Proterozoic felsic volcanism in the Pranhita–Godavari valley, India: its implication on the origin of the basin

Abstract

The Proterozoic sedimentary rocks in the Pranhita–Godavari Valley (PG Valley), South India, were deposited in diverse environments ranging from continental shallow shelf to deep basin, and occur as several unconformity-bound sequences. The sedimentary rocks also include felsic pyroclastics in different formations and at different stratigraphic levels. Repeated occurrences of intrabasinal pyroclastic rocks of similar composition suggest that the detritus might have been erupted from a common chamber, which was activated at different times, throughout the basin-filling episode. It is postulated that the mature Proterozoic crust of Indian craton acted as a ‘heat lens’, resulting in extensive partial melting at the lower crustal levels, localized stretching, and rifting of the craton leading to the formation of the intracratonic basin. The sedimentological attributes also support extensional setting, and the hypothesis may be extended for several Meso–Neoproterozoic cratonic basins in the Indian shield. The mechanism operated over the time span of 1.6–0.7 Ga and overlaps with the age of development of an extensive granite–rhyolite province in North America. The process of accumulation of heat at the lower crustal levels generating a heat lens is typical of the stationary phase of supercontinental cycles, and the origin of the cratonic basins. The origin of the PG Valley basin may be related to the fragmentation of a supercontinent of which the Indian craton was a part.