Shivaji P. Kokate¹, Shyam N. Mude^1*, Ravindrasing G. Pardeshi¹ and Harshal N. Babar²

¹Department of Geology, Fergusson College (Autonomous), Pune-411004(MS), India

²Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien-9740, Taiwan

(*Corresponding Author, E-mail:shyam.mude@fergusson.edu)

Abstract

The Palaeocene-Eocene Subathu Formation in the Nilkanth region near Rishikesh, Uttarakhand provides insights into the provenance, depositional environment, and tectonic setting prior to final India-Asia continent collision. Geochemical analysis of major oxides, trace elements, and rare earth elements from shale-dominated sedimentary rocks reveals a complex provenance. Discriminant function plots indicate the derivation of sediments from quartzose sedimentary sources, with minor input from mafic igneous sources. Trace element patterns suggest contributions from felsic igneous rocks, recycled sediments, and subduction-related components. The Chemical Index of Alteration (87.2*Avg.) indicates moderate weathering in the source area under semi-arid paleoclimatic conditions. Tectonic discrimination diagrams indicate that the deposition of sediments from Subathu Formation had occurred predominantly in an active continental margin setting. Rare earth element patterns exhibit varying degrees of fractionation, implying diverse sources ranging from mafic to felsic compositions. This multi-proxy geochemical study sheds light on the evolving paleoenvironmental conditions and sediment routing systems in the western Himalayan foreland basin leading up to the terminal India-Asia collision.

Keywords: Geochemistry, Subathu Formation, Provenance, Tectonic Setting, Paleoclimate, Depositional Environment, Himalaya