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The study examines about the red sand dune deposit locally designated as teri deposits; it is an omnipresent geomorphologic feature present in the coastal region of Thoothukudi and Ramanathapuram districts of Tamil Nadu, India. One of the inland teri sand dune outcrops is located around the Kuthiraimozhi village of Thoothukudi district in Tamil Nadu, India. Textural, mineralogical and geochemical studies were carried out in the teri sediments and its compact sandstone outcrops. The sediments are moderately sorted to well-sorted and finely skewed nature which indicates that fluvio-marine depositional environment. Geochemical analysis results of major, trace and rare earth elements for teri deposits help to predict the provenance, weathering status, depositional environment and climate. The geochemical study reveals that the sediments were derived from marine and non-marine sources. Teri sediments are geochemically classified as lithic arenite or wacke. Petrography and X-ray diffraction analysis reveal the predominance of quartz and feldspars along with the accessory minerals like ilmenite, rutile, garnet, magnetite, hematite, zircon, diopside, hypersthenes and biotite. Mineralogical observation illustrates that the teri sediments have originated from the weathering of felsic and mafic source rocks. The Chemical Index of Alteration (CIA) values of sediments represent moderate to the high status of weathering conditions in the source area. The depositional environment indicates that the sediments are fine-grained with high maturity index. Despite that the sediments are formed by fluvio-marine sources, the reddening character in the teri deposits is due to oxidation and leaching of iron-bearing minerals by percolating surface water from high rainfall and groundwater fluctuation of the aquifer under arid and semi-arid climate conditions.

Hydrogeochemical analysis was carried out to assess the suitability of groundwater for drinking, domestic, agriculture and industrial purposes in Sivagangai district, which is economically backward district of Tamil Nadu, India. Seventy ground water samples were collected during pre and postmonsoon season in the year 2017 from all over the district and analyzed for hydrogen ion activity, electrical conductivity, total dissolved solids, total hardness, Ca, Mg, Na, K, Cl, CO3, HCO3, SO4, total nitrate, and F. All the analytical results are compared with the corresponding guideline values of drinking water standards and the results show that groundwater in most part of the study area is potable except for a few locations in both seasons. The groundwater geochemistry is mostly controlled by rock water interaction and evaporation processes in both seasons as revealed from the Gibbs plot. The irrigation water quality parameters such as SAR, Na% and RSC results show that some of the groundwater samples are fit for agriculture. It is ascertained through hydrogeochemical analysis that the quality of groundwater is appropriate for drinking, domestic use, agriculture as well as industrial purpose and it can be utilized for industrial development to improve the socioeconomic status of the study area.

Calcrete is an impure limestone which is used as a substitute raw material resources for high-grade primary limestones like shell limestone, meta-sedimentary crystalline limestone in cement industries. They occur as a boundless deposit within the regolith profile sections rest over the basement rocks of granite quarry at Puthukulam Village, near Sathankulam region, Tuticorin District of Tamil Nadu, India. Geology of the area and schematic calcrete profiles stratigraphy are given. Field observation reveals that calcrete occurs as massive, laminated, oolitic, hardpan and lumpy forms in the study area. Micromorphological characters of calcrete of the area are revealing the displacive and replacive texture. And also the micritic and microsparitic calcite deposition is associated with regolith material. X-ray diffraction analysis reveals the general mineralogy and clay mineralogy of the calcrete. The major element geochemistry of calcrete through X-ray fluorescence spectrometry analysis (XRF) indicates that CaO, MgO, SiO 2 , Al 2 O 3 and Fe 2 O 3 are in a higher elevated concentration above 1% than other oxides, such as MnO, MgO, Na 2 O, K 2 O, TiO 2 and P 2 O 5. To evaluate the palaeoclimate significance, results of the proxies of mineralogy, clay mineralogy and major element geochemistry of calcrete are used.

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