Tectonic Framework and Evolution of India

Abstract

The first ever Tectonic Map of India was published by the Geological Survey of India in 1963 and was presented before the 22nd International Geological Congress, 19 64 . This map was revised by the Survey in 1968 and the manuscript of the revision was presented before the 23rd Internationa l Geological Congress, 1968. In 1970, the Oil and Natural Gas Commission published another Tectonic Map of India and this contains some additional data on the sedimentary basins. The paper deals with the interpretations pertaining to tect onic framework and evolution ofIndia, as prese nted in revi sed manu script of Tectonic map, 1972. They can be summarised as follows: 1. In the Precambr ian shi eld there are th ree distinct mega-cycles of volcanic-sediment­ ary metamorphic tectogenes is till about 1600 m.y.b.p. fo ll owed by three di stinct mega­ cycles of predominantly platform a nd aulacogen development interspersed by anorogenic plutonism and volcanism . The former st raddl ed the Archaean-Middle Proterozoic period while the latter developments happened during the Riphean and Vendian. 2. The Precambrian shield has been considered to be continuing to the north as the basement of the Himalaya. Subsequent reacti vati on of the same during the Caledonian and Hercynian tectogenesis and Cenozoic orogenesis is indicated by field evidences . Cenozoic orogenesis/reactivation affected the yo unger Caledonian and Hercynian pl atforms too. 3. The Tertiary and Quaternary orogenesis of the Himalaya is consid ered to be due to the activities along three principal mega-lineament sys te ms and th e rudimentary Cretaceous­ Eocene eugeosyncline of the 'Indus sutu re' see ms to be controlled by Hercynian tectonic pat­ tern and mega-linea ments. 4. Hercynian geosynclinal developments of the Karakorum-H im a laya and the Hindu­ kush are areally related and foll ow an E-W arcu ate trend (convex to the north) in the Kara­ korum Himalaya sector. 5. The so called 'eugeosynclines' of the 'Indus suture' are act ua ll y wes tward continua­ tions of the Mesozoic geosynclin es of so uthern Tibet. 6. Principal lineaments, as ev iden t from geological, geophysical a nd geomorphic data have been shown to have pl ayed a significanct role in se dimentation, metamorphism and de­ formation, magmatism a nd tectogenesis-orogenesis.