The geology of the Australia Plains area, northern Mt Lofty Ranges, South Australia

Abstract

The most northerly Kanmantoo Group sediments occur in a synclinorium near Australia Plains. They, and the underlying Proterozoic units, have been mapped. On the west of the syncline, the contact does not outcrop and it is not possible to determine whether an unconformity exists between the two. On the east, the contact is fault-bounded; probably by an extension of the Palmer Fault Zone. A flood plain and then a shallow marine or lacustrine palaeo­environment is postulated during the time of deposition of the Kanmantoo Group. Biotite grade metamorphism has been attained in the area; a slaty cleavage and a mineral lineation are variably developed. Micro scale investigations show that the cleavage and lineation are both due to preferentially-oriented grain growth in response to the stress field which was present during the single deformation period.