• SHASHANK SHEKHAR

      Articles written in Journal of Earth System Science

    • Kink bands in thrust regime: Examples from Srinagar—Garhwal area, Uttarakhand, India

      Shashank Shekhar A M Bhola P S Saklani

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      This paper deciphers the late stress systems involved in the development of kink bands in the perspective of thrust regime. In kink bands, the correlation coefficient for 𝛼-𝛽 plots is positive near thrusts and negative away from thrusts. The plots show nearly linear relationship near thrusts and non-linear relationship away from thrusts. The rotation was prominent mechanism of kink band formation near thrusts and rotation coupled with shearing, along the kink planes away from thrusts. Along thrusts 𝜎1 is horizontal E–W trend and it rotates to horizontal N–S trend away from the thrust. The proposed model establishes that (1) the shearing along kink planes led to angular relationship, 𝛽 > 𝛼 and (2) the kink planes of conjugate kinks could be used for paleostress analysis even in those cases where shearing along these planes has occurred.

    • Hydrogeological characterization and assessment of groundwater quality in shallow aquifers in vicinity of Najafgarh drain of NCT Delhi

      Shashank Shekhar Aditya Sarkar

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      Najafgarh drain is the biggest drain in Delhi and contributes about 60% of the total wastewater that gets discharged from Delhi into river Yamuna. The drain traverses a length of 51 km before joining river Yamuna, and is unlined for about 31 km along its initial stretch. In recent times, efforts have been made for limited withdrawal of groundwater from shallow aquifers in close vicinity of Najafgarh drain coupled with artificial recharge of groundwater. In this perspective, assessment of groundwater quality in shallow aquifers in vicinity of the Najafgarh drain of Delhi and hydrogeological characterization of adjacent areas were done. The groundwater quality was examined in perspective of Indian as well as World Health Organization’s drinking water standards. The spatial variation in groundwater quality was studied. The linkages between trace element occurrence and hydrochemical facies variation were also established. The shallow groundwater along Najafgarh drain is contaminated in stretches and the area is not suitable for large-scale groundwater development for drinking water purposes.

    • Influence of the water–sediment interaction on the major ions chemistry and fluoride pollution in groundwater of the Older Alluvial Plains of Delhi, India

      SHAKIR ALI ALI SHASHANK SHEKHAR TRUPTI CHANDRASEKHAR AKHILESH KUMAR YADAV NARESH KUMAR ARORA CHANDRASHEKHAR AZAD KASHYAP PROSUN BHATTACHARYA S P RAI PRABHA PANDE DORNADULLA CHANDRASEKHARAM

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      Fluoride (F$^{-}$ ) pollution in groundwater of the Older Alluvial Plain (OAP) of Delhi has been reported as a major problem. About 34% of the groundwater samples collected for this study had F$^{-}$ level beyond the permissible limit; with F$^{-}$ concentration in the range of 0.14–3.15 mg/L (average 1.20 mg/L). In this context, this article for the first time attempts on the genesis of major ions chemistry and F$^{-}$ pollution in groundwater of OAP Delhi by going beyond the statistical analysis to sediment geochemistry, chemical weathering processes and understanding of the processes using stable environmental isotopes ($^{2}$H and $^{18}$O). The XRD of the OAP sediments revealed the dominance of fluor-biotite, albite, calcite, quartz, and chlorite. Whereas, the separated clay revealed the dominance of chlorite, kaolinite, and illite minerals. The saturation index (SI) values indicated that the groundwater chemistry is in the process of further F$^{-}$ enrichment by way of sediment groundwater interaction. With the given mineralogy of the sediments, the dominance of major ions like Na$^{+}$), K$^{+}$, Mg$^{2+}$, Ca$^{2+}$, Cl$^{-}$ and F$^{-}$ has been attributed to chemical weathering of biotites, phlogopites, albite, and calcite during sediment–water interaction. While the dominance of SO$_{4}$ $^{2-}$ has been attributed to anthropogenic sources and confirmed by its association with heavier stable isotopes of hydrogen ($\delta^{2}$H: −50.44 to −40.02 per thousand) and oxygen ($\delta^{18}$O: −7.19 to −5.62 per thousand) indicating evaporative enrichment during isotopic fractionation.

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