Conflicts in stratigraphic classification of the Puranas of the Pranhita–Godavari Valley: review, recommendations and status of the ‘Penganga’ sequence
Asru Kumar Chaudhuri, Gautam Kumar Deb, Sarbani Patranabis-Deb, 2015. "Conflicts in stratigraphic classification of the Puranas of the Pranhita–Godavari Valley: review, recommendations and status of the ‘Penganga’ sequence", Precambrian Basins of India: Stratigraphic and Tectonic Context, R. Mazumder, P. G. Eriksson
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Understanding of the incompatibility of King’s three-fold classification of the Proterozoic (‘Purana’) rocks of the Pranhita–Godavari Valley, south India, and renewed mapping and stratigraphic studies, reveal that syn-depositional basin dynamics, with differential uplift and subsidence, was the major control on basin evolution and the development of multiple unconformity-bound successions. The unconformities demarcate six major successions, the Mallampalli/Devalmari, Somanpalli, Mulug, Penganga, Albaka and Sullavai groups, each with a very distinctive set of sedimentological attributes. There are at least five different conflicting classification schemes so far. The major problems in the classification of the succession appear to lie in the recognition of unconformities and unconformity-bound successions, and in stratigraphic nomenclature. Based on field geology, available age data and the concept of the megasequence, the Mallampali, Devalmari, Mulug and Somanpalli groups have been grouped into the Pakhal Supergroup. The question of combining the rest of the groups has been deferred until the resolution of the Albaka–Penganga relationship is achieved beyond doubt. The relationships between different stratigraphic units have been critically examined to reconstruct the stratigraphic history, events of sea-level change and palaeogeographical evolution.
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This Memoir provides a comprehensive review of the Precambrian basins of the four Archaean nuclei of India (Dharwar, Bastar, Singhbhum and Aravalli-Bundelkhand), encompassing descriptions of the time–space distribution of sedimentary–volcanic successions, the interrelationship between tectonics and sedimentation, and basin histories. Studies of 22 basins within the framework of an international basin classification scheme deepen an understanding of the basin architecture especially for cratonic basins. Most Indian sedimentary successions formed as cratonic to extensional-margin rift and thermal-sag basins, some reflecting mantle plume movement, subcrustal heating or far-field stress. This Memoir shows that Phanerozoic plate-tectonic and sequence stratigraphic principles can be applied to the Precambrian basins of large Archaean provinces. The differences between the stratigraphic architecture of the Indian Precambrian and examples of Phanerozoic basin-fill successions elsewhere are ascribed to variable rates and intensities of the controls on accommodation and sediment supply, and changes inherent in the evolution of the hydrosphere–atmosphere and biosphere systems.