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GEOGRAPHIC FEATURES
GEOLOGYMost
of the area is covered by the unconsolidated sediments of Quaternary age except in the
northwestern part, where isolated patches of Archaen Crystallines and Tertiary sandstone
are exposed. The Archaeans are mainly
represented by the Charnockite Group of rocks comprising garnetiferrous granulite and the
Khondalite Group of rocks made up of quartzite of genesses. The Tertiary sandstone (Cuddalore Formation) comprise pinkish, yellowish, reddish
(variegated colours) medium to coarse grained sandstone and clay stone. It is overlain by thin alluvium and exposed
towards north of Detached exposures of laterite and lateritic soil are seen in the northwestern part
of the district. A major part of the district is covered with the fluvial, fuvio-marine, Aeolian and
marine sediments of Quaternary age. The
fluvial deposits which are made up of sand, silt and clay in varying degree of admixture
occur along the active channels of Vaigai, Gundar, Manimuthar and Pambar rivers. They have been categorized into levee, flood basin,
channel bar/ point bar and paleo-channel deposits. The
paleo channel deposits comprise brown coloured, fine to medium sands with well preserved
cross-beddings. The fluvio-marine deposits are exposed in the Vaigai delta as deltaic plain,
paleo-tidal and dune flat deposits. The
deltaic plain and dune flats comprise medium, Grey brown sands. The paleo tidal flat deposits include black silty
clay, black clay and mud. In The Aeolian deposits comprise red sands which are in nature of ancient dunes and
occur over a 3.2 Km wide and 8 Km long stretch and lie parallel to the sea coast. These are separated by marshy deposits of black
clays. The sands are underlain by calcareous
hardpan. In The marine formation comprises coastal plain deposits of sand and clay in varied proportion. Marine calcareous hardpan occurs as low terraces and platforms, with admixture of quartz, limonite and garnet concentration.
Gypsum,
limonite, garnet sand, lime shells, salt, clays and building stones are the known mineral
potential of the area. All the occurrence are
of local nature only and are not of any economic significance.
GEOMORPHOLOGY AND GEOHYDROLOGY Major
part of the district is a gently sloping plain except for remnant hills in the western
area. Recent Quaternary studies have brought
out various erosional and depositional landforms of fluvial and marine regimes. The fluvial landforms comprise flood plains of
Vaigai, Varshalei, Pambar, Kottakkarai and Gundar rivers.
The marine landforms comprise sand mounds (Teri’s) and barrier dunes
along the present coast. The erosional
processes are manifested in the form of pediments and pedipalin around Kamuthi. Geohydrologically, the district has been divided into three zones with reference to
laterite, flood basin and coastal plain areas respectively.
Further, the area is demarcated into Manimuthar-Pambar basin, Vaigai delta and
Vaipar-Gundar basin. The Northwestern part of
the Ramanathapuram district exposes isolated patches of Archaeans crystallines and
Cuddalore Sandstone capped by laterite/lateritic soil.
The yields of bore wells of 60 to 90 m depth in the crystallines vary from 3 to 400
lpm draw down of 10 to 12m water head. The
saline aquifers in coastal tracts occur to a depth range of 80m from ground level followed
by fresh water aquifers. The quality of groundwater varies from alkaline through potable to high saline
types in the district. In
most places Ground water is available at a depth beyond 6 to 7m is saline. The fresh water available within 6 to 7 m depths
dries up quickly within 2 to 3 months after monsoon. There
is acute drinking water shortage felt in most part of the year. Hydrogeologically the district can be classified as
Omtofoir zones as detailed below: There are four Ground water zones available. Areas covered by sand dunes, beach ridges, pockets of strand plains, pockets of natural levees, pockets of Palaeo channels, pockets of pediments and valley fills covered by crystallines and tertiary sand stones. The depth of water level varies from few cm to 5 M the depth aquifers are saline. Deep and Confined Fresh Water Zones It occurs in the northern part of the district in Thiruvadanai Taluk. The thickness of the cretaceous aquifer is in the order of 20 to 30 M. This is underlined by crystalline basement. In the artesian belt area of Thiruvadanai Taluk of Ramanathapuram District, fresh ground water is available at a depth range of 350 m – 450 m in and around Thiruvadanai, Neerkundram, Vellaiyapuram and in some other places of Thiruvadanai Taluk. Moderate Quality Ground Water Zone This occurs in certain pockets of river course, pockets of Palaeo channels, parts
of pediments and valley fills and in major parts of stand plains.
This is marine and fluvial marine origin. The
formations explored upto 780m is found to unsuitable for any purpose.
The soils of Ramanathapuram District can be assorted into the main types viz.,
clay, coastal alluvium, sandy loam, alluvium, sandy and red soil clay, black cotton soil
is believed to have been derived from the Archaen gneisses where calcareous formation are
abundant. Calcium carbonate concretions of
various sizes and shapes are present in majority of the black soil area and this affects
the fertility of the soils. Black soil, as a
whole constituted about 46 per cent of the total soil.
River alluvium includes alternate layers of sand and clay for a huge thickness. River alluvium occurs in areas bordering the Vaigai
River. Coastal alluvium occurs in Kadaladi,
R.S.Mangalam, Mandapam, Ramanathapuram, Thiruppullani and Thiruvadanai blocks. There are vast stretches of saline and alkaline
soils found in the coastal blocks. Rameswaram
Island contains mainly sandy soil. The
fertility status of soil showed that nitrogen status of soil is low in all blocks and
phosphorus status of soil is also low in all blocks except Thiruppullani, Kamudhi and
Kadaladi where it is medium. The potash
content of soil is high in all the blocks. The
mineral resources of the soil include gypsum, limestone and magnesium. While Mudukulathur and Keelakarai regions account
for sizable deposits of gypsum. Rameswaram
Island contains large quantities of limestone deposits.
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