Palaeomagnetic Directions of the Deccan Traps of Rajahmundry, Andhra Pradesh, India

Abstract

The palaeomagnetic directions of the Deccan traps of Rajahmundry in Andhra Pradesh, India which are considered to be an outlier of the main Deccan traps of western and central India supports the evidence that the Indian sub‐continent has drifted northwards across the equator and rotated anticlockwise since the formation of the traps, as has been postulated by earlier workers. However these rocks are found to be normally magnetized (dip up 45° and declination 305° E) while a rock series, the Linga rocks, in the main Deccan trap area, considered to be contemporaneous with the Rajahmundry traps are reversely magnetized (dip down 48°, declination 164° E). Three possibilities are suggested by these conflicting results: (1) The Linga and Rajahmundry rocks are not geologically contemporaneous with one another. (2) Though belonging to the same age group they are separated by one or two million years and the Earth's field had been reversed in between their eruption and (3) both rocks erupted simultaneously. One, however, had self reversed and this self reversing mechanism had later been obscured. Of these possibilities, the second appears the more probable from both geological and palaeomagnetic evidence. Copyright © 1965, Wiley Blackwell. All rights reserved