TDS and EC in southeast direction which agrees with similar flow pattern deduced from ERT results.

Tracing buried pipelines using multi frequency electromagnetic

In this paper the application of multi frequency electromagnetic techniques to locate buried pipelines is described. The survey site has two pipelines of SUMED, one of the world chokepoints. At desert or arid areas, regular geophysical surveys usually are difficult to carry out. EM techniques could be the best among geophysical techniques to be used for this target at these conditions. The EM survey was performed using a GEM-300 multi-frequency electromagnetic profiler. It is of handheld electromagnetic induction-type that measures in-phase and quadrature terrain conductivity without electrodes or direct soil contact. An area of 60×15m was surveyed, that supposed SUMED pipeline existed. Six different frequencies, typically 2025, 2875, 4125, 5875, 8425, 12,025Hz, have been used simultaneously. The slice maps for in-phase and conductivity distribution at each frequency could help to trace the extension of the pipeline. Two pipelines were traced successfully with 20 m spacing of each others.

Hydro-Geophysical Investigation of Contaminant Distribution at a Closed Landfill in Southwestern Ontario, Canada

This paper presents a hydro-geophysical investigation into the landfill leachate distribution and subsurface geology at a closed site in southwestern Ontario, Canada, using geophysical mapping and hydrological modeling approaches. Conductivity mapping was first conducted over the study site using a frequency-domain EM terrain conductivity meter, revealing an anomalous high-con- ductivity zone of about 200 m (S-N) × 80 m (W-E) at the western half of the site. The DC resistivity survey was then carried out at this anomalous zone with eight S-N profiles and three W-E profiles measuring 200m in length using a Wenner-α configuration. Our resistivity survey results indicate that the landfill leachate travels mainly south-east wards over the upper aquifer, with a minor vertical component into the upper weathered portion of the silt/sand aquitard at some locations. No contamination seems to exist in the lower sand aquifer. The geophysical results were later used to develop two conceptualized models for hydrological modeling. Our numerical results predict the leachate distribution at the study site in the future, confirming that the contaminant will occupy the entire upper aquifer and the most of the aquitard in a time of 1000 years, and that the barrier of the aquitard will protect the lower sand aquifer from the leachate pollution. These findings are critical in evaluating the current leachate conditions and the existing compliance monitoring plan for potential implementation at this study site and other sites in elsewhere.

Mixing of hydrothermal water and groundwater near hot springs, Yellowstone National Park (USA): hydrology and geochemistry

Studies of hot springs have focused mainly on the properties of fluids and solids. Fewer studies focus on the relationship between the hot springs and groundwater/surface-water environments. The differences in temperature and dissolved solids between hot-spring water and typical surface water and groundwater allow interactions to be traced. Electromagnetic terrain (EMT) conductivity is a nonintrusive technique capable of mapping mixing zones between distinct subsurface waters. These interactions include zones of groundwater/surface-water exchange and groundwater mixing. Herein, hydrogeological techniques are compared with EMT conductivity to trace hot-spring discharge interactions with shallow groundwater and surface water. Potentiometric-surface and water-quality data determined the hydrogeochemistry of two thermally influenced areas in Yellowstone National Park, Wyoming (USA). Data from the sites revealed EMT conductivity contrasts that reflected the infiltration of conductive hot-spring discharge to local groundwater systems. The anomalies reflect higher temperatures and conductivity for Na+–Cl−-rich hydrothermal fluids compared to the receiving groundwater. EMT conductivity results suggested hot springs are fed by conduits largely isolated from shallow groundwater; mixing of waters occurs after hot-spring discharge infiltrates groundwater from the surface and, generally, not by leakage in the subsurface. A model was proposed to explain the growth of sinter mounds.

Pool patterning in a northern peatland: Geophysical evidence for the role of postglacial landforms

A hydrogeophysical study conducted in a 2200-ha peatland in central Maine shows evidence that a laterally continuous esker deposit extends below the peat soil following the direction of glacier retreat and coinciding with the presence of a pool system. Ground penetrating radar (GPR), electrical resistivity (ER) imaging and terrain conductivity measurements were constrained with limited hydrological measurements, direct sampling of inorganic sediments and radiocarbon dating of peat soils to develop a conceptual model for pool formation that could explain the unique pool patterning observed in other northern peatlands. GPR profiles revealed three-dimensional images of two esker crests below the easternmost edge of the pool area. GPR data was supported by ER imaging and terrain conductivity data and allowed for facies differentiation to infer processes related to esker formation during the glacier front retreat. Hydrologic data showed preferential flow of groundwater towards the esker, suggesting that pools may persist as a result of enhanced peat decomposition and carbon loss due to oxygenation and/or upward supply of alternative electron acceptors from the mineral soil along narrow, permeable inorganic esker crests. Variations in pool depths and radiocarbon dating of peat samples from the pool bottom support a model whereby pools originate at a focus centered along the two esker crests and subsequently spread laterally outwards.

Terrain And Laboratory Conductivity Studies Of Flood Plains Of Oluwatuyi/Oshinle Areas Of Akure

A shallow electromagnetic study (electrical conductivity and magnetic susceptibility measurements) and laboratory conductivity sampling of the flood plains of Oluwatuyi/Oshinle area of Akure have been undertaken. This is with the aim of correlating the terrain conductivity mapping with laboratory measurements to establish the effectiveness of the induced secondary currents in determining the effects of infiltrating leachates occasioned by heaps of refuse dumped in the course of River Elegbin in the study area. Quadrature and in-phase measurements in vertical and horizontal dipole modes were undertaken on seventeen traverses of various lengths. Laboratory conductivity measurements were conducted on twenty one water samples obtained from hand-dug wells. The horizontal dipole measurements exhibit higher conductivity values suggesting contamination of the upper strata from the ubiquitous refuse in the area. The lower conductivity values obtained from the vertical dipole mode may be due to the high retarding capability of abundant clay in the area to contaminant flow. The similarity in conductivity distribution obtained from field and laboratory studies show that terrain conductivity is strongly influenced by saturating fluid. The high magnetic susceptibility values obtained in northern course of the river suggests predominantly ferromagnetic dumps while the low values characterizing the central and southern course indicate predominantly domestic waste in the zone.

Shallow geophysical investigations at the Akhmim archaeological site, Suhag, Egypt

Ground penetrating radar, electromagnetic terrain conductivity, and electric tomography have proven to be effective tools if they are combined together to investigate archeological sites. We have conducted a geophysical survey at the Akhmim archaeological site, the main objective of our survey is to locate additional buried structures for further excavation. Geophysical data were acquired in the area using the GEM-300 multi-frequency terrain conductivity profiler, the SIR 2000 ground penetrating radar, and the Syscal R2 resistivity meter systems. The results of the integrated interpretation show a number of buried features and a strong linear zone about 1 m wide that coincides with the suspected trend of a buried wall. There appears to be two parallel ridges of strong reflections on either side, indicating two parallel walls extended East-West and a room is identified at the bottom left corner of the site. Moreover, the interpretation results of some selected GPR and dipoledipole resistivity profiles adjacent to the open-air museum suggest the existence of a second statue of Ramses II to the right of the previously discovered statue which could still be buried in the sand.

Terrain Conductivity Evaluation of Road Base Integrity in a Basement Complex Environment

Terrain Conductivity Evaluation of Road Base Integrity in a Basement Complex Environment