Geochronology of the Indian Precambrian


Author : M. S. Balasundaram & M. N. BalasubrahmanyanPublication : Bulletin of the Geological Society of MalaysiaVolume : 6Page : 212-226Year : 1973


Description

Bulletin of the Geological Society of Malaysia, Volume 6, Jul, 1973, pp. 212 – 226

 

Geochronology of the Indian Precambrian *

M.S. BALASUNDARAM AND M.N. BALASUBRAHMANYAN

Published by kind permission of the Director General, Geological Survey of India, Geological Survey of India, Calcutta

 

Abstract: Precambrian geochronology of India is now known with greater precision because of the dating of samples carefully selected, in respect of geological consideration and set up, from several areas in the past decade. Vestiges of older nuclei dating more than 3000 m.y. have been identified in southern, eastern and western India. The Charnockite-Khondalite supergroup (c.2900-2600 m.y.) is now considered to be older than the Dharwar supergroup; the Eastern Ghats (sensu stricto) rocks are now considered belonging to the Charnockite-Khondalite supergroup proper but with impress of events at 1650 m.y. and 1400 m.y. at about the same time as events in Cuddapah Basin, Nellore Schist Belt and Amgaon group. The Aravalli, Bailadila, Bengpal and Iron Ore groups are correlated with the Dharwar and range in age from c.2500-c.2000 m.y. The Delhi supergroup appears to be coeval with the lavas of the Gwalior \'series\'. 

Vindhyan sedimentation which started at c.1400 m.y. continued into Cambrian(?) unlike the Cuddapah supergroup where sedimentation ended by about 1300 m.y. The successively younger dates for the mobile belts from south to north, with respect to the southern nucleus, indicates a migration of geosynclines in the same direction. The Satpura \'group\' despite valid evidences for its abolition as a supergroup appears to indicate the reactivation of the Narmada-Son lineament at 950/1000 m.y. in part of eastern India. The manifestation of carbonatite and anorogenic granites dating 725 m.y. in southern India, high-level granites in western India, dating 730 m.y., Mylliem granite at 765 m.y. in eastern India and carbonatite in Rajasthan at 960 m.y. appear to be related to reactivation of lineaments in these areas at these dates. The overprint of mineraI ages at c.500 m.y. along the east coast is also suggestive of activity of lineaments but further studies are necessary to confirm this view.