Publication Name: PESA's Eastern Australasian Basin Symposium II
Authors: G.R. Holdgate, K.A. Cunningham, M.W. Wallace, S.J. Gallagher and D.H. Moore
Date Published: December 2004
Number of Pages: 35
Reference Type: Book Section
Abstract:Basalt flows across the central highlands of Victoria have sealed in-place early to middle Tertiary palaeodrainage systems that once provided clastic sediments to the flanking Otway, Murray and Gippsland basins. Gravels of the palaeorivers were mined in the past for gold. Modern aeromagnetic/radiometric coverage is used to map this palaeodrainage system; water-mineral exploration drilling provides detail of sediment composition.
Palaeodrainage into the basins occurs radially from highland blocks centred on St Arnaud and Bendigo. The rivers
discharged onto late Eocene to Miocene-aged peat swamps (coal) and delta/shoreline systems peripheral to the mainly marine carbonate environments of the Murray, Otway and Gippsland basins. The coal and gravel sub-basins include the Stawell to Horsham deep lead, the Wycheproof and Streatham sub-basins, the Campaspe-Goulbum valleys and the Warragul Sub-basin. Separating the two highlands is a major incised Loddon-Ballarat-Streatham-Port Phillip deep lead system that connects the Murray to the Otway and Port Phillip basins.
Early Tertiary coal and gravel basins formed along the lead systems, sediment isopachs suggest the ancestral Murray River could flow south to the Otway and Port Phillip basins. Radial flow directions off the highlands and a Murray source to the southern basins argue against the current east-west highland divide existing in the early-middle Tertiary, rather, two meridionally-orientated highlands lay parallel to the eastern highlands. The much younger (< 7 Ma) Plio-Pleistocene valley-infilling basalts flow from an east-west divide located up to 20 km south of the present, implying the modern eastwest divide formed as a result of Neotectonic uplift.