Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

P. M. Mohan ¹, K. Shephard ¹, N. Angusamy ¹, M. Suresh Gandhi ¹, G. V. Rajamanickam ¹

Affiliations
1 Department of Industries and Earth Sciences, Tamil University, Thanjavur - 613 005, IN

Abstract

Quaternary landforms between Vedaranyam and Rameshwaram on the east coast of India show a wide range from inland sand dune, flood plain, estuary, delta, cusp, beach, coastal dune, barrier ridge, mud flat, tidal creek to mangrove. The study area has been classified into inland, beach and offshore regions to evaluate the variation in the distribution of grain size and the depositional environments. 147 sediment samples were collected using hand augur along the beach (53) and inland (37) environments, and by Van Veen grab in the offshore area (57). Grain size analysis indicates that the area may have extended approximately 25 km towards inland from the present-day low water mark. In those days, the coast must have developed by almost similar processes as acting at present in the nearshore environment, and the sea level oscillation may have been significant in the past. Further, based on the present day rate of sedimentation, it is suggested that the study area may have developed within the last 1,50,000 years B.P.

Keywords

Quaternary Sedimentation, Coastal Geomorphology, Palk Strait, Tamil Nadu.

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G. V. Rajamanickam ¹, N. Chandrashekar ²

Affiliations
1 Department of Earth Science, Tamil University, Thanjavur - 613 005, IN
2 Department of Geology, V.O. Chidambaram College, Tuticorn - 620 008, IN

Abstract

No Abstract.

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E. Rajesh ¹, K. Anbarasu ², G. V. Rajamanickam ³

Affiliations
1 Department of Earth Sciences, Tamil University, Thanjavur - 613 403, IN
2 Departmenotf Geology, National College, Trichy - 620 001
3 Department of Disaster Management, SASTRA Deemed University, Thanjavur - 613 403

Abstract

Silica sand samples of Marakkanam region have been studied to understand the textural variation of the sediments. The study area has been divided into three groups, namely, Mudaliyarkuppam, Kakapallam and Agaram (Pallarnpakkarn, Vadaagaram and Urani) on the basis of relief. Frequency curves of the silica sands in the study area show a polymodal distribution in Mudaliyarkupparn and Agaram group and bimodal distribution at Kakapallam Group. Mudaliyarkuppam samples are coarser to medium grained, poorly sorted, fine to strongly fine skewed and platy to mesokurtic in nature. On the other hand, Kakapallam Group is represented by its coarser size, very well sorted; fine skewed and leptokurtic in nature. Agaram Group is characterized by medium sands, moderately sorted, fine skewed to nearly symmetrical skewed and mesokurtic. Bivariant plots show a distinct grouping with an influence of offshore environment at Mudaliyarkuppam Group and, channel bar and dune environment at Kakapallam and Agaram Group.

Keywords

Sedimentology, Grain size, Silica sands, Marakkanam, Tamil Nadu.

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P. Udayaganesan ¹, N. Angusamy ², A. R. Gujar ³, G. V. Rajamanickam ⁴

Affiliations
1 Alagappa Government Arts College, Karaikudi - 630 003, IN
2 Fortesque Metals Group, Perth, AU
3 National Institute of Oceanography (Council of Scientific and Industrial Research) Dona Paula - 403 004, IN
4 Sri Sairam Group of Institutions, Chennai, IN

Abstract

Quartz grain surface micro textures of 12 samples collected from the beach were examined under scanning electron microscopy to understand the role of coastal processes on their transportation and deposition. The study area has been divided into three sectors on the basis of drainage, geomorphology and nature of the beach and shelf topography. Surface textures of the northern sector display an array of mechanical features like conchoidal fracture, V marks and impact pits, indicating the dominance of mechanical processes. However, silica precipitation in the form of globules indicates an added influence of chemical processes in the Northern sector. The presence of chemical features in northern sector, where energy level is high, corroborates the addition of quartz grains from paleo-sediments, from the nearby Tertiary and Cretaceous formations. Central sector quartz grains display the signatures of chemical and mechanical processes. The presence of step like furrows in southern sector is an indicator of fluvial low energy conditions, and supplements the role of littoral currents in depositing the quartz grains along the coastal region.

Keywords

Surface Texture, Quartz, SEM, Central Tamil Nadu Coast.

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M. Suresh Gandhi ¹, G. V. Rajamanickam ²

Affiliations
1 Department of Earth Sciences, Tamil University, Thanjavur - 613 005, IN
2 Department of Disaster Management, SASTRA Deemed University, Thirumalaisamudaram, Thanjavur - 613 402, IN

Abstract

In order to use foraminifera as a tool for siltation studies, benthic foraminiferal studies of both living and dead have been undertaken in the Palk Strait, East coast of India. Forty Two offshore sediment samples upto 10 m water depth in eight transects have been collected using Lafond-Dietz snapper. The study has yielded a total of 102 benthic foraminiferal species. It has been observed that benthic foraminifera are abundant at Mandaparn and Devipattinam transects with high diversity in living species while the Manalmelkudi transect has displayed less abundance with the low diversity. The living/dead ratio is 6.6 % in Manalmelkudi and 24.57 % in Devipattinam. Based on the living/dead ratio, the raté of sedimentation has been estimated to be more in the south of Manalmelkudi than in the north. Unlike in the adjacent Gulf of Mannar and Bay of Bengal, an abrupt reduction in the diversity of benthic foraminifera, abnormality in the shape and size of the tests of species of Lagena, Asterorotalia, Quinqueloculina, Spiroloculina, Pararotalia, etc., and the presence of agglutinated foraminifera in the Palk Strait, in fact, suggests the prevailing high turbidity and in turn siltation, leading to an unfavourable environment in the present study area.

Keywords

Benthic Foraminifera, Siltation, Palk Strait, Tamil Nadu.

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G. V. Rajamanickam ¹, A. R. Gujar ²

Affiliations
1 Dept. of Earth Sciences, Tamil University, Thanjavur - 613 005, IN
2 National Institute of Oceanography, Dona Paula, Goa - 403 004, IN

Abstract

Bivariate plots of the textural parameter data suggest overlapping environments. Such as river/beach to JB, beach/dune/river to AB and dune/beach to VB sediments.

Keywords

Sedimentology, Grain Size Parameters, Depositional Environments, Bays, Maharastra.

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K. Anbarasu ¹, G. V. Rajamanickam ²

Affiliations
1 Department of Geology, National College, Tiruchirapalli - 620 001, IN
2 Department of Earth Sciences, Tamil University, Thanjavur - 613 005, IN

Abstract

The causes for coastal erosion around Pondicherry and Ennore were analysed. Wave refraction patterns exhibit convergence of wave energy around Ennore leading to erosion. The presence of artificial structures of Chennai port jetties has had its influence on the erosion around Ennore. But the coastal erosion around Pondicherry is neither man-induced, nor wave-powered, but may be ascribed to cymatogenic downwarping, which is a neotectonic activity. River migration pattern around Pondicherry suggests that the area has been subjected to downwarping in the Quaternary.

Keywords

Coastal Erosion, Neotectonics, Pondicherry, Ennore, Tamil Nadu.

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