Palaeomagnetic Results on Gondwana Dykes from the Damodar Valley Coal-fields and their Bearing on the Sequence of Mesozoic Igneous Activity in India

Abstract

Summary Detailed palaeomagnetic measurements have been carried out on twelve dolerite dykes intruding a belt of Gondwana coalfields exposed in the Damodar valley region and stretching between the Rajmahal traps on the east and the Deccan traps on the west. The problem of age and correlation of the dolerite dykes activity with either the Rajmahal or the Deccan traps activity has been examined in the light of the palaeomagnetic data on these formations. The palaeomagnetic data suggests that the Rajmahal-Sylhet group of traps on one hand and the Deccan traps on the other do not represent independent igneous activities as was hitherto believed and that they are phases of a continuous Mesozoic igneous activity which began on the eastern side with a more or less contemporaneous eruption of lavas giving rise to the Rajmahal, Sylhet and Rajmahendri traps, and which passed through a hypabyssal phase giving rise to the coalfield dykes to the west of Rajmahal traps and then again manifested itself further west in the vast sequence of lava flows constituting the Deccan traps.