Enayam Port

Tamil Research Institute
RAPID TECHNO-ECONOMIC FEASIBILITY REPORT FOR
DEVELOPMENT OF COLACHEL PORT AT TAMILNADU
FINAL REPORT
particularly rich with its large number of microhabitats due to its exposure to wide range of climatic conditions
and its southern most geographic position in the subcontinent.
3.2.2.2. Geoporphology and Geology
The Southern Granulite Terrain (SGT) of India, covering the states of Tamil Nadu and Kerala and the marginal
zones of Southern Karnataka, was earlier considered to be the southern extension of the Granite-Greenstone
terrain of Dharwar Craton exposed at a deeper tectonic level. This concept was based on the observation that
the grade of metamorphism gradually increases from north to south. Geochronological and isotopic studies have
brought to light that the southern part of the SGT lying south of Palghat – Cauvery Lineament (PCL) has a
geological history distinctly different from the Dharwar Craton. These studies have shown that the terrain lying
north of PCL shows crustal growth during the period from 3400 to 2500 Ma. In contrast, crustal growth in the
terrain south of PCL is considered to have taken place predominantly during Post-Archaean times, as constrained
by Nd model ages (Harris et al., 1994). T
his terrain might have witnessed several cycles of metamorphism, the most pervasive being the 550Ma Pan-
African granulite facies event as constrained by isotopic systematics (Unnikrishnan Warrier et al., 1995b;
Jayananda et al., 1995, Bartlett et al., 1995, Ghosh et al., 1998).
In view of the contrasting geological history recorded by the terrains north and south of PCL, the SGT has been
divided into the northern Archaean Craton (Dharwar Craton) and the southern Proterozoic (Pandian) Mobile Belt
(GSI, 1994) with the PCL marking theboundary between them.
Crystalline rocks of Archaean to late Proterozoic age occupy over 80% of the area of the state, while the rest is
covered by Phanerozoic sedimentary rocks mainly along the coastal belt and in a few inland River valleys. The
hard rock terrain comprises predominantly of Charnockite and Khondalite groups and their migmatitic
derivatives, supracrustal sequences of Sathyamangalam and Kolar groups and Peninsular Gneissic Complex
(Bhavani Group), intruded by ultramafic-mafic complexes, basic dykes, granites and syenites.
The sedimentary rocks of the coastal belt include fluviatile, fluvio-marine and marine sequences, such as
Gondwana Supergroup (Carboniferous to Permian and Upper Jurassic to Lower Cretaceous), marine sediments
of Cauvery basin (Lower Cretaceous to Paleogene), Cuddalore / Panambarai Formation (Mio-Pliocene) and
sediments of Quaternary and Recent age.
In Kanyakumari District, heavy mineral concentrations in beach sand occur as detached patches along the east
coast between Colachel and Kanyakumari over a distance of about 75km. A total of 45,75,605 tonnes of
heavy mineral concentrates have been estimates by the Atomic Minerals Division on the beach between
Thingattanam and Illinjam, Midalam and Colachel, Colachel – Manavalakurichi, Vajakkalurollankodu,
Chinnavillai-Manavalakurichchi, Periakattuthurai-Manakkudi and from Manakkudi to Kovakulam in Kanyakumari
District. The sands between
A total of 1.68 million tonnes of shell limestone occurs near Kovalam, Kanyakumari, Lipuram, Vattakottai and
Kanagappapuram in Agastheeswaram Taluk of Kanyakumari District. About 81,300 tonnes of shell limestone
occur north of Rameswaram.
Moreover, in Kanyakumari District, irregular pockets of phlogopite were traced near the contact of charnockite
and leptynite close to Tiruvidamkode and Eraniel. They are not of economic importance.
Geomorphology Kanyakumari district is bordered by Western Ghats (Ridge and valley complex) in the West.
Western Ghats form an elevation of 200 m amsl from these foothills in the west. The areas gently slope to
southeast towards the Gulf of Mannar attaining an elevation of 25 to 30 m amsl. The eastern and central tracts
are quite barren, but there are a few isolated knife edged hillocks. The coastal tracts are occupied by the marshy
swamps and number of sand dunes (Teri sands). The prominent geomorphic units identified in the district through
CP1832-FR-AX-05-CP-Initial Environmental Examination-Ed4.docx AX05 - 30
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