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Jayagopal Madhavaraju,Alcides N. Sial,Reghunathan Rakhinath,Sooriamuthu Ramasamy,이용일,Ariputhiran Ramachandran 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.2
A petrographic, carbon, oxygen and strontium study of the carbonate succession of the shallow marine Kallankurichchi and Niniyur formations of the Cauvery Basin, Tamil Nadu, India was conducted to understand the isotopic variations in seawater during Maastrichtian-Danian. The limestones from both the Kallankurichchi and Niniyur formations show large variations in Mn and Sr concentrations and high Mn/Sr ratios indicate alterations of primary isotopic signatures during shallow burial diagenesis. The limestones of both the Kallankurichchi and Niniyur formations show negative δ13C (‒4.73 to ‒0.49‰ VPDB; ‒5.63 to ‒1.87‰ VPDB; respectively) and δ18O values (‒8.89 to ‒3.66‰ VPDB; ‒8.56 to ‒5.41‰ VPDB; respectively). The carbon and oxygen isotope composition, δ13C vs. δ18O plot and Mn/Sr ratio suggest that the measured δ13C and δ18O values have been significantly altered during diagenesis. The limestones from both the Kallankurichchi and Niniyur formations show large variations in 87Sr/86Sr values (0.709310 to 0.711962; 0.708280 to 0.708398, respectively) which are higher than 87Sr/86Sr ratios of the contemporary Lower Maastrichtian (87Sr/86Sr: 0.707760) and Danian (0.707819 to 0.707833) seawaters. The elevated 87Sr/86Sr ratios in the limestones of the Kallankurichchi Formation suggest that these limestones were significantly modified by pore fluids during meteoric diagenesis. The observed large fluctuations in 87Sr/86Sr ratios in the Niniyur Formation resulted from variations in riverine input. One sample from the Niniyur Formation exhibits an unaltered 87Sr/86Sr ratio (0.707828) which is interpreted to indicate an age of 65.02 Ma.
Jayagopal Madhavaraju,Subin Prakash Rajendra,이용일,Erik Ramirez Montoya,Sooriamuthu Ramasamy,Rufino Lozano SantaCruz 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.6
Mineralogical and geochemical (major, trace and rare earth elements) studies were carried out on the clay samples of the Terani Formation, South India to investigate the paleoweathering, source rocks characteristics and tectonic setting. The chemical index of alteration (CIA), plagioclase index of alteration (PIA) values and A-CN-K diagram indicate that clays were generated from source rocks of the upper continental crust affected by intense chemical weathering. The chondrite-normalized REE patterns show considerable LREE enrichment, HREE depletion with significant negative Eu anomalies. The REE patterns, elemental ratios like Al2O3/TiO2, Cr/Ni, Eu/Eu*, (La/Lu)cn, La/Sc, Th/Sc, La/Co, Th/Co, and Cr/Th, discriminant function diagram, various bivariate and ternary plots indicate the contribution of sediments from felsic and intermediate source rocks. The discriminant-function-based tectonic setting diagrams reveal passive margin setting for the source area of the Terani Formation.