• SAYANDEEP BANERJEE

Articles written in Journal of Earth System Science

• Grain-scale anatomy of the Bundelkhand granite: Implications for the interplay of magmatic to sub-magmatic deformation mechanisms

Grain-scale structures of the granitoid rocks from the north-western part of the Bundelkhand craton, central India are analysed with the aid of an optical microscope and electron probe micro analyser. Although field-based studies and quick microscopic observations suggest an overall porphyritic texture ofthe Bundelkhand granitoid, detailed microstructural observations reveal a significant deviation from the first-order igneous porphyritic texture. Here, we show that the Bundelkhand granitoid has three distinct grain-scale structures: (i) original pristine igneous structures, (ii) ductile deformation-related structures, and (iii) brittle fracturing-related structures. Based on microstructural evidences, we argue that the deformation-induced structures (both brittle and ductile) are not restricted to solid state, rather thesestructures initiated in the sub-magmatic stage and nucleated in partially crystallised magma during the magmatic to sub-magmatic event of the crystallisation history.

• Magnetic susceptibility investigation of the saline water intrusion problem: The LAMP-BHU protocol

A protocol is presented to perform bulk magnetic susceptibility (BMS) analysis of simulated seawater/saline water using MFK2-FA Multi-Function Kappabridge instrument at Laboratory for Analyses of Magnetic and Petrofabric (LAMP), BHU to obtain a correlation between BMS and hydrogeological data such as salinity and conductivity. This LAMP-BHU Protocol involves the preparation of simulated saline water. It has been developed after BMS measurement of 20 simulated seawater samples in different frequencies, i.e., F1 (976 Hz), F2 (3904 Hz), and F3 (15616 Hz) to prepare a standard data. This standard data is further validated with field data. Fourteen water samples are collected from the field, and hydrogeological data (salinity and conductivity) and BMS at three different frequencies were measured. Further linear regression analysis is performed on the measured data. This protocol yields efficient results with F3, followed by F1 and F2 having an R$^{2}$ value of 0.84, 0.60, and 0.54, respectively, for salinity, and 0.79, 0.51, and 0.40, respectively, for conductivity. Salinity and conductivity are showing a negative trend with all the frequencies. This protocol enables to delineate saline water intruded zone or extent of saline intrusion using BMS analysis. The proposed protocol is a rapid and efficient mode of determination of the saline water intruded zones in the coastal aquifers for prioritisation of groundwater assets facilitating freshwater availability in coastal areas.

$\bf{Highlights}$

$\bullet$ Protocol is developed for Saline water intrusion studies using magnetic susceptibility measurements.

$\bullet$ Magnetic susceptibility, salinity and conductivity was measured for simulated and field samples.

$\bullet$ Inverse relationship observed between magnetic susceptibility w.r.t. salinity and conductivity.

$\bullet$ High frequency magnetic susceptibility provides better results for gradual increase in salinity.

• An integrated assessment of the geomorphic evolution of the Garhwal synform: Implications for the relative tectonic activity in the southern part of the Garhwal Himalaya

The geomorphic changes over the earth’s crust are influenced by tectonic activities. These geomorphic changes are remnants of deformation that occurred in the recent geological past. Geomorphic features can be quantified to assess relative tectonic activity and response of landscape to active tectonics, regional structures, lithology and climate. To achieve the objectives, we evaluated the relative tectonic activity of the Garhwal synform, for which six major river basins were selected. The relative tectonic activity of all the basins is computed based on quantitative analysis of geomorphic indices. Quantitative analysis of each geomorphic parameter has been carried out, and a combined product of relative tectonic activity index (TAI) was derived for each basin. The TAI is classified into three classes based on their relative tectonic activity; basins having TAI value ${\leq}$1.75 (basins I, II and III) are placed in very high tectonic activity class, basin with a value ranging >1.75 to ${\le}$2.0 are categorised as moderately active basins (basin ‘IV’), while basins having values >2.0 are less active (basins V and VI). A relative tectonic activity map of the area surfaces for the prioritisation of each basin based upon their TAI. Furthermore, analysis of the longitudinal profile of rivers for knickpoint, precipitation and temperature variability over the last 100 years and seismic events since the last 100 years have been studied to interpret the tectonic regime and their influence on landscape evolution. The regional seismicity data suggest that the area falls in a seismic gap and has not experienced a great earthquake in recent history but have received seismic events of moderate intensity in the past. We opine that the Garhwal synform is tectonically active, and thus, significant steps should be taken for seismic risk assessment along with preventive measures. We also suggest that the influence of tectonic activities in the southeastern part of the Garhwal synform comprised by basins V and VI is relatively less than the rest of the basins. Finally, the six basins were prioritised based on their relative tectonic activity.

$\bf{Highlights}$

$\bullet$ Assessment of geomorphic indices from 30 m shuttle radar topography mission-digital elevation model (SRTM-DEM) in six drainage basins of the Garhwal Himalaya.

$\bullet$ Six river basins categorised under relative tectonic classes based on the calculation of geomorphic indices.

$\bullet$ Correlation of the large-scale geological setting and drainage basin dynamics contemplated with field evidence and regional seismicity.

$\bullet$ Quantification of relative tectonic activity index (TAI) of six river basins in the Lesser Himalaya of the Garhwal Himalaya.

• # Journal of Earth System Science

Volume 132, 2023
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019