Palaeomagnetism of some Indian Rocks

Abstract

Hitherto, no palaeomagnetic data for India are available earlier than the Jurassic, 130 M.y. The remanent magnetic directions of oriented samples from one Jurassic and four pre-Cambrian rock formations in India have now been determined. One pre-Cambrian formation gave very scattered direction: the other four formations gave well-defined directions and their magnetic stability was demonstrated by a.c. and thermal demagnetization. The three pre-Cambrian results enable values of the ancient latitude and orientation of India to be estimated at 500, 600 and 750 M.y., assuming the ancient field to have been an axial dipole. By making use of these new results, together with similar data by other workers for Australia, North America and Europe, it can be shown that, as far as the scanty data goes, the rate of drift in latitudes and orientation of the four continents has been of roughly the same magnitude throughout the period since 750 M.y.