In India, pre-Cambrians are generally divided into Achaean and Purina. The Purina was further subdivided into the Cuddapahs and the Undarns. All pre-Cambrian rocks are unfossiliferozes and comprise gneisses, schist’s, marbles, quartzites, granites, limestones, dolomites and aphyllies.
The Achaean rocks occur in the southern part of the peninsula, Bundelkhand region, southern Bihar and Orissa, the Eastern Ghats, Aravalli system, some parts of the central ranges of the high Himalayas.
The Darian system derives its name from the rocks in the Darian district of Karnataka. These rocks cover the major part of Karnataka (best developed in Schemata and Chitaldurg districts), in Bihar (Ranchi, Gaya and Hazaribagh districts), in Orissa (Sundargarh, Keonjhar districts) and in Madhya Pradesh (Baster, Blight, Reba and Jabalpur districts).
The rocks of this system are highly metamorphosed into gneisses, schist, marbles and quartzites. These rocks are believed to have been deposited between 2,100 and 3,500 million years ago.
The Aravalli system is said to date back to. 3,500 million years. The Sapura basin of metamorphosed sediments and igneous rocks found in Nagpur, Bandera and Blight districts of Maharashtra, Chimaera and Raipur districts of M.P. Sambalpur, Sundargarh districts of Orissa have developed between 860 to 1,000 million years. The Bundelkhand gneiss occurs in southern U.P. and Madhya Pradesh. Mayurbhanj, Keonjhar districts of Orissa, Singh hum district of Bihar, Tiruchiraplli, Salem district of Tamilnadu, Bellary district of Karnataka, Warangal. Algona districts of Andhra Pradesh. The Dharwar rocks are economically important as they contain gold, copper, chromite, iron ore, zinc ore, lead ore etc.
The Purana Era
The Cudahy system:
The rocks belong to the Cuddapah system, derive the name from the Cuddapah district of Andhra Pradesh and were first developed some 600 to 1400 million years ago. The rocks of this system occur in the Cuddapah and Kummel districts of Andhra Pradesh. They also occur in Chhotnagpur, Gaya, and Mangy, south Singh hum of Bihar, Chhattisgarh, Gwalior, Baster, Bijawar and Jabalpur of M.P. This system is rich in copper ore, barites, nickel, jasper, and cobalt and sand-grade limestone. The chief rocks of this system were unfossiliferous clay, slates, quartzite’s, sandstone and limestone’s.
The Vindhyan system:
This system derives its name from the great Vindhyan Mountains and consists of shale’s, slates, sandstones and limestones. Except a few traces of animal and vegetable life, this group of rocks is devoid of any recognizable fossils. The system of rocks is well-developed in some valley, Reba region of M.P., Sarnbalpur district of Orissa, Krishna valley, Planed tracts in Andhra Pradesh.
The Dravidian Era
Cambrian to middle carboniferous:
The Rocks of this system are mostly found in extra peninsular region i.e. in the Spite valley, Kula valley in central Himalayas and Gradual, Kumauni region of U.P.