K-Ar ages of a number of samples from Rajmahal and Deccan Traps and from basaltic dykes of Gondwanas have been measured. The results suggest that the Early Rajmahals erupted in the middle of early Cretaceous (∼ 110 my) and probably continued to be active till the end of Cretaceous. Deccan activity started in Gujarat-Kathiawar area in Early Paleocene and spread over almost the entire area in next 5–7 my. However, in the north-eastern region of the traps around Chindwara and Amarkantak, the basalts were laid in the middle of the Eocene (∼ 47 my). The measured ages of Deccan dykes suggest a subdued hypabyssal activity continuing till the end of Eocene or beyond.
The K-Ar ages of Gondwana extrusions exhibit contemporaneity with Deccan activity even for the dykes which are located right close to the Rajmahal outcrops; indicating no regular drift of the foci of volcanic activity. A distant dyke from Cuttack gives an early Rajmahal age, and therefore probably indicates the vast extent to which Rajmahal activity manifested itself.