Conglomerate Horizons in South-Central Rajasthan and their Significance on Proterozoic Stratigraphy and Tectonics of the Aravalli and Delhi Fold Belts

The Proterozoic sequences of South-Central Rajasthan are contained in the Lower to Middle Proterozoic Aravalli and Middle to Upper Proterozoic Delhi fold belts. The stratigraphic relations within these fold belts as well as the basement-cover relations are beset with several problems. The conglomerate horizons have been studied to address some of these problems. Based on the conglomerate horizons, representing erosional unconformities, the Aravalli Supergroup has been sub-divided into three groups and the Delhi Supergroup of the South Delhi fold belt into two groups with constituent formations. These horizons are also useful in identifying three stages of basin evolution for the Aravalli fold belt. The Middle Aravalli Conglomerate is the most prominent representing mid-Aravalli hiatus, and corresponding to the Debari Transgressive Stage which followed the Delwara Rifting Stage in the Lower Aravalli in a system of ensialic distensional tectonics where triple-junctions and pull-apart basins are formed. The Upper Aravalli has been the Jharol Ocean Opening Stage, the oceanic/transitional crust having been consumed at a median ultramafic suture line during the formation of the Aravalli fold belt. The South Delhi fold belt has also multi-stage development history with the Barr Conglomerate representing the base of the youngest Delhi sequence.