PALEOMAGNETISM OF DYKE SWARMS FROM THE DECCAN VOLCANIC PROVINCE OF INDIA

Palaeomagnetic results of 19 dykes situated south of Narmada river (21 degrees 30' N, 74 degrees 15' E) in Dhule district of the Maharashtra state, India are reported. Of the 19 dykes, 11 dykes exhibit a normal magnetic polarity, and 4 dykes a reverse polarity. The remaining 4 dy kes yielded mostly scattered and unstable sample directions. The norma l and reverse directions are almost antipodal. The characteristic rema nence is indicated to reside in magnetite, and is most probably primar y. The N-Pole position corresponding to the mean directions of 11 dyke s (7 normal and 4 reversed) based on a minimum of 4 sample characteris tic directions per dyke is at 37.2 degrees N, 80.5 degrees W (A(95) = 9.7 degrees). This pole is concordant with the Deccan Superpole, indic ating a similar age of magnetization for the Deccan basalt flows and t he dykes intruding them. A joint consideration of similarity of palaeo poles of the dykes and the lava flows, magnetic polarity of dykes, and their stratigraphic positions of intrusions in the lava flow sequence support the view that the volcanic activity in the Deccan area spanne d a short duration. The post-trappean tectonic activity resulting in t he dyke swarms may possibly have coincided with the opening of the Ara bian Sea and the rifting of the Seychelles-Mascarene oceanic plateau.