The Source of the Deccan Trap Flows

A study of the Deccan Trap flows around Sagar, Madhya Pradesh, has led to a consideration of the problem of the source of the flows, and of the distances to which individual flows may have travelled.

Assuming that the flows issued from fissures, now seen as dykes, it is difficult to account for the source of the flows that make up more than half the Deccan Trap outcrop where no dykes are found, unless it be assumed that the flows were capable of travelling long distances. In the limited area studied some of the flows have been followed for 40 to 80 miles without showing signs of thinning, and they may well have extended for very much further. It is possible, therefore, that the flows originated in those areas where dykes are found, namely in Cutch, Saurashtra, the N. Konkan, the Tapti and Narmada valleys, and the Gondwana basins of the Satpuras and further east, and that they travf'lled long distances to other parts of the outcrop.

Recent geodetic computations by E. A. Glennie support this view, and in particular suggest that the main source of the lavas was off the west coast of India north and south of Bombay, where remarkable gravity anomalies are found.

To have covered such large areas the flows must have been extremely fluid, and the possible causes of their fluidity are briefly considered.