The Pamatta Pass Canyon Complex: Neoproterozoic Wonoka Formation, Flinders Ranges, South Australia

Abstract

Deposition of the late Proterozoic Wilpena Group is characterised by numerous sequence boundaries or regional disconformities that reflect the tectono-stratigraphic history of the Adelaide Geosyncline. The most prominent of these are related to kilometre-sized incised valley systems within the lower Wonoka Formation. Alternative subaerial and submarine origins have been proposed. Recent work substantiates the subaerial model as it accounts for several lines of evidence the submarine model could not adequately answer. The Wonoka Formation in the Pamatta Pass Canyon Complex was first observed by Binks (1971). Observations made during field mapping support a subaerial origin and record evidence for multiple phases of canyon incision. A pre-Wonoka Formation phase of deformation (probably related to the Penguin Orogeny in northwest Tasmania, or the Beardmore Orogeny in Antarctica) is interpreted to have existed. Syn-depositional tectonism is likewise attributed to this event. Compressional deformation during the Delamerian Orogeny subsequently deformed the entire sedimentary prism in a complex array of NNE/SSW folds.