Relationship between northwestern Tasmania and East Gondwanaland in the Late Cambrian/Early Ordovician: Paleomagnetic evidence

Abstract

The 71 samples from 11 sites in the lower Upper Cambrian turbiditic red siltstone and mudstone of northwestern Tasmania have revealed a high‐temperature component which passes a fold test, indicating an age older than Late Devonian. The mean direction of D = 58.3°, I =11.1°, α 95 = 10.4°, k = 20.2, is interpreted as of primary or early diagenetic origin, and gives a paleomagnetic pole position at (19.4°S, 28.9°E) with DP = 5.3°, DM = 10.5°. This pole position falls on the Late Cambrian to Early Ordovician part of the East Gondwanaland apparent polar wander path, indicating that if northwestern Tasmania were separated from East Gondwanaland during the Neoproterozoic breakup of the supercontinent Rodinia, it had been accreted to East Gondwanaland by at least the Early Ordovician. Two over‐print poles, one at (50.4°S, 177.4°E) with DP = 6.5°, DM = 6.9°, and the other at (62.0°S, 102.6°E) with DP = 9.9°, DM = 11.3°, suggest that there could have been more than one overprinting event in the region during the breakup between Australia and Antarctica in the late Mesozoic and early Tertiary.