Palaeomagnetism of upper permian red beds in the Wardha Valley, Central India

Abstract

For a detailed palaeomagnetic research on Upper Permian red beds in the Wardha Valley (Central India) 265 samples from 47 sites at 6 localities were investigated.

The samples from 3 localities (17 sites) appeared to be completely remagnetized during Early Tertiary times by the vast Deccan Trap flood basalts effusions. The samples from 22 sites of the other three localities (results from 8 sites rejected) could become cleaned from hard secondary Deccan Trap components by detailed thermal demagnetization.

The resulting primary magnetization component reveals a mean direction (regardless of polarity, 7 sites normal, 15 sites reversed): D = 101.5°, I = +58.5°, α95 = 6.5°, N = 3. This mean direction corresponds to a pole position at 129° W 4° N (dp = 7°, DM = 9.5°). This pole position fits well with other acceptable Late Permian—Early Triassic pole positions for the Indian subcontinent. From these acceptable results, a mean Permo-Triassic pole for the Indian subcontinent was computed at: 125° W 6°N. This Indian Permo-Triassic pole position, when compared with data from other Gondwanaland continents, suggests the hypothesis of an early movement between India and Africa before Permo-Triassic times.

The partial or total remagnetization of some Indian red beds, mainly of Gondwana age, during Deccan Trap times is explained as acquisition of viscous Partial Thermoremanent Magnetization. This mechanism was advanced by Briden (1965), Chamalaun (1964) and Irving and Opdyke (1965).