Heavy Minerals and Granulometric Studies in Coastal Sediments from Keelakarai to Periyapattinam, Gulf of Mannar, East Coast of India

Abstract

In this study, granulometric and heavy minerals analysis were carried out in coastal sediment samples from Keelakarai to Periyapattinam, Gulf of Mannar, east coast of India to examine the feasibility of energy conditions that had prevailed during the deposition and its respective heavy mineral assemblages. Out of 40 samples, the backshore area are fine grained, whereas the foreshore area is enriched with mixed grains ranging from coarse to medium grained in size in the alternate samples. Most of the samples were classified under moderately sorted and moderately well sorted in the backshore area, wherein at the foreshore it is poorly to moderately sorted in nature. Most of the sample falls under leptokurtic curve while few other locations fell under mesokurtic. Fine skewed nature is observed in the foreshore samples. Most of the samples are unimodal and few are bimodal. The unimodality at the location reflects the lack of sediment deposition by the rivers. The bimodality is ascribable due to the discharge of fine sediments from small rivers like Gondar and Vaippar. The presence of fine sediments is the reflection of depositional environment which is corroborated with the strong wave divergence that prevails in this region. The coarse grained nature in the foreshore might be due to the prevailing high-energy environment, where the wave is orthogonally converging. Individual heavy mineral weight percentage is analyzed and it varies from 5.5 to 31.55%. The lowest values were noticed in 9 samples, whereas the highest values were observed in the stations 5, 7, and 15 which receives more than 15% of heavies. Based on the Isodynamic separation studies it is observed that the magnetite and ilmenite were found more at 0.3 A. Further, from the textural analysis, it is clear that the area from Keelakarai to Periyapattinam is generally experiencing the depositional environment as evident from positive skewness with the exception of three locations which are undergoing erosion as evident from negative skewness. This study shows that in the field of placer deposit investigations, it is significant to correlate the techniques like granulometric, Frantz Isodynamic separator and bromoform separation.