The Permian Geology, Physiography and Landscape Evolution of Northeastern Victoria

Abstract

Northeast Victorian diamictites (tillites) and interstratified traction deposits (fluvioglacials), now mapped in detail and interpreted as glacial, contain: uni- and multidirectionally striated clasts; striated clasts with environmentally diagnostic shapes (wedges and bullets); and occasionally striated fossiliferous (Siluro-Devonian faunal assemblages) and non-fossiliferous erratics. The sequences represent proximal sedimentation associated with a wasting ice-front, south of the Wangaratta area. Associated with these sediments are seven pavement surfaces, recognised as glacial (one - a miniature roche moutonnee) and indicating ice-movement from south to north. Petrographic data show derivation of non-fossiliferous erratics from local and distant source terrains south of the study area. Palaeontological data show derivation of the exotic fossiliferous erratics from beyond the present southern margin of the Australian craton. Local preservation and general distribution of glacial deposits reflects original Permian topography rather than subsequent graben tectonics. There is no geological evidence for an Ovens Graben. The present landscape reflects tilt-block tectonics similar in structural pattern to that developed across the north of the state, and is in part at least a preserved Permian feature. The radiometric age of basalt in Glenrowan Gap (on the western side of the Ovens tilt-block) demonstrates the Gap's existence before 36 Ma. Glacials suggest a relict Permian ice-spill path to the NW.