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The Proterozoic Delhi Supergroup occupies three NE-SW trending linear belts in the northeastern part of the Aravalli mountain range, where its 10 km thick volcano-sedimentary sequence is classified into unconformity-based three groups: the Raialo, the Alwar, and the Ajabgarh. The palaeocurrent patterns and palaeoenvironmental setting of these rocks indicate multiple palaeoslopes and locate the provenance to the east and south.
The interrelationship of sedimentary facies and palaeoenvironments of the Delhi Supergroup can best be explained by an evolving intracratonic rift-basin model, comparable to several well-studied continental rift basins. The initial down-sag produced a N-S trending basin which received thick carbonate facies of the lower Raialo Group. Associated with early rifting, conglomerate-sandstone facies association of the middle Raialo developed in isolated grabens. The oligomict conglomerate was deposited along the border faults in the wave and tidal reworking zones and graded to beach sandstone towards the basin centre. Continued extension across the basin axis resulted in outpouring of basic to acid volcanics of the upper Raialo. Renewed rifting and associated major vertical tectonism produced some new grabens and caused wider submergence at the onset of the Alwar sedimentation. Coarse clastics of fluvial origin developed along fault scarps in the proximal southern parts as 100–2800 m thick conglomerate bodies grading to marginal marine sandstones northwards and towards the graben centres. Subsequently, the intervening highlands between grabens were gradually exposed. Another sea-level rise under the influence of a still wider downwarping resulted in submergence of all the interbasin highlands and unification of all the smaller basins into a wider basin, wherein the carbonate and psammo-pelitic assemblage of the Ajabgarh Group was deposited on multi-lagoonal tidal flats. Sedimentation was intermittently interrupted by basin-wide subaqueous volcanism.
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