Paleo-environmental study of the Raniganj and Barakar Formations: Implications from the Geochemical and Geomechanical Aspects of Sandstone and Shale

Abstract

ABSTRACT The study considers the impact of the degree of weathered material constituting the sedimentary rocks on the strength of the Lower Gondwana coal measure rocks. The dependence of the strength of primary rocks on the alteration indices has been previously studied, but it is unknown for secondary/ sedimentary rocks. Therefore, in this paper, Lower Gondwana coal measure rocks (sandstone and shale) from the most productive coalfields of India, the Barakar and Raniganj coalfields, have been studied geochemically and geomechanically to find out their correlation. Geochemically, the study revealed that an arid, non-marine, and deltaic depositional environment prevailed during the sedimentation of Barakar and Raniganj Formations. The provenance was deduced to be mafic igneous. It was also deduced that the Lower Gondwana sandstone is clay-rich, and the sandstone samples fall in the shale field in the chemical classification scheme for terrigenous clastic sediments. The weathering indices, along with the uniaxial compressive strength (UCS) of the Barakar and Raniganj Formation coal measure rocks, have been assessed. The dependence of UCS on the weathering indices has been evaluated, and positive relationships were obtained.