The fan faults of Peninsular India and the origin of the Himalayas

Abstract

Mesozoic, Tertiary, Quaternary and Holocene faults, from the Indian subcontinent outside the Himalayan belt, that can be dated with confidence, are briefly described and it is pointed out that, with the exception of the Kirthar and perhaps the Sulaiman shear zones, all are normal and some of them are active. Plotted on a map all these faults seem to converge like a fan, to a point in the Arabian Sea. Also there seems to be a distinct and progressive younging of the faults in the anticlockwise sense. These facts appear difficult to explain, but may prove to be of value in any geotectonic study of the region. If the late and post-Mesozoic faults of the Peninsula are normal and some are even active, the Peninsula must be under tension. Earlier it appeared that a oroclinal rotation of the sub-continent was adequate to explain the phenomenon, for the faulting could have been largely preceded the collision with the northern landmass. However, the discovery of Quaternary-Holocene faults throws doubts on this supposition for this subcontinent has been obviously under tension since at least the Mesozoic. Some other explanation may, therefore, have to be sought for these phenomena.