Título del libro: Chemostratigraphy: Concepts, Techniques, And Applications
Título del capítulo: Geochemistry of Late Cretaceous Sedimentary Rocks of the Cauvery Basin, South India: Constraints on Paleoweathering, Provenance, and END Cretaceous Environments
MADHAVARAJU JAYAGOPAL;
Autores externos:
Idioma:
Inglés
Año de publicación:
2015
Palabras clave:
Europium; Europium compounds; Feldspar; Geochemistry; Granite; Mixtures; Nickel; Rare earths; Rocks; Sandstone; Shale; Trace elements; Weathering; Cauvery basin; Chemical index of alterations; Geochemical variations; Immobile trace elements; Paleoweathering; Provenance; South India; Upper continental crust; Sedimentary rocks
Resumen:
The Late Cretaceous sandstones, siltstones, claystones, and shales of the Ariyalur Group of the Cauvery Basin were analyzed for their major, trace, and rare earth elemental geochemistry. They show relatively higher percentage of K2O than Na2O, and affinity with the K-feldspar. The sandstones and siltstones are depleted in most trace elements relative to upper continental crust (UCC), except for a few elements (Ni, Cr, and Ba), which are slightly enriched. The claystone and shale samples of the Ariyalur Group are enriched in Co, Ni, Cr, and Ba as compared to UCC. The average Chemical Index of Alteration (CIA) values and the A-CN-K diagram for sandstones, siltstones, claystones, and shales suggest that these were derived from weakly to moderately weathered source rocks. Intense chemical weathering in the source area during the deposition of sandstones and shales of the upper Kallamedu Formation is indicated by higher CIA and Plagioclase Index of Alteration (PIA) values. A silicic source for rocks of the Sillakkudi, Kallankurichchi, Ottakkovil, and lower Kallamedu formations is indicated by higher ratios of SiO2/Al2O3, SLREE/SHREE, La/Sc, Th/Sc, Th/Co, LaN/YbN, and La/Co; lower ratios of Cr/Th and Cr/Zr; and low values of TiO2, Sc, Cr, and Ni as well as Eu anomalies. Immobile trace element ratios, Eu anomalies, and rare earth element (REE) patterns strongly support that tonalitic gneiss, granodiorite, and granitic rocks of the Dharwar Craton could be the source rocks for most of the Ariyalur Group. REE modeling suggests that the average composition of the Sillakkudi, Kallankurichchi, Ottakkovil, and lower Kallamedu formations represents a mixture of sediments derived from a provenance consisting of 60% tonalitic gneiss, 25% granodiorite, and 15% granite. The upper Kallamedu Formation, however, shows a distinct variation in REE pattern together with high values of Cr and Ni and high Cr/Th ratios, and suggests some variation in the source rocks. The mixing calculations reveal that the average upper Kallamedu rocks can be represented by a mixture of 40% tonalitic gneiss, 30% basalt, 25% granodiorite, and 5% granitic rocks. Hence, the observed geochemical variations in the upper Kallamedu Formation could have been influenced by the Deccan Trap volcanism. © 2015 Elsevier Inc. All rights reserved.
Entidades citadas de la UNAM:
ISBN:
9780124199828
Editorial:
Elsevier Inc. Nombre de la publicación:
Geochemistry of Late Cretaceous Sedimentary Rocks of the Cauvery Basin, South India: Constraints on Paleoweathering, Provenance, and END Cretaceous Environments
Página inicial:
185
Página final:
214
