Paleomagnetism of some Gondwana red beds from central India

Abstract

SUMMARYOriented samples were collected for paleomagnetic research from red horizons of the Gondwana sediments at a few localities in central India. The specimens were subjected to both alternating-field and thermal demagnetization and were measured on astatic magnetometers. Usually a stable direction of magnetization was observed only after thermal treatment.The following results were obtained:(1) The Upper Permian Kamthi Beds reveal a mean direction of magnetization given by D = 79.4 °, I = +61.6 ° (pole position 21.05°S 50.4°W; dp= 2.8 ° and dm = 3.7°);(2) The Lower Triassic Mangli Beds have D = 100.1 °, I = +62.8 ° (pole position 7.3°S 55.7°W; dp = 5.7 ° and dm = 7.3°);(3) The Upper Triassic Pachmarhi Beds have D = 117.2 °, I = +48.9 ° (pole position 10.15°N 49.9°W; dp = 4.0 ° and dm= 6.1 °).These results combined with earlier data indicate that the Indian subcontinent has made a sinistral rotation of about 90 ° during Upper Paleozoic through Mesozoic times, without a considerable meridional shift.

The paleomagnetism of the Salt Pseudomorph Beds of Middle Cambrian age from the Salt Range, West Pakistan

“…This arrangement is not fully in agreement with the computer fit of the southern continents proposed by Smith and Hallam [ 1,20]. The Upper Paleozoic paleomagnetic data of the subcontinent do not support a position near East Africa [9]. More research is needed to conclude whether this discrepancy is significant.…”

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

“…This difficult lithological distinction between the Mangli and the Kamthi beds caused some ambiguities. For instance, the Mangli beds at the type locality have been originally mapped as Kamthis (Hughes, 1877, p. 71), and the red beds directly south of Wun (79"l'E ZO"3'N) quoted as Kamthis by Wensink (1968), have been described in fact as equivalent to the Mangli beds (Hughes, 1877, p. 75;Pascoe, 1959Pascoe, , p. 1062. The age of this whole red-bed sequence might reach from a Late Permian-(Kamthi beds) up into an Early Triassic age (hlangli beds).…”

“…Compact argillaceous sandstones of a deep red to purple colour and red argillaceous shales, both of Lower Gondwana age, are found in this Wardha area. These red beds have been divided into the Upper Permian Kamthi beds (type locality sampled in the present study), and the slightly younger Mangli beds (type locality sampled by Wensink, 1968). However, in the field a distinction between the Mangli beds and the upper part of the Kamthi beds is difficult.…”

“…The age of the Taroba beds is somewhat doubtful, but might be Late Permian as indicated by Wensink (1968).…”

“…Altogether 389 specimens, 2.5 cm diameter and 2.2 cm height, were obtain- *** Wensink (1968) has studied some of the red beds exposed at the Wagdara quarry, Balar Hill and Tabora localities palaeomagnetitally, but the present collection is much more extensive. The age of the Taroba beds is somewhat doubtful, but might be Late Permian as indicated by Wensink (1968).…”