• DEVOJIT BEZBARUAH

      Articles written in Journal of Earth System Science

    • Petrography and whole-rock geochemistry of Oligocene Barail Sandstones of Surma basin: Implications for tectono-provenance and paleoclimatic condition

      PRADIP BORGOHAIN FARUQUE HUSSAIN M DEVOJIT BEZBARUAH VANTHANGLIANA V PARAKH PROTIM PHUKAN MANASH PRATIM GOGOI BUBUL BHARALI

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      The Oligocene Barail Sandstones of Surma basin from parts of Champhai District of Mizoram, northeast India has been studied for their tectono-provenance setting using petrography and geochemistry. The studied sandstones are poor to moderately sorted, subarkosic to sub-litharenite and show dominance of quartz (avg. 54.46%) followed by feldspars (avg. 7.22%), rock fragments (avg. 4.98%), mica (avg. 5.89%), matrix (avg. 14.47%) and cement (avg. 12.98%). Dominance of polycrystalline and undulatory monocrystalline quartz indicates contribution from medium grade metamorphic sources, primarily of granite gneisses. High concentration of SiO$_{2}$ with moderate to low concentration of Al$_{2}$O$_{3}$, Fe$_{2}$O$_{3}$, MgO, Na$_{2}$O and K$_{2}$O resembles the composition of upper continental crust. Moreover, moderate to high concentration of Th and V, depleted value of Ni along with TiO$_{2}$/Zr suggests derivation of sediments from felsic sources. The ratios of Eu/Eu* (avg. 0.63) and La$_{\rm {N}}$/Lu$_{\rm{N}}$ bears resemblance with the upper continental crust. Overall analyses show that the sediments were derived from the felsic terrain of neighbouring orogens probably represented by granite-gneisses and have undergone a moderate degree of weathering (avg. values of CIA: 70.20, CIW: 81.03, PIA: 77.63, WIP: 38.45, ICV: 1.06, I$_{\rm{w}}$ = 2) in a semi-humid to humid climatic conditions [Q$_{\rm{p}}$ /(F + RF):Q$_{\rm{t}}$ /(F + RF) = 0.20].

    • Springs of Pasighat, a valuable resource for the community: A hydrogeological study carried out using geoelectrical resistivity technique

      MONJIL RAJKONWAR BHABAJEET DIHINGIA UTTAM GOSWAMI DEVOJIT BEZBARUAH

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      Many springs occur in and around Pasighat. Eight major springs of the area were considered for the study. These springs are Dimple type, Fault dam type, and a combination of Fault dam and Border type. The highest discharge is 263.23 L/sec and the lowest is 1.91 L/sec. The aquifers are terrace deposits that comprise of unsorted boulders, cobbles and pebbles in sandy matrix and the springs occur at the base of different terrace levels. Due to the scarcity of dug wells or deep tube wells, subsurface investigations were done using vertical electric sounding (VES). VES data generated at six locations show H-type situation. The aquifers are at shallow depth, unconfined, and have good hydrogeological prospects. At the T$_{2}$ terrace, volume of water stored is 42,14,512.5 m$^{3}$ and the combined discharge of springs is 38,257.92 m$^{3}$ /day. These springs are recharged by precipitation and influent streams. Springs of the study area are aligned along the Himalayan Frontal Thrust (HFT) and its splays, and they have a major role in the evolution of these springs. The springs were formed due to topographic breaks and less permeable collapsed debris. Local people use spring water for the household, irrigation, laundry, and fisheries.

      $\bf{Highlights}$

      $\bullet$ Springs present along the base of the terraces have the highest discharge of 263.23 L/sec.

      $\bullet$ These springs are genetically related to HFT.

      $\bullet$ Terrace aquifers are suitable for groundwater development and groundwater flows from influent streams and foothill regions towards Siang River.

      $\bullet$ Spring water is used by local people for household, irrigation, laundry, and fisheries and proper management of these springs will ensure good supply of water in future.

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