scholarly journals Pore resistivity variation by Resistivity imaging technique in sedimentary part of main Gadilam river basin, Cuddalore District, Tamil Nadu, India

2021 ◽  
Vol 13 (1) ◽  
pp. 268-277
Author(s):  
R. Ravi ◽  
S. Aravindan ◽  
C. Ramachandran ◽  
Sanjay Kumar Balabantaray ◽  
B. Selvaraj ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
River Basin ◽  
Tamil Nadu ◽  
Saline Water ◽  
Groundwater Potential ◽  
High Resistivity ◽  
Clay Layer ◽  
Clayey Sand ◽  
Low Resistivity ◽  
Matching Techniques

Electrical resistivity is the only property of physics which give information of subsurface moisture content in the formation, Hence geophysical electrical resistivity survey was carried out to investigate the nature of shallow subsurface formations and geological contact in the main Gadilam river basin of Cuddalore District in Tamil Nadu. Twenty-seven vertical electrical soundings (VES) were conducted by Schlumberger configuration in the basin. Data is interpreted by curve matching techniques using IPI2 WIN software, layer parameters like apparent resistivity (?a) and thickness (h) interpretation were exported to Geographic Information System (GIS). Interpretation distinguishes three major geoelectric layers like topsoil, sandy clay layer, clayey sand layer along the contact zone in the basin. Interpreted VES sounding curves are mostly four-layer cases of QH, H, HA and KH type. Investigation demarcates lithology of subsurface and hydrogeological set up by employing maximum possible electrode sounding to infer saline water and freshwater occurrence based on resistivity signals. Zone of groundwater potential map was prepared with the combination of resistivity (?= ?1+ ?2+ ?3+ ?4) and corresponding thickness (T= T1+T2+T3+T4). High resistivity value of >200 ? m and low resistivity value of <10 ? m show the occurrence of alkaline and saline water within the formation aquifers as a result of possible rock water interaction and saline water dissolution. Four-layer resistivity cases from the matched curve (namely KH, AH, QA, and KA type) show the resistivity distribution/variation. It separates the freshwater depth wish from 1 to 140 ? m in fluvial sediments. Flood basin, sandstone and clay layer with low resistivity value of 3.16 - 7.5 ? m indicates contact with saline and freshwater aquifer. The Iso – resistivity map delineates saline water and freshwater zones with in the fourth layer cases in the same locations to indicate the irrational way of abstracting groundwater, resulting in saltwater ingress.

scholarly journals Characterisation of subglacial water using a constrained transdimensional Bayesian transient electromagnetic inversion

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 75-94 ◽  
Author(s):  
Siobhan F. Killingbeck ◽  
Adam D. Booth ◽  
Philip W. Livermore ◽  
C. Richard Bates ◽  
Landis J. West
Keyword(s):  
Electrical Resistivity ◽  
Saline Water ◽  
Radar Data ◽  
High Resistivity ◽  
Transient Time ◽  
Fractured Bedrock ◽  
Transient Electromagnetic ◽  
Seismic Shear ◽  
Time Domain Electromagnetic ◽  
Ground Penetrating

Abstract. Subglacial water modulates glacier-bed friction and therefore is of fundamental importance when characterising the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude; hence, liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of transient (time-domain) electromagnetic (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (Multimodal Layered Transdimensional Inversion – MuLTI) to the inversion of TEM data using independent depth constraints to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier, Midtdalsbreen, with depth constraints provided by co-located ground-penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 102 Ωm ± 1000 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (100 Ωm ± 15 %). High-resistivity material, 5×104 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with those from co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydrogeological interpretation of the subsurface, we propose a new 3-D interpretation in which the Midtdalsbreen subglacial material is partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water.

Detecting fault zone characteristics and paleovalley incision using electrical resistivity: Loma Blanca Fault, New Mexico

Geophysics ◽  
2021 ◽  
Vol 86 (3) ◽  
pp. B209-B221
Author(s):  
Heather Barnes ◽  
Johnny R. Hinojosa ◽  
Glenn A. Spinelli ◽  
Peter S. Mozley ◽  
Daniel Koning ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Fault Zone ◽  
Water Table ◽  
Unsaturated Zone ◽  
Late Quaternary ◽  
Rio Grande ◽  
Rio Grande Rift ◽  
High Resistivity ◽  
Low Resistivity ◽  
Sand And Gravel

We have combined electrical resistivity tomography (ERT), geologic information from boreholes and outcrops, and hydrogeologic data to investigate field-scale fault-zone cementation of the Loma Blanca Fault in the Rio Grande Rift. We have collected electrical resistivity data from 16 transects and geologic samples from 29 boreholes (completed as groundwater wells to 30 m depth) across and around the fault. The 2D ERT profiles, whose interpretations are constrained by geologic data, indicate (1) a high resistivity zone in cemented portions of the fault below the water table and (2) in the unsaturated zone, a low-resistivity feature along the cemented portions of the fault. The high-resistivity zone below the water table is consistent with a 10% reduction in porosity due to the fault zone cementation. With the same porosity in the unsaturated zone, the low-resistivity feature in the cemented fault zone is consistent with saturation >0.7, in contrast to saturation 0.2–0.7 for sediment outside of the cemented fault zone. In addition, subsurface samples and ERT profiles delineate a buttress unconformity (i.e., steeply dipping erosional contact) corresponding to a paleovalley margin. This unconformity truncates the cemented fault zone and separates Pliocene axial-fluvial sand (deposited by an ancestral Rio Grande) from late Quaternary sand and gravel (deposited by the Rio Salado, a Rio Grande tributary). The cemented fault zone in the southern portion of the study area is a hydrogeologic barrier; north of the buttress unconformity, where the cemented fault zone has been removed by erosion, the fault is not a hydrogeologic barrier. The integration of geologic, geophysical, and hydrogeologic observations is key to developing our understanding of this complex system, and it allows us to demonstrate the utility of ERT in detecting subsurface fault-zone cementation.

scholarly journals GEOELECTRIC PROSPECTION OF COPPER OCCURRENCE IN FOLDING LAYERS IN THE SUL-RIOGRANDENSE SHIELD (BRAZIL)

2018 ◽  
Vol 36 (3) ◽  
pp. 1
Author(s):  
Shaiely Fernandes Santos ◽  
Cesar Augusto Moreira ◽  
Fernanda Teles Gomes Rosa ◽  
Karolliny Borssatto ◽  
Marly Aparecida Silva
Keyword(s):  
Electrical Resistivity ◽  
Geophysical Methods ◽  
High Resistivity ◽  
Electrical Tomography ◽  
Mineral Research ◽  
2D Inversion ◽  
Copper Sulfides ◽  
Low Resistivity ◽  
Quartz Veins ◽  
Probable Presence

ABSTRACTSulfide prospecting with the geophysical methods, such as electrical resistivity and induced polarization, are promising due to the contrast of electrical resistivity and chargeability, where deposits with disseminated sulfides or filoneans are characterized by low resistivity and high polarizability. This work carried out a study of geophysical prospecting by means of tomographic acquisition in mineral copper occurrence, in the region of Caçapava do Sul. Three acquisition lines were performed by means of electrical tomography technique using a Dipole-dipole arrangement, with a length of 400 m and a spacing of 5 m between the electrodes, arranged in perpendicular layout to the structure of the area, represented by a large synclinal where research galleries with carbonates and copper sulfides were recognized in the ridge. The 2D inversion models and 3D multilevel maps indicate central and lateral regions with high resistivity and chargeability with indication of probable presence of copper sulfide, possibly housed in quartz veins. Peripheral zones with moderate resistivity and chargeability infer possible areas with presence of argilization, zones with high chargeability and low resistivity are likely to be zones of sulfation and possible silicification zones with high resistivity and low chargeability, observed in the vicinity of the probable mineralized zones.Keywords: Chargeability, Mineral Research, Resistivity, Sulfide, 3D Multilevel modeling.RESUMO A prospecção de sulfetos por meio de métodos geofísicos de eletrorresistividade e polarização induzida são altamente efetivos devido ao contraste de resistividade elétrica e cargabilidade, uma vez que os depósitos com sulfetos disseminados ou filoneanos são cvaracterizados por baixa resistividade e alta polarizabilidade. Esse trabalho realizou aquisição de tomografia elétricas em ocorrência mineral de cobre, na região de Caçapava do Sul (RS). Foram realizadas 3 linhas de tomografia elétrica em arranjo dipolo-dipolo, com 400 m de comprimento e 5 m de espaçamento entre eletrodos, dispostas de forma perpendicular à crista de um anticlinal, onde no passado foram reconhenhecidos carbonatos e sulfetos de cobre, em galerias de exploração mineral. Os modelos de inversão 2D e mapas de multiníveis 3D indicam regiões centrais e laterais com alta resistividade e alta cargabilidade com provável zona de sulfetos alojados em veios de quartzo. Zonas periféricas com moderada resistividade e cargabilidade sugerem a presença de argilização; zonas com alta cargabilidade e baixa resistividade são prováveis zonas de sulfetação e altos valores de resistividade e baixos de cargabilidade indicam zonas de silicificação.Palavras-chave: Cargabilidade, Pesquisa Mineral, Resistividade Elétrica, Sulfeto, Modelamento Multinível 3D.

scholarly journals Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion

2019 ◽  
Author(s):  
Siobhan F. Killingbeck ◽  
Adam D. Booth ◽  
Philip W. Livermore ◽  
Charles R. Bates ◽  
Landis J. West
Keyword(s):  
Electrical Resistivity ◽  
Time Domain ◽  
Saline Water ◽  
Radar Data ◽  
High Resistivity ◽  
Fractured Bedrock ◽  
Geological Interpretation ◽  
Seismic Shear ◽  
Time Domain Electromagnetics ◽  
Ground Penetrating

Abstract. Subglacial water influences the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude, hence liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of time domain electromagnetics (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (MuLTI) to the inversion of TEM data constrained by independent depth constraints, to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier Midtdalsbreen, with depth constraints provided by co-located ground penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 102 Ωm ± 100 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (100 Ωm ± 15 %). High resistivity material, 5 × 104 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydro-geological interpretation of the subsurface, we propose a new 3D interpretation of the Midtdalsbreen subglacial material partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water.

scholarly journals Geoelectrical Survey for Evaluation of Groundwater Potential Within the Basaltic Terrain of Chikotra River Basin, Maharashtra (India)

2021 ◽  
Vol 5 (2) ◽  
pp. 72-84
Author(s):  
Khan Tahama ◽  
Gautam Gupta ◽  
J. D. Patil
Keyword(s):  
Cross Sections ◽  
Planning Process ◽  
Groundwater Potential ◽  
Groundwater Exploration ◽  
High Resistivity ◽  
Groundwater Exploitation ◽  
Aquifer System ◽  
Low Resistivity ◽  
Distance Weighted ◽  
Basaltic Terrain

Geoelectrical data was acquired using Wenner array over 23 sites with constant electrode separation of 70 m over Chikotra Basin, Dist. Kolhapur, Maharashtra (India). The spatial variation maps of resistivity at depths from 2 to 70 m were plotted using Inverse Distance Weighted (IDW) technique for interpolation in ArcGIS 10.5 to obtain a comprehensive subsurface hydrogeological representation of the study area. High resistivity (>140 Ωm) up to 20m depth, indicative of massive basalts is deciphered towards the NE part of the study area, while the NW sector reveal low resistive (up to 40 Ωm) feature at shallow depths due to fractured basalts, thus conducive for groundwater exploration. Alluvium deposits and columnar jointed basalts in the central part depicts as EW trending conductive (< 30 Ωm) feature suggesting prospective groundwater zone. Low resistivity (6-50 Ωm) from shallow to deeper depths (up to 70m), in the southern region can be identified as potential aquifer system. Longitudinal geoelectric cross-sections are generated over four profiles to identify the lateral and vertical variation in geology and groundwater potential zones. The western and central part of the northern profile (A-A') is highly resistive with resistivity of the order of 80-140 Ωm constituting compact basalts and thus devoid of water. Low resistive zone (30 Ωm) in the eastern part suggests groundwater at shallow depths. Low resistivity zones ranging from 10-50 Ωm is observed at different depth levels over the central profile (B-B') which can be tapped for groundwater exploitation. Several sites over profiles C-C' and the southern-most D-D' suggest promising aquifer zones. Because defining prospective groundwater zones in hard rock terrain is difficult, it’s crucial to look into a river basin’s hydrogeological arrangement early on in the planning process.

scholarly journals Groundwater Potential Zoning in Upper Gadilam River Basin Tamil Nadu

2015 ◽  
Vol 4 ◽  
pp. 1275-1282 ◽  
Author(s):  
S. Venkateswaran ◽  
R. Ayyandurai
Keyword(s):  
River Basin ◽  
Tamil Nadu ◽  
Groundwater Potential
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