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May, 2022 ||  Volume  26  No.03

Volume 26(3) (2022),3-6

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Regional magnetic surveys in part of Delhi Fold Belt, Rajasthan (India) and implications for basement structure and mineralization

S. Bangaru Babu*1, A.V. Kulkarni2, M. Lakshmana3 and Dinesh Gupta4

3 Geophysics Division, Geological Survey of India Training Institue, Bandlaguda, Hyderabad, 500068, India
2Geophysics Division, Geological Survey of India, Seminary Hills, Nagpur, 440006, India
4Ex-Geological Survey of India, Kolkata, 700016, India


This paper presents the results of regional ground magnetic surveys carried out over an area of 4200 sq. km in parts of Ajmer and Bhilwara districts, Rajasthan, India. The study area falls in the Obvious Geological Potential (OGP) zone associated with economic mineral deposits of India. The survey was conducted for delineating the extension of various rock sequences within the Proterozoic Delhi Fold Belt (DFB). The survey brought out a strong NE-SW trending magnetic anomaly over the rocks of DFB and a mild anomaly in the northwestern part of the area, which is covered by the thick sediments of the Marwar Basin (MB) basin. The NE-SW trending anomaly in the area could be attributed to the exposed/near-surface Archaean basement that has come closer to the surface as a result of Delhi Fold Belt (DFB) tectonics. The anomaly trend brought out the clear picture of the magnetic basement within the Bhilwara Supergroup and their sub-surface structures and associated mineralization, if any. The qualitative analysis of the magnetic data delineated the contact of the significant litho units (Marwar Basin and Delhi Fold Belt). The Euler depth solutions also provided an idea about the magnetic source depths and a cluster of shallow depth solutions have been generated over the Delhi Fold Belt, which may be due to the weak susceptibility of the weathered layer. The amplitude power spectrum has been attempted for estimating the depth interfaces for each selected profile. The average depth to the basement of each profile is estimated as 1.5 km. The contacts between different litho units are also marked. The 2D modeling of a few representative profiles across the DFB reveals that the average magnetic basement depth is about 1.5 km. It is concluded that, the contact zone between Marwar Basin (MB) and Delhi Fold Belt (DFB) is structurally controlled. The results of this study has brought out significant structural features which can form favorable target areas.


Hydrogeochemical investigations of arsenic-rich groundwater using multivariate statistical analysis

N. M. Refat Nasher1,2,* and Sharmin Zaman Emon3

1Department of Geography and Environment, Jagannath University, Dhaka-1100, Bangladesh
2Graduate School of Human Development and Environment, Kobe University, Hyogo-657-0011, Japan
3Centre for Advanced Research in Sciences (CARS), University of Dhaka, Dhaka-1000, Bangladesh


Multivariate statistical analysis has been applied to assess the chemical characteristics of high arsenic groundwater from central-southern part of Bangladesh. A total of 43 shallow groundwater samples were collected and analyzed. The groundwater is almost neutral. The results of cations and anions trends are Na>Ca>Mg>K and HCO3>Cl>SO4>NO3, respectively. Alkalinity has significant positive correlation with Mg, Ca and K, which suggest silicate weathering as the major processes of controlling groundwater geochemistry. The significant positive correlation between Na and Cl indicates the seawater intrusion into groundwater. R-mode cluster allows variables into four groups. Alkalinity, Mg, K in the first, Ca in the second and Na and Cl in the third cluster, indicate silicate weathering, carbonate dissolution and seawater intrusion, respectively. R-mode factor analysis allows variables into four components having eigen values more than 1 which represent 72.5% of total variances. Component 1 is positively loaded with K, Mg, P and Alkalinity suggesting the silicate weathering. Component 2 positively loaded with Na and Cl, suggests seawater influences into groundwater. Component 3 positively loaded with Ca, suggest the carbonate dissolution. The Q-mode cluster analysis indicates that the as shows highest concentrations with highest Fe concentrations and lowest Mn concentration, suggesting the relatively high anoxic conditions of aquifer.


Interpretation of the backscattering coefficient for distinct Indian lakes using Sentinel-1 SAR imagery

Anand S. Joshi *1 and Ashish B. Itolikar 2

*1Department of Basic Sciences and Humanities, MKSSS’s Cummins College of Engineering for Women, Pune - 411052, India
2Applied Science Department, Jawaharlal Nehru Engineering College, MGM University, Aurangabad - 431003, India


Active Microwave Remote Sensing (MWRS) is used to monitor the ecological imbalances in the lake. The MWRS uses the C- band Synthetic Aperture Radar (SAR) sensor to transmit a vertically polarized signal and either receive it in vertically or horizontally polarized (VV or VH) form. The SAR sensor records the interaction of its transmitted signal with surface water in the form of the backscattering coefficient (?0), which is the monitoring parameter. In the present work, 14 distinct surface water of lakes are monitored with the SAR data from Sentinel –1. All downloaded Sentinel–1 SAR datasets are for the post-monsoon month i.e., October 2021. Pre-processing and image processing of the Sentinel–1 SAR dataset were performed for the retrieval of the maximum, minimum, and mean ?0 values in VV and VH polarization for the distinct lakes. The comparative study of maximum and minimum ?0 for the VV and VH polarization shows that the VV polarization mode is more sensitive to surface water changes. The maximum and minimum mean ?0 values in the VV polarization mode among the distinct lakes are found to be -17.08 dB and -24.18 dB, respectively. The present work analyzes the ?0 values for these lakes and provides a new light on the causes in their fluctuations.


Variability of atmospheric electric parameters during pre-lockdown and lockdown periods of 2020 – 2021 at Tirunelveli (Tamilnadu, India)

C.P. Anil Kumar1*, N. Venkatesh1, Arul Asir2, and C. Selvaraj1

1Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Krishnapuram, Tirunelveli– 627011, Tamil Nadu, India
2Popes College, M.S. University, Tirunelveli- 628251, Tamil Nadu, India


We got unique opportunity to carry out the globally improved air pollution-based atmospheric electricity experiments from 2020 to 2021. This period composes of lockdown phases of the Covid-19 pandemic. Tirunelveli (8.70N,77.80E) in Tamil Nadu, is one of the southern Indian peninsular stations for the observations of atmospheric electric parameters (AEP). A comparative study of AEP has been made during the pre-pandemic period and the lockdown period imposed to control the spread of Novel Corona virus infection with the help of ground-based indigenously developed atmospheric electric instruments. The analysis of both 2020 and 2021 data showed a marked difference in electric field and air-Earth (AE) current density. The difference in the AEP pattern is attributed to some extent to the decrease in aerosol loading caused by minimum human activities, drastically reduced emissions from industry, building construction, quarrying and mining, cement plants, vehicular emission, and stoppage of particulate matters, etc, which seem to have reduced the resistivity load in a global electric circuit (GEC).


Nitrate contamination in groundwater of Coimbatore district (South India) and human health risk assessment

Karung Phaisonreng Kom1*, B. Gurugnanam1, and V. Sunitha2

1Centre for Applied Geology, The Gandhigram Rural Institute, Gandhigram, Dindigul-624302, Tamil Nadu, India
2Department of Geology, Yogi Vemana University, Kadapa-516005, Andhra Pradesh, India


This study aims to determine the nitrate ?(NO?_(3 )^-) concentrations in groundwater and their harmful effects on human health when consumed by drinking in the Coimbatore district, South India. For this purpose, 55 groundwater samples were collected through borewells during November and December 2020 from various parts of the study area. The results of the study revealed that 36.36% of the samples had NO_(3 )^– concentration greater than the World Health Organization (WHO) recommended limit (50 mg/L) for drinking purposes. The relationship between the hydrochemical parameters and possible sources were studied using the principal component analysis (PCA) method. The results indicate that anthropogenic activities like excessive use of fertilizers, animal waste, septic tanks, municipal sewage, and wastewater may be responsible for the high nitrate ?(NO?_(3 )^-) content. The non-carcinogenic health hazards caused by high nitrate content in groundwater were calculated using the hazard quotient (HQ) model for adults, children and infants. The results suggest that 38.18% of samples for adults, 72.73% of samples for children, and 78.18% of samples for infants have an HQ value > 1 (safe value = less than or equal to 1). Therefore, the health risk assessment (HRA) indicates that infants and children in the study area are more susceptible to non-carcinogenic risks than adults. This finding could serve as a valuable guide for policy makers, which could help them better understand the groundwater quality and the non-carcinogenic risks caused by elevated nitrate in the region's groundwater.


Hydrogeochemistry and groundwater evaluation in and around Badel, Y.S.R Kadapa district, Andhra Pradesh (India)

B.Muralidhara Reddy1, V. Sunitha2*, B.Suvarna2, Y.G. Sai Sudha2, and K. Sai Krishna3

1Department of Earth Sciences, Yogi Vemana University, Kadapa-516005, Andhra Pradesh, India
2Department of Geology, Yogi Vemana University, Kadapa-516005, Andhra Pradesh, India
3Department of Geology, Kakatiya University, Warangal, Telangana-506009, India


This study intends to evaluate hydrogeochemical properties of groundwater for drinking and irrigation purpose in and around Badvel area of Y.S.R Kadapa district (Andhra Pradesh). To accomplish this objective, twenty five groundwater samples were collected and analyzed for quality parameters viz pH, EC, TDS, TH, Ca2+, Na+, K+, CO32-, HCO3-, SO42-, Cl-, NO3- and F-. Most of the groundwater samples are above the safe limits of W.H.O standards. Total dissolved solids (TDS), total hardness (TH), electrical conductivity (EC), chloride, sulphates, fluoride, nitrate levels in groundwater are beyond acceptable limits. The Gibbs plot indicates that groundwater samples fall within the field of rock dominance which is the predominant hydrogeochemical factor controlling the water chemistry. Piper's diagram reveals that water is of Na+-K+-Cl--SO42- type. Agricultural water quality indices like percent sodium, sodium adsorption ratio, kellys ratio, magnesium hazard, permeability index, potential salinity, soltan classification were also determined. Percent sodium (% Na) of 80% of water is under doubtful class. 36% of groundwater samples are unsuitable for irrigation with respect to magnesium hazard. 100% of groundwater belongs to undoudtful category in terms of Permeability Index (PI), Potential Salinity (PS) and Kelly’s Ratio (KR). Based on our study, majority of groundwater samples fall under the unsuitable category for drinking and irrigation purposes and requires proper groundwater management techniques.


An overview of micropalaeontological (pollen and diatom) research in endangered wetlands of Assam: Prospect for future study

Amulya Saxena1*, Abhijit Mazumder1, Dhruv Sen Singh2 and Samir Kumar Bera1

1 Birbal Sahni Institute of Palaeo sciences, 53 University Road, Lucknow – 226007(U.P.), India
2 Geology Department, Lucknow University, Lucknow – 226007(U.P.), India


This paper deals with the micropalaeontological (pollen and diatom) records available from Assam wetlands located in the northeastern part of India. Pollen studies reveal the changing climatic conditions (from wet to dry and vice versa) within Holocene on the basis of changing vegetational patterns of the region. On the other hand, the studies on diatom are mostly the reporting of the different recent diatom species from wetlands. Very few multiproxy researches have been done on both pollen and diatom to decipher the palaeoclimatic changes, except two studies from separate regions. Furthermore, this paper also deals with the preliminary systematic research of the surface samples collected from three different environmental set-ups of forest to establish the correlation between these environmental set-ups and its biological components. The non-arboreal pollen taxa are predominating in forest area, which is almost devoid of diatom; while open land area is characterized by arboreal pollen taxa as well as high abundance of diatom, mainly oligotrophic and pollution indicator diatom species. This study is hence used to reconstruct the shifts of environmental set-ups (due to palaeoclimatic changes) in the past after analysing the core samples collected from the same regions. This review will be a pathfinder for future researchers to study both the proxies for vegetational and climatic variations during Holocene in and around Assam wetlands.