Deformation of the Proterozoic successions in the Pranhita–Godavari basin, south India—a regional perspective

Abstract

A number of Proterozoic intracratonic basins, namely Cuddapah, Pranhita–Godavari (PG), Abujhmar, Indravati, Ampani, Chattisgarh and Khariar basins, occur to the immediate west of the Eastern Ghats granulite belt (EGGB) in India. Of these, the PG basin hosts an axial outcrop of late Paleozoic–Mesozoic Gondwana rocks flanked on either side by Proterozoic sedimentary successions. Among the latter, the Somanpalli Group in the eastern part and the Penganga and Yellandlapad Groups in the western part show contractional folds, imbricate thrusts and cleavage. These deformed rock groups and the Pakhal Group in the western belt include shallow to deep marine sedimentary successions. Stratigraphic relations indicate that the major episode of deformation in the PG basin occurred prior to deposition of the unconformably overlying Sullavai Group. The latter is a Neoproterozic, undeformed fluvial sequence with some aeolian intercalation. Deformed successions also occur in other Proterozoic basins of the south Indian craton, notably those in the Nallamalai fold belt (NFB) along the eastern part of the Cuddapah basin. The major fold–fault structures in the arcuate NFB vary in trend from NNW–SSE in the southern part to NE–SW in the northern part. At least one phase of folding and thrusting predates the ∼1000 Ma old event in the EGGB. Deformation associated with the Grenville and later Pan-African tectonic mobility has imprints on the Neoproterozic Kurnool Group in the Palnad sub-basin (northern NFB). The major structural trend in the PG basin is NW–SE, except for the Yellandlapad area in the southern part, where late superposed folds trend E–W. The deformation along the eastern margin of the Chattisgarh basin, its southern extension in Khariar, Ampani and Indravati basins may also be related with the main (Grenville) deformation in the EGGB. A regional, Mesoproterozic episode of basin closure and inversion is thus evident from the Proterozoic cratonic successions west of the Eastern Ghats. This occurred prior to a regional development of Neoproterozoic successions at these sites.