Geology
The Archean gneisses and schists, which are the oldest rocks of the Indian Shield, constitute a considerable area of Peninsular India. The Dharwar (Super Group) and the Peninsular Gneissic Complex are the classified groups of the Precambrian rocks of India. The extent of the Archean system is depicted as the dominant system of South India in the pictured Geological Map of India.
In most stratigraphic schemes, the peninsular gneisses are shown as the younger Archaean strata situated above the Sargur Group. Granitization of the older sedimentary–volcogenic sequence are reported as sources of the peninsular gneisses made up of polyphase migmatites, gneisses and granites ranging in composition from granodiorite to tonalite.
The rocks of the Dharwar Group, which are mainly sedimentary in origin, occur in narrow elongated synclines resting on the gneisses found in Bellary district, Mysore and the Aravallis of Rajputana.
The supracrustal rocks of the Dharwar Group of the southern Indian Peninsula, as depicted in the geological map of South India, have the Peninsular Gneiss as the basement rock formation, also stated to be the remobilized basement. Migmatization of pre-existing metasedimentary and meta–igneous rocks are considered the contributors to formation of the composite gneiss.
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