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Benthic Foraminifera and siltation studies along the
Depositional Environment between Mandapam and
Kodiyakkarai, Palk Strait, East Coast of India
M.Suresh Gandhi and K. Kasilingam
Department of Geology, University of Madras, Chennai- 600 025
Email: surgan@yahoo.co.uk
ABSTRACT
Palk Strait is situated between India and Srilanka endangered with heavy
siltation. It is strategically an important channel, as it is shared by India
and Sri Lanka without the scope of international navigation. Of late, the
coastal ecosystem of the strait is endangered by the shallowing nature of
the bay due to silty sedimentation. In order to know the effect of siltation
an attempt has been made in this region using foraminiferal studies. A
total of 72 sediment samples have been collected in nine stations
between Mandapam and Vedaranyam. In that, 122 species belonging to
54genera, 40 families, 24 super families and 5 suborders were identified.
Of which, 38 species are provided as living specimens. Among the
species present, Ammonia beccarii, Ammonia dentata, Osangularia
venusta, Elphidium crispum, Asterorotalia trispinosa, Quinqueloqulina
seminulam, Pararotalia nipponica exhibit prolific abundance. From the
distribution of foraminiferal studies, it understood that the species are
more enriched in southern part of Palk Strait compare to the northern
part. The organic carbon content in the study area varies from 0.05 % to
3.40 %. At Kodiyakkarai carbonate content reaches 19.5% at 7m depth.
The higher carbonate content at Thondi and Kottaipattinam is probably
due to the accumulation of high order broken shell debris dumped
through the creek. Based upon the living dead ratio and the organic
matter distribution it is confirmed that the southern part is more favor for
living condition. Sedimentation also more in the southern part between
Mandapam and Manalmelkudi compare to the northern part. Cluster
analysis indicates that three different genus dominant in particular stations
like Mandapam and Thondi represent the biotope at 0.82 level of
clustering and the species Rosalina globularis is more abundant in that
stations. Attankarai and Manalmelkudi show the level of clustering of 0.87
with dominant of Ammonia beccarii. The stations Devipattinam,
Kottaipattinam and Sethubavachattiram shows the level of clustering at
0.9 and dominant of Pararotalia.Some genera like Asterorotalia, Lagena,
Elphidium, Quinqueloqulina, Pararotalia and Spiroloculina are in broken,
distorted and corroded are noticed in all the stations. The high order of
broken species and aberration in forams is stations like Mandapam,
Devipattinam, Thondi and Sethubavachattiram indicate the presence of
higher churning action of currents. The overall depletion of foraminifera in
the strait indicates the unfavorable environmental conditions for living
species.
The Fourth IGCP 588: PREPARING FOR COASTAL CHANGE 19