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

N. Angusamy ¹, G. Victor Rajamanickam ¹

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

Abstract

Frequency distribution of heavy minerals along the southern Tamil Nadu coast from Mandapam to Kanyakumari shows selective deposition of heavies with respect to their densities. In Kanyakumari sector in the south, the heavies are concentrated in coarser sands, in the central Tuticorin sector in medium sands, and in the northern Mandapam sector in fine sands. Weight percentage distribution of heavies shows poor concentration at Mandapam that can be ascribed to strong progradational activity and wave-divergent conditions. A higher concentration of heavies in the ephemeral stream mouths in Tuticorin sector is due to the arcuate nature of the coastline, strong convergence of orthogonals and a basinal structure, all of which enable trapping of sediments carried by littoral currents. The poor concentration of heavies in Manappad sector, despite wave-convergent condition, is due to the straight alignment of the coastline without any arcuate bays. The enrichment of heavies in Kanyakumari sector is attributable to the arcuate coastiine and a downwarped basinal structure.

Keywords

Heavy Minerals, Beach Sands, East Coast, Tamil Nadu.

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P. M. Mohan ¹, G. Victor Rajamanickam ¹

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

Abstract

Along the east coast of India between Chennai and Pondicherry, 163 sediment samples were collected from different sub-environments of the beach representing low water mark (LWM), foreshore (FS), berm crest (BM), backshore (BS), dune (DU), and beach ridge or strandline (SL), upto 1m depth, at fifteen stations, spaced at a distance of approximately 10 km interval, Out of four size ranges (-420 to +350μ, -210 to +177μ, -105 to +88μ and the fraction consisting of the highest percentage in the sediment - first mode), the +88μ size range shows rich concentration of heavies (8.26 to 96.6 %). The heavy mineral content in the bulk sediment samples ranges from 0.55 to 22.95 %. This concentration may be due to the winnowing by wave action and selective sorting processes. Erosion exposes one of the stations in the beach ridge, up to 4 m depth from the surface and shows a higher concentration of heavy minerals. This information, along with analytical results of the stations from the surface upto one metre depth, indicating heavy mineral concentration of 8%, suggests the possibility of buried placer deposits at about 2 to 4 m depth along the beach ridge. Based on this prognostication, a random station was selected i.e. near Mahabalipuram and manual boreholes were drilled. These boreholes have confirmed the existence of buried placer deposits having concentration of 8 to 88 % of heavy minerals around 1.5 to 4 m depth of beach ridge. R mode and Q mode factor analyses indicate the possible environmental parameters prevailing at the time of deposition as well as under the present conditions in the stations.

Keywords

Strandlines, Factor Analysis, Economic Geology, Buried Placer, Chennai, Pondicherry, East Coast, Tamil Nadu.

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P. M. Mohan ¹, G. Victor Rajamanickam ¹

Affiliations
1 Department of Industries and Earth Sciences, Tamil University, Thanjavur-613005, IN

Abstract

Twenty five sediment samples, from seven traverses, were collected from the southwestern continental shelf of India. A variation in the organic matter from zero to 1 1.26% and carbonate from 7 to 96% is noticed. The stations located off the river mouth areas show high amount of organic matter and low amount of carbonate content, whereas outershelf sediments display high amount of organic matter and carbonate contents. However, in between these two zones, at the depth of 35 to 65 m, the concentration of organic matter and carbonate is found to have a considerable decrease in amount. It is inferred that this zone might be a paleo beach environment admixtured with present day marine environment.

Keywords

Organic Matter, Carbonate, Pleistocene Shoreline, Continental Shelf, Marine Geology.

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S. Manickam ¹, G. Victor Rajamanickam ², R. E. Benjamin ³

Affiliations
1 A.P.S.A. College, Tiruppattur - 630 211, IN
2 Department of Industries and Earth Sciences, Tamil University, Thanjavur - 613 005, IN
3 School of Economics, Madurai Kamaraj University, Madurai - 625 021, IN

Abstract

A comprehensive analysis of the economic viability of manganese nodule mining in India through the adoption of the standard capital budgeting techniques is attempted. The study includes both 3-metal plant (Copper, Nickel and Cobalt) and 4-metal plant (Copper, Nickel Cobalt and Manganese). Most of the studies carried out in the developed countries in the past conclude that this new ocean mining venture is not eccnomicaily viable. Hence, in this study, an attempt is made to find out any change that leads to significant improvement in the viability of the project by comparing the economic status of the industry between two periods, June 1987 and July 1990. The results of the research show that the Internal Rate of Return (lRR) of the 3-metal plant is 8.1% in June 1987 prices and the IRR for the 4-metal plant is 15.2%. But the IRR of 3-metal plant is 45.3% in July 1990 prices and 40.4% for the 4-metal plant. The results clearly point out that the project becomes viable in 1990 prices. This vast improvement in the economic status of this industry can largely be attributed to the enormous hike in the annual revenue of the project. Thus, the deep ocean holds out a beacon of hope to the world in general and India in particular for future supply of nodule metals.

Keywords

Mineral Economics, Mn-Nodules, Central Indian Ocean.

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R. Baskaran ¹, S. Selvaraj ¹, G. Victor Rajamanickam ²

Affiliations
1 Department of Geology, National College, Tiruchirapalli- 620 001, IN
2 Department of Disaster Management, School of Civil Eng, SASTRA, Thanjavur- 61 3 402, IN

Abstract

Silica sands of commercial value occur as patches of varied areal extent along the coast near Marakkanam in Tamil Nadu north of Pondicherry. There are many geomorphic features here. A study of these landforms and the deposits is attempted with a view to bring out the possible relationship between the geomorphic features and the deposits.

Keywords

Silica Sands, Geomorphic Features, Marakkanam Area, Tamil Nadu.

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P. M. Mohan ¹, G. Victor Rajamanickam ¹

Affiliations
1 Department of Industries and Earth Sciences, Tamil University, Thanjavur-613005, Tamil Nadu, IN

Abstract

Between north of Pondicherry and Ennore (12°03' to 13°12' N - 79° 53' to 80° 15' E) two geomorphic units such as beach and beach ridges and their associated units (Low Water Mark (LWM). Foreshore (FS). Berm (BM). Backshore (BS), Dune (DU) and Beach Ridge (SL) are selected for the present study to understand the micro level variation in the depositional environment. The samples mostly show medium to fine size, well sorted to moderately sorted, very coarse skewed to fine skewed and platykurtic to leptokurtic nature. Graphic mean, standard deviation, skewness and kurtosis confirm that the sediments are of typical beach origin. Frequency curves indicate that the dune samples represent unimodal and others show bimodal to poly modal source of influence. Based on bivariant plots the samples of dune, berm, backshore, foreshore and low water mark with strandline deposits are classified.

Keywords

Sedimentology, Depositional Environments, Grain Size, Tamil Nadu.

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