March 2020

VOLUME 24, ISSUE 2, MARCH 2020
Journal of Indian Geophysical Union Indian Geophysical Union

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CONTENTS
Research Articles
Geothermal study in gas hydrate reservoir dominated by meandering channel system 1
Uma Shankar*, Udham Singh Yadav, Anand Prakash, and K. Sain
Evaluation of Linear structures in Dadra and Nagar Haveli, Western India: implication to
Seismotectonics of the study area 10
Naveen Kumar*, Kapil Mohan, Rakesh K. Dumka and Sumer Chopra
Crustal structure from gravity and magnetic Data in parts of Nalgonda and Khammam Districts,
Telangana (India) 22
D.C. Naskar*, P.K. Chakraborty, Ramasatish Thota and Anurag Tripathi
Nepheline syenite: A potential alternative for feldspar in the mineral industry- A case study from SE India 33
Sridhar Nalluri and Mallikarjuna Reddy Ragi*
Estimation of the natural recharge due to monsoon rainfall using entropy tool in the part of Vindhyan
fringe belt of Ahraura and Chunar blocks of Mirzapur district (U.P.), India 39
R. Kumar, N.P. Singh* and A.K. Singh
Fluoride zonation in Dharmapuri district of Tamil nadu (India) 46

Mayakannan and S. Vadivel *
Characterization of groundwater chemistry using multivariate statistical analysis in parts of

Nellore mica schist belt (Andhra Pradesh), India 52
Golla Veeraswamy*
Assessment of Groundwater Quality with respect to Fluoride in Somavathi River basin,

Ananthapuramu District (Andhra Pradesh), India 60
U. Suresh and U. Imran Basha*
J.Ind.Geophys. Union, 24(2) (2020), 1-9
Geothermal study in gas hydrate reservoir dominated by

meandering channel system
Uma Shankar1*, Udham Singh Yadav2, Anand Prakash3, and K. Sain4
1
Department of Geophysics, Institute of Science, BHU, Varanasi-221005, India
2
Oil and Natural Gas Corporation Ltd., GHRTC, Panvel, 410221, Navi Mumbai, India
3
Oil and Natural Gas Corporation Ltd., SPIC, Panvel, 410221, Navi Mumbai, India
4
Wadia Institute of Himalayan Geology, Dehradun-248001, Uttarakhand, India
*Corresponding author: umashankar@bhu.ac.in
ABSTRACT
The bottom-simulating reflectors (BSRs) are widely observed on multi-channel seismic data in the Mahanadi basin, East coast of India. To extend the spatial coverage of
geothermal gradients determined at site (NGHP-01-19) of the Expedition-01 of Indian National Gas Hydrate Program (NGHP), we estimate the geothermal gradients from
observed BSRs. A new 3-D topographic correction is applied to the estimated geothermal gradients after calibration with the drilling results. The differences between the
estimated geothermal gradient and values corrected for 3-D terrain effect vary only up to 1.8o C/km. A systematic difference between estimated geothermal gradient and the 3-D
corrected geothermal gradient values are observed along the seismic line passing through Site NGHP-01-19 in a prominent channel-levee complex system. The difference may
be due to either over simplification in the assumption of seafloor-temperature or the 1-D thermal conductivity-depth trend defined at Site NGHP-01-19 in the regionally
changing channel-sand and levee-clay sediment section. In general, good correspondence between the estimated and bathymetric corrected geothermal gradient suggests that
BSR derived geothermal gradient are well determined and can be used with confidence to extend thermal mapping across the basin.
Keywords: Gas hydrate, BSR, Channel, Geothermal gradient, 3-D topographic modeling, Mahanadi basin.
INTRODUCTION The Mahanadi basin is a major sedimentary basin located in

Gas hydrates are inferred and recovered worldwide along the northeastern part of the east coast of India (Figure 1). The
continental margins and permafrost regions, where the basin is characterized by thick accumulation (8-10 km) of
pressure and temperature are favorable for gas hydrate sediments (Curray, 1991; Bastia, 2006). Sediment input to the
stability (e.g. Kvenvolden, 1998). The thickness of the gas Bay of Bengal is dominated by the Ganges-Brahmaputra river
hydrate stability zone (GHSZ), varies widely within oceanic system, which drains much of the Himalayas. The resulting
regions depending on the temperature, pressure, methane sediment influx has built the Bengal Fan, the world’s largest
concentration and pore fluid salinity. Gas hydrate occurrences sediment accumulation. The maximum sediment thickness
are mostly inferred from seismic data by observing an reaches to 22 km on the Bangladesh shelf (Curray, 1991). The
anomalous bottom-simulating reflector (BSR) with the overall sediment flux that is received in the Mahanadi basin is
characteristics of reverse polarity with respect to the seafloor mainly from the Mahanadi river systems (Mahanadi,
reflection, cross-cutting dipping reflectors, and mimicking the Brahmani, Baitarani and Dhamara Rivers) with a sediment
seafloor topography (Sloan, 1998; Sain et al., 2012; Shankar load to the basin of the order of 7.10 × 109 kg/yr
and Riedel, 2013). The BSR marks the boundary between gas (Subramanian, 1978) and the total organic carbon (TOC) in
hydrate bearing sediments above and water-/free-gas-bearing the Mahanadi basin is estimated to be more than 1.5% (Sain
sediments below. The presence of a BSR on a seismic section and Gupta, 2008) that favors the formation of gas hydrates in
provides an efficient way to determine the geothermal this region.
gradient assuming conductive heat flow (Yamano et al., 1982; Various seismic indicators of the occurrences of gas hydrates
Davis et al., 1990; Hyndman et al., 1992; Shankar et al., were identified on multichannel seismic (MCS) data in the
2012). central and deeper parts of the Mahanadi basin (Bastia, 2006;
Determination of geothermal gradient yields valuable Collett et al., 2008; Mathur et al., 2008; Prakash et al., 2010;
information to understand the thermal regime of shallow Sain et al., 2012; Shankar and Riedel, 2014). The indicators
subsurface gas hydrate stability zone, fluid migration and pore include bottom-simulating reflectors, enhanced reflections
fluid expulsion (Grevemeyer and Villinger, 2001; He et al., below the BSR often associated with channelized (cut-and-
2007; Shankar and Riedel, 2010). The geothermal gradients fill) deposition, as well as seismic chimneys, acoustically
are mostly measured by either seafloor probe measurements transparent semi-vertical zones with advecting cold fluids
that measure the in situ thermal gradient and thermal (Bastia, 2006). The BSR occurs at about 200 m to 350 mbsf in
conductivity to depth of typically 15-20 meter below seafloor the central portion of the basin. Continuous, seismically
(mbsf), or borehole temperature gradients that extends much strong BSRs couldn't be identified on some profiles in the
deeper in sediment column. Calculating heat-flow values basin. In contrast, the top of a high-reflectivity zone is
further requires knowledge of the thermal conductivity interpreted as the base of the gas hydrate stability zone
typically determined from the recovered sediments. However, (BGHSZ) with free gas accumulations below, causing the
the direct measurement of temperature (and estimating heat high reflectivity (Collett et al., 2008; Shankar and Riedel,
flow) is a very slow procedure and provides information only 2014). Previous work showed that the Mahanadi basin is
at discrete locations, and is also very costly in marine characterized by geothermal gradients ranging from 40 to 55o
environment. C/km (Sain et al., 2011). The in-situ temperature
1
Uma Shankar et al., J.Ind.Geophys. Union, 24(2) (2020), 1-9
measurements during drilling and well logging in the GEOLOGICAL SETTING

Mahanadi basin at site NGHP-01-19 shows a geothermal
The Mahanadi offshore basin covers an area of about 80000
gradient of ~52o C/km (Collett et al., 2008) and a BSR depth
km2 in the Bay of Bengal, south of Bengal shelf, with water
of 205 mbsf (Collett et al., 2008; Shankar and Riedel, 2014).
depth ranging from 100 to 2500 m (Dangwal et al., 2008).
The relatively steep to gently-dipping continental slope is
characterized by a variety of structural settings and
depositional environments including slope and basin floor
fans, channel-levee complexes, canyon cut and fill sequences,
as well as polygonal faulting (Bastia et al., 2010a). The
seafloor morphology of the basin is fairly smooth and
seaward dipping reflectors are common (Bastia et al., 2010b).
The tectonic formation of the Mahanadi basin resulted from
rifting and break-up of Gondwanaland during the Jurassic
period (Sastri et al., 1981). The Mahanadi deep water basin
has accommodated more than 8 km of Upper Cretaceous to
recent sediments. The thick sediments in the Mahanadi basin
were supplied from the Ganga-Brahmaputra deltaic system
during Mio-Pliocene times. During the Early Paleogene, the
basin experienced passive margin carbonate and finer clastics
sedimentation, while during the Neogene, it received major
fan sediments from the Ganga-Brahmputra system (Bharali et
Figure 1(a). Details of bathymetric map of the Mahanadi basin al., 1991). In the Mahanadi basin, Tertiary meandering
and the NGHP Expedition-01 holes. The box in the inset shows
the study area in Mahanadi Basin. Drill sites are shown by black channel system and early fan-type deposits are predominant
dots. The locations of 2D multi-channel seismic lines are shown features, which have been important controlling factors in
by bold gray line overlain by BSR/BGHSZ depth using color sediment distribution (in terms of grain size) and thus gas
scale. (b) Time slice of seismic amplitude, taken from a 20 ms hydrate accumulations. Paleogene and Neogene sections in
thick window just beneath the base of gas hydrate stability from
the Mahanadi deep water basin sections exhibit channel
3D seismic data over the dotted box (shown in Figure 1a)
displaying sediment fairway system of meandering channel-fills complexes that are highly flowing (Nath et al., 2006). A
and early development of fan deposits (After Shankar and Riedel, flowing channel-levee complex often results in submarine fan
2014). lobes towards the deeper part of the basin. Incised valley and
valley fill sequences are also prevalent from Paleogene and
Results of the NGHP Expedition-01 (Collett et al., 2008),
Neogene periods.
provide an opportunity to constrain regional geothermal
gradients derived from BSRs on seismic data by using the in- Within the Mahanadi basin, a rift zone trends in a NE-SW
situ temperature measurements as calibration point, which can direction. This rift zone lies to the SE of the outcropping
decrease the overall uncertainty of seismically derived NW–SE-trending Gondawana aged Permo -Triassic
geothermal gradients. The effect of topography on subsurface Mahanadi rift zone (Fuloria et al., 1992; Subrahmanyam et al.
geothermal gradient is an important issue in interpretation of 2008). Its structural setting contains the NE–SW-striking
geothermal studies. In this study we use available 2D MCS Jurassic–Lower Cretaceous fault pattern that controls a
reflection data in the Mahanadi basin to report detailed system of depressions and highs. Significant volcanic activity
geothermal gradients estimated from BSR depth using in-situ is observed in both the Permo–Triassic and the Jurassic–
temperature measurements of NGHP Expedition-01 at site Lower Cretaceous rift zones (Fuloria et al., 1992).
NGHP-01-19. These estimated geothermal gradients are then
corrected for the thermal effects of 3-D bathymetric relief. We The eastern boundary of the Mahanadi offshore basin in the
use the finite element modeling code (Harris et al., 2011) to Bengal basin is represented by a major fault (Fuloria, 1993),
simulate seafloor bathymetry and geothermal gradient along and in the southwestern part, the basin is limited by the 85°
seismic lines. Simulated geothermal gradients are corrected East Ridge. Analysis of geophysical data at the margin
for terrain effect, using three-dimensional Blackwell indicates that the 85° East Ridge meets the eastern continental
correction (Blackwell et al., 1980), which considers the margins of India (ECMI) at Mahanadi basin and continues
possible topographical influence on geothermal gradient northward up to Rajmahal traps (Subrahmanyam et al., 1999;
estimated from BSR depths. Subsequently these values are Krishna, 2003; Subrahmanyam et al., 2008, Bastia et al.,
compared with the estimated geothermal gradient to evaluate 2010a).
focused fluid flow related features.
2
J.Ind.Geophys. Union, 24(2) (2020), 1-9 Uma Shankar et al.,
DATA AND METHODS

Geothermal gradient derived from BSR depth
To understand the spatial variation of geothermal gradient
along the seismic lines, we require seafloor temperature and
temperature at BSR depth. We estimate geothermal gradients
from the depths of identified BSR using existing approaches
(Ganguly et al., 2000; He et al., 2007; Horozal et al., 2009;
Shankar and Riedel, 2010; 2013). Using the depths of BSR as
geothermal gradient proxy allows derivation of almost
continuous profiles of geothermal gradient along the seismic
lines. Therefore, the overall geothermal gradient distribution
derived from the BSR depths can be much less biased than
that from direct measurements at discrete locations. The BSR-
derived geothermal gradients are known to be largely
consistent with direct measurements and less sensitive to short
time scale changes in water bottom temperature than probe
measurements (Grevemeyer and Villinger, 2001). We derive
geothermal gradient from BSR depth using a simple Figure 2. Measured in-situ temperature versus water depth of
NGHP Expedition-01 in Mahanadi Basin. Blue line represents
conductive modeling approach and empirical relation as:
temperature versus depth profile in the water column from CTD
measurement in our study area. Black line shows the linear fit to
CTD profile and in-situ measured temperature data and its linear
 TBSR  TSeafloor  , ……………………………(1) regression in equation (2).
GD  1000   
 D 
Our BSR-derived geothermal gradient at site NGHP-0-19 is
where, GD is the geothermal gradient in °C/km, TBSR and 51.92 °C/km, which is consistent with the value of 53(±2)
TSeafloor are the temperatures in °C at the BSR and seafloor °C/km determined from in situ temperature measurements at
respectively, and D is the depth from the seafloor to the drill Site NGHP-01-19. The estimated gas hydrate stability
estimated depth of the BSR in meters. zone at well site location is 205 m. This is matching well with
the depth to the base of methane hydrate stability zone
Seafloor temperature TSeafloor is estimated using the linear predicted from the phase diagram, assuming pure methane
regression from in-situ temperature measurement at Site and pore water salinity of 35 ppt (Sloan, 1998), similar to the
NGHP-01-19, which is also comparable with the one BSR depth at 205 m observed on the seismic section (Collett
oceanographic Conductive Temperature-Depth (CTD) et al., 2008).
measurement from the study area shown in Figure 2, can be
represented by a formula as: Seismic and in-situ temperature data
Here, we present four seismic sections (location in Figure 1b)
TSeafloor  8.10  0.002  z ,........................................................(2) to mark various depositional systems in the Mahanadi basin.
The regional MCS lines were acquired by GX Technology for
where, z is water depth in meter. Reliance Industries and subsequently provided by the
Directorate General of Hydrocarbons (DGH), India to the
The temperature at the BSR (TBSR) was estimated using the NGHP (Collett et al., 2008). Previously, some observations
experimental stability condition for the methane–seawater were made from these data with reference to gas hydrate
system (Bouriak et al., 2000), which is based on pure methane occurrences in the shallow sub-surface sediments (Shankar
and standard sea water salinity (35 ppt). The term D in and Riedel, 2014). The complete data set is used for defining
equation (1) is determined by assuming uniform interval geophysical drilling targets, overall site selection, and drilling
velocity of 1600 m/s for the entire GHSZ, which is safety for NGHP Expedition-01. The BSR and BSR-like
approximated from the MCS stacking velocities, and the features are mapped along all available time-migrated seismic
acoustic log and VSP-data (Collett et al., 2008). We further lines and show a clear association to channel-complexes
assume a hydrostatic pressure regime and calculated the (Figure 1b). Figure 3 shows a seismic section oriented SW-
pressure using a constant water density of 1030 kg/m3. NE crossing Site NGHP-01-19, which was drilled at ~1422 m
water depth (Collett et al., 2008).
3
Figure 3. Resistivity log at site NGHP-01-19 is superimposed on time-migrated seismic section, which is two similar channelized free-
gas accumulations (dashed orange color). The channel-levee complex consists of a narrow zone of stacked high amplitude events,
flanked on both sides by reflection free zones. Top of the high reflectivity zone interpreted as BGHSZ is confirmed by geothermal
modeling from in situ temperature measurements shown by dotted green line. The upper panel shows the estimated geothermal gradient
(black dash line) interpreted, and modeled BGHSZ (blue dash line) constrained by BSR and 3-D topographic corrected geothermal
gradient.
Figure 4 shows a seismic section oriented NW-SE crossing The BSR is in contrast not clearly identifiable towards the SE
Site NGHP-01-18 that was drilled at ~1374 m water depth. in the deeper portion of the basin. Alternatively, high seismic
The seismic profile does not show a clear BSR; however, the reflectivity below the projected BSR may indicate the
top of high reflectivity zone matches well with the geothermal presence of free gas and thus the BGHSZ. Numerous faults
modeling of the expected BGHSZ (Shankar and Riedel, identified in the deeper part of the seismic section extend up
2014). to seafloor and form a polygonal pattern. The BSR is
estimated at the drill site NGHP-01-08 at a depth of 256 mbsf
The seismic line crossing site NGHP-01-08 (drilled at a water using a constant velocity of 1600 m/s for the entire sediment
depth of 1689 m) is oriented NW-SE and shows a distinct column (Collett et al., 2008).
BSR, which cuts seaward dipping reflectors (SDR) (Figure 5).
Figure 4. The NW-SE oriented time-migrated seismic section crossing the Site NGHP-01-18. Channel-levee complex consists of a
narrow zone of stacked high amplitude events, flanked on both sides by reflection free zones. Top of the high reflectivity zone interpreted
as BGHSZ and confirmed by geothermal modeling (shown by green dashed line). High reflectivity zone is outlined by dashed orange
color. Gas chimney is observed in the middle of seismic section displaying the pull-up structure. The upper panel shows the estimated
geothermal gradient (black dash line) with 3-D topographic corrected geothermal gradient (blue dash line) from the interpreted BGHSZ.
4
Figure 5. The resistivity log is superimposed on NW-SE oriented time-migrated seismic section crossing the Site NGHP-01-08. BSR is
observed on the northwestern part of the seismic section and marked with arrow. Top of the high reflectivity zone interpreted as BGHSZ
and confirmed by geothermal modeling is shown by green dotted line. High reflectivity zone just below BSR outlined by dashed orange
color. Upper panel shows the estimated geothermal gradient (black dash line) constrained by observed BSR and 3-D topographic
corrected geothermal gradient (blue dash line) from the interpreted BGHSZ. Seaward dipping reflectors (SDR) marked with arrow.
Figure 6. The resistivity log superimposed on NW-SE oriented time-migrated seismic section crossing at Site NGHP-01-09. The top of
the high reflectivity zone interpreted as BGHSZ and confirmed by geothermal modeling shown by green dotted line. High reflectivity
zone outlined by dashed orange color. Upper panel shows the estimated geothermal gradient (black dash line) and 3-D topographic
corrected geothermal gradient (blue dash line) from the interpreted BGHSZ.
The BSR originates from the northwest slope and extends up 6 shows a seismic section oriented NW-SE crossing Site
to 9 km towards the Southeast (Figure 5). The seismic line NGHP-01-09, that was drilled at ~1935 m water depth. The
shows a sedimentary section dominated by slope processes. seismic profile does not show a clear BSR; however, the top
The seafloor is relatively flat with gentle slope. However, the of high reflectivity zone matches well with the geothermal
seismic section about 12 to 25 km to the southeast shows modeling of the expected base of gas hydrate stability zone
evidence of sediment overburden and possible faulting. Figure (BGHSZ) (Shankar and Riedel, 2014).
5
During drilling operations at Site NGHP-01-19 (water depth complex characterized by a high-amplitude reflector-package.
~1434 m), seven attempts were made to measure in situ The observed channel-levee complex on seismic section
temperature, and six provided usable in-situ temperature data consists of a narrow zone of high amplitude events, flanked
(Collett et al., 2008) up to 301.4 mbsf. The seafloor on both sides by reflection free zones. The stacked high
temperature intercept was determined as 4.8 ± 0.2°C and the amplitudes represent channel-sands whereas the low-
geothermal gradient was calculated as 53 ± 2°C/km. Initial reflectivity zones at the flanks are the levee-clays (Figure 3).
analyses of the borehole temperature data shows consistent Evidence of a free gas zone below the BGHSZ as mapped on
results between the BGHSZ predicted from BSR depth and line crossing site NGHP-01-18, shows an apparent chimney-
the predicted BGHSZ from in-situ temperature measurements like structure of reduced seismic reflectivity (Figure 4), often
in the borehole. The shipboard calculated seafloor associated with cold vents (e.g. Riedel et al., 2002, Ryu et al.,
temperature and geothermal gradient was 4.8°C and 52°C/km 2009). The depths of the BSR for seismic sections are
respectively (Collett et al., 2008). estimated using acoustic velocity 1600 m/s for the entire
sediments above the BSR (Collett et al., 2008). The observed
3-D topographic corrections over estimated geothermal BSR depth on seismic sections appears to closely
gradient corresponding to the predicted depth of the BGHSZ from the
A 3-D topographic numerical simulation is carried out for the geothermal modeling of the BGHSZ.
precise representation of bathymetric effect on geothermal A continuous BSR was identified along the NW portion of the
gradients. Bathymetry has the potential to alter the thermal MCS line crossing site NGHP-01-08 (Figure 5). The
field by increasing the thermal gradient under bathymetric identified BSR is parallel to the seafloor and characterized by
lows and decreasing it under bathymetric highs due to high reflection amplitude, reversed polarity relative to the
focusing and defocusing effect. High-resolution bathymetry seafloor, and is cross-cutting dipping strata (Figure 5).
derived from multichannel seismic data shows obvious relief However, BSR appears terminating near site NGHP-01-08.
in the study area. Our strategy for correcting the thermal field The low-reflectivity zone near the seafloor along this seismic
is based on techniques formulated by Blackwell et al. (1980). section documents a different acoustic envelope suggesting a
For each geothermal gradient we construct a grid of seafloor slope fan depositional environment. Transparent zone
temperatures based on three-dimensional bathymetry grid observed may be due to possible mudflow. The younger
from ETOPO1 of National Geophysical Data Center (NOAA) sediments are cut by numerous vertical to sub-vertical
(www.ngdc.noaa.gov/mgg/global/global.html), and conductivity,
polygonal fault systems associated with differential
temperature and depth (CTD) from the study area. Seafloor compaction and fluid expulsion (Bastia et al., 2010b).
temperatures are projected onto a horizontal plane defined at Enhanced seismic reflections below the BSR are
the top of the seafloor using the best fitting thermal gradient. characterized by strong amplitudes compared to the
Finally, this surface is fit with a Fourier series and upward surrounding reflectors suggesting the presence of free-gas
(depth positive down) continued to generate the thermal below the BSR (Figures 3-6).
perturbations created by the bathymetry. As the best fitting
gradient used in the projection step is also the unknown, it is Geothermal modeling is performed to predict the depth of the
solved iteratively. The bathymetrically induced gradients are BGHSZ, using in-situ temperature measurements where no
subtracted from the observed gradient to generate the clear isolated BSR is seen in the seismic data. This modeling
background thermal gradient. We use the finite-element approach is useful as a search-tool of the aerial extent of the
modeling code, developed by Harris et al., (2011) to simulate BGHSZ where a BSR is not easily identified (e.g. due to fluid
geothermal gradient estimated from the BSR depth along migration, faulting, or where the BSR is draped by or
seismic lines in the Mahanadi basin. Simulated geothermal conformable to layered sediments). Modeled BGHSZs are
gradient values are corrected for 3-D terrain effects and shown with green dashed line on seismic section (Figures 3-6)
compared with the estimated geothermal gradient value along to understand any changes in BSR depth and amplitude across
seismic profiles. the 2D seismic profiles, to potentially define fluid-migration
pathways along faults, and identify zones affected by
RESULTS AND DISCISSIONS deflections of the geothermal gradients by topography.
The available MCS data from the Mahanadi basin are re- Using the BSR as a proxy for the BGHSZ, we determine the
investigated to characterize the occurrences of gas hydrate potential gas hydrate stability thickness of the Mahanadi basin
constraining the drill site information during NGHP along available seismic sections and its ranges from 200-241
Expedition-01. No clear, continuous and high-amplitude BSR m. The geothermal gradients estimated from the BSR depths
is identified throughout the seismic sections crossing Sites along seismic lines vary from ~43 to 93 oC/km (Figure 3-6).
NGHP-01-19, 18 and 09 (Figures 3,4 and 6). The dominant The geothermal gradient distribution closely correlates with
depositional elements are separated by the channel–levee the bathymetry. Higher geothermal gradient occurs in the
6
deeper water depth and lower geothermal gradient is observed topographic correction are less than 2.0 0C/km. However, a
in the shallower part of the seismic lines. In general it is systematic increase in this difference is seen along the seismic
expected to have a general east-ward increasing trend in section. This may be due to an over-simplification in the
geothermal gradients. application of seafloor-temperature varying only by water-
depth (equation 2) or a regional change in thermal
In order to investigate the apparent correlation of geothermal conductivity from the difference in the physical properties of
gradient with topography, we follow the method given by channel-sands and levee-clays.
Blackwell et al. (1980). The three-dimensional perturbations
using this method generally produce a small change in the Figure 7 shows a comparison between geothermal gradient
geothermal gradient based on the available bathymetry data. estimated from the BSR/BGHSZ depth and the 3-D
We compare the geothermal gradients along seismic lines topographic corrected geothermal gradient along seismic
estimated from the depth of BSR and or BGHSZ and then lines. The correlations between the thermal gradients have R2
apply three-dimensional topographic corrections to these values more than 0.97 and generally increasing towards
estimates. Figures 3-6 show the results of applying the 3-D deeper sea and following topographic trend. The estimated
topographic geothermal gradient along seismic lines. The 3-D and 3-D topographic corrected geothermal gradients show
topographic corrected geothermal gradient (blue dash line) is good correlation and improve the confidence over the
in good correspondence with the estimated geothermal estimated geothermal gradient values from BSRs/BGHSZs for
gradient (black dash line) (Figures 3-6). The difference of further interpretation of seismic data along with the
geothermal gradients from the regional estimates and the 3-D geothermal data.
Figure 7. Cross-plot between geothermal gradients estimated from the BSR/BGHSZ depth and 3-D topographic corrected geothermal
gradient along seismic lines shown in figures 2-5. The geothermal gradient generally increases towards deeper sea. Red line shows the
best linear fit to the geothermal gradient values. R2 values of linear fit for all the lines are more than 95%.
7
CONCLUSIONS Collett, T.S., Riedel, M., Cochran, J.R., Boswell, R., Presley, J.,
Kumar, P., Sathe, A.V., Sethi, A., Lall, M. and Sibal, V.,
We use bathymetry gridded and seafloor temperature data 2008. NGHP Expedition 01 Scientists, 2008. National Gas
coupled with a finite element method to analyze the effect of Hydrate Program Expedition 01 Initial Reports: Directorate
topography on geothermal gradients estimated from the depth General of Hydrocarbons, New Delhi.
of BSR and/or BGHSZ in the study area. The terrain effect on Dangwal, V., Sengupta, S. and Desai, A.G., 2008. Speculated
geothermal field in the Mahanadi basin shows very small Petroleum Systems in Deep Offshore Mahanadi Basin in
Bay of Bengal, India: In proceeding of 7th International
variation in geothermal gradients (maximum up to 1.8oC/km). Conference and Exposition on Petroleum Geophysics,
The seismic data show that the study area in Mahanadi basin Hyderabad, India.
is dominated by channel-levee complexes of the Bengal fan Davis, E.E., Hyndman, R.D. and Villinger, H., 1990. Rates of
and in contrast to the singled turbidities of sand-rich fluid expulsion across the northern Cascadia accretionary
Mahanadi system. The BSR-derived geothermal gradient prism: constraints from new heat flow and multichannel
varies from 43 to 93 oC/km along the seismic lines and seismic reflection data. J. Geophys. Res., 95, 8869-8889.
Fuloria, R.C., Pandey, R.N., Bharali, B.R. and Mishra, J.K.,
generally follows the bathymetry trend. The good agreement 1992. Stratigraphy, Structure and Tectonics of Mahanadi
between the estimated and simulated BSR derived geothermal offshore Basin. J. Geol. Soc. India, 29, 255-265.
gradient suggests that the Mahanadi basin may be thermally Fuloria, R.C., 1993. Geology and hydrocarbon prospects of
stable. The gas hydrate deposits are in equilibrium with the Mahanadi Basin, India. In: Biswas, S.K. (Eds.) Second
overall thermal regime and have not been disturbed by recent seminar on petroliferous basins of India: Part 2. Indian
tectonic events (faulting), changes in sedimentation rate from Petroleum Publishers, 1, 355-369.
Ganguly, N., Spence, G.D., Chapman, N.R. and Hyndman, R.D.,
the channel-levee systems, or affected by fluid advection.
2000. Heat flow variations from bottom simulating
ACKNOWLEDGEMENTS reflectors on the Cascadia margin. Marine Geol., 164, 53-68.
Grevemeyer, I. and Villinger, H., 2001. Gas hydrate stability and
The authors wish to thank those who contributed to the the assessment of heat flow through continental margins.
success of Expedition 01 of Indian National Gas Hydrate Geophys. J. Int., 145, 647-660.
Harris, R.N., Schmidt-Schierhorn, F. and Spinelli, G., 2011.
Program (NGHP-01). I would like to thank Prof. Rob Harris,
Heat flow along the NanTroSEIZE transect: Results from
OSU, USA for providing me 3-D terrain effect modeling IODP Expeditions 315 and 316 offshore the Kii Peninsula,
program. Japan. Geochemistry Geophysics Geosystems, 12, Q0AD16,
doi:10.1029/2011GC003593.
Compliance with Ethical Standards He, T., Spence, G.D., Riedel, M., Hyndman, R.D. and Chapman,
N.R., 2007. Fluid flow and origin of a carbonate mound
The authors declare that they have no conflict of interest and offshore Vancouver Island: Seismic and heat flow
adhere to copyright norms. constraints. Marine Geol., 239, 83–98.
Horozal, S., Lee, G.H., Yi, B.Y., Yoo, D.G., Park, K.P., Lee,
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Krishna-Godavari and Mahanadi basins: new data. J. Geol. saturation of gas hydrate in the Krishna-Godavari Basin,
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Section A: Earth Planet. Sci., 87, 77-88.
Received on: 28.01.2020; Revised on: 14.03.2020; Accepted on: 19.02.2020
9
Evaluation of Linear structures in Dadra and Nagar Haveli, Western India:

implication to Seismotectonics of the study area
Naveen Kumar1, 2*, Kapil Mohan1, Rakesh K. Dumka1 and Sumer Chopra1
1
Institute of Seismological Research, Raisan, Gandhinagar – 382 009, Gujarat, India
2
Department of Earth Science, Gujarat University, Navrangpura, Ahmedabad, Gujarat-380009
*Corresponding author: naveen5attri@gmail.com
ABSTRACT
This is the first report and analysis on the study of faults and lineaments from the Dadra and Nagar Haveli (U.T) and surroundings together with the northern part of
Konkan coastal belt of western India. The study has been carried out using photo-geological interpretations followed by field investigation. The slickenside-bearing
fault planes, normal faults, strike-slip faults, brittle shear zones, lineaments and extensional fractures have been mapped. The interpretation of lineament fabric,
fracture traces and the rosettes constructed for the different domains clearly indicate the predominance of nearly N-S oriented fractures accompanied by conjugate sets
along NE - SW and NW - SE directions, with a subordinate set of the E-W fractures. The basic dykes are found emplaced along the pre-existing fractures having
roughly N–S to NE– SW, NW–SE and E-W. The NW-SE and E-W dykes are found sheared and displaced by the N-S trending faults. The study area falls within the
Panvel seismic zone and the recent seismicity has also been witnessed in the vicinity of N-S trending linear geological features. The presence of seismicity,
slickenside bearing fault planes, brittle shear zones, extensional features and deformed dykes suggests that the study area has experienced the neotectonic activities
and still seismically active.
Keywords: Slickenside, Lineaments, faults, Panvel seismic zone, Dadra and Nagar Haveli, Western India
INTRODUCTION (Mohan et al., 2007) and thus presently seismically active.

The dykes, sills and plugs are important components of
The west coast of India has witnessed repeated rifting
the magmatic eruptive system of the Deccan Trap. Three
events from Late Triassic/Early Jurassic to Late
large dyke systems trending (i) N-S along the west coast
Cretaceous, with the opening of the Kachchh rift,
and the Konkan coastal belt, known as west coast swarm,
followed by Cambay and Narmada rift (Biswas, 1987).
(ii) the east-west trending Narmada- Tapti swarm in the
The opening of these three rifts on the western margin of
northern region of western India and (iii) the Nashik-Pune
the Indian plate led to the opening of the Indian Ocean
swarm in the central-western Deccan (Vanderkluysen et
with the separation of the Indian-Madagascar plate from
al., 2011) are seen here. The brittle sheared dykes have
Africa (Courtillot et al., 1988). Madagascar separated
been reported by Misra et al., (2014) from the Mumbai
from the Indian plate with the activation of the NE-SW
region of Konkan coastal belt. The deformation in dykes
trending Mega Shear (Reeves et al., 2002).
due to the stress barrier are also noticed by Babar et al.,
Simultaneously, the ENE-WSW trending faults
(2017).
reactivated by block faulting, displaced the Moho in the
region (Kaila et al., 1981). The NNW-SSE trending West The use of Satellite and GIS data are considered important
Coast fault is significant fault zones that might have in the study of structural geology to extract lineament,
driven the key role in the tectonics of the western faults and other structures that provide us an outline of the
continental fringe of India (Chandrasekharam, 1985; tectonic events (Nahmi et al., 2016). In hilly terrain one of
Biswas, 1987). The West Coast fault was probably the useful application of remote sensing tools is the
inactive during Triassic–Jurassic and reactivated in identification of geological lineaments and faults of
Cretaceous–Early Paleocene (Biswas, 1987). The Panvel tectonic significance using satellite data and digital
flexure is a regional monocline (Auden, 1949) which dips elevation model (DEM). The remote sensing applications
in West with ~2–15° angle and formed at 65– 64 Ma cover many geological fields of studies, such as structural
(Hooper et al., 2010) or 63–62 Ma and afterwards by geology, mineral exploration, groundwater, lineaments
rifting India from Seychelles (Sheth and Pande, 2014). and structure features delineation (Abdullah et al., 2013.
The surge in dips of the volcanic flows to the Arabian Sea The objective of the present study is to identify the
delineates the Panvel Flexure presence along the western deformational features and to prepare a structural map of
fringe of India (Dessai and Bertrand, 1995; Sheth, 1998). the studied area, using satellite imagery and DEM derived
The dykes in the region explain the extent and the trend of products in a geospatial environment followed by the
this flexure (Dessai and Bertrand, 1995). The Panvel geological fieldwork. We covered 50 km2 area in the field
flexure was termed as a syn- or post-rift extensional fault mapping and a larger area by remote sensing. By
structure consist of tilted fault blocks (Dessai and combining all these features with earthquake events (1856
Bertrand, 1995; Dessai and Viegas, 1995). The area along to recent), a seismotectonic map of the study area has
the 150 km axis of Panvel flexure currently shows been prepared. We also present the location of new
microseismicity from shallow to deep (~2–15 km) levels lineaments and faults mapped from the Dadra and Nagar
10
Naveen Kumar et al. J.Ind.Geophys. Union, 24(2) (2020), 10-21
Haveli (U.T) and its surroundings. The identification of of faulting during Pliocene (Krishnan, 1953). In south
Lineaments in the study area will provide valuable data to Gujarat, the Deccan Trap flow dips in western direction
interpret the tectonic evolution, seismic behavior, and present as a monocline flexure structure, the axis of
deformation scenario and will be useful in seismic hazard this structure pass through Kalyan and Panvel in
assessment of the Dadra and Nagar Haveli region. Maharashtra (Rao et al., 1991). This flexure is called as
the Panvel flexure it is fractured along its axis and
Regional Geology and Tectonics witnessed many hot water springs along its length (Rao et
The Lithostratigraphy and the chemo-stratigraphy of the al., 1991). In the early tertiary period, western India
Deccan large volcanic province is well studied by Beane perceived a large tectonic event resulting in the formation
et al., (1986), Mitchell and Widdowson (1991), of west coast fault along with the Precambrian basement
Widdowson et al., (2000), Ramakrishnan and and the formation of Panvel Flexure is also related with
Vaidyanadhan, (2008) and Peng et al., (2014). The study this event (Crawford, 1971; Cox, 1988; Mahoney, 1988).
area is located in the western coastal region of western White et al., (1987) suggested that the NNW-SSE trend of
India in the northern part of the Konkan coastal belt west coast fault and parallel fracture system (that runs and
(Figure-1). It is bounded by the west coast fault in the controls the west coast of India and the Panvel Flexure)
west and Western Ghats escarpment in the east. The could be an expression of the extending and breaking of
coastal tract extending between Dadra and Nagar Haveli continental lithosphere in reaction to rifting, while Burke
and Dahanu (Maharashtra) are dominated by the Deccan and Dewey (1973) suggested that the west coast fault and
basalt, trachyte and rhyolite complex with dykes of its fracture system are parallel to one limb of the triple
dolerite. The west coast of India was developed as a result junction situated around Cambay.
Figure 1. The Tectonic map of Western India (after Biswas, 1987; Sheth, 1998), KMF-Kachchh Mainland Fault, KHF-Katrol
Hill Fault, ECF-East Cambay Fault, WCF-West Cambay Fault, NKF-North Kathiawar Fault, SNF-Son-Narmada Fault, NTF-
North Tapti Fault.
12
J.Ind.Geophys. Union, 24(2) (2020), 10-21 Naveen Kumar et al.
METHODOLOGY various image enhancement techniques were used. These

techniques were used to increase the photographic
The LISS III image of the year 2013, with a resolution of
distinction of the various features in the images. The
23.6 m has been used in present study along with the
processed images from original data were produced with
SRTM digital elevation model (DEM) and survey of India
an objective to increase the information that can be easily
(SOI) toposheets of 1:50,000 scale for identification of
interpreted from the various data sets.
lineaments in very rugged topography. The satellite
images (LISS-III) and DEM (SRTM) were processed to Seismicity in the study area
delineate the linear features, the GIS platforms were used
to enhance the interpretability of remote sensing data. In The Dadra and Nagar Haveli region has been experiencing
rugged terrains, it becomes very difficult to identify the the earthquake events since 1856. Two historic events
linear features of importance, so that the use of remote (Magnitude Ms 5 in 1935 and Magnitude Ms 5.7 in 1856)
sensing tools makes it easy to identify the linear features were reported from the southern part of the study area
viz. lineaments and faults. Images with cloud and (Chandra, 1977; Bansal and Gupta, 1998). More than 200
vegetation covers, etc., were rejected. The Deccan trap number of earthquakes were recorded between M 1 to 5.7
remains densely vegetated during and after the monsoon. (Chandra, 1977; Bansal and Gupta, 1998; ISC; IMD and
So, images from months of December to April were ISR) in the study area. The earthquake epicentres with
preferred. For effective display and better interpretations, historic events above magnitude 3 are given in Table 1.
Table 1. List of Earthquakes >3 Magnitude in the study area from the year 1856 to recent.
Depth Magnitude
Year Latitude Longitude Ref.
(Km.) (M)
25/12/1856 20 73 5.7 Chandra (1977)
20/07/1935 20 73 5 Bansal and Gupta (1998)
21/6/1989 20.09 72.91 4.1 ISC
02/09/1998 20.46 72.995 13.2 3.3 NDI
12/02/2003 20.139 72.503 13.9 3.1 NDI
15/05/2004 20.296 73.149 5.8 2.4 NDI
04/11/2005 20.179 73.41 5 3.1 NDI
05/12/2016 20.506 73.391 3 ISR
25/12/2017 20.006 73.097 10 3.9 ISR
25/12/2017 19.8 73.2 5 3.4 IMD
11/11/2018 19.9 73.0 10 3.2 IMD
24/11/2018 19.9 72.8 10 3.3 IMD
28/01/2019 20.427 73.743 14.7 3 ISR
1/2/2019 20.033 72.964 10 3.3 ISR
1/2/2019 19.959 72.882 10 3.4 ISR
1/2/2019 20.057 72.964 10 3.6 ISR
1/2/2019 19.928 72.959 10 3.7 ISR
20/01/2019 19.918 72.464 3.1 3.5 IMD
7/2/2019 20.027 72.847 10 3.1 ISR
13/02/2019 20.34 72.658 10 3.2 ISR
20/02/2019 20.048 72.91 10 3.4 ISR
1/3/2019 19.984 72.772 10 4.4 ISR
9/3/2019 19.859 72.556 48.6 3 ISR
11/3/2019 20.118 72.928 10 3.4 ISR
2/4/2019 19.923 72.768 14.5 3.1 ISR
15/4/2019 20 72.8 5 3.4 IMD
20/07/2019 20.0 72.90 10.0 3.5 ISR
13
RESULTS AND DISCUSSION planes are susceptible to erosion (Whiteside, 1986;

Doblas, 1998; Kranis, 2007). The slickensides zone is
We studied sub-horizontal and sub-vertical outcrops in the
well exposed for a depth of 2-4 m in the road cuttings
field at rocky areas, road cut sections, quarries, river bed.
(Figures 2a and b). The slickenlines are steeply inclined
We documented the new lineaments, brittle shears, normal
towards south-southwest on the fault surface (Figures 2a
faults, slickenside fault planes and slipped markers (Petit,
and b). The slickenlines are smooth to the touch in the
1987; Doblas, 1998; Passchier and Trouw, 2005; Fossen,
downward direction and rough in the upward direction
2010).
(Figure 2b). This suggests that the missing western block
Structural Features moved down relative to the block east of the fault
(Doblas, 1998; Argles, 2010). The exposed bedrock along
Striated Faults Planes, Brittle Shears
the rock cutting is mainly basalt which is found sheared
Mainly strike-slip and normal faults are mapped from the with very closely spaced fractures developed due to the
study area. A normal fault has been mapped near Kilvani faulting. The presence of normal fault with trend N170o
village; the fault trends N170o with a sharp dip of 72o in suggests the NE-SW extension of the study area.
SW direction (Figures 2a and b). It is marked by
In several exposures, sub-vertical NE to NS trending
spectacular development of slickensides, filled by fine-
brittle shears (Figure 3a-d) are mapped. Since these shears
grained white calcite and zeolites. Generally, they present
were mapped in sub-horizontal outcrops, they suggest a
on fresh outcrops showing, thin (~1–5 mm), mineralized
strike-slip deformation (Petit, 1987; Passchier and Trouw,
(secondary quartz, zeolite and calcite.) fault planes,
2005).
displaying dominantly a normal slip. These mineralized
Figure 2. (a) Normal fault near Kilvani village (20°18'1.70"N, 73° 5'53.55"E) road exposures with strike N170o and dip amount
70o in SW direction, (b) Slickensided fault plane showing the direction of movement by black arrows.
14
Figure 3. (a) Dextrally slipped fracture, (b-d) sinistrally slipped fractures at river bed of Dongarkhadi river
(Loc 20° 9'49.02"N, 72°59'35.19"E).
The markers such as mineralized fractures, veins (Figure Lineaments

4a) and dykes (Figure b-e) close to Meghwal and Luhari
The lineament map has been generated and the results of
villages slipped sinistrally and dextrally respectively, the analysis show that these lineaments show maximum
along ~NE– SW to ~N–S vertical to sub-vertical, strike- resemblance with the trend of the tectonic structures
slip faults. The strike-slip brittle shears (Figure 4a and c) present in the study area. The lineament density analysis
are prominent in the central part of the study area with has been performed in GIS platform by dividing study
dominantly sinistral shear. The dextral brittle shears area into four sectors, the results of the lineament
were occasional. Secondary mineralization (Figure 4a density analysis show that the highest density of the
and c) seen often along with brittle, made the shear lineaments is in the central portion of the study area
sense indicators more noticeable. Extension fractures (Figure 5a), while the lowest lineament density in
(Figure 4d-e), indicating tension normal to their strikes, alluvial portion. The high lineament density (Figure 5a)
observed in the central portion (in black circle) were
are common in the study area. Their ~E–W trends
correlated with the regional tectonic features (along the
(Figure 4d-e) are equally dominant near Lohari village.
axis of Panvel flexure) present in the study area.
Infield, extension fractures were recognized on sub-
Structurally, the Panvel flexure strikes in the north-south
horizontal outcrops by their sub-parallel strikes direction. The Panvel flexure extends from 16o to 21o N
(Hodgson, 1961; Shah et al., 2007), closely and equal approximately (Chandra, 1977). Furthermore, the
spacing (Eig and Bergh, 2011; Gudmundsson, 2011), interpretation of rose diagram and overlay analysis
and orthogonal adjoining against another set of shows that most of the lineaments/linear geological
fractures/shear planes (Caputo 1995, 2010; Herman, features are parallel to sub-parallel (N–S direction) to
2009). tectonic structures (Figure 5b inset).
15
Figure 4. (a) Mineralized sheared planes at Meghwal (Loc: 20°12'52.36"N, 73° 1'21.57"E). (b) Sinistrally offset dyke near
Luhari (Loc: 20°12'9.87"N, 72°58'34.68"E). (c) Dextrally slipped dyke along N-S strike-slip fault (Loc: 20°12'52.36"N,
73° 1'21.57"E). (d-e) Extensional fractures on sub-horizontal outcrops in Dongarkhadi River bed (Loc 20° 9'49.02"N,
72°59'35.19"E).
16
Figure 5. Structural lineament map of the area: a) lineament density map in which the flat area shows low concentration as
compared to flanks, (b) rose diagram of lineaments with a major trend in N-S direction (inset).
Figure 6. Mosaic of LISS-III images of the study area merged into a false-colour composite (FCC) image. Bright red colors
dense vegetation, greenish to greyish colors barren areas and blue, dark blue to black colors water bodies. Dykes marked on this
image (blue lines). Rose plots of the different areas (corresponding white rectangles) show the trends of the dykes.
17
Dykes were possibly emplaced along the shear after the

movement along the extensional fractures probably during
The dykes in the study area cut through the entire pile of the formation of Panvel Flexure in Paleocene (Sheth and
lava flows. These being fracture filling their orientations Pande, 2014). The Panvel flexure is an active fault
are very significant in the structural analysis. The dykes (Mohan et al., 2007). The study area has experienced
are generally steeply inclined or vertical, and on aerial more than 200 earthquakes between magnitudes M 1 to
photographs, maybe traced over long distances in 5.7 since year 1856 to March 2019, thus the active
continuity with fracture traces. In Figure 6, the strike structural feature source of these earthquakes may exist in
rosettes are separately shown for the four different sectors. this region. The seismicity in the study area supports the
From these diagrams, it is evident that in the study area, tectonically active nature because the epicentres of these
four major trends viz. N-S, NE-SW, NW-SE and E-W are earthquakes fall along the tectonic features present in this
more or less equally represented, whereas in the central region (Figure 7). The faults and lineaments mapped are
portion the N~S trend is more predominant as compared parallel with the Panvel flexure fault and the presence of
to the other trends. The predominance of N-S trending seismicity along it, also supports the presence of active
dykes in the central portion of the study area may be faults present in the region. The geomorphic anomalies
easily explained considering the warping of lava flows in related to the linear geological features confirm the
this region along N-S axes of Panvel flexure. In this presence of several possible faults in different parts of the
context, the observations by Auden (1949); Ghodke study area. In the light of the results of present studies, it
(1978) in Kolaba and Panvel area “there is some is thus evident that the basalt flows in the study area have
relationship both in direction and in area of concentration been warped on nearly north-south axes, producing a
between the major dykes of the Konkan and the Panvel system of fractures, many of which are now represented in
flexure”, is highly significant. The dykes can be, treated as the form of dykes. The lineaments trending NE - SW and
natural fractures dilated by a combination of crustal NW – SE directions are similar to the joints pattern that
extension and magma pressure (Anderson, 1951). developed parallel to the axial planes of folds of orogenic
The NNW-SSE and ENE-WSW trending dykes are cross- belts. The lineaments may have been developed during the
cut by N-S trending dykes and offset by N-S trending formation of Panvel flexure due to the outpouring of a
faults, which indicate that the youngest phase of tectonic huge pile of lava. The "flexuring" in Panvel flexure is the
movement resulted in the formation of Panvel flexure, result of the warping of the crust in response to rifting
lineaments and associated dykes. The N-S trending dykes (Devey and Lightfoot, 1986).
Figure 7. (a) Seismotectonic map of western India (b) Seismotectonic map of the study area.
18
Figure 8. Different linear and other structural features associated with lineaments encountered during the field survey (a) linear
ridge and triangular facets, (b) Linear valley with lineament, (c) and (d) spring associated with lineament.
The geomorphic indicators like the linear valley, 2. The maximum density of lineaments are seen along
triangular facet, water springs have helped to delineate with the trend of the Panvel flexure and the overall
lineaments of tectonically importance (Figure 8). The trend of these geological linear structures falls in
distribution of earthquakes in and around the study area NNE-SSW direction which also corresponds to the
suggests an exclusive relation between their linear trends trend of Panvel flexure.
with the linear geological structures present in the area. 3. The trend and drainage pattern of major river
Therefore, the geomorphic indicators of tectonic features Damanganga and its tributaries are also controlled by
and the spatial distribution of earthquakes concord that the the NNE-SSW trending faults and lineaments.
study area is tectonically active. Therefore, these lineaments and drainage patterns are
CONCLUSION strongly controlled by the regional tectonic structures
present in the study area.
The present study, focused on the Dadra and Nagar Haveli 4. Several new lineaments and faults are recognized,
area of Konkan Coastal Belt region, has attempted to
which are associated with linear features like straight
study the lineaments and dykes and their implication to
stream channels, linear ridges, triangular facets and
the seismotectonic of the study area. The key findings are
slickensides faults in the field.
mentioned below.
5. The higher lineament density along the Panvel
1. The interpretation of lineament fabric, fracture trace flexure fault and the presence of seismicity along its
and the rosettes constructed for the different domains, axis, the offset, sheared, stretched and faulted basic
clearly indicate the predominance of nearly N-S dykes along the N-S trending strike-slip faults,
oriented fractures, accompanied by conjugate sets concords well with the presence of N-S directed,
along NE - SW and NW - SE direction, with a strike parallel stress in the area.
subordinate set of the E-W fractures, suggesting that 6. The westerly monoclinal dips thus confirm the
both the horizontal compression and the vertical continuation of Panvel flexure, along with various N-
hosting were responsible for the deformation. S, NNW-SSE trending faults in the study area.
19
ACKNOWLEDGEMENT Chandra, U., 1977. Earthquakes of peninsular India, a

seismotectonic study. Bull. seismol. Soc. Am., 67(5),
The authors are thankful to the Director General and 1387-1413.
Director, ISR for his encouragement and permission to Chandrasekharam, D., 1985. Structure and evolution of the
publish this work. Authors are thankful to Disaster western continental margin of India deduced from
Management cell Dadra and Nagar Haveli, India for gravity, seismic, geomagnetic and geochronological
providing the fund to conduct this research work under studies. Physics Earth Planet. Int., 41(2-3), 186-198.
project DNH/1255. The authors are also thankful to the Courtillot, V., Feraud, G., Maluski, H., Vandamme, D.,
editor and two anonymous reviewers for their constructive Moreau, M.G. and Besse, J., 1988. Deccan flood basalts
comments and helpful suggestions, which has improved and the Cretaceous/Tertiary boundary. Nature,
the quality of the work. 333(6176), p.843.
Crawford, A.R., 1971. Gondwanaland and the growth of
Compliance with Ethical Standards India. J. Geol. Soc. India, 12(3), 205-221.
Dessai, A.G. and Bertrand, H., 1995. The “Panvel Flexure”
The authors declare that they have no conflict of interest along the Western Indian continental margin: an
and adhere to copyright norms. extensional fault structure related to Deccan magmatism.
Tectonophysics, 241(1-2), 165-178.
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21
Crustal structure from gravity and magnetic Data in parts of Nalgonda and
Khammam Districts, Telangana (India)
D.C. Naskar1*, P.K. Chakraborty2, Ramasatish Thota2 and Anurag Tripathi2
1
Southern Region, Geological Survey of India, Hyderabad-500068
2
Eastern Region, Geological Survey of India, Kolkata-700091
Corresponding author: drdcnaskar@gmail.com
ABSTRACT
Regional geophysical survey, employing gravity and magnetic methods, have been carried out in 3600 sq. km area of Palnadu and Srisailam sub-basins of
the Cuddapah basin and adjoining gneissic terrain towards north. The objective of the survey was to delineate subsurface structural features. The Bouguer
anomaly (BA) map has brought out negative gravity anomaly with amplitude of 55 mGal in the range from -30 mGal in the eastern part to -85 mGal in the
western part. The area surveyed is characterized by high gravity anomaly towards northern and eastern part and low to medium gravity anomaly in the
central and western part, except a small gravity high closure near Tummurukota. The elongated residual high gravity nosing trending in nearly N-S
direction and flanked by residual gravity lows on either side, is inferred as basement high below Kurnool sediments. Similarly, magnetic anomaly (TF)
map shows bipolar magnetic anomalies in the northern and eastern parts; magnitude of anomalies ranging between -1449 nT to 1855 nT. Northern and
eastern parts are dominated by small bipolar anomalies. The high magnetic anomaly peaks in the northern and eastern parts may be contributed to the
basement granite gneisses, composed of biotite-hornblende gneiss and migmatite and other Dharwar Group of rocks which are widely exposed in these
areas. Presence of wide spread Narji limestone in the central and western part of the studied region, may have contributed for low to medium intensity
magnetic anomaly. High intensity magnetic anomaly closures between Regalagadda and Tummurukota, reflected as a zone of high analytic signal, may be
attributed to Peddavuru schist belt towards western part. The radially averaged power spectrum of gravity data has brought out three interfaces at depths of
around 5.8 km, 1.8 km and 1.1 km, and for magnetic data two interfaces at the depths of 2.08 km and 1.2 km respectively. The interfaces brought out by
both the gravity as well as magnetic data, may represent the range of basement depth in the northern and northeastern margin of Cuddapah basin. The
linear clustering, trending in N-S direction of Euler depth solutions towards eastern part has been brought out, whereas curvilinear and NW-SE trending
linear cluster towards western part may be inferred as geologic/ faulted contacts.
Keywords: Gravity and magnetic methods, Cuddapah basin, Euler 3D solutions, structures.
INTRODUCTION Lambapur-Peddagattu and Chitrial in Nalgonda district,

Koppunuru in Guntur districts and Somasila in Nellore district
Potential field involving gravity and magnetic methods have (Dhana Raju et al., 1993; Sinha et al., 1995; Gupta et al.,
wide applications in geophysical mapping and mineral 2010; Ramesh Babu et al., 2012). Deep Seismic Sounding
exploration as they pick up responses from concealed (DSS) by Kaila et al., (1987) and gravity modeling by Singh
geological structures which sometimes promote formation of and Mishra, (2002), indicates presence of 10-11 km thick
mineral deposits (Grant and West, 1965; Paterson and Reeves, sedimentary pile over a 40 km thick crust in the eastern part of
1985; Sharma, 1986; Blakeley, 1995; Nabighian et al., 2005). the basin. The eastern margin of the basin is demarcated by a
The crescent-shaped intracratonic Proterozoic Cuddapah basin thrust contact, along which the metamorphic of the Eastern
(CB) located on the eastern part of Dharwar craton is a Ghat Mobile Belt (EGMB) are brought over it. Ramam and
remarkable tectonic and orogenic belt of Peninsular India. Murty, (1997) have suggested a foreland basin set-up behind a
King, (1872) conducted the pioneering geological work over collision belt for the CB where high order of crustal sagging
CB. After his monumental work, Coulson, (1934) carried out was possible. Subsequent subsidence and gravity-induced
detailed geological mapping in western part of the basin in block faulting produced isolated sub-basins like Srisailam and
connection with asbestos occurrences. The marginal part of Palnadu where younger sediments were deposited (Figure 1).
Srisailam and Palnadu sub-basins in the northern part of CB In present study area, the variations in lithology and structure
has shown immense potential of unconformity-related would give rise to density and susceptibility contrasts
uranium mineralization (Ramesh Babu et al., 2012). Authors invoking gravity and magnetic studies to bring out subsurface
from AMD have conducted exploration work for Uranium geological architecture. Structurally weak zones in the belt are
prospects in different parts of the basin since 1980's. They common exploration targets which act as locales for possible
established potential zone of Uranium mineralization like mineral-charged hydrothermal deposits.
Tmmalapalle-Giddankipalle area in Kadapa district,
22
D.C. Naskar et al. J.Ind.Geophys. Union, 24(2) (2020), 22-32
Figure 1. Different sub-basins of Cuddapah basin (northern part) (after Ramesh Babu et al., 2012).
Figure 2. Geological map, parts of Khammam and Nalgonda districts, Telangana.
GEOLOGY OF THE STUDY AREA Kurnool and Palnadu sub-basins overlies these. Srisailam and
Palnadu sub-basins-potential geological domains for
Regionally, the Proterozoic CB hosts 6-12 km thick volcano- unconformity-related uranium mineralization, are located in
sedimentary sequence belonging to Cuddapah Supergroup and the northern and northeastern part of CB covering Nalgonda
Kurnool Group (King, 1872; Nagaraja Rao et al., 1987; and Guntur districts. Srisailam sub-basin occupies nearly
Ramam and Murty, 1997). The basement predominantly 3000 sq. km area and exposes Srisailam Formation, the
consists of Archaean gneisses. The western half of the CB is youngest member of Cuddapah Supergroup. Srisailam
undeformed and sediments have normal depositional contact Formation mainly comprises intercalated sequence of
with the crystalline basement, while those in the eastern half quartzite, siltstone and grey shale and quartzite are often
are tightly folded (Nallamalai Fold belt; NFB). The eastern ferruginous (Nagaraja Rao et al., 1987). The Palnadu sub-
margin has thrusted contact, where Archaean gneisses and basin is smaller and occupies an area of 3400 sq. km,
Dharwar metasediments are thrusted over Narji formation of comprising sequences of arenaceous, argillaceous, and
Kurnool Group. The Cuddapah sediments are predominantly carbonate sediments, belonging to Kurnool Group. These
arenaceous to argillaceous with subordinate calcareous units sediments unconformably overlie the older Cuddapah
and are well developed in Papaghni, Nallamalai and Srisailam sediments in the eastern part, whereas older granitoids form
sub-basins (Figure 1). Neoproterozoic Kurnool sediments basement in the north (Figure 2).
dominated by carbonate facies and are well developed in
23
J.Ind.Geophys. Union, 24(2) (2020), 22-32 D.C. Naskar et al.
GEOPHYSICAL SURVEYS correction is applied to the observed ground magnetic (TF)

data of each station by observing magnetic variation at field
Data acquisition, processing and instruments base established at Nadikudi Camp. The IGRF corrections are
The Autograv Gravimeter (CG-5) and Total Field applied to the magnetic data, using IGRF-10 coefficients for
Magnetometer (GSM-19T) were deployed for gravity and the ‘2015-20’ epoch to evaluate magnetic anomaly at each
magnetic data acquisition. Differential Global Positioning station. The Oasis Montaj (vol. 8.5) package of Geosoft,
System (DGPS) with Base and Rover unit was utilized for (2015) is used for preparation of various gravity and magnetic
determination of elevation of gravity stations. A bench mark anomaly maps, considering WGS-84 datum and UTM
at Dachepalli Inspection Bungalow (Lat: 16° 35’ 38.15" N; projection system. Bouguer gravity and magnetic anomaly
Long: 79° 44’ 05.03" E; MSL: 86.600 m) was used to reduce maps are gridded at 1000 m interval and, contours are drawn
the DGPS heights to MSL. A hand-held GPS was deployed to on 1 mGal and 50 nT intervals, respectively.
record the locations (Latitude & Longitude) of the G-M
Physical properties of rock samples
stations. Physical properties viz. density and magnetic
susceptibility are measured with Electronic Balance (Afcoset, A total number of 102 rock samples were collected from
India; Model: FX-400) and MS-2 Magnetic Susceptibility different locations for measurement of density and magnetic
Meter (Make Bartington, UK) respectively. First, instrument susceptibility values. The objective is to analyze gravity and
drift correction is applied to the station gravity readings. Then, magnetic responses of the litho-units with reference to their
observed gravity value of each station is calculated with physical properties determined from the representative rock
respect to field base established at Geophysical Camp, samples. The samples are megascopically identified, and
Nadikudi (TS: 56 P/10) which was referred to the temporary grouped as per their mineralogical make-up. Granite/ granitic
gravity base at Narsaraopet Camp Base (Lat: 16° 14' 53.16" N gneiss rock samples show density in the range 2.59-2.74
; Long: 80° 03' 33.49" E ; Elev. 69 m; Base value: 978389.973
gm/cc, limestone in the range 2.65-2.81 gm/cc and quartzite in
mGal) (Nagaraja et al., 2017). This gravity base was
the range 2.47-2.86 gm/cc. Granite samples show high order
connected to IGSN-71 base (with base value 978448.040
of magnetic susceptibility more than 100 x 10 -6 CGS units.
mGal, Lat: 16° 18' 40" N, Long: 80° 37' 10" E) at Vijayawada
Junction rail road station, at south end no. 4, in front of post RESULTS AND DISCUSSIONS
office, Vijayawada, Krishna district, Andhra Pradesh.
Bouguer gravity anomaly was calculated using the Qualitative and quantitative analyses of gravity and magnetic
International Gravity Formula (IAG, 1980 reference) and data have been carried out on the basis of different anomaly
reducing the observed gravity values to mean sea level maps, depth solutions etc. to characterize the area with special
assuming an average crustal density of 2.67 gm/cc. Diurnal attention to the subsurface features.
Figure 3. Bouguer anomaly contour map, parts of Khammam & Nalgonda districts, Telangana.
24
Bouguer gravity anomaly margin of Srisailam and Palnadu sub-basin (Ramesh Babu et
al., 2012). In this context, this basement high may assume
The present gravity survey in the northeastern part of the CB
importance for similar type of U-mineralization in this area.
(Palnadu sub-basin), has brought out negative gravity anomaly
N-S steep gradient linear contours represented by gravity
with amplitude of 55 mGal in the range from -30 mGal to -85
lineaments (L6 to L8) towards eastern part of the area, are
mGal (Figure 3). The area surveyed is characterized by high
possibly attributable to faulted contact where deformation of
gravity anomaly towards northern and eastern part and
crustal layers in the form of faults and folds are quite evident
medium to low gravity anomaly in the central and western
because of westward movement of EGMB against foreland
part except a small high gravity closure near Tummurukota.
CB. These steep gradient contours in eastern part have
The regional Bouguer anomaly map (Figure 4) has brought
produced elongated residual highs towards east in residual
out this general characteristic very well. Cuddapah basin is
gravity map (Figure 6) and prominently seen as linear gravity
characterized by strong negative gravity anomaly (Figure 5)
high on first order vertical derivative map (Figure 7). Major
(Singh and Mishra, 2002). A high gravity anomaly nosing is
part of the central and western part are characterized by
prominent from Damarcherala to Gurajala and is well
medium to low Bouguer anomaly over the metasediments of
reflected as a high residual gravity anomaly on residual
Kurnool Group of rocks comprising Banganapalle quartzite
gravity map (Figure 6) as well as first order vertical derivative
and wide spread Narji limestone of Palnadu sub-basin. High
map (Figure 7). Kurnool Group of sediments composed of
gravity anomaly towards eastern and northern part represents
limestone (rock samples 38, 56, 446 and 956; measured
basement gneissic complex and Dharwar encompassing CB.
density 2.65-2.76 gm/cc) and quartzite (rock samples 479 and
Lower Crustal influence on this high gravity anomaly is
964; measured density 2.47-2.63 gm/cc) are located in this
obvious due to the obducting EGMB in the eastern margin.
area. This elongated residual gravity high trending in nearly
High gravity anomaly closure near village Tummurukota
N-S direction and flanked by residual gravity lows on either
towards west on Bouguer anomaly map are prominently
side, is inferred as basement high below overlying Kurnool
reflected as residual high in the western part on both residual
sediments. Gneissic basement and overlying Banganapalle
gravity map and first order vertical derivative map (Figures 6
quartzite, are the main pay horizons for unconformity related
and 7). This residual high is interpreted as due to Peddavuru
Uranium mineralization towards the northern and northeastern
schist belt in the western part of the basin.
Figure 4. Regional Bouguer anomaly contour map, parts of Khammam & Nalgonda districts, Telangana.
25
Figure 5. Bouguer Gravity map of Cuddapah basin with present study area.
Figure 6. Residual Bouguer gravity anomaly map, parts of Khammam and Nalgonda districts, Telangana.
26
Figure 7. First vertical derivative map of Bouguer anomaly, parts of Khammam and Nalgonda districts, Telangana.
Figure 8. Magnetic (TF) anomaly map, parts of Khammam and Nalgonda districts, Telangana.
Magnetic (TF) anomaly and west central parts are dominated by low to medium
intensity magnetic anomaly (Figure 8). Upward continued
Magnetic anomaly (TF) map (Figure 8) shows bipolar magnetic map and aeromagnetic map (Figures 10 and 11) also
magnetic anomalies ranging between -1449 nT to 1855 nT. clearly depict this general trend of magnetic anomaly.
Northern and eastern parts are dominated by small bipolar Presence of wide spread Narji limestone in the central and
anomalies. The analytic signal map of magnetic data (Figure western part may have contributed for low to medium
9) has also brought out predominantly high magnetic anomaly intensity magnetic anomaly in this sector. Very good
peaks in these parts. Upward continued magnetic anomaly correlation has been obtained in aeromagnetic as well as
map (Figure 10) and aeromagnetic map (Figure 11) also show ground magnetic data. Residual gravity high between
high intensity magnetic anomaly towards northern and eastern Damaracherla and Pandugula and further south (Figure 6)
part of the area. Rock samples (355 and 356, granite; which inferred as basement high, is associated with high
measured susceptibilities 720.2×10-6, 511.8×10-6 in cgs units) magnetic analytic signal closures (Figure 9). High intensity
show high order of magnetic susceptibility values. These high magnetic anomaly closure between Regalagadda and
magnetic anomaly peaks seems to be caused by the basement Tummurukota in the western part (Figure 8) which is
granite gneisses composed of biotite-hornblende gneiss and reflected as a zone of high analytic signal (Figure 9) may be
migmatite and Dharwar Group of rocks which are widely the response of Peddavuru schist belt.
exposed in northern and eastern part of the area. The western
27
Figure 9. Analytic signal map of magnetic (TF) anomaly, parts of Khammam and Nalgonda districts, Telangana.
Figure 10. Regional magnetic anomaly map, parts of Khammam and Nalgonda districts, Telangana.
Figure 11. Aeromagnetic anomaly map, parts of Khammam and Nalgonda districts, Telangana.
28
QUANTITATIVE ANALYSIS OF GRAVITY AND

MAGNETIC DATA
Radially averaged power spectrum of gravity and 3D Euler depth solutions of gravity data
magnetic data
The 3D Euler deconvolution of Reid et al., (1990) is a
Spectral analysis of gravity and magnetic data is a technique applied to the gridded potential field data to
conventional technique which has wide applications in determine the position, depth and nature of sources on the
determination of depths of geological features, such as basis of gradient of potential field. The Structural Index (SI) is
basement (Maus and Dimri, 1996) as depth of anomalous based on the nature of geological feature and the geometry of
body controls the shape of power spectrum. Spectral analysis the body and is a measure of rate of change of potential field
of gravity and magnetic data of study area was carried out with distance from the source. Solutions of Bouguer gravity
using radially averaged power spectrum (Spector and Grant, anomaly for grid cell size 500 m, SI 0 and window size 10
1970; Naidu and Mathew, 1988). The radially averaged have been superimposed on Bouguer anomaly contour map
power spectrum of gravity data (Figure 12) brought out (Figure 14). The depth range <1500 m leveled with red solid
mainly three interfaces at depths around 5.8 km, 1.8 km and circle, dominates the western part over Peddavuru schist belt,
1.1 km whereas the spectral results of magnetic data, (Figure and west central part over Narji limestone. The remaining
13) brought out mainly two interfaces at depths around 2.08 northern and eastern part are dominated by a deeper depth
km and 1.2 km. The interfaces brought out both from gravity range of 1500-2500 m leveled with blue solid circle and green
and magnetic data may represent the range of basement depth solid circle with depth >2500 m. The linear clustering trending
in the northern and northeastern margin of CB. A volcano- in N-S direction are seen mostly towards eastern part whereas
sedimentary sequence of 6-12 km belonging to Cuddapah curvilinear and NW-SE trending linear cluster towards western
Supergroup and Kurnool Group was envisaged in CB (Kaila part. These linear and curvilinear clustering of depth solutions
et al., 1987; Nagaraja Rao et al., 1987; Singh and Mishra, may be inferred as due to geologic/ faulted contacts. The
2002) over gneissic basement. Gneissic basement is also structural and geomorphic lineament map (Figure 15) show
exposed towards the northern part of CB. In this context, the lineaments in almost all direction but there is no significant
estimated depth of basement within a range of 1.1-5.8 km in match is seen with the Euler depth solutions showing
the marginal part of CB appears to be practical. clustering lineaments.
Figure 12. Radially averaged power spectrum of Bouguer gravity anomaly.
29
Figure 13. Radially averaged power spectrum of magnetic (TF) anomaly.
Figure 14. Bouguer anomaly contour map along with Euler depth solutions (SI=0), parts of
Khammam and Nalgonda districts, Telangana.
30
Figure 15. Structural and geomorphic lineaments map, parts of Khammam and Nalgonda districts, Telangana.
CONCLUSIONS 1.8 km and 1.1 km. Whereas the spectral results of magnetic
data has brought out two interfaces at depths around 2.08 km
The results of gravity and magnetic (TF) surveys conducted and 1.2 km. The interfaces brought out both from gravity and
on regional basis have brought out informative and useful magnetic data may represent the range of basement depth in
inferences about the subsurface crustal structure of the study the northern and northeastern margin of CB.
area which are summarized below. (vi) The linear clustering, trending in N-S direction of Euler
(i) The elongated residual gravity high trending in nearly N-S depth solutions, are seen mostly towards eastern part whereas
direction from Damaracherla to Gurajala, flanked by residual curvilinear and NW-SE trending linear cluster towards
gravity lows on either side, and associated with high magnetic western part. These linear and curvilinear clustering of depth
analytic signal closures, is inferred as basement high below solutions may be inferred as geologic/ faulted contacts.
overlying Kurnool sediments. (vii) Based on the geophysical results, a detailed geological
(ii) High gravity anomaly closure near Tummurukota is and geophysical investigation is recommended to ascertain
prominently reflected as residual gravity high. This residual the unconformity related U-mineralization potential of the
high correspond to the Peddavuru Schist belt in the western inferred elongated basement high between Damaracherla to
part of the basin. Gurajala towards the northern margin of Palnadu sub-basin.
(iii) Gneissic basement and overlying Banganapalle quartzite,
ACKNOWLEDGEMENT
are the main pay horizons for unconformity related Uranium
mineralization towards the northern and northeastern margin The authors are thankful to the DG, GSI for giving permission
of Srisailam and Palnadu sub-basin (Ramesh Babu et al., to publish the paper. The authors are thankful to the learned
2012). Basement high in these areas may assume importance reviewers for valuable suggestions and comments which
for similar type of U-mineralization. greatly helped to improve the manuscript. Thanks are due to
(iv) The high magnetic anomaly peaks in the northern and the Chief Editor for editing the manuscript. The authors also
eastern parts may be contribution by the basement granite thank Chief Editor for his kind support and encouragement.
gneisses composed of biotite-hornblende gneiss and
migmatite and Dharwar Group of rocks which are widely Compliance with Ethical Standards
exposed. The authors declare that they have no conflict of interest and
(v) The radially averaged power spectrum of gravity data has adhere to copyright norms.
brought out mainly three interfaces at depths around 5.8 km,
31
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32
Nepheline syenite: A potential alternative for feldspar in the mineral industry- A

case study from SE India
Sridhar Nalluri and Mallikarjuna Reddy Ragi*
Department of Geology, Kakatiya University, Warangal- 506009, Telangana (India).
*Corresponding Author: mallikragi@gmail.com
ABSTRACT
Nepheline syenite is an undersaturated, medium to coarse grained plutonic igneous rock. This unique rock is referred as alkaline rock which is distributed
in several locations across India within different geological and tectonic configurations. The rock is deficient in silica with respect to alkalies and alumina.
Compositionally the nepheline syenite is enriched with K-Na feldspar and nepheline as the predominant mineral along with minor mafic minerals like
pyroxene, hornblende and biotite. Present paper elucidates the significance of nepheline syenite as an important alternate for feldspar, which is being used
in many industries. The main advantage of using nepheline syenite compared to feldspar is due to its high potassium and sodium contents, which is togeth-
er (K2O + Na2O) around 14 wt. % and in feldspars around 9-12 wt. %. With regard to alumina in nepheline syenite, it is usually 20-25 wt. %, while in
feldspar, 16-18 wt. %. The SE part of India has several nepheline syenite complexes of economic importance, which need a special attention, as it is con-
sidered as a vital substitute for feldspar. The industrial application and suitability of nepheline syenite in glass making, ceramics, fillers, coatings, insula-
tion and fertilizers, emphasizes its economic significance. The relative increase in demand from major markets for nepheline syenite over feldspar is likely
to increase in future.
Keywords: Nepheline syenite, feldspar, glass and ceramic industry, Indian subcontinent.
INTRODUCTION
In nepheline syenite, the nepheline is a feldspathoid mineral K2O + Na2O around 14 wt.%, in comparison, in feldspars, it is
having a composition of (Na, K) AlSiO4 and generally forms around 9-12wt.% and also alumina in nepheline syenite, is
small grains and usually inter crystallized with the feldspar. 20-25wt.% and in feldspars, 16-18wt. %, (ii) products made
Chemically, it is close to alkali feldspars, but they are defi- from the nepheline syenites are devoid of crystalline silica
cient in silica (Tait et al., 2003). In spite of the volumetric impurities, (iii) high mineral brightness of nepheline and low
abundance of nepheline syenite in India, still it is not consid- level of dark mineral impurities compared to feldspar, (iv) the
ered yet as a potential resource for exploration as in case of presence of high alkali/alumina ratio in nepheline syenite than
many high value minerals. The scope of this paper is to pro- feldspar will help to reduce the quantity of usage of raw mate-
ject and promote the exploration and exploitation activities of rial to achieve a comparable fluxing action, and (v) less health
available nepheline syenite resources, which may be a poten- hazards associated with exploitation of nepheline syenite.
tial substitute for the exhausting feldspar resources. Various
nepheline syenite complexes of India are emplaced into the Alkaine complexes of SE Indian margin and their geologi-
basement rocks confined to different geographic locations. cal characteristics
Around 170 alkaline rock locations have been documented Indian subcontinent has several documented alkaline com-
from India, including the major nepheline syenite complexes plexes with variable age span which are widespread in differ-
as well. However, the proportionality of the nepheline syenite ent geological and tectonic setups. Out of the reported ones,
relative to the associated rocks in different geological situa- some are composed exclusively of nepheline syenite or alkali
tions varies. At some locations, this rock occupies the bulk feldspar syenites, associated with other non alkaline litho
portion of the plutons, whereas in other locations, it occurs as types. South eastern margin of the Indian shield marked by a
minor outcrops. India is a large consumer of the feldspar min- cratonic boundary between the Eastern Dharwar Craton
eral compared to other countries, the ceramic tile and glass (EDC) and Eastern Ghats Mobile belt (EGMB), hosts several
manufacturing industries use feldspar and quartz as the main such nepheline syenite alkaline complexes (Upadhyay, 2008).
components. Due to the nearly identical physical and chemi- Among them, two alkaline provinces i.e. Bastar alkaline prov-
cal properties of feldspars and nepheline (Tables 1 and 2), ince and the Cuddapah intrusive province (CIP) (Madhavan et
nepheline syenite can be used as a substitute for feldspar in al., 1995, 1999) are known to intrude the entire NE-SW
the ceramic industry, thereby reducing the high import costs stretch of southern India. The main alkaline complexes of the
of feldspar. To withstand the growing demand for ceramics in Bastar province are Rairakole, Khariar (Upadhyay et al.,
the construction industry, the nepheline is used as a substitute 2006), Koraput (Bhattacharya and Rajib, 2005) and Kunava-
for feldspar. Nepheline is relatively enriched in alkalies and ram (Upadhyay et al., 2006). Among the identified and well
alumina than the alkali feldspars and hence it has been found documented alkaline complexes of India the Kunavaram alka-
to be a better natural substitute for feldspar in all industries. line body is the largest, with 30 Km length and 2.5 Km width,
The main advantage of using nepheline syenite compared to chiefly composed of nepheline syenite.
feldspar is due to (i) high potassium and sodium contents,
33
Sridhar Nalluri and Mallikarjuna Reddy Ragi J.Ind.Geophys. Union, 24(2) (2020), 33-38
Table 1. Comparison of common chemical, crystal and physical properties of feldspars and nepheline.
Chemical Crystal Specific Hardness

S.No Mineral
composition system gravity (Mohs)
Monoclin-
1 Orthoclase KAlSi3O8 2.6 6-6.5
ic
2 Microcline KAlSi3O8 Triclinic 2.5 - 2.6 6
2.6 -
3 Albite NaAlSi3O8 Triclinic 6-6.5
2.63
2.74 -
4 Anorthite CaAl2Si2O8 Triclinic 6-6.5
2.76
Hexago-
5 Nepheline (Na, K)AlSiO4 2.5 - 2.6 5.5- 6
nal
Table 2. Comparison of chemical analysis data (Major oxide %) of feldspars and nepheline.
S.No Mineral Composition
Phase Major oxides
Potassium 16.92 % K2O

1 Orthoclase Aluminum 18.32 % Al2O3
Silicon 64.76 % SiO2
Oxygen ----------------

Aluminum 18.32 % Al2O3
2 Microcline
Oxygen ----------------
Sodium 5.72 % Na2O

Calcium 10.36 % CaO
3 Plagioclase Aluminum 18.83 % Al2O3
Oxygen --------------------

Sodium 15.91 % Na2O
4 Nepheline Aluminum 34.90 % Al2O3
Oxygen ----------------------
(Source: Mineralogy data base: Mindat.org)
The Cuddapah intrusive province is another notable alkaline Purimetla (Leelanandam, 1980; Ratnakar and Leelanandam.,
region, where alkaline rocks are prominently identified at 1986) and Uppalapadu (Krishna Reddy, et al., 1998). The
different locations, which includes the nepheline syenites as salient features of various nepheline syenite complexes of
well. The main nepheline syenite complexes of CIP are Bastar and Cuddapah intrusive provinces (Figure 1) are pre-
Elchuru (Leelanandam et al., 1972; Madhavan et al., 1989), sented in Table 3.
34
J.Ind.Geophys. Union, 24(2) (2020), 33-38 Sridhar Nalluri and Mallikarjuna Reddy Ragi
Figure 1. Geological map of the Eastern Ghats Belt (Dobmeier and Raith, 2003; Upadhyay, 2008) and its contact with the Archaean
cratons. Occurrence of major nepheline syenite complexes along the contact zones are indicated by star symbol.
Table 3. Alkaline plutons and their characteristic lithological assemblage along with aerial extent in Bastar and Cuddapah intrusive prov-
inces of Eastern Dharwar Craton.
S.No Pluton Aerial extent Rock types
1 Khariar ̴ 87Km2 Mesocratic nepheline syenite, nepheline syenite, syenite, ijolite, amphibolite.
2 Koraput 3.5Km2 Mafic syenite, felsic syenite, nepheline syenite and perthite syenite.
3 Kunavaram 75km2 Nepheline syenite, syenite and nepheline monzonite, mesocratic and
melanocratic varieties of the nepheline syenite
4 Elchuru 16 Km2 Shonkinite, malignite, nepheline syenite, lamprophyre
5 Purimetla 7 Km2 Malignite, hornblende syenite, nepheline syenite, lamprophyre
6 Uppalapadu 30 Km2 Nepheline syenite, hornblende syenite, ferro syenite
DISCUSSION
Petrographical and petrochemical characteristics of the
nepheline syenites from SE India
Based on the model proportions of felsic and mafic constit- sphene, allanite, apatite, zircon are among the accessories
uents, nepheline syenites are classified into two types meso- found in association with the felsic and mafic minerals.
cratic and leucocratic. Feldspar (microcline or orthoclase)
and nepheline are the prime felsic representatives that con- Compositionally, the nepheline syenites are considered as
stitute the bulk composition of the rock, which together undersaturated rocks, which are enriched in alkalies
constitute about 90-95% in felsic and 70-80% of volume in (Na2O+K2O) and alumina with respect to silica (Figure 2A).
mesocratic nepheline syenites. Texturally, the nepheline Based on the alumina saturation, these rocks can be classi-
syenites are holocrystalline and show porphyritic texture, fied as peralkaline (Na2O+K2O>Al2O3), peraluminous
consisting of phenocrysts of subhedral nepheline and feld- (Al2O3>Na2O+K2O) and metaluminous (Al2O3 <Na2O+K2O)
spar (perthitic or non perthitic; potassic or sodic). The iron (Figure 2B). The presence and absence of plagioclase ena-
bearing phases that are seldom found in association with bles to classify these rocks as subsolvous and hypersolvus
leucocratic varieties are magnetite and/or hematite. Calcite, varieties respectively. Except a few, most of the Indian
35
nepheline syenites are miaskitic (Mol.Prop.(Na2O+K2O/Al2O3 teristically enriched in K2O, Na2O+K2O, Al2O3 (Figure 2 A,
<1) and are peraluminous to metaluminous along with high B, C and D) and depleted in MgO, MnO, Fe2Ot, TiO2 and
concentration of K2O over Na2O (Figure 2D). In contrast P2O5 (Table 4). The high potassium content along with their
the agpaitic nepheline syenites are peralkaline and enriched peraluminous to metaluminous nature of the SE Indian
in Na2O over K2O (Mol.Prop.(Na2O+K2O/Al2O3 >1)). The mi- nepheline syenites are taken into consideration for substitut-
askitic nepheline syenites show nepheline as the feldspath- ing the feldspar, which is being largely imported from vari-
oid, whereas in agpaitic nepheline syenites leucite is the ous countries throughout the globe.
feldspathoid. The SE Indian nepheline syenites are charac-
Figure 2. Binary relationship of major elements of SE Indian nepheline syenite. A. enrichment of total alkalies; B. characteristic alkalies
and alumina enrichment; C. enrichment of Al2O3; D. enrichment of K2O over Na2O.
Table 4. Major element abundance (wt.%) of nepheline syenite from Bastar and Cuddapah intrusive provinces of SE India.
S.No Bastar province Cuddapah intrusive province
Pluton Khar Khar Kora Kora Kun Kun Elc Elc Pur Pur Upp Upp
SiO2 54.51 53.8 58.49 60.96 53.63 51.43 56.27 52.43 55.39 55.39 57.01 60.74
TiO2 0.14 0.59 0.41 0.43 0.28 0.71 0.32 1.3 0.8 0.8 0.12 0.06
Al2O3 22.85 20.95 17.49 17.53 22.27 22.65 19.27 18.96 22.33 22.33 19.48 19.58
Fe2O3 0.88 4.21 4.35 3.7 5.3 4.78 3.57 5.43 4.33 4.33 3.92 2.73
MnO 0.05 0.1 0.1 0.07 0.15 0.12 0.07 0.08 0.09 0.09 0.06 0.05
MgO 0.02 0.53 2.04 1.88 0.21 0.67 0.85 4.16 0.62 0.62 0.58 0.09
CaO 3.1 3.23 2.31 1.84 2.31 3.16 1.69 3.07 2.12 2.12 1.57 0.74
Na2O 6.79 5.69 3.89 3.12 6.52 6.21 6.15 4.71 5.47 5.47 7.08 6.84
K2O 9.57 9.48 7.99 7.89 8.76 8.49 8.19 9.87 7.46 7.46 8.51 7.25
P2O5 0.1 0.32 0.42 0.35 0.08 0.14 0.18 0.61 0.22 0.22 0.05 0.01
Na2O+K2O 16.36 15.17 11.88 11.01 15.28 14.7 14.34 14.58 12.93 12.93 15.59 14.09
Total 98.04 98.9 97.49 97.77 99.51 98.36 96.56 100.62 98.83 98.83 98.38 98.09
Abbreviations: Khar- Khariar; Kora-Koraput; Kun - Kunavaram; Elc- Elchuru; Pur-Purimetla; Upp – Uppalapadu. (Note: Refer-
ences are given at the respective places in the text).
36
J.Ind.Geophys. Union, 24(2) (2020), 33-38 Sridhar Nalluri and Mallikarjuna Reddy Ragi
Possibility of substitution of nepheline syenite for feldspar ensures its suitability to get the clear visibility for the glass.
in different industries The versatile use of glass in various domains like house hold
glass articles, lab glass ware, bottle making, flat glass and
(i) Ceramic industry
window glass in construction of houses, fiber glass etc. will
Alkali feldspars and nepheline are of major importance in progressively modify the practical use of the glass.
ceramic industry because of their high Al, Na and K contents.
Experimental studies conducted so far on nepheline syenite to Along with the ceramic and glass manufacturing, the substitu-
assess its suitability for substitution of feldspar in ceramic tion of nepheline in place of feldspar, may also be possible for
manufacturing, proved successful. Experiments were carried various enamel/coatings, pigments and in fertilizer industries.
out on Elchuru nepheline syenite with special reference to its However, extraction of nepheline from the nepheline syenite
density, viscosity, firing resistance, surface abrasion re- is not always as easy task when compared to feldspar mining.
sistance, thermal shock resistance and chemical resistance Nepheline syenite consists of nepheline, feldspar along with
(Reddy and Asadi. 2011), indicate that it has more fluxing other complex mafic minerals. Magnetic separation and flota-
nature than the feldspars and confirm the suitability for the tion methods are found to be unsuitable techniques to recover
replacement of feldspar with nepheline syenite. Alkalies that appreciable amounts of potassium values nepheline syenite.
are produced from the nepheline syenite are used as flux to However, experimental studies conducted on nepheline sye-
reduce the melting temperatures and viscosity of ceramic mix- nite of Uludag massive, the Bursa Orhaneli region of western
ture, which helps in accelerating the melting process and save Turkey, revealed that the best results can be obtained using
the fuel charges. Substitution of the nepheline syenite in place combination of the high intensity dry magnetic separation and
of feldspar in various manufacturing segments will help us flotation between -200+38 µm particle sizes (Burat et al.,
conserve the available feldspar resources, saving the import 2006). As a matter of fact the high intensity dry magnetic
costs of the same and preserve the resource for the future gen-
separation is not so economical than the high intensity wet
erations.
magnetic separation. Chemical leaching with dilute sulphuric
(ii) Glass industry acid could recover only ~40% of the potassium values. The
potassium values present in nepheline syenite of Koraput are
Since the density of nepheline syenite and quartz is nearly recovered through roasting with calcium chloride followed by
similar, the nepheline syenite is used as a flux to reduce the water leaching. From the preceding statement, it is possible to
viscosity and melting temperature of glass as well. The pres- recover ~99.6% K2O value at 900 °C temperature and 30 min
ence of alumina within the feldspars and nepheline in nephe- of roasting time (Jena et al., 2014).
line syenite, would enhance the durability and
strength/hardness, resistance to scratching and improves the Comparatively, the SE Indian nepheline syenite is best suita-
thermal endurance. The low iron content imparts the white ble than feldspar in ceramic and glass industry as it has high
color to the leucocratic nepheline syenite powders, which Al2O3 and K2O+Na2O content (Table 5).
Table 5. Comparison of chemical compositions of feldspar and nepheline syenite in terms of their suitability
in ceramic and glass industries.
Feldspar Feldspar SE Indian Nepheline
Constituent
(Ceramic) (Glass making) syenite average values
SiO2 75 68.9 55.83
Al2O3 15 18.75 20.47
Fe2O3 0.3 0.07 3.96
CaO ---- 1.85 2.27
K2O 3.3 3.85 5.66
Na2O 4.5 7.15 8.41
K2O + Na2O 7.8 11.00 14.07
Note: Feldspar values for ceramic and glass making are after Loughbrough (1993) and Harben (1995) respectively.
CONCLUSIONS
1. The growing demand for the use of feldspars in India 3. Since feldspar and nepheline are considered as identical
warrants the substitution of feldspar with nepheline sye- twins in terms of their physical and chemical properties,
nite in future. it is possible to make substitution of nepheline in place of
2. SE India has potential resources of nepheline syenite but feldspar
their commercial viability and feasibility in replacing the 4. Experimental studies on nepheline syenite of Elchuru and
feldspar mineral needs to be studied further. Koraput alkaline complexes, revealed their suitability for
substituting the feldspar with nepheline syenite.
37
5. Increasing use of the available feldspar would rather end Leelanandam, C., Narsinga Rao, K. Mallikarjuna Rao, J. and
up the resources in the near future. Keeping this in view Madhavan, V., 1972. Occurrence of nepheline syenites near
the substitution of feldspar with nepheline syenite will Elchuru, Andhra Pradesh, Curr. Sci., 41, 39.
Leelanandam, C., 1980. An alkaline province in Andhra Pradesh.
definitely help to overcome the present and future de-
Curr. Sci., 49, 550-551.
mands of the industry. Loughbrough, R., 1993. Portugal’s minerals, Industrial minerals,
308, 51-52.
ACKNOWLEDGEMENTS Madhavan, V., Mallikarjuna Rao, J., Subrahmanyam, K., Krishna
S.G. and Leelanandam, C., 1989. Bedrock geology of Elchu-
Authors are thankful to the Head, Department of Geology,
ru Alkaline Pluton, Prakasam District, Andhra Pradesh.
Kakatiya University, Warangal for the necessities provided Geol. Soc. India, Memoir. 15, 189-205.
during this study. We would like to thank the editor of the Madhavan.V. Mallikarjuna Rao, J., Chalapathi Rao., N.V. and
journal and the two anonymous reviewers for their comments Srinivas, M., 1995. The multifaceted manifestations an in-
and suggestions, which helped greatly in shaping the manu- trusive province around the intra cratonic Cuddapah basin,
script. India. In: Magmatism in relation to Diverse Tectonic Set-
tings (Eds; Srivastava, R.K. and Chandra, R) A.A. Balkem,
Compliance with Ethical Standards Rotterdam, 93-105.
Madhavan,V., Mallikarjuna Rao, J. and Srinivas, M., 1999. Mid
The authors declare that they have no conflict of interest and Proterozoic Intraplate Alkalilne Magmatism in the Eastern
adhere to copyright norms. Dharwar Craton of India: the Cuddapah Province. J. Geol.
Soc. India, 53, 143-162.
REFERENCES Ratnakar, J. and Leelanandam, C., 1986. A petrochemical study
of the Purimetla alkaline pluton, Prakasam District, Andhra
Bhattacharya, S. and Rajib, K., 2005. Petrological and geochemi-
Pradesh, India. Neues. Jb. Mineral. Abh, 156, 99-119.
cal constraints on the evolution of the alkaline complex of
Koraput in the Eastern Ghats Granulite belt, India. Gondwa- Reddy, R.K. and Asadi. S.S., 2011. An experimental study for
na Res., 8(4), 596-602. identification of suitable low cost alternative flux material in
Burat, F., Kangal, O. and Onalan, G., 2006. Alternative mineral manufacturing of red body ceramic glazed tiles: A model
in the glass and ceramic industry: Nepheline syenite. Miner- study. Mat. Sci. Res. India, 8(2), 289-295.
als Engineering, 19, 370-371. Tait, K.T., Sokolova, E., Hawthorne, F.C. and Khomyakov, A.P.,
Dobmeier, J.C. and Raith, M.M., 2003. Crustal architecture and 2003. The crystal chemistry of nepheline. Canadian Miner-
evolution of the Eastern Ghats Belt and adjacent regions of alogist. 41, 61-70
India. In: Yoshida, M., Windley, B.F., Dasgupta, S. (Eds.), Upadhyay, D., 2008. Alkaline magmatism along the southeastern
Proterozoic East Gondwana: Supercontinent Assembly and margin of the Indian shield: Implications for regional geo-
Breakup, Geol. Soc., London, Special Pub., 206, 145-168. dynamics and constraints on craton–Eastern Ghats Belt su-
Harben, P.W., 1995. The industrial minerals handbook, Metal turing. Precamb. Res., 162, 59-69.
Bulletin, 62-65. Upadhyay, D. and Raith, M.M., 2006. Petrogenesis of the
Jena, S.K., Dhawana, N., Rao, D.S., Misra, P.K., Mishra, B.K. and Kunavaram alkaline complex and the tectono thermal evolu-
Das, B., 2014. Studies on extraction of potassium values from tion of the neighboring Eastern Ghats Belt granulites, SE In-
nepheline syenite. Int. J. Mineral Processing. 133, 13-22. dia. Preca. Res., 150, 73-94.
Krishna Reddy, K., Ratnakar, J. and Leelanandam, C., 1998. A Upadhyay, D., Raith. M.M., Mezger, K., Bhattacharya, and Kin-
petrochemical study of the Proterozoic alkaline complex of ny, P.D., 2006. Mesoproterozoic rifting and Pan-African
Uppalapadu, Prakasam alkaline province, Andhra Pradesh.
continental collision in SE India: evidence from the Khariar
J. Geol. Soc. India, 53, 41-52.
alkaline complex. Contrib. Mineral. Petrol., 151, 434-456.
38
Estimation of the natural recharge due to monsoon rainfall using entropy tool in
the part of Vindhyan fringe belt of Ahraura and Chunar blocks of Mirzapur
district (U.P.), India
R. Kumar1, N.P. Singh2* and A.K. Singh1
1
Geophysics Division, Geological Survey of India, Central Region, Nagpur, India
2
Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi-221005, India
*Corresponding Author: singhnpbhu@yahoo.co.in
ABSTRACT
In this article, an attempt is made to estimate the groundwater recharge rate due to monsoon rainfall using entropy tool in the part of Vindhyan fringe belt
of Ahraura and Chunar blocks of Mirzapur district, Uttar Pradesh. The depth of water table (DTW) measured at twelve different locations of study area
and the monsoon rainfall recorded in the district during the post-monsoon months of the years 2009-2011, are used as the input for this study. The
marginal entropies of the monsoon rainfall and DTW, the conditional entropy of DTW due to rainfall, joint entropy of DTW and rainfall and mutual
entropy in between DTW and rainfall are calculated for the period 2009 to 2011. The amount of monsoon rainfall contributes to the groundwater storage,
which is estimated by the ratio of the mutual information between DTW and the monsoon rainfall to the marginal entropy of the monsoon rainfall. The
estimated recharge rate due to monsoon rainfall for this period is found to be 11.1%.
Keywords: Entropy, Depth of water table, Chunar, Ahraura, Vindhyan fringe belt, Mirzapur district.
INTRODUCTION store and transmit significant amount of groundwater. These

aquifers largely contain sands, pebbles, gravels, fractures in
The phenomenon of occurrence of groundwater in geological
hard rocks and caverns in limestones.
formations is well explained in Bowen (1928). The igneous
and metamorphic rocks contain nearly 20% of the total The groundwater resource is continuously replenished by the
subsurface groundwater in the globe and the rest of the recharge of groundwater during monsoon seasons and thereby
subsurface groundwater lies in sedimentary rocks (Figure 1). an optimum level of groundwater resource is always
Groundwater occurs in pore spaces between grains in maintained in the subsurface. Thus the recharging of
alluvial/sedimentary rocks, and in a limited areal extent in groundwater is of vital importance for maintenance of this
secondary porosity, generally developed due to weathering, precious resource of the nature. The importance of
fracturing, jointing, faulting, etc., within the hard rock areas, groundwater recharge has been duly realized over the time on
in fractured zones of metamorphic rocks, and in openings in account of over exploitation of groundwater and deficient
lavas formed at the time of their compaction. The main types recharge due to the irregularity and failure of monsoon.
of groundwater resources occur in aquifers, which can collect,
20 % in Igneous and
Metamorphic Rock
80 % in Sedimentary Rock
Figure 1. Distribution of groundwater in subsurface rocks (after Bowen, 1928).
Further, groundwater recharge is a key component in any Estimating recharge rate can be based on a wide variety of
model of groundwater flow or contaminant transport. The models which are designed to represent the actual physical
word recharge has different meaning to different peoples, viz. processes. The methods, commonly in use for estimation of
someone concerned with crop growth may consider recharge natural groundwater recharge, include groundwater balance
as the amount of water that moves beneath the root zone, thus method, soil water balance method, zero flux plane method,
adding to the soil moisture, while the other who is interested one-dimensional soil water flow model, inverses modeling
in determining the characteristics of an aquifer may view technique, isotope and solute profile techniques (Healy,
recharge as the amount of water that reaches and contributes 2010). The most commonly used methods for estimation of
to the storage of the aquifer (Younger, 2007). natural groundwater recharge in India include empirical
39
R. Kumar et al., J.Ind.Geophys. Union, 24(2) (2020), 39-45
methods and groundwater level fluctuation method. Based on value of about 5-9% in the same formation having a
the studies undertaken by different scientists and significant clay content using an empirical method. In view of
organizations regarding correlation of groundwater level several studies on groundwater recharge due to rainfall, in
fluctuation and rainfall, some empirical relationships have present work an attempt is made to estimate the natural
been derived for computation of natural recharge to recharge of groundwater during monsoon seasons of 2009-
groundwater from rainfall (GEC, 1997). 2011in the part of Vindhyan fringe belt of Ahraura and
Chunar blocks of Mirzapur district, U.P., India.
Athavale et al. (1992) has suggested that about 15-20% of
seasonal rainfall contributes to groundwater recharge in the
Indo-Gangetic plains, and this figure falls to only 5-10% in LOCATIONS AND GEOLOGY OF STUDY AREA
peninsular hard rock regions. Rangarajan and Athavale (2000) The study area located in the parts of Vindhyan fringe belt of
estimated average natural recharge rate of about 10.11% of Ahraura and Chunar blocks of Mirzapur district (Uttar
seasonal rainfall for fifteen granitic and gneiss area in varying Pradesh), is bounded between latitudes 24057’54’’ and
climatic and hydrogeological provinces in India using tritium 25006’50’’N and longitudes 82050’23’’ and 83004’22’’E and
injection. The Groundwater Estimation Committee (GEC) in falls in the Survey of India Toposheet nos. 63K/16, 63L/13,
1997 estimated a rainfall recharge rate of about 10-12% in 63O/04 & 63P/01 at 1: 50,000 scales (Figure 2). The area is
weathered, granite, gneiss, schist with low clay content and a largely flat and gently undulating except at few places.
Figure 2. Location of study area
Geologically, the study area is represented by Vindhyan basin formed in response to intra-plate stresses (Bose et al.,
Supergroup of Meso to Neoproterozoic age. The Vindhyan 2001). Groundwater in Kaimur Group may occur in the
Supergroup is composed mostly of low dipping formations of weathered and fractured sandstone provided that the zone is
sandstone, shale and carbonate, with a few conglomerate and connected with recharging sources. The Kaimur Group of the
volcanoclastic beds, separated by a major regional and several VindhyanSupergroup is of special significance because it
local unconformities (Bhattacharyya, 1996). The regional consists dominantly of silica clastic rocks, lying
unconformity occurs at the base of the Kaimur Group and unconformably over the carbonate-rich Semri Group of
divides the sequence into two units: the Lower Vindhyans Lower Vindhyans Super Group. Therefore, the rocks from the
(Semri Group) and the Upper Vindhyans (Kaimur, Rewa and Kaimur Group hold strong evidence regarding the changing
Bhander groups). The out crop pattern of the Supergroup environment of deposition, climatic conditions and tectonics
resembles a simple saucer-shaped syncline. It is generally and weathering conditions, during the Mesoproterozoic era
believed that the Vindhyan basin was a vast intra-cratonic (Mishra and Sen, 2010).
40
J.Ind.Geophys. Union, 24(2) (2020), 39-45 R. Kumar et al.,
Hydrogeology and Soil of the Area (Vindhyan Super Group of rocks) is expected below the
surface soil cover (Krishnan, 1982). The major soil type is
The main streams that run across the study area are Kalkali sandy to loam type (Figure 3). They are brownish in colour
and GaraiNadi with few minor tributaries. The occurrence and and favourable for growing all kinds of crops, preferably
movement of groundwater is mainly restricted within the barley, sugarcane, berseem and paddy. Older alluvial upland
weathered and fractured sandstone/shale (Amaresh and soil represents the different stages of soil development
Prakash, 2003). The southern portion of study area is covered resulting from a sub-humid to a humid climate. The alluvial
by thin surface soil with varying thicknesses ranging from 1-4 soils of the study area are developed from the alluviums of the
m and few exposures of Vindhyan sandstone, and thickness of Ganga plains.
overburden increases towards northern side. The bedrock
Figure 3. View of sandy to loam type soil in study area.
Climate and Rainfall Jaynes (1957 and 1982) defined the principle of maximum
entropy (POME), and thereafter the concept of entropy has
The study area falls in the subtropical region and its climate is undergone to a rapid development stage with promising
classified as tropical to subtropical type, characterized by a results and entropy theory has been applied in many different
hot summer and severe winter. The maximum temperature in fields such as ecology, biology, data mining, economics and
the summer is recorded to be 47oC and the minimum financial time-series analysis etc. (Darbellay and Wuertz,
temperature 3oC in the winter. At times when the area is under 2000; Carranza et al., 2007; Sato, 2008; Karamanos, 2009;
the grip of cold wave due to sweeping cold winds of northern Sy, 2001; Zhou et al., 2010). Recently, it has also been
Himalaya, the temperature drops to as low as freezing point. applied extensively in hydrology and water resources for
The area experience three distinct seasons namely; summer, measuring information contents of random variables and
rainy and winter. Winter usually commence from middle of models, evaluating information transfer between hydrological
November and extends till end of February, whereas summer processes, evaluating data acquisition systems, designing
starts from April extend up to the middle of June. Rainy water quality monitoring (WQM) networks and assessment of
season starts normally by the third week of June and natural recharge in aquifers (Mogheir et al., 2004; Karamouz
continues till September or early part of October. The study et al., 2009; Mondal and Singh, 2010, Mondal et al., 2012,
area receives greater part of the annual rainfall through south- Ndatuwong and Yadav, 2012, Islam et al., 2017).
west monsoon between June and September.
Shannon, (1948) defined a quantitative measure of uncertainty
Entropy Theory associated with a probability distribution or the information
Shanon, (1948) has proved that Boltzman’s entropy is the content of the distribution in terms of entropy, called Shannon
only function which satisfies the requirements for a function entropy or informational entropy. The uncertainty can be
to measure the uncertainty in a measure. He described entropy quantified with entropy taking into account all the different
as the amount of uncertainty in any probability distribution. kinds of available information. Thus, entropy is a measure of
41
n m
the amount of uncertainty represented by the probability 1
distribution and is a measure of the amount of chaos or the H(Y|X) = ∑ ∑ p(xi , yj ) log 2 ( ) (6)
p(yi |xj )
lack of information about a system. If complete information is i=1 j=1
available, entropy = 0. Otherwise, it is greater than zero The joint entropy H(X, Y) is the total information content in
(Singh, 2000). both X and Y given as
n m
Let Ei stand for an event and pi for the probability of 1
occurrence of the event Ei. Let there be n events E1, …, En H(X, Y) = ∑ ∑ p(xi , yj ) log 2 ( ) (7)
p(xi , yj )
with probabilities p1,…, pn. Then a measure of information I i=1 j=1
is defined as a logarithmic function expressed by (Shannon,

The mutual entropy, MI(X, Y) , is the information between
1948),
X and Y. It is a quantity that measures a relationship between
1 two random variables that are sampled simultaneously. It can
I(pi ) = log 2 ( ) (1) be defined as the information content of X which is contained
pi
in Y. It can be interpreted as the reduction in uncertainty in X
From the n number of information values, I , the expected due to the knowledge of the random variable Y, and is given
information content of a probability distribution called as
entropy, can be derived by weighing the information values I
n m
by their respective probabilities pi as p(xi , yj )
MI(X, Y) = ∑ ∑ p(xi , yj ) log 2 ( ) (8)
n
p(xi )p(yj )
i=1 j=1
1
H = ∑ pi log 2 ( ) (2)
pi It can also be expressed as
i=1
MI(X, Y) = H(X) − H(X|Y) (9)

where H stands for entropy. The unit of information measures
depends on the logarithmic base used. If a base 2 is used, then MI(X, Y) = H(X) + H(Y) − H(X, Y) (10)
the unit is bit; for a logarithmic base 10, the unit is decibel,
and for logarithmic base e the unit is nat (natural units). Thus, MI(Y, X) = H(Y) − H(Y|X) (11)
the value of entropy, H, varies from infinity to zero for
MI(Y, X) = H(Y) + H(X) − H(Y, X)(12)
probability distribution ranging from 0 to 1.
Therefore, considering rainfall as an independent random
Marginal, joint, conditional and mutual entropies are referred
variable (Y) and DTW as the dependent variable (X) , the
to as information coefficients or measures. The two discrete
percentage of rainfall, Re (%) , contributing to the natural
variables X and Y, with values Xi, i =1,2,….,n; Yj and j =
recharge of an unconfined aquifer can be obtain as (Mondal
1,2,….,m, defined in the same probability space which has a
and Singh, 2010)
discrete probability of occurrence p(x i) and/or p(yj). The
marginal entropy H(X) or H(Y) can be defined as the measure MI(X, Y)
of the total amount of uncertainty or the indirect measure of Re (%) = . 100 (13)
H(Y)
the total amount of information content of a single process, X
METHODOLOGY AND RESULTS
or Y. It is given as (Mogheir and Singh, 2002)
The hydrological data are taken from the Groundwater
n
1 Department U.P., Geophysical Survey Division Mirzapur,
H(X) = ∑ p(xi ) log 2 ( ) (3)
p(xi ) Uttar Pradesh. The total monsoon rainfall data recorded from
i=1
the district for the same period is used to determine the
m
1 contribution of rainfall to groundwater storage of the area. For
H(Y) = ∑ p(yj ) log 2 ( ) (4) analyzing the relationship between more than one variable,
p(yj )
j=1 the joint or conditional probability is required as cross
The conditional entropy (or equivocation) H(x|y)or H(y|x) tabulation or contingency table. This is a type of table in a
quantifies the amount of information needed to describe the matrix format that displays the (multivariate) frequency
distribution of the variables.
outcome of a random variable X or Y given that the value of
another random variable Y or X is known. It is given as In Table 1, the range of DTW is from the minimum 1.00
n m m,bgl to the maximum 5.00 m,bgl values with a class interval
1
H(X|Y) = ∑ ∑ p(xi , yj ) log 2 ( ) (5) of 1.00 m,bgl which is used as the dependent variableX. The
p(xi |yj ) rainfall value with class interval of 100 mm during the
i=1 j=1
monsoon period is used as the independent variableY.
42
In Table 2 and 3, the marginal entropy of rainfall and DTW distribution. The join entropy of the water level and rainfall is
are obtained from the probability distribution of the variables. obtained using Eq. (7) as shown in Table 5. The mutual
The obtained result is shown in Table 2 and 3, respectively. information between rainfall and DTW in the study area is
calculated using Eq. (9) or (10).The ratio between the mutual
In Table 4 and 5, the conditional entropy of water level, 𝑋 entropy and the marginal entropy of rainfall gives the
given the rainfall, 𝑌 is evaluated from conditional probability recharge due to the monsoon rainfall using Eq. (13).
Table 1.Cross tabulation of data set
y(i), Monsoon rainfall (mm) i = 1 i = 2 Total

x(j), DTW (m, bgl) 100-200 200-300
j = 1, 1-2 5 6 11
j = 2, 2-3 10 6 16
j = 3, 3-4 7 0 7
j = 4, 4-5 2 0 2
Total 24 12 36
Table 2.Marginal entropy of rainfall
Marginal entropy of rainfall

pi 0.667 0.333
log2(1/pi) 0.585 1.585
pilog2(1/pi) 0.390 0.528
Marginal entropy of rainfall, H(Y) = 0.920 bits, calculated from Eq. (3)
Table 3.Marginal entropy of DTW
Marginal entropy of DTW

pj log2(1/pj) pjlog2(1/pj)
0.306 1.710 0.523
0.444 1.170 0.520
0.194 2.363 0.459
0.056 4.170 0.232
Marginal entropy of DTW, H(X) = 1.734 bits, calculated from Eq. (4)
Table 4.Conditional entropy of DTW due to rainfall
Conditional entropy of DTW due to rainfall

0.208 0.500
pi/j 0.417 0.500
0.292 0.000
0.083 0.000
0.471 0.500
pi/jlog2(1/pi/j) 0.526 0.500
0.518 0.000
0.299 0.000
Conditional entropy of DTW due to rainfall, H(X/Y) = 1.540 bits, calculated from Eq. (5)
43
Table 5.Joint entropy of DTW and rainfall
Joint entropy of DTW and rainfall

0.139 0.167
pi,j 0.278 0.167
0.194 0.000
0.056 0.000
0.396 0.431
pi,jlog2(1/pi,j) 0.513 0.431
0.459 0.000
0.232 0.000
Joint entropy of DTW and rainfall, H(X,Y) = 2.460 bits, calculated from eq. (6)
Where,
ACKNOWLEDGEMENT
pi= Probability distribution of rainfall.
The authors are thankful to the staffs of Groundwater
pj= Probability distribution of DTW.
Department U.P., Geophysical Survey Division Mirzapur,
pi/j = Conditional probability distribution of rainfall and
Uttar Pradesh and to the Division of Geophysics, Geological
DTW.
Survey of India, Central Region, Nagpur, Maharashtra for
pi,j= Joint probability distribution of rainfall and DTW.
providing the data and necessary facilities required for
completion of this work.
Mutual entropy, MI (X, Y) = 1.734 – 1.540 = 0.194 bits,
calculated from Eq. (9). Compliance with Ethical Standards
= 1.734 + 0.920 – 2.460 The authors declare that they have no conflict of interest and
= 0.194 bits, calculated from the Eq. (10). adhere to copyright norms.
0.194
Recharge rate, Re (%) = × 100 = 11.1, calculated
1.734
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Resour. Mang., 16, 37-49. for data mining. J. Stat Comput. Simul., 69(2), 171-201.
Mogheir, Y., De Lima, J.L.M.P. and Singh, V.P., 2004. Younger, P.L., 2007. Groundwater in the environment: an
Characterizing the spatial variability of groundwater quality introduction. Blackwell Publishing, UK.
using the entropy theory: II. Case study from Gaza Strip. Zhou, P., Fan, L. and Zhou, D., 2010. Data aggregation in
Hydrol. Process., 18, 2579-2590. constructing composite indicators: a perspective of
information loss. Expert Syst. Appl., 37, 360-365.
45
Fluoride Zonation in Dharmapuri District of Tamil Nadu (India)

A. Mayakannan and S. Vadivel *
Post Graduate and Research Department of Geography, Government Arts College, Kumbakonam- 612002, India.
* Corresponding author: sivavavel@gmail.com
ABSTRACT
Globally, 200 million people rely on water resources which are contaminated with fluoride. The high concentration of fluoride naturally found in groundwater, causes serious
health problem to the local population. In Dharmapuri District of Tamil Nadu, a high concentration of fluoride has been found in groundwater. The main objective of the
present study is to explore and identify the fluoride zones of this district. Samples are collected for 55 places and fluoride zone maps are prepared for the study region. As a
result, the variation of fluoride was observed between pre and post monsoon period. In contrast, the number of fluoride zones decreased in pre monsoon period than the post
monsoon period. However, the fluoride concentrations are constant in this district. As a result, the people of this area are facing many health issues.
Key words: Fluoride, Water quality, Ground water, Dharmapuri district, Tamil Nadu
INTRODUCTION increase in the number of dental cases by more than eight

times during the reference period (2007-08 to 2008-09) is
Ground water resources are often contaminated with
mainly due to the fluoride content in the water. Fluoride
fluorides. The high concentration of fluoride naturally found
intake of 1 mg/l per day is considered essential for healthy
in groundwater, causes serious health problems to the local
growth of teeth and bones, but level higher than the
population. The probability of occurrence of high fluoride
permissible limit of 1.5 mg/l is considered dangerous to the
concentration in ground and surface water has also been
health (Ambade et al, 2012). Deficiency of fluoride leads to
studied in various countries. In Tamil Nadu, the high
dental problems and the higher concentrations lead to dental
concentration of fluoride in groundwater is found in
as well as skeletal fluorosis (Behera et al, 2012). Fluoride
Dharmapuri and Salem districts, closely followed by
reduces secretion of thyroid gland by affecting iodine in the
Coimbatore, Madurai, Trichy, Dindugal and Chidambaram
body, which may lead to mongolism (Dutta et al, 2010). High
districts. The more dependence on groundwater to convene
fluoride intake over a long period of time, can cripple one’s
ever-increasing demands of domestic, agriculture and
life (Saxena et al, 2003). Water with high fluoride content is
industrial sectors, has resulted in over utilization of
generally soft, has high pH and contains large amount of
groundwater resources.
silica and this leads to fluorosis. This problem is acute in
According to Indian standards, the maximum permissible India and almost 80 per cent of the rural population depends
limit of fluoride concentrations is 1mg/l (BIS, 2012). on untreated ground water for potable water supplies
Drinking water is being provided to the people of Dharmapuri (Sudhakar and Mamatha, 2004).
district in limited areas through the Hogenakkal Water Project
only, when water flows in the Cauvery River. Thereafter, STUDY AREA
during long summer days, they get drinking water through Dharmapuri District is chosen as the primary unit of
community/own bore wells which are 200 to 300 feet deep, investigation to investigate the “zonation of Fluoride Areas”.
occasionally touching even 700 feet. Hence, in the present This district is located approximately between 11o.47′and
study, we aim to examine the occurrence of fluoride zones in 12o.33′ North and between 77o.02′ and 78o.40′ East. The total
Dharmapuri district. geographical area is around 4498 Sq. km. The climatic
condition of the district is hot and dry in summer from March
OVERVIEW to May and winter is very cold and misty from November to
In Dharmapuri district, fluoride is found to be in excess in February. The average rainfall is 902.1mm. According to the
many places, and as such, excess fluorides are the main issues census 2011, this district had a population of 1,502,900 out of
in this part of Tamil Nadu (Central Ground Water Board, which male and female were 1, 12,490 and 7, 30,410
2009). CaCO3 and NO3 concentrations are found in more than respectively. Dharmapuri district forms a part of the upland
permissible limit in this district. The entire district is facing plateau region of Tamil Nadu with many hill ranges and
water scarcity and out of eight blocks, seven are over undulating plains. The western part of the district between
exploited and one of them, facing critical situation. Kumar et Pennagaram and Denkanikottai has hill ranges belonging to
al. (2007) have examined the status of fluorosis in the north Mysore Plateau with a chain of undulating hills. The southern
western districts of Tamil Nadu from five contiguous districts, boundary of the district is occupied by the Shevaroy hill
namely Dharmapuri, Erode, Krishnagiri, Salem and Vellore. ranges. The plains occupying the central, eastern and
southern parts of the district have an average elevation of 488
The morbidity and relatively lower life expectancy in
m above msl. The Plateau region along the western boundary
Dharmapuri district have been linked with worm infestation
and the north-western part of the district, has an average
and fluorosis, poverty, poor sanitation and hygiene (The
elevation of 914 m above msl.
Human Development Report of Tamil Nadu, 2011). The
46
A. Mayakannan and S. Vadivel J.Ind.Geophys. Union, 24(2) (2020), 46-51
METHODOLOGY reclassified, using weighted overlay technique. Accordingly,

Seven years water samples fluoride data (2011-2017) fluoride zones are identified and spatial fluoride maps are
covering 55 places, were collected from the State Ground and prepared for the entire district.
Surface Water Resources Data Centre, Chennai for pre and RESULT AND DISCUSSION
post monsoon period recorded in the months of July and
January. The fluoride attributes are added in ArcGIS9.1 Fluoride zonation areas of Dharmapuri Districts during pre
software to depict raster maps. These maps are classified, and post Monsoon periods, 2011-2017, are shown in Figure 1.
Veppampatti
Vellichandai
Veddakattamaduvu
Theerthamalai
Thadinaickenpatty
Taluk Office
Sunkarahalli
Solaikottai
Salur
Regadahalli
Pulikarai
Pikkili
Perumbalai
Periyampatti
Pappireddipatty
Papparapatti
Thoppur
Neruppur
Narthampatty
Nakkalpatti
Nagadsampatti
Namandahalli
Menasi
Kottayur
Mattlampatti
Marandahalli
M.velampatti
Krishnapuram
Konangihalli(b.agraharam
Kottapatti
Kilanur
Karimangalam
Kammampatti
Kambainallur
Kadathur
Kadagathur
K.Vetrapatti
Jammanahalli
Jakkasamudram
Indoor
Hogenkkal
Hanumanthapuram
Gurubarahalli
Gopinathampatti
Elavadai
Ettiyampatti
Chettipatti
Chellamudi
Belrampatti
Bandarahalli
Bairanaickanpatty
B.S. Agraharam
Alamarathupatti
Ajjampatty
A.velampatti
0.00 0.50 1.00 1.50 2.00
Post Monsoon Pre Monsoon
Level of Fluoride (ppm) During Pre and Post Monsoon Period
Figure 1. Fluoride Zonation Areas, Dharmapuri Districts (Pre and Post Monsoon 2011-2017)
47
J.Ind.Geophys. Union, 24(2) (2020), 46-51 A. Mayakannan and S. Vadivel
Fluoride Areas during Pre monsoon (2011-2017) particularly in 17 villages, are observed as containing
Table 1 reveals the fluoride zones of Dharmapuri district moderate fluorides (0.71-0.90ppm). In contrast, 14.22 per cent
during the course of pre monsoon from 2011 to 2017. During of the study area is observed with high fluoride (0.91-
pre monsoon period (Figure 2), the very low fluoride 1.10ppm) zones, chiefly in 11 villages. These areas are
(<0.50ppm) zones (0.81%) are recorded in 5 villages. These perceived in three broader areas in the south eastern part, two
zones are located as two small patches in the central part, one small patches in the southern margin, three small patches at
small patch in the central northern part and two small areas in the central part, four tiny places and one small patches in
the central south eastern part of the district. The low fluoride western part and one broader area and three tiny spots in the
(0.51-0.70 ppm) zones (21.42%) are observed in 15 villages northern part of the district. The very high fluoride
of Dharmapuri district. Three larger areas around the centre, (>1.11ppm) zones (0.94%) are observed only in 7 villages of
two small areas in the north eastern part and one small area in the study area. This area is recognized in two small areas in
the south western part are identified with low fluoride areas. the eastern part, two small patches at the central part and one
Similarly, the moderate fluoride zones are established in 17 tiny place in the western part of the district.
villages of the study area. 62.61 per cent of the district areas,
Figure 2. Fluoride zonation map of the Dharmapuri districts (Pre Monsoon 2011-2017).
Table 1. Fluoride occurrences in villages of Dharmapuri district during Pre- monsoon period from 2011-2017
S. Concentration Number Areas in
Name of the Villages
No of fluoride of Villages Percentage
1 Very Low B.S. Agraharam, Krishnapuram, Narthampatty, Menasi, Jammanahalli, 5 0.81
Elavadai, Kambainallur , Neruppur, Alamarathupatti, Kadagathur,
2 Low Papparapatti, Theerthamalai, Bairanaickanpatty, Indoor, Kadathur, 15 21.42
Kottapatti, Veddakattamaduvu, Gopinathampatti, Nakkalpatti, pulikarai.
Ettiyampatti, Namandahalli, Vellichandai, Belarampatti, Kottayur,
Hogenkkal, Chellamudi, Perumbalai, Thoppur, Thadinaickenpatty,
3 Moderate 17 62.61
Karimangalam, Periyampatti, Regadahalli, Gurubarahalli, Pikili,
M.Velampatti, A.Velampatti.
Marandahalli, Jakkasamudram, Hanumananthapuram, Nagadasampatti,
4 High Konangihalli, Kammampatti, 11 14.22
Sunkarahalli, Bandarahalli, Kilanur, Chettipatti, Pappiredipatty.
Taluk office, Ajjampatty, Mattlampatti, Solaikottai, Veppampatti, Salur,
5 Very High 7 0.94
K.vetrapatti.
Total 55 100.00
48
Fluoride Areas during Post monsoon (2011-2017) into the entire part of the district excluding the very low, low,
high and very high fluoride zones.
Table 2 shows fluoride zones of Dharmapuri district during
post monsoon period from 2011 to 2017. The very low Similarly, the high fluoride (0.91-1.10ppm) zones (21.30%)
fluoride (<0.50ppm) zone (0.34%) is recorded in only one occurred in 10 villages, specifically one large belt found in
village at central western part (Figure 3). Similarly, 16.2 per eastern margin that stretches from north to south, two broader
cent of the district area was registered in low fluoride (0.51- areas and one small part in southern margin, one small area
0.70ppm) zone. This region spreads over 18 villages. and six small patches at the central part, one small area in the
particularly in a large areas of central part, one broader and western part and one larger area and four small parts in the
one small patch in the western part, five small patches along north eastern part of the district. 1.72 per cent of the district
the northern margin, three small patches along the eastern area is observed having very high fluoride (>1.11ppm) zones.
margin and two small areas and two tiny spots in the south These areas are located in three small patches in the north
eastern region of the district. However, 60.43 per cent of the eastern region, two small areas in the southern margin and
study area is occupied by moderate fluoride (0.71-0.90ppm) one small place at the central part of the study area.
zones covering 20 villages of this district. This area extends
Figure 3. Fluoride zonation map of Dharmapuri Districts (Post Monsoon 2011-2017).
Table 2. Fluoride occurrences in villages of Dharmapuri district during post monsoon period from 2011-2017
Number
Concentration Areas in
S. No Name of the Villages of
of fluoride Percentage
Villages
1 Very Low B.S. Agraharam 1 0.34
Neruppur, Chellamudi, Kottayur, Vellichandai, Karimangalam,
Periyampatti, Pulikarai, Ettiyampatti, Alamarathupatti, Kadagathur,
2 Low 18 16.21
Narthampatty, Kadathur, Elavadai, Meansi, Jamanahalli, Chettipatti,
Bairnaickanpatty, Kottapatti.
Hogenkkal, Konangihalli,Nagadasampatti, Thadinaickenpatty, Belrampatti,
Marandahalli, Pikkili, Paparapatti, Nakkalpatti, Bandarahalli,Krishnapuram,
3 Moderate 20 60.43
Kambainallur, Gopinathampatti, M.velampatti, Indoor, A. Velampatti,
Ragadahalli, Veddakattamaduv, Theerthamalai, Thoppur.
Kammampatti, Taluk Office, Jakkasamudram, Matlampatti,
4 High Hanumanthapuram, Sunkarahalli, Gurubarahalli,Ajjampatty, Salur, 10 21.30
Veppampatti.
Perumbalai, Namandahalli, Solaikottai, Pappireddipatty, K.vetrapatti,
5 Very High 6 1.72
Kilanur.
Total 55 100.00
49
J.Ind.Geophys. Union, 24(2) (2020), 46-51 A. Mayakannan and S. Vadivel
Variations of Fluoride Areas, Dharmapuri District (Pre monsoon period than the post monsoon period. However, the
and Post Monsoon period: 2011-2017) fluoride intensity shows an increase of minimum 0.01 mg per
litre (A.velampatti, Elavadai, Veddakattamaduvu) and
When comparing the seven years of fluoride data (average) maximum 0.4 mg per litre (Chettipatti) in 31 villages. As a
for pre and post monsoon (2011-2017) period, the results result, the fluoride level was increased in pre monsoon period
(Figure 4) clearly indicate that the fluoride concentrations are than the post monsoon period. Accordingly, the fluoride zones
negatively registered in 24 villages and the values range and its concentration are constant in this district. Hence, the
between -0.36 mg per litre (Perumbalai) and -0.01 mg per litre people are drinking the fluoride water, which creates health
(Thoppur). Therefore, the fluoride area gets decreased in pre issues like dental, skeletal and non-skeletal problems.
Veppampatti
Vellichandai
Veddakattamaduvu
Theerthamalai
Thadinaickenpatty
Taluk Office
Sunkarahalli
Solaikottai
Salur
Regadahalli
Pulikarai
Pikkili
Perumbalai
Periyampatti
Pappireddipatty
Papparapatti
Thoppur
Neruppur
Narthampatty
Nakkalpatti
Nagadsampatti
Namandahalli
Menasi
Kottayur
Mattlampatti
Marandahalli
M.velampatti
Krishnapuram
Konangihalli(b.agraharam
Kottapatti
Kilanur
Karimangalam
Kammampatti
Kambainallur
Kadathur
Kadagathur
K.Vetrapatti
Jammanahalli
Jakkasamudram
Indoor
Hogenkkal
Hanumanthapuram
Gurubarahalli
Gopinathampatti
Elavadai
Ettiyampatti
Chettipatti
Chellamudi
Belrampatti
Bandarahalli
Bairanaickanpatty
B.S. Agraharam
Alamarathupatti
Ajjampatty
A.velampatti
-0.40 -0.20 0.00 0.20 0.40 0.60
Variations of Fluoride (ppm) Level Between Pre and Post Monsoon Period
Figure 4. Variations of Fluoride Zonation Areas, Dharmapuri Districts (Pre and Post Monsoon 2011-2017)
50
CONCLUSION in Rajnandgaon district of Chhattisgarh state in central

India, Int. J. Environ. Sci., 3(2), 851-858.
Based on the present study, a number of very low, low, Behera, B. and Das, M., 2012. Studies on groundwater pollution
moderate, high and very high fluoride zones are identified due to iron content and water quality in and around
during pre and post monsoon period in Dharmapuri district. jagdalpur, Bastar district, Chhattisgarh, India, J. Chemical
Accordingly, the variations of fluoride level between pre and and Pharma. Res., 4(8), 3803-3807.
Bureau of Indian Standards 2012. Indian Standard Drinking
post monsoon period revealed that the fluoride concentrations
Water - Specification (Second Revision) 2012, B Manak
are negatively registered in 24 of 55 places. However, the Bhavan, 9 Bahadur Shah Zafar Marg New Delhi 110002.
fluoride level was decreased in pre monsoon period than the Central Ground Water Board, 2009. Annual Report,
post monsoon period. As a result, the fluoride areas and its http://cgwb.gov.in/documents/Ground%
concentration are static in this district. The people living in 20Water%20Year% 20Book%202009-10.pdf. Jamnagar
House, 18/11, Man Singh Road Area, New Delhi, Delhi
this area are facing many health consequences.
110001.
Dutta. J., Nath, M. and Chetis, M., 2010. Monitoring of fluoride
ACKNOWLEDGEMENTS Concentration in groundwater of small tea garden in
Sonitpur District, Assam, India: Correlation with physic-
This research was supported by the Indian Council of Social chemical parameters, Intern. J. Chem. Tech. Res. 2(2),
Science Research, Aruna Asaf Ali Marg, JNU Institutional 199-1208.
Area, New Delhi-110 067, funded for Full–Term Doctoral Kumar, H.R., Khandare, A.L., Brahmam, G.N., Venkaiah, K.,
Fellowship, The authors thank for assistance. Reddy, G. and Sivakumar, B., 2007. Assessment of current
status of fluorosis in northwestern districts of Tamil Nadu
Compliance with Ethical Standards using community index for dental fluorosis. J. Hum. Ecol.,
21, 27-32.
The authors declare that they have no conflict of interest and Saxena, V. and Ahmed, S., 2003. Inferring the chemical
adhere to copyright norms. parameters for the dissolution of fluoride for the
dissolution of fluoride in groundwater, Environ. Geol., 45,
REFERENCES 156-163.
SudhakarRao, S.M. and Mamatha, P.R., 2004. De-fluoridation of
Ambade, B. and Rao, C.M., 2012. Assessment of groundwater water by IISc method. Provisional Indian Patent
quality with a special emphasis on fluoride contamination (application under consideration). The Human
Development Report of Tamil Nadu, 2011.
51
Characterization of groundwater chemistry using multivariate statistical analysis

in parts of Nellore mica schist belt (Andhra Pradesh), India
Golla Veeraswamy
Department of Geology, Sri Venkateswara University, Tirupati, 517502, Andhra Pradesh, India
Email id: veeraswamygolla33@gmail.com
ABSTRACT
The aim of the current study is to identify ground water chemistry through multivariate statistical techniques, using both factor analysis and cluster analysis. It is controlled by
geogenic influence in the groundwater, agriculture activity like usage of fertilizers, rainwater infiltration and flow of water, dissolving of silicate group of minerals like soda-
feldspars and plagioclase feldspar, besides weathering processes. 40 groundwater samples have been collected from the Nellore mica schist belt area of the Nellore district in
Andhra Pradesh (South India) and analyzed for different physicochemical parameters, like pH, electrical conductivity (EC), total dissolve solids (TDS), hardness, alkalinity,
primary cations sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), anions bi-carbonates (HCO3−), chloride (Cl−), sulphide (SO42−) and fluoride (F−). The
structural equation modeling has been carried out through MINITAB. 2 and XLSTAT software’s. Gibb's diagram highlighted the source of the origin of these chemical
parameters due to rock-water interaction. Normalized bivariate plots indicate that the chemical elements are generated from the silicate weathering in the study area, where
overall, the groundwater chemistry has been found responsible for dissolution of the ferro magnesium minerals (silicate group of minerals).
Key words: Groundwater chemistry, Factor analysis, Cluster analysis, Gibbs diagram, Scatter plots diagram, Nellore mica schist belt
INTRODUCTION sewage, can all lead to the contamination of groundwater in

aquifer. Groundwater is almost globally important for human
Water is a fundamental product with an unparalleled value
consumption as well as for the support of habitat and for
after air and assumes a huge part in the biosphere (in creatures
maintaining the quality of base flow to rivers. Groundwater is
and plants kingdoms), air and lithosphere (Aderogba, 2005;
internationally essential for human utilization and in addition
Mayer's, 2005; Nagaraju et al., 2017; Veeraswamy et al.,
for the help of living organisms and for keeping up the nature
2019a, b). It is used in human settlements for drinking,
of the base stream to waterways (Ravikumar and Somashekar,
sanitation, washing and agriculture. Water can occur as
2011).
surface water in lakes, rain, and stream and in addition to
groundwater wells, boreholes, and springs. Groundwater In a part of the Nellore mica schist belt, a comprehensive
assets are dynamic in nature and are influenced by factors like geochemical examination was carried out in order to identify
industrialization, and urbanization and thus, its preservation is groundwater quality. The analysis was done to detect possible
of fundamental importance. Ascertaining the quality of water sources of pollution and to a general characterization of the
is important before its utilization for different purposes, like, water quality in the studied area, which was carried out by
drinking, rural, recreational and mechanical utilizations means of multivariate statistical tools like Principal
(Brindha and Elango., 2011; Mohan Babu and Viswanadh, Component Analysis, cluster analysis and mapping tools to
2013; Nagaraju et al., 2014a). Hydrochemical assessment of understand the groundwater hydrochemistry, identify its
groundwater is also important (Aghazadeh and Mogaddam, control mechanisms, and evaluate the groundwater quality
2010), as the quality of water plays a prominent role in both comprehensively.
agricultural production and human health. The
hydrogeochemical investigations are also helpful in STUDY AREA
identifying quality of water (Nagaraju et al., 2014b; The study area belongs to a part of the Nellore schist belt. It is
Karthikeyan et al., 2011). The hydrochemistry of groundwater included in the toposheet Nos. 57 N/12, N/15, N/16 and
reveals the natural processes involved in governing the covers an area of 247.79 km². It is located between
chemical elements dissolved in water, major part of which longitudes 79° 42' 30'' E and 79° 54' 30'' E and latitudes 14°
comes from the weathering of rocks and soils and a minor 13' 0'' N and14° 16' 30'' N and lies in a subtropical climate
part from atmospheric precipitation (Nagaraju et al., 2006). with a mean annual temperature of 24.3ºC to 40ºC. The
Anthropogenic disturbances are also increasingly play a role humidity is usually in the range of 6–84 %. The annual
in the changing of groundwater quality. The over-exploitation normal rainfall of the study area is about 1084 mm. The mean
of aquifers for agricultural, industrial and urban uses along daily maximum temperature in the district is about 40°C in
with structural and climatic conditions increases the May and the mean daily minimum temperature is about 20°C
possibility of deterioration of groundwater. Discharge of in December/ January, most of the study are is occupied by
untreated or inadequately treated waste water, contaminated dendritic pattern. (www.cgwb.gov.ap.in; Sarma, 1998). The
agricultural runoff from farms and discharge of untreated study area is shown in Figure 1.
52
Golla Veeraswamy J.Ind.Geophys. Union, 24(2) (2020), 52-59
Figure 1. Location Map of the Study Area
GEOLOGY OF THE STUDY AREA garnet-mica schist, sillimanite quartzite, garnetiferous

amphibolites, banded ferruginous quartzite, staurolite-
The Nellore schist belt extends parallel to the eastern border
anthophyllite rock, bedded tuff, bedded barite-magnetite rock,
of the Cuddapah basin as an N-S trending actuate belt over a
calc-silicate rock, crystalline limestone, etc. They are
length of 300 km between podili (Prakasm district) in the
migmatised and the migmatites and schist, in turn, are
north and Naidupet in the south, with width ranging between
intruded by mafic-ultramafic, granites, mica-pegmatite, etc.
8 and 10 km (Saha et al., 2015). It consists of two distinct
The low-grade rocks from part of the Nellore metamorphics
groups of rocks viz. the older upper amphibolites facies
and contains quartz-chlorite-biotite schist, quartz chlorite
metamorphic rocks in the eastern and southern part and the
schist, metabasalt, and tuff. Phyllite and quartzite and Kandra
younger greenschist facies rocks in the western side
igneous complex forms part of the Nellore metamorphic
(Jaganndhan, 1861;APSAC, 2018).The high-grade rocks,
terrain. Geological map of the study area is shown in Figure
designated as older Nellore group, include kyanite-staurolite-
2.
53
J.Ind.Geophys. Union, 24(2) (2020), 52-59 Golla Veeraswamy
Figure 2. Geological Map of the Study Area
Table 1. Minimum, maximum, standard deviation and average values of different constituents of analysed water samples
S. No. Constituents Min Max Average S.D

1 Calcium (Ca) (mg/l) 113 359 172.65 48.26
2 Magnesium (Mg) (mg/l) 23.84 250 131.89 46.36
3 Sodium (Na) (mg/l) 60 310 154.33 60.07
4 Potassium (K) (mg/l) 1 40 8.83 8.67
5 Bicarbonate (HCO3) (mg/l) 144 598 407.23 129.13
6 Carbonate (CO3) (mg/l) 04 72 26.20 17.57
7 Sulphate (SO4) (mg/l) 80 200 139 33
8 Chloride (Cl) (mg/l) 16.60 68 46.81 11.59
9 Fluoride (F ) mg/l 0.80 2.00 1.30 0.23
10 Total dissolved solids (mg/l) 406 910 113 112.89
11 Hardness as CaCO3 (mg/l) 120 915 553 112.89
12 Alkalinity as CaCO3 (mg/l) 160 321 251.40 43.19
13 pH 6.40 9.0 7.25 0.57
14 Specific conductance (µmhos/cm) 625 1400 851.05 173.67
METHODOLOGY bicarbonate, chloride, and sulphate by adopting the standard

procedures (Tripathi et al., 2012; APHA, 2012, Adejo et al.,
Overall, 40 groundwater samples were collected in the study 2015). The obtained results were processed in MINITAB 18
area of the Nellore mica schist belt, in pre-washed and dried software to make the factor analysis and R-mode hierarchical
polyethylene bottles. The location of samples was traced by cluster analysis. Moreover, Gibbs and scatter plots diagram
using GPS tracker and they were shown in the Figure 1. The were plotted for identifying the processes controlling the
water samples were analyzed to estimate for physic-chemical groundwater chemistry and the geology map of the study area
parameters such as pH, electrical conductivity (EC), total was prepared with help of ARC GIS software 10.1. The
dissolved solids (TDS), major cations such as calcium, physico chemical parameters, minimum, maximum, average,
magnesium, sodium and potassium, and anions such as values were shown in Table 1.
54
RESULT AND DISCUSSION on all and the 20.66% percent of the total variance of
65.995%. It is positively loaded with electrical conductivity,
Factor Analysis chlorides and hardness (Wang, Jie et al., 2017). It is assigned
Principal component analysis (PCA) is a data diminution to geogenic influence in the groundwater as a result of the
technique to abridge a number of original variables into a rock-water interaction. The highest amount of electrical
smaller set of combined dimensions, or factors for easy conductivity and total dissolve solids indicate the mineral
handling and elucidation of data (Davis, 1986). Varimax dissolution in the water especially contributed by calcium and
rotation is the most useful method for this analysis (Cloutier magnesium-bearing minerals like calcite, muscovite and
et al., 2008; Yidana et al., 2010). Therefore, in the current biotite (Elumalai et al., 2017). The amount of chloride
study, the principal component analysis (PCA), using varimax indicates sea water mixing with the freshwater aquifer system
orthogonal rotation was applied to the 10 standardized in the in the study area. It’s located nearest to the Bay of
physicochemical data and it has yielded 10 factors. Among Bengal. The Second Eigen vector explains 13.876% percent
10, we consider the first 4 factors, because they explained of the total variance of 65.995%. It is positively correlates
75.0% of the total variance, among the studied wells. These with the calcium and sulphates due to the presence of the
factors variances exceed 70% and they are sufficient to calcium-bearing rocks, while high sulphates are caused due to
explain the mechanisms controlling groundwater chemistry. agriculture activity like usage of fertilizers, rainwater
Further, to comprehend which factors have more effect on infiltration and flow of water (Singh et al., 2017). The third
water chemistry, evaluation of Eigen value is important. Eigen vector attributed 13.088% percent of the total variance
Eigen values which were 1.0 or greater are considered most of 65.995% heavily weighted with the pH magnesium (Mg2+),
significant. (Dou Lei et al., 2008). The usage of the factor sodium (Na+), and potassium (K+), fluoride and alkalinity.
analysis is to explain the structure within the variance and The Main contributer to rock-water interaction is dissolvent of
covariance matrix of the multivariate data grouping. The the silicate group of minerals like soda and plagioclase
analysis produced nine factors which together justify 65.995 feldspars. Similarly, fluoride is derived from the weathering
% of the total variance. The rotated loading, Eigenvalues, of granite schist and mineral apatite (Jung et al., 2016). The
percentage of variance and cumulative percentage of variance Fourth Eigenvector represented the highly loaded bi-
and all the six factors are shown in Tables 2 and 3 carbonate (HCO3−). The highest concentration of bi-
respectively. The primary Eigenvalue is 2.893 and variability carbonates dissolved in groundwater is due to the weathering
20.663 and this is the main factor and the second the of silicate and carbonate minerals, along with the degradation
Eigenvalue is 1.943 and variability is 13.876. Similarly, third, of organic matter (Figure 3). A scree plot shows the
fourth, fifth, sixth, seventh eighth and ninth have an eigenvalues on the y-axis and the number of factors on the x-
Eigenvalue 1.832, 1.015, 0.745, 0.377, 0.285, 0.137, 0.013 axis. It always displays a downward curve. The point where
with variability 13.088, 7.254, 5.320, 2.694, 2.035, 0.976, and the slope of the curve is clearly leveling off (the “elbow)
0.090 respectively. The first Eigen vector is heavily weighted indicates the number of factors that should be generated by
the analysis.
Table 2. Shows Eigen values and cumulative percentages
Eigen values:
F1 F2 F3 F4 F5 F6 F7 F8 F9
Eigenvalue 2.893 1.943 1.83 1.015 0.745 0.377 0.285 0.137 0.013
Variability (%) 20.66 13.876 13.08 7.254 5.320 2.694 2.035 0.976 0.090
Cumulative % 20.663 34.539 47.62 54.88 60.200 62.894 64.929 65.905 65.995
55
Scree plot
3.5 100
3
2.893
80
Cumulative variability (%)

2.5
1.943 1.832
Eigenvalue
60
2
1.5
40
1.015
1 0.745
20
0.5
0.377 0.285
0.137
0.013
0 0
F1 F2 F3 F4 F5 F6 F7 F8 F9
axis
Figure 3. Scree plot diagram between eigenvalues and the number of factors, indicating downward trend.
Table 3. Results of factor Analysis
Factor pattern
F1 F2 F3 F4 F5
EC 1200 0.810 0.492 0.091 0.073 0.270
H
P 6.9 -0.447 0.291 0.545 0.183 -0.074
Ca 133 -0.048 0.521 -0.304 -0.313 -0.254
Mg 106 0.381 -0.491 0.535 0.010 -0.239
Na 60 -0.322 0.175 0.518 -0.210 0.003
K 21 0.076 0.313 0.427 -0.306 0.008
HCO3 274 -0.594 -0.116 0.052 0.273 0.324
CO3 30 -0.324 0.644 -0.045 0.656 -0.218
Cl 342 0.448 -0.109 0.369 0.116 -0.356
SO4 149 0.107 -0.426 -0.188 0.276 0.231
F 1.3 -0.103 0.196 -0.425 -0.011 -0.278
TDS 780 0.810 0.493 0.091 0.073 0.271
Hardness 475 0.580 -0.249 0.045 0.366 -0.210
Alkalinity 268 -0.326 0.067 0.575 0.052 0.132
Variability (%) 20.663 13.876 13.088 7.254 5.320
Cumulative % 20.663 34.539 47.627 54.880 60.200
Cluster analysis carbonates. The second cluster grouping with the Mg+, Cl+,
hardness, So4-, are formed from the dissolution of the
The Dendrogram represents the complete linkage between the
minerals, saline water intrusion and updates derived from the
13 variable in 40 groundwater sample, which forms three
agriculture activity (Prasanna et al., 2019). The third cluster
cluster groups, as shown in Figure 4. From this dendrogram,
indicates grouping with the pH, CO3-, HCO3-, Na+. It is
the first cluster class indicates high relationship, strongly
formed due to weathering of the silicate and carbonate group
correlated between the EC, TDS, K+, Ca+, which indicate the
of minerals like feldspar and calcium-bearing minerals
rock-water interaction and dissolution of the mineral like
.
56
Dendrogram
Complete Linkage, Correlation Coefficient Distance
26.91
51.27
Similarity
75.64
100.00
EC TDS K Ca Mg Cl Hardness SO4 pH CO3 HCO3 Na
Variables
Figure 4. Dendrogram of cluster analysis of water quality data
Figure 5. Mechanism controlling the ground water chemistry, based on Gibbs method
Source -rock deduction by Gibbs method water samples (anions) fall in rock-water interaction field
indicating importance of mineral dissolution in this area
This method is used to identify the possible basic source of (Hounslow, 1995; Nagaraju et al., 2006).
the water samples (Hounslow, 1995). Although the initial
composition of groundwater originates from rainfall, it is Normalized bivariate plots
changed by rock weathering, evaporation (Gibbs, 1970).
It indicates the source of chemical elements in the water. It
When TDS is plotted against Na/ (Na+ + Ca+) and Cl-/ (Cl-
suggests that the groundwater samples fall in the silicate
+HCo3-), it gives information on the mechanism that controls
weathering region due to weathering and dissolution of
the chemistry of water. Gibb’s diagram for the study area is
silicate minerals like biotite, chlorite, muscovite, talc,
shown in Figure 5, which shows that the majority of the
feldspars and amphiboles in the study area (Veeraswamy et
water samples (cations) are out of the plot and most of the
al., 2019a, b) as shown in Figure 6.
57
Figure 6. Normalized bivariate plots
CONCLUSIONS were generated due to groundwater passing through the

underground rocks like granite. hornblende schist, quartzite,
Multivariate analysis comprises a set of techniques dedicated
pegmatite. Further, principle component analysis reveals
to the analysis of data sets with more than one variable. Out
geogenic influence in the groundwater as a result of the rock-
of that cluster analysis is an efficient way of displaying
water interaction (dissolution of ferro magnesium minerals).
complex relationships among many variables. Higher
Besides, the normalized bivariate plots indicate that the origin
similarities are clustered and linked first. After two objects are
of the chemicals relate to weathering processes of silicate
clustered, their correlations with all other objects are
group minerals. Finally, the main cause of chemical elements,
averaged. Factors are hypothetical variables very much
originated through the rock water interaction.
related to the forces acting in the sampling area and give the
essence of the data and possibly the natural processes ACKNOWLEDGEMENT
underlying that relationship. The model is presented in the
I thank to Dr A. Nagaraju, Department of geology, S V
varimax rotated factor matrix in which the 3 factors explain
University, Tirupati for preparing the manuscript.
80% of the data. Cluster analysis represents the weathering of
the silicate group of minerals like muscovite, quartz, feldspar Compliance with Ethical Standards
and some amount of the calcium-bearing minerals in the study
The authors declare that they have no conflict of interest and
area. Gibb's diagram indicates that the chemical elements
adhere to copyright norms.
58
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59
Assessment of Groundwater Quality with respect to Fluoride in Somavathi

River basin, Ananthapuramu District (Andhra Pradesh), India
U.Suresh, and U.Imran Basha*
Department of Geology, Sri Venkateswara University, Tirupati, Andhra Pradesh, India
*Corresponding author: Imrandudekulla@gmail.com
ABSTRACT
The hydrogeochemicalstudy was conducted both in the pre and post monsoon seasons of Somavathi River basin (India) to know the principal controlling mechanisms
of fluoride in groundwater. The fluoride concentration along with some physico-chemical parameters in groundwater, were determined using established standard
practices. Petrographic observations of host rocks coupled with molar ratios of chemical species studies exemplify that weathered material developed over the
granitegneiss, mica-schist, amphibolites, granitic intrusive and pegmatite veins due to weathering and extensive water-rock interaction, resulted into higher
concentration of fluoride in groundwater. The fluoride concentrations in the villages varied from 1.5 to 2.90 mg/L with highest fluoridevalue at Nallamada (2.90
mg/L) and lowest at 1.5. mg/Lin the pre and post monsoons. From the study, it is found that the alkaline pH and high bicarbonates are responsible for release of
fluoride bearing minerals into groundwater.The major water facies were Ca-Mg-Cl and Ca-HCO3. Moreover, the arid climate of the region,the granitic rocks and the
low freshwater exchange due to periodical drought conditions,are factors responsible for the higher incidence of fluorides in the groundwater resources. In addition,
most wells appear suitable for irrigation activities according to RSC, % Na and SAR.
Keywords:Fluoride contamination, Groundwater, Somavathi River basin, Monsoon, Andhra Pradesh
INTRODUCTION 2018a). However, prolonged intake of high fluoride in

drinking water can surely cause fluorosis (Adimalla, et al.,
The problem of excessive fluoride in ground water in
2019; Narsimha and Sudarshan, 2017; Fanand Simard,
India was first reported in 1937 in the state of Andhra
2018). In groundwater, the natural concentration of
Pradesh (Shortt et al.,1937).In India, approximately 62
million people including 6 million children, suffer from fluoride depends on the geological, chemical and physical
fluorosis because of consumption of water with high characteristics of the aquifer, the porosity and acidity of
fluoride concentrations (Susheela et al.,1993; Kotecha et the soil and rocks, the temperature, the action of other
al., 2012;Ramesh et al., 2017.,Unde et al.,2018). It is chemical elements, and the depth of wells. The aqueous
known that, the drinking water is the major contributor of ionic concentrations of groundwater may influence the
fluoride (75–90% of daily intake) (Saralakumari and Rao, fluoride solubility behaviour in the presence of excessive
1993; Raoet al., 2016).The major health problems sodium bicarbonates and the dissociation activity of
associated with excess fluorides in humans are, dental fluoride will be high (Tirumalesh et al., 2007). In general,
fluorosis, mottling of teeth, skeletal fluorosis, and
fluoride is released into groundwater from fluorine-
deformation of bones in all age groups (Susheela et al.,
bearing minerals such as fluorite, fluorapatite, biotite,
1993; Latha et al., 1999).The concentration of fluoride
apatite, muscovite, hornblende, villiaumite, tremolite,
found in the groundwater samples was higher compared to
the Indian Drinking Water Standard of maximum sellaite, cryolite, topaz, fluocerite, yttrofluorite, gagarinite,
permissible limit of 1 mg/L. Whereas the values of bastnasite, microlite, sphene, wohlerite, fluormica,
fluoride were lower than the maximum tolerance limit 1.5 epidote, amphibole, lepidolite, montmorillonite, kaolinite,
mg/L recommended by the World Health Organization pegmatite, mica, clays, villuanite, phosphorite, and some
(WHO) (BIS 2003;WHO 2004). Ingestion of water with micas weathered from silicates, igneous, and sedimentary
fluoride concentration above 1.5 mg/L causes fluorosis rocks, especially shale (Adimalla et al., 2018a,b; Ayoob
(Madhnure et al., 2007) as mentioned before. and Gupta, 2006; Narsimha and Rajitha, 2018a;
The major source of fluoride is the fluorite mineral, which Narsimhaand Sudarshan, 2017, 2018b) and high rates of
may be found in granite, gneiss and pegmatite. The evaporation and low precipitation in arid and semiarid
process of weathering of rock, releases fluoride in soil and areas can also contribute to the fluoride enrichment
groundwater. The alkaline water can mobilize fluoride (Adimalla and Venkatayogi, 2017, Rao, et al., 2014). It is
from fluorite with precipitation of calcium carbonate, found that, Anantapur District is one of the major fluoride
because the solubility of CaF2 increases with an increase affected districts of Andhra Pradesh. Earlier, many studies
in NaHCO3 rather than with other salts (Handa, 1975; were reported regarding fluoride for instance, the dental
Saxena and Ahmed, 2001). A small amount of fluoride is fluorosis levels of 43% have been reported in Anantapur
essential to maintain bones and formation of dental enamel District of Andhra Pradesh (Reddy and Prasad, 2003).
(Adimalla and Venkatayogi, 2017; Adimalla, et al., Similarly, the relationship between renal stones and their
60
U.Suresh, and U.ImranBasha J.Ind.Geophys. Union, 24(2) (2020), 60-74
fluoride content has been discussed by Sathish et al. granite/granodiorite. The hornblende-biotite granite/gneiss
(2008). Dental fluorosis, attributable to high fluoride is medium to coarse grained varying in colour with
content, is reported from Anantapur District, Andhra different shades of grey. In thin section, it exhibits
Pradesh (Venkateswara Rao and Mahajan, 1989; hypidiomorphic granular texture and composed of
Bhagavan and Raghu, 2005). In the present study area, the plagioclase, quartz, with minor orthoclase and accessories
concentration of fluoride in the ground water vary like hornblende, biotite, epidote, sphene, apatite and
from 1.56 to 2.6 mg/l in the pre monsoon season and chlorite. It is dominantly exposed surrounding the schist
ranges from 1.8 to 2.90 mg/l in post monsoon season. belt and is more gneissic in the west. Alternate layers of
High weathering rates and enhanced circulation of leucocratic and melanocratic bands define gneissosity. The
leucocratic layer is mainly composed of quartz and
water in the weathered rocks due to intensive and
feldspar while the melanocratic layer is predominantly
long time irrigation are responsible for the leaching
composed of biotite and hornblende. Overall mineralogy
of fluoride from their parent minerals present in soils and
of the gneiss is of granodiorite/tonalite but contains less of
rock,hence, the present study was conducted to assesthe
plagioclase and more of orthoclase and quartz.
fluoride geochemistry in somavathi River basin, of Andhra
Pradesh,India (Rajasekhar et al., 2018). Further, Syn to post kinematic plutons and tongues
younger biotite granite occurs covering a large part of the
STUDY AREA
area in the western part. It is considered equivalent to
The Somavathi River basin follows a straight course along Closepet granites. The granite forms monolithic blocks,
NE direction for 50 km and then takes a northerly turn and bare tors and knolls and constitute the hill ranges. It is
flows innearly northerly direction along the kadiri schist coarse grained, porphyritic, massive and feebly foliated
belt. The present study area falls in AnantapurDistrict, with foliation trending NNW-SSE along the margins. In
which is one of the chronically drought affected hand specimen, it is composed of quartz, pink-grey
Rayalaseema districts. It is located between 77° 48' 25´Ń feldspar and small amounts of biotite. Thin section studies
and 78° 02´ 45´´ N longitudes and 14° 05´ 55´´ and 14°26´ of it shows quartz, orthoclase, plagioclase, little
48´É asshown by Figure 1. The Rocks of Dharwar Super microcline, biotite, and hornblende with accessory apatite,
group, Peninsular Gneissic Complex-II (PGC-II) and sphene and muscovite. The quartz reefs have a dominant
basicintrusives form the geology of the areaare shown by NW-SE trend.Dolerite dykes have intruded the granitoids
Figure 2. Thematic map such as geology is prepared and the schist belt rocks. These dykes are abundant in the
through topographic maps, field data,and RS data through
northern and western part of the area. Most of the dykes
ArcGIS software (Shekhar and Pandey, 2015).The
have ENE-WSW to E-W trend and few are having NW-
Dharwar Super group is represented by the
SE trend. These are compact, medium to coarse grained
KadiriMetamorphics, which occur as an NE-SW trending
and show spheroidal weathering. In thin section, it is
belt (Kadiri Schist Belt) and as small lenticular outcrops
composed to plagioclase (andesine to labrodorite
within PGC-II. These rocks include metamorphosed acid
composition), augite and hornblende.Futher,granites and
volcanics with litho-units like quartz porphyry, rhyolite,
gneisses of the Peninsular Gneissic Complex are seen
rhyodacite, quartz-feldspar porphyry and metabasics like
hornblende-andesite basalt and quartz-muscovite-sericite surrounding the schist belt on all sides and north of
schist, amphibolites, pyroxenite and thin bands of Dorigallu, they together form basement to the
autoplastic conglomerate. The lithounits in the schist belt geologicalformations of the Cuddapah Super Group. The
have tectonic contact with the adjoining granodiorite overall mineralogy of the constituent lithounitsindicates
/tonalite, hornblende - biotite granite/gneiss. Among the that the schist belt has undergone low grade
lithounits, schist belt and acid volcanics are the dominant metamorphism of green schist facies.KSB comprises of
ones. Quartz porphyry forming higher grounds are meta-acid to basic volcanics sequence with sheared/faulted
exposed to the west of Kadirinayakuni Tanda. margins bounded by tonalite-granodiorite-monzodiorite
Complementary parallel shear zones are seen and granite-syenogranite suites of diapiric intrusions on
discontinuously all along the length of the schist belt. The both sides of the belt (Suresh et al., 2010). The
major part of the area is occupied by the PGC-II. It lithostratigraphic succession of the KSB was first given by
comprises mainly hornblende-biotite granite/gneiss, biotite Ranga, (1972).
65
J.Ind.Geophys. Union, 24(2) (2020), 60-74 U.Suresh, and U.ImranBasha
Figure 1. Location map of the study area
Figure 2. Geological map of the study area
METHODOLOGY contamination. The ground water samples were then

analyzed to assess various chemical water quality
The study area includes Somavathi River basin,
parameters such as Na, K,Ca, Mg, Cl, HCO3, F and
Ananthapur District, Andhra Pradesh.Thirty two
SO4according to APHA–AWWA–WPCF (1995). The pH
groundwater samples were collected from bore wells
and electrical conductivity of thewater samples were
during the pre and post monsoon seasons of 2016. First,
measured by using a portable pHmeter (Model-
the water was left to run from the sampling source for 4–6
CyberscanEutech pH 510) and EC meter (Systronic,
min to pump out the volume of water standing in the
Model 306) respectively. The cations like Naand K were
casing before taking the final sample and then water
determined by flame photometer, Ca weredetermined by
samples were collected in pre-cleaned, sterilized
titrimetric method, whereas anions like Cl andSO4 were
polyethylene bottles of 2L capacity . The samples were
determined by argentometric method and turbiditymethod
taken by holding the bottle at the bottom to avoid any
respectively. The fluoride concentration wasmeasured by
66
using the following SPADNSFlouride Reagent concentrations of groundwater varyied between 408-
Solution,500 mL of sample aliquot was takenin a round 2065mg/L. Further, the TDS is classified as fresh, if it is
bottom flask, then concentrated H2SO4, glassbeads and less than 1000 mg/L; brackish, if it is in between 1000 and
Ag2SO4 (at a rate of 5 mg/mg Cl if concentrationis greater 10,000 mg/L; saline, if it varies from 10,000 to
than 7000 mg/L) were added to it. Theflask was attached 100,000 mg/L; and brine, if it is more than 100,000 mg/L.
to distillation unit. Then the flask washeated until the Based on the BIS standard, TDS range has been classified
temperature of the flask content reachedexactly 180 o C. In into three categories, namely good, moderate and poor for
the SPADNS method, fluoride reactswith the dye lake, range of 0 to 500 mg/L, 500 to 2000 mg/L and more than
dissociating a proportion into a colourlesscomplex anion 2000 mg/L respectively.Accordingly, majority of
(ZrF62- ) and the dye. As the amount offluoride increases, groundwater in the present study region brackish and
the colour produced becomes progressivelylighter. A saline category. Among the cations, Na+ is the most
calibration standard ranging from 0–1.4 mg/L fluoride was dominant in the Somavathi river basin groundwater and its
prepared by diluting an appropriatevolume of standard concentration ranged from 27 to 378 mg/L. Moreover, one
fluoride solution. To 50 mL of standardsolution, 10 mL of and half times of groundwater samples show higher than
SPADNS reagent was added andmixed well. The the maximum allowable limit of 200 mg/L in the study
spectrophotometer was set to 570 nm andcalibration graph region. The higher concentration of sodium may be
was prepared from different standardfluoride derived from the dissolution of minerals and soil salts as
concentrations. When the graph gave a straightline, the well as the influence of anthropogenic sources (Todd and
instrument was ready for measurement of Mays, 2005). The concentration of Mg2+ in groundwater
fluorideconcentrations. The detection limit and analytical ranged from 4 to 65 mg/L. The concentration of Ca2+
range offluoride were 1.5 –2.9 mg/L respectively. AR ranged between 39 and 223 mg/L. A high chloride
gradechemicals were used throughout the study. To concentration of groundwater appear the result of leaching
prepare allthe reagents and calibration standards, double from the soils and also from the effect of domestic wastes,
distilledwater was used. Then the analysed parameters domestic effluents, fertilizers, leakages from septic tanks
were assessed to RSC, % Na and SAR to know the water and road salt used to de-ice roads in the winter, apart from
quality suitability for drinking and irrigation purposes. natural sources such as rainfall, the dissolution of fluid
inclusions, and chloride-bearing minerals, which also
RESULTS AND DISCUSSION
indicate an index of pollution (Van der Meer and Todd,
Major ion chemistry 1980; Adimallaet al., 2018a,b). In the present study, the
concentration of chloride ranges from 25 to 829mg/lat
The analytical results of pH, electrical conductivity (EC),
obuladevara cheruvu.According to the World Health
total dissolved solids (TDS), total hardness (TH), calcium
Organization (WHO, 2004) drinking water specifications,
(Ca2+), magnesium (Mg2+), sodium (Na+), potassium
the permissible limit in the absence of an alternate source
(K+), bicarbonate (HCO3−), carbonate (CO32−),sulphate
for chloride is 600 mg/L. The results revealed that only
(SO42−), nitrate (NO3−), and fluoride (F−) concentrations of
4.1% of groundwater samples show higher than the
the groundwater samples are presented in Tables 1 and
600 mg/L in the study region. The maximum allowable
2inpre and post monsoon conditions.The groundwater is
limit of sulphate for drinking purpose is 400 mg/L as
mostly alkaline in nature in the Somavathi river basin with
suggested by the World Health Organization (WHO,
pH concentration ranging from 8.2 to 8.6. The EC
2004).
concentration varies between 642-3247 µS/cm.TDS
Table 1.Concentration of major ions in Groundwater during pre-monsoon
Results in mg/L (* MicroSeimen/cm)
Physical parameters pH EC TDS Ca Mg Na k HCO3 CO3 F SO4 Cl
max 8.2 3247 2065 223 65 378 44 632 82 1.5 120 523
min 8.5 717 456 47 14 27 1 126 20 2.6 60 37
67
Table 2.Concentration of major ions in Groundwater during post-monsoon
Results in mg/L (* MicroSeimen/cm)
Physical Parameters pH EC TDS Ca Mg Na k HCO3 CO3 F SO4 Cl
Max 8.3 2396 1524 215 51 356 23 410 154 1.8 120 829
Min 8.6 642 408 39 4 52 2 108 49 2.9 30 25
Fluoride geochemistry drinking purposes in the study region. Fluoride

concentrations variation is shown in Spatial distribution
In Somavathi river basin, the collected bore well samples
maps Figures3 and 4.It is clear from the distribution map
which were situated in highly weathered areas are found to
of fluoride that except for extreme northern and southern
be having high fluoride concentrations when compared to
parts of the study area, all other areas have excess fluoride.
less weathered areas. Obviously, the degree of weathering
The highest fluoride concentration is noticed in the
appears to be the apparent reason for high incidence of
Nallamadapart of the study area. Moreover, United States
fluorides especially in these areas. In order to determine
Public Health Services (US PHS 1987) observed that the
possible variations of season on the fluoride contents of
recommended limit of fluoride in the drinking water
the groundwater, in different seasons, samples have been
majorly relies on the climatic conditions of the region.
collected and analysed during December 2016. The result
Therefore, in the Indian context, the desirable and
in Tables1 and 2 indicated that there is no appreciable
maximum allowable limit of fluoride in drinking water is
variation. fluorine is the most electronegative of all
fixed as 0.6 to 1.2 mg/L, conducive to dental caries.When
elements and occurs primarily as a negatively charged ion
fluoride concentration is less than 0.5 mg/L,it promotes
in water (Hem 1985; Adimalla, et al., 2018a. Intake of
development of strong bones, but when the concentration
small concentration is beneficial for human health.
range between 0.5 and 1.5 mg/L, it promotes dental
However, in the present study area, the concentration of F
fluorosis in children Similarly, when fluoride
ranged from 1.5 to 2.9 mg/L,in the ground water of the
concentration ranged from 1.5 to 4.0 mg/L it promotes
study region .Compared with the WHO guidelines
dental and skeletal fluorosis specially when its
majority of the groundwater samples were unsuitable for
concentration is greater than 4.0 mg/L.
Figure 3. Spatial distribution of flouride ( pre-monsoon) in the groundwater samples of the study area.
68
Figure 4.Spatial distribution of flouride (post monsoons) in the groundwater samples of the study area.
Figure 5. Piper Diagramme for descrimating hydro -geochemical facies
69
Water facies During Pre-monsoon, the SAR values of all the samples
are classified as good for irrigation. During pre-monsoon,
Water facies were identified using piper classification
the SAR concentration ranges from 0.97 to 7.48 with a
(Piper, 1953). From the result it is found that the major
mean of 3.34 and in the case of post-monsoon, it varies
water facieswere Ca-Mg-Cl and Ca-HCO3 in both seasons
from 1.47 to 9.52 with a mean of 4.60. During both the
(Figure 5).
monsoon periods, all SAR values are found to be less than
Water quality evaluation for dinking 10 and hence according to the SAR classification, the
groundwater belonging to the study area is safe for
The values obtained for various physico-chemical irrigation.
parameters of pre and post monsoon seasons after carrying
out the analysis of the groundwater are presented in Tables Residual Sodium Carbonate (RSC)
1 and 2. The pH values varied from 8.3-8.6 indicating its The quantity of bicarbonate and carbonate in excess of
alkaline nature. The sodium and bicarbonate values varied alkaline sediments (Ca and Mg) also influence the
from 27 to 378 mg/L and 126 to 632 mg/L respectively. suitability of water for irrigation purposes. When the sum
The fluoride concentration varied from 1.5-2.90 mg/L of carbonates and bicarbonates is in excess of calcium and
with highest fluoride level at Nallamada (2.90 mg/L) and magnesium, there may be possibility of complete water
lowest at M.Cross (0.54 mg/L). having high concentration of carbonate and bicarbonate
over alkaline earth metals, there is a tendency for calcium
Groundwater Quality for Irrigation purpose
and magnesium to precipitate as the water in the soil
The water used for irrigation is an important factor in becomes more concentrated. As a result, the relative
productivity of crop, its yield and quality. The quality of proportion of sodium in the water is increased in the form
irrigation water depends primarily on the presence of of sodium carbonate. This effect is highly unfavourable to
dissolved salts and their concentrations. The suitability of agriculture activities. Precipitation of Ca and Mg
groundwater for agricultural purposes depends on the (Raghunath,1987). in water having high concentration of
effect of mineral constituents of water on both plants and bicarbonates, there is tendency for calcium and
soil. Sodium absorption ratio and Residual sodium magnesium to precipitate as carbonates. According to the
carbonate are the most important quality criteria, which U.S. Department of Agriculture, groundwater having less
than or equal to 1.25 cations expressed epm is safe water
influence the water quality and its suitability. The values
for irrigation purpose and more than 2.5 epm of RSC is
of SAR, RSC and % Na are tabulated in Table 3.
not suitable for irrigation purposes (Nordstrom,
Sodium Absorption Ratio (SAR) 1982).Residual sodium carbonate (RSC) was calculated
using the formula:
Sodium absorption ratio is also used to determine the
suitability of groundwater to irrigation as it gives a RSC =(CO3- +HCO3-) - (Ca++ + Mg++)
measure of alkali/sodium hazard to crops. The sodium or
Where RSC and the concentration of the constituents are
alkali hazard for irrigation water is classified in terms of
expressed in meq/l
SAR and it is important for agriculture and human
pathology. SAR is an expression pertaining to cation make Based on the RSC value, during both the monsoon period,
up of water and soil solution. However it varies the RSC values falls within the safe limit and according to
considerably due to physiography, geology, hydrology and the residual sodium carbonate factor, the water is observed
anthropogenic activities. From the SAR, it was observed to be suitable for irrigation.
that groundwater samples of the study area has high
Percentage of Sodium (%Na)
alkaline hazard during the pre-monsoon seasons of the
year 2016. Utilisation high to very high alkaline hazard Irrigation water with high Na% may cause sodium
waters for irrigation may be harmful to soil which may accumulation and calcium deficiency in the soil leading to
lead to low permeability and poor cultivation in the study a breakdown of its physical properties. Therefore the
area (Todd and Mays, 2005). Sodium absorption ratio development of adequate drainage, high leaching and use
(SAR) is given by the relation (Karanth 1987). of organic matter are required for its management in the
area. Wilcox (1948) used % sodium and specific
SAR = (Na+)/(Ca2+ + Mg2+)1/2/2] conductance in evaluating the suitability of groundwater to
irrigation. Sodium-percentage determines the ratio of
where all the ions are expressed in meq/L
70
sodium to the total cations. All concentration values are The classification of groundwater samples from the study
expressed in equivalents per million. area with respect to the percent sodium and EC is shown
in Figure 3. During both the monsoon periods, only about
Percent sodium is calculated as follows 20% of the sample stations fall in the doubtful region
% Na = {(Na + K) x 100} / (Ca + Mg + Na + K) reflecting that majority of the wells in the study area are
found to be good for irrigation
Table 3. Shows the SAR, SODIUM%, RSC in pre and post monsoon conditions.
Sample SAR %Sodium RSC

Number Pre Post Pre Post Pre Post
1 2.75 1.88 26.18 29.60 -3.83 -1.83
2 4.31 2.63 41.20 26.33 -2.37 -5.31
3 3.72 3.74 41.35 40.68 -1.98 -1.90
4 0.97 4.15 17.42 43.76 -1.17 -1.04
5 2.20 3.19 33.66 36.45 -0.46 -1.84
6 3.50 7.06 39.75 64.67 -1.76 1.27
7 3.34 2.22 31.65 26.99 -6.75 -3.28
8 2.25 2.28 29.06 25.67 -1.39 -5.52
9 7.48 1.47 47.97 20.40 -5.43 -0.91
10 2.23 4.72 32.28 56.67 -0.80 0.16
11 2.00 2.37 24.87 38.01 -4.95 -0.96
12 3.38 5.20 38.27 54.36 -4.14 -0.17
13 2.13 3.48 28.05 37.18 -3.46 -3.62
14 2.80 3.80 27.90 42.75 -4.98 -1.59
15 3.49 4.14 39.13 45.78 -2.60 -0.18
16 4.65 7.62 38.23 61.36 -6.87 1.37
17 4.12 7.20 38.81 61.06 -4.58 -0.97
18 3.25 3.53 30.25 41.16 -7.62 -2.66
19 1.39 9.52 22.09 70.75 -1.85 1.07
20 2.73 2.73 28.01 28.76 -6.93 -6.33
21 3.28 3.58 41.82 38.17 -1.69 -1.88
22 3.53 3.13 34.18 32.86 -5.69 -5.40
23 1.92 5.91 30.51 50.73 -1.47 -2.31
24 7.34 4.22 56.15 40.54 -0.87 -5.48
25 4.88 4.45 40.62 40.64 -5.62 -6.25
26 2.98 8.33 28.27 54.74 -6.50 -6.21
27 2.35 7.45 27.80 55.34 -4.60 -4.06
28 2.85 3.37 28.68 33.84 -5.44 -6.60
29 3.30 5.25 38.09 48.38 -4.33 -3.72
30 2.66 7.71 37.86 63.82 -1.51 -1.52
31 3.85 5.64 40.21 60.07 0.43 -0.38
32 2.52 4.20 36.04 51.74 -1.63 -0.34
33 4.77 3.60 44.99 32.85 -1.17 -5.86
34 4.55 6.48 42.38 63.00 -1.48 -0.26
71
Rock-waterinteraction The results shows that the maximum samples fall in the
central portion of the Gibb’s diagram during both pre-
Gibbs (1970), proposed a mechanism that control the
monsoon and post-monsoon. It could be concluded that
chemical composition of the major dissolved constituents
the chief mechanism controlling the chemistry of
of water.The formulas for calculating the ratios are given
groundwater of the study area is the rock-water
below
interaction(Figure6).It is endorsed by the bivariate plots
(1) (Na + K) / (Na + K + Ca) and (2) Cl / (HCO3 + Cl) (Figure 7) of the ions (Golla et al., 2019;Etikalaet al.,
2019).
Figure 6.Gibbs Ratio Digram
Figure 7. Normalized Bivariate plots
72
CONCLUSIONS fluoride enrichment. Modeling Earth Systems and

Environment, 4(2), 841-852.
From the study it is found that the fluoride is released in
Adimalla, N. and Venkatayogi, S., 2017. Mechanism of
to the groundwater due to the alkaline nature of fluoride enrichment in groundwater of hard rock aquifers
groundwater and the weathering of fluoride bearing in Medak, Telangana State, South India. Environ. Earth
minerals present in the rocks.TheFluoride concentration Sci., 76(1), 45.
varies from 1.5-2.9 mg/L.It is further endorsed by the Ayoob, S. and Gupta, A.K., 2006. Fluoride in drinking water:
scatter plots. Moreover the minor samplesare suitable for a review on the status and stress effects. Critical reviews
in environmental science and technology, 36(6), 433-
drinking purposes,while majortlyis affected by the 487.
fluoride in the study area of Somvathi river basin. It BIS, 2012. Drinking Water-Specification. Bureau of Indian
appears that the fluoride contents of the original igneous Standards. New Delhi IS: 10500.
rocks were transferred to sedimentary rocks and to Bhagavan, S.V.B.K. and Raghu, V., 2005. Utility of check
metamorphic rocks and then to the soils. The dams in dilution of fluoride concentration in ground
water and the resultant analysis of blood serum and urine
concentration of fluoride ion in groundwater is attributed
of villagers, Anantapur District, Andhra Pradesh,
to the rocks through which it flows. Fluoride bearing pink India. Environmental geochemistry and health, 27(1),
and porphyritic granites have been located in several high 97-108.
fluoride tracks ofSomavathi river basin.The analysed Dissanayake, C.B., 1991. The fluoride problem in the ground
water samples are suitable for irrigation activities as per water of Sri Lanka—environmental management and
the values of RSC, % Na and SAR concerned. The major health. Int. J. Environ. Studies, 38(2-3), 137-155.
Etikala, B., Golla, V., Li, P. and Renati, S., 2019.
water facies were Ca-Mg-Cl and Ca-HCO3. The Gibbs Deciphering groundwater potential zones using MIF
classification shows that, the groundwater is influenced by technique and GIS: a study from Tirupati area, Chittoor
rock weathering followed by evaporation process. This District, Andhra Pradesh, India. HydroResearch, 1, 1-7.
finding is endorsed by the bivariate plots as well . Fan, W.L. and Simard, A., 2018. U.S. Patent No. 10,058,317.
Washington, DC; U.S. Patent and Trademark Office.
ACKNOWLEDGEMENT Golla, V., Arveti, N., Etikala, B., Sreedhar, Y., Narasimhlu,
K. and Harish, P., 2019. Data sets on spatial analysis of
I would like to thank Dr. U. Suresh , Asst. Professor of
hydro geochemistry of Gudur area, SPSR Nellore district
Geology, Sri Venkateswara University, Tirupati For by using inverse distance weighted method in Arc GIS
supporting in my research work and anonymous 10.1. Data in brief, 22, 1003-1011.
reviewers, whose comments have greatly improved this Handa, B.K., 1975. Geochemistry and genesis of
manuscript. I also thankful to the Chief Editor, O.P. Fluoride‐ Containing ground waters in India.
Groundwater, 13(3), 275-281.
Pandey for valuable suggestions regarding my research Hem, J.D., 1985. Study and interpretation of the chemical
paper.I also thanks to Department of Geology, Sri characteristics of natural water (Vol. 2254). Department
Venkateswara University for supporting to carry out my of the Interior, US Geological Survey.
research work. Kotecha, P.V., Patel, S.V., Bhalani, K.D., Shah, D., Shah,
V.S. and Mehta, K.G., 2012. Prevalence of dental
Compliance with Ethical Standards fluorosis and dental caries in association with high levels
of drinking water fluoride content in a district of Gujarat,
The authors declare that they have no conflict of interest India. The Indian J. medical Res., 135(6), 873.
and adhere to copyright norms. Latha, S.S., Ambika, S.R. and Prasad, S.J., 1999. Fluoride
contamination status of groundwater in Karnataka. Curr.
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VOLUME 24, ISSUE 2, MARCH 2020

Journal of Indian Geophysical Union Indian Geophysical Union

Associate Editors Vice-Presidents

Editorial Team Honorary Secretary

Fluoride zonation in Dharmapuri district of Tamil nadu (India) 46

Characterization of groundwater chemistry using multivariate statistical analysis in parts of

Assessment of Groundwater Quality with respect to Fluoride in Somavathi River basin,

Geothermal study in gas hydrate reservoir dominated by

INTRODUCTION The Mahanadi basin is a major sedimentary basin located in

measurements during drilling and well logging in the GEOLOGICAL SETTING

DATA AND METHODS

Received on: 28.01.2020; Revised on: 14.03.2020; Accepted on: 19.02.2020

Evaluation of Linear structures in Dadra and Nagar Haveli, Western India:

INTRODUCTION (Mohan et al., 2007) and thus presently seismically active.

METHODOLOGY various image enhancement techniques were used. These

RESULTS AND DISCUSSION planes are susceptible to erosion (Whiteside, 1986;

The markers such as mineralized fractures, veins (Figure Lineaments

Dykes were possibly emplaced along the shear after the

ACKNOWLEDGEMENT Chandra, U., 1977. Earthquakes of peninsular India, a

Received on: 16.10.19; Revised on: 26.12.19; Accepted on: 27.12.19

INTRODUCTION Lambapur-Peddagattu and Chitrial in Nalgonda district,

Figure 2. Geological map, parts of Khammam and Nalgonda districts, Telangana.

GEOPHYSICAL SURVEYS correction is applied to the observed ground magnetic (TF)

QUANTITATIVE ANALYSIS OF GRAVITY AND

Figure 12. Radially averaged power spectrum of Bouguer gravity anomaly.

Figure 13. Radially averaged power spectrum of magnetic (TF) anomaly.

REFERENCES covering parts of Guntur and Krishna districts, Andhra

Received on: 14.10.19; Revised on: 28.01.20; Accepted on: 17.02.20

Nepheline syenite: A potential alternative for feldspar in the mineral industry- A

Chemical Crystal Specific Hardness

2 Microcline KAlSi3O8 Triclinic 2.5 - 2.6 6

S.No Mineral Composition

Phase Major oxides

Potassium 16.92 % K2O

Potassium 16.92 % K2O

Sodium 5.72 % Na2O

Potassium 8.06 % K2O

(Source: Mineralogy data base: Mindat.org)

S.No Pluton Aerial extent Rock types

4 Elchuru 16 Km2 Shonkinite, malignite, nepheline syenite, lamprophyre

5 Purimetla 7 Km2 Malignite, hornblende syenite, nepheline syenite, lamprophyre

6 Uppalapadu 30 Km2 Nepheline syenite, hornblende syenite, ferro syenite

Received on: 20.08.19; Revised on: 12.02.20; Accepted on: 18.02.20

INTRODUCTION store and transmit significant amount of groundwater. These

Figure 1. Distribution of groundwater in subsurface rocks (after Bowen, 1928).

Figure 2. Location of study area

Figure 3. View of sandy to loam type soil in study area.

is defined as a logarithmic function expressed by (Shannon,

MI(X, Y) = H(X) − H(X|Y) (9)

Table 1.Cross tabulation of data set

y(i), Monsoon rainfall (mm) i = 1 i = 2 Total

Table 2.Marginal entropy of rainfall

Marginal entropy of rainfall

Table 3.Marginal entropy of DTW

Marginal entropy of DTW

Table 4.Conditional entropy of DTW due to rainfall

Conditional entropy of DTW due to rainfall

Table 5.Joint entropy of DTW and rainfall

Joint entropy of DTW and rainfall