K. Deepthi

Geochemical characteristics and depositional environment of Kalpakkam, southeast coast of India

Sediments from Kalpakkam, southeast coast of India were geochemically analyzed to document the provenance, tectonic setting, and role of chemical weathering. The sediments are dominated by quartz (Si), and the higher concentration of Si suggests the presence of quartz (±feldspar) dominated terrigenous sands. The study demonstrates that the sediments are derived from the granitic to gneissic or from a sedimentary source. Beach sediments are deposited in a passive continental margin setting and seabed sediments are deposited in active continental margin. In the A–CN–K diagram, most of the samples fall in the lower part, i.e., below the plagioclase feldspar joint which indicates a low degree of alteration. Only S6 falls just above the plagioclase feldspar joint, close to the AK boundary suggesting a slightly advanced weathering of sediment and source. Beach and seabed sediments lie close to CNK and FM region suggesting the presence of ferromagnesian minerals (likely to be pyroxene) except S6 which falls in the inner triangle of the minerals feldspar, garnet, and biotite in A-CNK-FM diagram. Both CIA and CIW values depict the unweathered nature of the sediments under humid to semi-humid climatic conditions.

Mineralogical Characterization in the Marine Environment of Kalpakkam, Southeast Coast of India

Sediments from Kalpakkam in the southeast coast of India were analyzed to characterize heavy mineral distribution. The mineral deposits are fine-grained in nature, and temporal and spatial variations are observed in mineral deposits. Iron mineral peaks observed indicate that hematite is present in the samples. The abundance of iron-based minerals explains the occurrence of black grains in the beaches of Sadras and Kokillamedu. In the rest of the region, the mineral distribution is found to be poor and patchy. Uranium-based radioactive minerals are present in the study area, viz., Uranmicrolite, Dessauite, Dumontite, and Sedovite. The common light minerals are quartz and caminite and the heavy minerals that are not iron-rich are tungusite, charoite, glagolevite, mangazeite, falkmanite, augelite, and struvite. Heavy minerals concentrated in the intertidal tide zone show well-developed swash marks by their typical alignment during the process of swash and backwash. Caminite is formed due to the reaction of seawater with hydrothermal fluids in a midoceanic ridge; its presence in the beach indicates the extent of onshore-offshore sediment transport. The heavy mineral distribution pattern along the Kalpakkam-Mahabalipuram stretch reveals the influence of energy conditions and energy fluctuations that are capable of transporting high-density minerals.

Monitoring Chlorophyll – a Concentration in the Coastal Waters of Kalpakkam (India): Application of a Regional Algorithm using Oceansat – 2 Ocean Colour Monitor

The study aims for the quantitative assessment of chlorophyll concentration and their distribution in the coastal waters of Kalpakkam (Tamil Nadu, India) using the normalised water leaving radiance from the OCEANSAT-2 Ocean Colour Monitor (OCM-2) with in situ chlorophyll concentration. The site specific regional algorithm is based on the sigmoid relationship of the band ratio (nLw490/nLw555) and generates a polynomial relation. The validation of chlorophyll concentration yields a high correlation (r2 = 0.92) with 21 independent in situ samples. The study demonstrated the application potential of OCM-2 in assessing the biological conditions of coastal waters. The chlorophyll distribution predominates towards north depending on the local climatic conditions.

Textural and depositional processes of surface sediments of Kalpakkam, Southeast Coast of India

To understand the influence of human disturbance on the sediment processes along Kalpakkam coast, India, beach and seabed sediments at 200 m, 500 m, and 1 km into the sea were collected monthly for one year and analyzed. Coarser material close to the tidal inlets (river) and manmade structures (sea wall) indicate the effect of these features in altering the grain size distribution from the general trend. The bivariant plots confirm the dominance of deposition under beach environment. The CM diagram (C — one percentile grain diameter, M — median) divulges that the deposition takes place by suspension and rolling of sediments with C < 1 mm. Linear discriminate function analysis for sediments at Kalpakkam indicates a shallow marine environment for all the samples collected. On the multigroup multivariant discriminant functions V1-V2 diagram, the bulk of the samples from Kalpakkam to Mahabalipuram fall in the field of beach deposition. These results show that reworked sediments, submerged during the Holocene marine transgression are being deposited on present-day beaches by waves, currents and rivers in the study area. Though a high wave energy environment is prevailing in the study area, dominant northward sediment transport along the Kalpakkam-Mahabalipuram coast is not altered due to human interventions. Beach building activity in front of the sea wall ensures the safety of Indira Gandhi Centre for Atomic Research (IGCAR) from wave actions without causing any significant changes to the coastal environment.