Journal of the Geological Society, London, Vol. 155, 1998, pp. 525–539. Printed in Great Britain Formation and reactivation of the Cambrian Kanmantoo Trough, SE Australia: implications for early Palaeozoic tectonics at eastern Gondwana’s plate margin T. FLÖTTMANN1, P. HAINES2, J. JAGO2, P. JAMES1, A. BELPERIO3,4 &J.GUM2 1Department of Geology and Geophysics, University of Adelaide, SA 5005, Australia (e-mail: tfl
[email protected]) 2Department of Applied Geology, University of South Australia, The Levels, SA 5095, Australia 3Mines and Energy, South Australia, 191 Greenhill Road, Parkside, SA 5063, Australia 4Present address: Minotaur Gold, 1a Gladstone Street, Fullarton, SA 5063, Australia Abstract: The Kanmantoo Group is a thick and largely metamorphosed sedimentary succession that filled an isolated arcuate Cambrian basin (Kanmantoo Trough) which formed within continental Gondwana, and now lies on the southern margin of the present Australian continent. Kanmantoo Group sediments unconformably overlie Neoproterozoic and older Cambrian rocks. We consider that the geometry of the southern part of this trough was influenced by strike-slip movement along an intra-continental tear fault. To the north, the basin changes to a style dominated by orthogonal extension and eventually tapers and dies out normal to the tear fault. Balanced sections show that the kinematic style and strain distribution developed during early Palaeozoic inversion was controlled by the specific architecture of the Kanmantoo Trough. Early Palaeozoic tear faulting could have linked contrasting subduction polarities along the then contiguous palaeo-Pacific margin of Gondwana. The Kanmantoo Trough is considered to have formed at a passive margin related to east-directed subduction in what is now the Australian continent.