K. Zaidi¹, S. Rais¹, Anis^2*, A. Khan¹, N. Kumar³ and M. Singh⁴

¹Department of Geology, Aligarh Muslim University, Aligarh-202002, India

²Department of Geology, ³Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Lucknow-226025, India

⁴Centre of Advanced Study in Geology, University of Lucknow, Lucknow-226007, India

*E-mail: anisgeology74@gmail.com

Abstract

The geochemical study of the Chirimiri sandstones of Talchir Formation has been carried out to investigate about the provenance, weathering signatures and tectonic setting. Major oxides suggest that the Chirimiri sandstone is compositionally immature with low content of SiO2/Al2O3 ratio. It is arkose to lithic-arenite type. The weathering indices like CIA and CIW and Th/U ratio suggest that Chirimiri sandstones suffered low to moderate chemical weathering. The chondrite normalised REE patterns of enriched LREE and flat HREE with negative Eu/Eu* anomaly along with trace element ratios of Th/Sc, Cr/Th and Zr/Sc suggest that these sediments were dominantly derived from the rocks of intermediate composition. Among these rocks some contains high Gd/Yb and HREE content. The Chirimiri sandstones were derived from passive margin setting, where the basin had undergone local (small scale) rifting prior to Gondwana disintegration. The Chirimiri basin can also be considered as a locally pull-apart basin and its sediments show geochemical signatures analogous to the basins of active continental margin setting.

Keywords: Geochemistry, Lower Gondwana, Chirimiri sandstones, Talchir Formation, Son-Mahanadi Gondwana basin, India