CHAPTER II

GEOLOGY AND HYDROGELOGY OF THE STUDY AREA

2.1 Introduction

The southern granulite terrain is a mosaic of crustal blocks consisting of

Charnockite highland massifs separated from each other by low-land shear zones

extending in different directions viz. NE-SW, E-W and NW-SE. The tectonic frame

work of south India shield region (SISR) has been studied by various Geological and

Geophysical methods and reviewed by various workers (Drury and Holt, 1980; Drury

et.al 1984; Radhakrishnen, and John mothai 2004; Chetty, 1996; Ramakrishna, 2003).

These studies have identified major shear zones within SISR namely Palghat cavery shear

zone (PCSZ) Mayar- Bhavani Shear Zone(MBSZ). Mettur Shear Zone (MTSZ) and

Achankovil Shear Zone(ACSZ) as shown in Figure (2.1) and Figure (2.1a).

In this, the very important shear zone is Achankoil shear zone. It consists of

garnet-biotite-graphite gneisses and garnetiferous charnockite and khondalites (garnet-

sillimanite-biotite-graphite), cordierite gneiss. It occurs to the south of the Palghat-

Cauvery tectonic zone (Drury and Holt, 1980; Drury et.al., 1984). On the west of this

zone, charnokites form the massifs of the Western Ghats and the Eastern part is

predominantly of gneisses. This southern predominance of meta-sedimentry rocks such as

quartzites, sillimanite quartzites, calc-granulites, garnet and cordierite bearing meta-

pelites. In the Northern part of this region, calc-silicates and crystalline limestone occur

as thick sequences for a few tens of meters thickness.

The study area is divided into two parts one of them is delination of the ground water

in hard rock area near Abisekapatti,near Tirunelveli and the other part is to characterize

Figure 2.1 Geological frame work of south India (Drury et al, 1984)

Figure 2.1a Shows the Southern granulite major shear zone (after Chetty, 1996)

ground water along the coastal area of Thuthukudi, Tamilnadu. The location, geology and

Hydrogeology are described below

2.2 Location of the study area

a) Abisekapatti

The Tirunelveli District in southern India, is located in the world map, between

08°8’ and 09°23’ latitude and 77°09’ and 77°54’ longitude. Tirunelveli district is

bounded on the north by Virudhunagar district, east by Thuthukudi district, south by Gulf

of Mannar, South west by Kanniyakumari district and west by Kerala state. The total

geographical area of the district is 6823.06 sq.km and is divided into nine taluks namely

Ambasamudram, Nanguneri, Palayamkottai, Radhapuram, Sankarankovil, Shencottai,

Sivagiri, Tenkasi and Tirunelveli.

The geophysical data was collected near Abishekapattil (E77o 39

’ 18

” and 8

o 45’

58”) 10 km NW of Tirunelveli Town, Southern Tamilnadu, India Figure (2.2). It is

located in the Tirunelveli district of Tamilnadu and lies near Achankovil shear Zone

(ACSZ) in southern part of Tamilnadu. ACSZ is widely recognized in the literature as a

major transcrustal shear zone (Windley et al., 1994; Kroner and Brown, 2005). The

ACSZ is a dominant NW-SE trending strike-slip shear zone that appears as a major

lineament in aeromagnetic and satellite images, and separates a vast supracrustal

sequence of Trivandrum Block (TB) that lies in the south of the shear zone from

predominantly granulite facies rocks of Madurai Block (MB) in North (Drury et al.,

1984).

The study area lies within the Achankovil Thamiraparani Shear Zone (ATZ)

(Manimaran et al.,2001). The rock melt extrusion occurred in the study area and also

neotectonic activities and Micro seismic activities were reported by Rajamanikam and

Figure 2.2 Location map of the study area (after Manimaran .et.al 2001)

Chandrasekar (2000) along the lineaments bounding the different tectonic units in

Peninsular India. The geological evaluation of the south Indian area is more complex and

hence requires better understanding of the present study area. Taking in to account of

these incidences, geoelectrical studies were carried out. While geological studies can

provide information on the surface manifestation of the shear zones, only geoelectrical

investigations can provide significant depth information, especially regarding the nature

and extension of geological contacts, fault zones at different depths.

b) Thuthukudi

The study area Thuthukudi (780

7’30’’E and 8048’45’’N), lies in the east coastal

belt Tamil Nadu (Figure 2.3) in India, Southern India Topographic elevation varies from

27 m (amsl) to a few meters (amsl) near Thuthukudi town and slopes from west to east.

The slope is gentle in the western and the central part and nearly flat in the eastern part.

The land is utilized for cultivation of cotton, maize and some medicinal plants.

Some of the land is fallow and some is barren with vegetation such as thorny shrubs with

thin cover of dry grass and palms. The area receives rainfall during the northeast

Monsoon season, which is active during the months of October, November, and

December. The long-term average annual rainfall of Thuthukudi town is 568 mm (IMD

data). The study area has large number of open wells and bore wells they are being used

for domestic and irrigation purposes.

2.3 Geological formation of the study area

Tirunelveli district of Tamilnadu is the southern part of the Indian Precambrian

Shield comprising a wide variety of geological formations ranging from Precambrian to

recent period. Major portion of the district is covered by plain topography. North West

and western portion of the district are gently sloping to undulating. Parts of

Figure 2.3 Location map of the study area

Ambasamudram, Tenkasi, Shencottai and Sivagiri taluks are covered by high hills in the

west. These hills form part of the western ghats. There are number of waterfalls in the hill

ranges. The plain area of the district can be divided into two elevating stages viz below

150 and 150-300m. The Tamirabarani is the major drainage system covers the central part

of the district.

Different types of Charnockitic rocks and metasedimentary gneissic formations

are distributed throughout the Tirunelveli district. They can be classified into granitoid,

non-garnetiferous mica, hornblende gneisses and mixed gneisses associated with

migmatities. Migmatitic assemblage of garnetiferous biotite gneisses (Khondalitic),

garnetiferous quartzo- felspathic granulites(leptynitic). The charnockitic rocks of the

Tirunelveli and non-garnetiferous quartzo-felspathic granulites (alskitic) district are

conformable in strike and in south and south west part of the district. The central part of

the district is reported with predominant zone of quartzite beds and associated crystalline

limestone and calc gneisses with intercalated layers and bands of pyroxene granulites

within the quartzite beds (Narayanaswamy and Lakshmi, 1967).The major

lithostratigraphic units in the study area include garnet bearing charnockites, garnet and

sillimanite rich metapelitic (khondalitic) and garnetbiotite-quartz-feldspar gneisses

underlain by black cotton soil (Barun et al, 1998; Shabeer et al, 2005).

The geological structure consists of an earlier period of folding about a NW-SE

axis, followed by a second stage cross-folding about a NNW-SSE axis, and discordance

of rock types as well as structural elements in the north-east part of the district by a zone

of thrust. The charnockitic rocks thus appear to have been subjected to two periods of

deformation, granitic intrusion and metamorphic episodes.

Limestone is available at several places in the district. The major part comes from

the crystalline limestone deposit occurring near Ramayanpatti, Thalaiyuthu, and

Padmaneri. A total reserve of 4.06 million tones limestone up to depth of 15.2 meter in

Ramayanpatti band and 5.08 million tonnes up to a depth of 15.25 meter in Thalaiyuthu

has been estimated.

The limestones available here contain Calcium Oxide (CaO) from 34.97 to 55.49

percent, Magnesium Oxide (MgO) from 0.31 to 7.24 percent. The Padmaneri band

consists of six limestone lenses with an aggregate strike length of about 800 meter. The

average width is 4.75 meter 0.199 million tonnes of cement grade limestone is estimated

from this band. The Singikulam band extends over a strike length of 17 km. It contains

seven limestone lenses with an aggregate strike length of about 6.4 km. and average width

of 13 meter. About 3.160 million tons of cement grade limestone is estimated from this

band.Six bands of good quality limestone occur near Pandapuli and 4, 34,000 tones of

limestone suitable for the manufacture of cement and chemical industries have been

estimated. Light traces of sulphides occur in and around Pattankadu and Munradaippu.

This mineral is of no economic importance by National Informatic Centre, Tirunelveli.

Occurrence of red garnet sands in the beds of the river Nambiar and Ovari has

been recorded. The proportion of garnet is 75% in the rich deposits and 45% in the

surface sands. Local concentration of Ilmenite sands are noticed near Vijayapatti and

Kuttankuli.

The rock types met within the district can be broadly classified into three groups

as detailed below.

1. Charnokite group of rocks of Archean period with Hypersthene mainly in

Sankarankovil, Sivagiri and Tenkasi taluks.

2. Gneissic group of rocks of Archean period consisting of

a) Granitoid mica gneiss

b) Granitic mica gneiss and Leptinites

c) Mixed and composite gneiss

3. Shell lime stone, tuffaceous kankar, tertiary kankar, coastal and their lands of

quartenery period, recent to Holocene age.

The dominant minerals are Limestone, Gypsum,Garnet sand, Ilmenite and Blue

metal. The main country rocks of the district are : (1) grantioid non-garnetiferous mica

and hornblende gneisses and mixed gneisses associated with migmatites in northeast

Tinnevelly, and (2) a migmatitic assemblage of garnetiferous biotite gneisses

(khondalitic), garnetiferous quartzo-felspathic granulites (alaskitic) in south and south-

west Tirunelveli. There is a predominanca of quartzite beds and associated crystalline

lime stones and calc-silicate rocks, together with intercalated layers and bands of

pyroxene granulites within the quartzite beds in the central parts of the district. Pyroxene

granulites, invariably containing hypersthene occur as narrow bands and lenses following

the foliation of the garnetiferous gneisses; they also occur as alternating parallel bands

and layers in the quartzites and the intermediate gneissis charnockitic rocks. The main

zone of charnockitic rocks is found in the north-west part of the district in Sankarankovil-

Tenkasi plains and adjacent Western Ghat ranges. Runs of gneissic as well as acid

micropertitic charnockites occur parallel to the regional strike. The charnockitic rocks are

generallyassociated with garnetiferous gneisses and are almost completely absent in the

predominantly granitoid gneissic terrain in the north-east and eastern parts of the district.

The regional strike of foliation and banding, which is conformable in all rock

types throughout the district, is generally NE-SW in the west and south-west Tirunelveli,

veering to WNW-SSE to EW in the south-eastern parts of the district. The strike abruptly

changes to NNW-SSE or NS about a NW-SE line passing through Srivaikuntam,

Thalaiyuthu and Sankarankovil.

The charnockitic rocks throughout the district reveal foliation and banding

conformable in strike and dip with the enclosing gneissic country rocks and associated

meta-sedimentary and meta-volcanic/hypabyssal rocks. A study of the structural and

tectonic history of the district reveals that there is an earlier period of folding, about a

NW-SE axial trend, the folds plunging probably to the SE as indicated by closures of

certain rock formations. A second stage of folding, either later or immediately

succeeding the above, appears to have refolded the earlier folds about a NNW-SSE axis.

One such major cross-fold is the main structural element exposed in the Tirunelveli

district.

The charnockitic suite of Tirunelveli has undergone two periods of deformation

with accompanying metamorphism and granitic intrusions. Nowhere in the district are

seen granitic or other intrusives cutting across the strikes of foliation and banding; even

the later pegmatites and vein-quartz conform to the foliation strikes. It would, therefore,

appear that the khondalite-charnockite suite and associate gneisses and migmatites of

Tirunelveli belong to a deep-seated hypo-metamorphic, syntectonic (palingenetic)

migmatite complex.

The area under investigation of Thuthukudi in the Gulf of Mannar presents great

interest because it is an industrial belt consisting of many major industries involved in the

production of chemicals, petrochemicals and plastics. In addition, a major harbor, thermal

power plant, heavy water plant and human activities from around Thuthukudi have

altered the ecosystem prominently

The area investigated forms the southern part of the South Indian Granulite facies

terrain, which includes part of Madurai Block (MB) and the Kerala Khondalite Belt

(KKB). The southern part of MB is represented by charnockites in the western part and

gneisses in the eastern part which are inter-banded with supracrustals chiefly of meta-

sedimentary sequences mainly made up of quartzite, carbonate and metapelite with a

minor metabolic component. KKB is bounded by the Cardamon Hills in the north and the

Nagerkoil Charnockite Massif in the south, which consists of high-grade supracrustals.

The MB and KKB, which are separated by the Achankoil Shear Zone (AKSZ), are mostly

similar in geochronologic characteristics (Santosh et al, 2003; Harris et al,

1994).Gneisses, charnockites, and quartzites of Archaean age, calcareous sandstone and

shell limestone of tertiary age, and alluvium of recent age underlie the area. The Archaean

groups of formations are crystalline and metamorphic, and finely foliated with a general

NW–SE trend described by Balasubramanaian et al, (1993). The formations, including

quartzites as ridges in the western part, are weathered, jointed, and fractured. recent to

sub-recent sand occupies coastal areas. It consists of coarse and calcareous grits

sandstone and shell limestone. The area is covered with black soils in the western part,

red soil (sandyloam to sandy soil) in the central part and alluvial sandy soils in the eastern

part. The maximum soil thickness is about 3 m. The sandy soils originated from

sandstones and these have low soil moisture retentivity. The alluvium soils are wind-

blown sands and shells constitute beach sand and coastal dunes, which have very low soil

moisture retentivity.

This area is underlain by Archaean complex of rocks that occupy western part of

the study area. It includes ridges of quartzites, bands of charnockites and peninsular

gneisses which are weathered, jointed and fractured at places. The tertiary formation

overlies the Archaean complex with marked unconformity, consists of calcareous

sandstone and shale limestone. These are medium-to-fine grained, compact and

fossiliferous in nature. The thickness of the formation varies from few to few tens of

meters. Recent to sub-recent sand occupies most of the coastal areas. It consists of coarse

and calcareous grits, sandstone, shale limestone. Accumulation of windblown sands and

shale’s constitute beach Sand and coastal dunes.

2.4 Hydrogeology of the study area

The district is part of the composite east flowing river basin, Between Vaippar and

Nambiar , as per the Irrigation Atlas of India. The Tambarabarani, Vaipar and Nambiar

are the important sub-basins.

Thamarabarani, Nambiar, Chittar and Karamaniar are the important rivers

draining the district. Tamarabarani originating from Papanasam flows thorough the

district. The Nambiyar river originates in the eastern slopes of the Western ghats near

Nellikalmottai about 9.6 km west of Tirukkurugundi village at an altitude of about1060 m

amsl At the foot of the hills, the river is divided into two arms. The main armis joined by

Tamarabarani at the foothills. Chittar originates near Courtallam andflows through

Tenkasi and confluences with Tamarabarani. The hilly terrains haveresulted in number of

falls in the district. There are three major falls in Manimuttar reservoir catchments area

and there are few falls in the Tamarabarani river also. A series of falls in Chittar river in

Courtallam comprising Five Falls, Honey Falls, Mainfalls and Old Courtallm Falls are

some of the important falls in the area. The drainagpattern in general is dendritic.

YEAR JANAUARY FEBRUARY MARCH APRIL MAY JUNE

R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP.

2005 10.6 - 63 50.9 180 23.6 - 12 130.8 137 16.7 - 45 0.7 - 90

2006 36.1 27 0.0 - 100 92.5 245 26.3 - 52 21.1 - 30 6.0 -14

2007 32.2 13 8.0 - 56 0.6 - 98 56.8 3 7.0 - 77 11.4 63

2008 3.8 - 87 91.1 401 264.6 887 58.9 7 0.4 - 99 3.3 -53

2009 6.8 - 76 0.2 -99 16.8 -37 79.5 44 17.0 - 44 1.2 -83

YEAR JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER

R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP.

2005 19.6 19 14.9 - 34 13.2 - 68 99.3 - 34 235.0 35 119.3 42

2006 0.4 - 98 7.7 - 66 47.8 17 309.8 104 337.2 93 24.7 - 71

2007 30.9 87 37.9 68 21.5 - 47 196.2 29 111.9 - 36 62.3 - 26

2008 9.0 -45 49.9 122 3.5 - 91 357.9 136 180.0 3 54.5 - 35

2009 0.7 - 96 18.7 - 17 33.9 - 17 56.0 - 63 386.6 122 47.9 -43

R/F - Arithmatic average of rainfall % dep. - depatures of rainfall

(by Hydromet division, India meterological department)

Table 2.1 Tirunelveli district rainfall for last five years in mm

Month Normal 1996 1997 1998 1999 2000

January 50.2 22.30 2.39 2.67 6.67 37.47

February 30.2 35.34 0.00 3.00 66.68 143.97

March 41.3 6.40 14.56 0.00 0.80 24.04

April 59.8 98.12 68.98 11.13 26.93 20.65

May 38.0 23.36 72.53 103.35 35.34 16.96

June 29.6 35.00 4.90 23.62 39.69 55.23

July 26.4 31.44 7.51 53.38 8.11 9.39

August 23.3 23.63 10.88 45.07 3.39 95.86

September 30.2 35.11 25.20 4.62 41.71 74.09

October 166.0 230.34 290.67 67.75 193.93 24.78

November 208.2 71.00 436.83 188.26 188.17 186.00

December 111.6 116.97 156.71 290.21 42.30 137.72

Total Rainfall 814.8 729.01 1091.96 793.06 653.72 826.16

Month Normal 2001 2002 2003 2004 2005

January 50.2 80.16 6.40 0.58 36.57 4.92

February 30.2 26.54 75.83 104.25 16.62 27.50

March 41.3 9.53 29.30 100.72 5.82 68.17

April 59.8 118.79 91.00 0.78 91.15 180.49

May 38.0 26.73 82.91 29.55 135.02 25.46

June 29.6 24.43 4.12 20.18 59.16 20.28

July 26.4 29.58 5.14 19.19 9.53 80.50

August 23.3 10.80 35.68 15.48 26.12 19.91

September 30.2 22.03 13.66 10.34 101.48 32.77

October 166.0 141.32 213.12 185.84 220.09 84.68

November 208.2 195.97 241.82 256.57 260.55 248.45

December 111.6 79.52 17.85 56.89 32.37 178.36

Total Rainfall 814.8 765.40 816.83 900.37 994.48 971.49

Month Normal 2006 2007 2008 2009

January 50.2 54.49 24.80 9.28 8.89

February 30.2 1.80 3.52 83.3 NIL

March 41.3 124.23 7.44 377.19 31.63

April 59.8 25.51 131.64 103.4 72.01

May 38.0 35.95 10.97 4.94 24.07

June 29.6 28.60 87.78 10.32 21.38

July 26.4 26.80 46.49 35.22 59.94

August 23.3 25.38 33.11 72.00 25.97

September 30.2 63.04 79.70 20.63 30.56

October 166.0 361.28 187.03 345.6 126.59

November 208.2 287.23 181.90 183.1

December 111.6 19.31 126.16 94.78

Total Rainfall 814.8 1179.66 920.54 1339.76

Table 2.2 Tirunelveli District month wise Rainfall in mm (National Informatic Centre, Tirunelveli)

a) Tirunelveli district

The district is underlain by both porous and fissured formations. The important

aquifer systems in the district are constituted by i) Weathered and fractured hard rock

formations of Archaean age. ii) Porous sedimentary formations ranging in age from

Tertiary and Recent. The porous formations are found as small patch in the southeastern

part of the district and include sandstones, Limestones, Laterite and Clays from Tertiary

to Quaternary. Ground water generally occurs under phreatic conditions in the weathered

mantle and under semi-confined conditions in the fissured and fractured zones at deeper

levels. The thickness of weathered zone in the district is in the ranges up to 30m bgl. The

yield characteristics of wells vary considerably depending on the topographic set-up,

lithology and nature of weathering. to 13.65 m bgl during pre-monsoon and

0.47 m bgl to 13.25 m bgl during post-monsoon. Table 2.1 and Table 2.2 shows the

Tirunelveli District rainfall for the past few years.

b) Thuthukudi district

The Thuthukudi district is part of the composite east flowing river basin,

“Between Gundar and Nambiyar” as per the Irrigation Atlas of India. Nambiyar,

Tambraparani, Kallar,Vaippar and Gundar are the important sub basins. The river

originating from the Western Ghats and Tamil Nadu uplands control the drainage network

of the district. A few streams originate in the hillocks within the district and confluence

directly with the sea after flowing 10 km to 20 km. Vaipar, Tambraparani and

Karamanaiyar are the major rivers draining the district. All the rivers are ephemeral in

nature and the run off is generated in heavy rainfall period only. Isolated occurrence of

calcareous sandstone and fossiliferous limestone are seen in coastal area on the south as

tern side. The shallow aquifer is developed through dug wells and deeper aquifer through

YEAR JANAUARY FEBRUARY MARCH APRIL MAY JUNE

R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP.

2005 8.2 - 80 23.6 - 24 68.5 64 204.7 232 22.3 - 42 18.0 - 13

2006 69.2 67 3.2 - 90 120.7 189 28.6 - 54 34.9 - 10 26.4 28

2007 19.8 - 52 0.1 -100 7.5 - 82 119.7 94 9.1 - 76 94.2 357

2008 9.4 -77 53.2 71 400.5 860 106.4 73 2.9 - 92 11.0 - 47

2009 8.2 -80 0.0 - 100 28.2 -132 69.9 13 25.8 - 33 15.3 - 26

YEAR JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER

R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP. R/F %DEP.

2005 82.5 257 17.8 3 29.5 - 7 76.0 - 45 265.8 37 206.9 113

2006 26.7 16 25.4 48 44.0 39 382.9 176 393.9 103 21.1 - 78

2007 48.1 108 30.9 80 84.4 166 152.3 10 161.2 - 17 113.0 16

2008 41.4 79 74.0 330 21.3 - 33 322.0 132 171.3 - 12 77.5 - 20

2009 54.1 134 30.0 74 27.9 - 12 115.0 - 17 405.4 109 133.0 37

R/F - Arithmatic average of rainfall % dep. - depatures of rainfall

(by Hydromet division, India meterological department)

Table 2.3 Thuthukudi district rainfall for last five years in mm

tube wells. The dug well can sustain a pumping of 4 to 6 hours while the tube wells can

sustain a pumping of 6-8 hours. The water-bearing properties of crystalline formations,

which lack primary porosity, depend on the extent of development of secondary inter

granular porosity. These aquifers are highly heterogeneous in nature due to variation in

lithology, texture and structural features even within short distances (Mondal et al, 2009).

The hydrology of Thuthukudi area under the influence of northeast monsoon

constitutes a unique water body in the Gulf of Mannar along the southeast coast of India

and is being rapidly affected by industrialization during the past few years. Table 2.3

show the Thuthukudi District rainfall for the past few years. The district is underlain by

both porous and fissured formations. The important aquifer systems in the district are

constituted by i) unconsolidated and semi consolidated formations and ii) weathered and

fractured crystalline rocks. The porous formations in the district include sandstones and

clays of recent to sub-recent and Tertiary age (Quaternary). The recent formations

comprising mainly sands, clays and gravels are confined to major drainage courses in the

district. The maximum thickness of alluvium is 45.0 m bgl, whereas the average thickness

is about 25.0 m. The water-bearing properties of crystalline formations which lack

primary porosity depend on the extent of development of secondary intergranular

porosity. The occurrence and movement of ground water in these rocks are under

unconfined conditions in the joints, fissures and dependent on the nature and extent of

pores and interconnection of fracture zones.