Texture, mineralogy and geochemistry of Teri sediments from the Kuthiraimozhi deposit, Southern Tamilnadu, India: implications on provenance, weathering and palaeoclimate

Abstract

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.

Nutrient Variability Mapping and Demarcating Management Zones by Employing Fuzzy Clustering in Southern Coastal Region of Tamil Nadu, India

“…The physiography of the study area falls under flat alluvial plain. The soil consists of coastal sands and alluvium derived from the black soil of the quaternary period [30] and some forest areas covered by Theri lands, red sand dunes locally known as 'Theri'. Major soil orders of the study area are Entisols, Inceptisols and Vertisols, and the soil texture varies from coarse loamy to clayey.…”

Petrography and geochemistry of the Upper Cretaceous Gryphaea Limestones, Kallankurichi Formation, Ariyalur Group, Trichinopoly, Southern India: Implication for palaeoenvironment

“…Geomorphological, sedimentological, and biological factors reflect climate changes. Evaporite mineral and major element geochemistry are the two important proxies used for palaeoclimate investigation in the evaporite deposit of Tunisia and Rajasthan (Sinha et al, 2006;Smykatzkloss and Roy, 2010) and the Pandalkudi calcrete profile (Udayanapillai et al, 2021). Calcite, dolomite, halite, anhydrite, and gypsum are important evaporite minerals that represent proxies for the arid environment.…”

“…Highly soluble major oxides Na2O, MgO, K2O, and un-soluble hydrolysate TiO2, Al2O3 and Fe2O3 are used as proxies to interpret the palaeoclimate studies of the Gryphaea limestone profile of the study area. The ratio of alkaline/hydrolysate is generally low in the humid climate and high in the arid climate (Sinha et al, 2006;Udayanapillai et al, 2021). Ratio value of Na2O/Al2O3 (0.15), Na2O/Fe2O3 (0.03), Na2O/K2O (0.88), Na2O/TiO2 (1.8), and CaO/MgO (102.9) of the gryphaea limestone profile samples of the study area are given in (Table 4) and ratio plot for climate model diagram related to depth are given in the diagram (after Udayanapillai et al, 2015Udayanapillai et al, , 2021Fig 10).…”

“…The ratio of alkaline/hydrolysate is generally low in the humid climate and high in the arid climate (Sinha et al, 2006;Udayanapillai et al, 2021). Ratio value of Na2O/Al2O3 (0.15), Na2O/Fe2O3 (0.03), Na2O/K2O (0.88), Na2O/TiO2 (1.8), and CaO/MgO (102.9) of the gryphaea limestone profile samples of the study area are given in (Table 4) and ratio plot for climate model diagram related to depth are given in the diagram (after Udayanapillai et al, 2015Udayanapillai et al, , 2021Fig 10). The ratio value of < 0.1, 0.1 to 1, and >1 are treated as humid, semi-arid, and arid climates respectively, Geochemical ratio plots of gryphaea limestone samples collected from the study area fall on the semi-arid and arid climate prevailing during the depositional environment.…”

“…Salinization factor is established by the geochemical ratio of Na2O/K2O. When the above ratio is greater than 0.01, it represents a semi-arid and arid climate (Udayanapillai et al, 2015(Udayanapillai et al, , 2021. The averageNa2O/K2O ratio of the limestones is 0.88.…”