Basal Tuffs and Contemporaneity of the Chattisgarh and Khariar Basins Based on New Dates and Geochemistry

Abstract

AbstractTime bracketing of thousands-of-meters-thick, unmetamorphosed, fossil-free sedimentary successions is a long-standing challenge in Indian Proterozoic stratigraphy. Limited geochronologic ages from either the basal or the upper part of the successions prevent workers from constraining the precise age interval for individual basin fill, leaving aside the issue of correlatability between different basin sequences. This article deals with silicic tuff units from the basal part of two areally separated Proterozoic sedimentary successions of central India, the Singhora Group of the Chattisgarh Supergroup and the Khariar Group. The Singhora tuff is enriched in large ion lithophile (Rb, Ba, Th, etc.) elements and light rare earth elements and in a discrimination diagram falls within the volcanic arc granite field. U-Th-Pb electron probe microanalyzer geochronology of monazite and zircon grains from the Singhora tuff revealed several age data clusters, namely, ∼2500, ∼2100, ∼1800, ∼1500, and ∼1000 Ma. In c...