Glen, R. and Roberts, J. 2012.   Formation of Oroclines in the New England Orogen, Eastern Australia. In: (Ed.) Stephen Johnston, and Gideon Rosenbaum, Oroclines, Journal of the Virtual Explorer, Electronic Edition, ISSN 1441-8142, volume 43, paper 3, doi:10.3809/jvirtex.2012.00305

Formation of Oroclines in the New England Orogen, Eastern Australia

R.A. Glen

Geological Survey of New South Wales, NSW Department of Trade and Investment, Box 344, Hunter Regional Mail Centre NSW 2310 Australia. <>

National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth & Planetary Sciences, Macquarie University, Sydney NSW 2109 Australia.

J. Roberts

School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney NSW 2052 Australia.


Most of the New England Orogen comprises a convergent margin, in which Middle Devonian to latest Carboniferous continental margin arcs, forearc basin and subduction complexes were developed above a west-dipping subduction zone. The subsequent history is marked by an early and middle Permian hiatus in arc magmatism, followed by a resumption of west-dipping subduction from the late Permian to Triassic. The geometry of the southern New England Orogen is dominated by a northern, well-established oroclinal fold pair, developed in a subduction complex and overlying Permian rocks, and by a southern oroclinal fold pair, more controversial in acceptance. Our data sustain the presence of the two southern oroclines or megafolds, and suggest that they formed by anticlockwise fold rotation over a possible time span of ~40 million years, beginning in the latest Carboniferous and continuing into the middle Permian. By generating an oroclinal model that takes into account the fold-thrust deformation style of the forearc basin, along with multiple deformation, variations in directions and amounts of shortening, as well as vergence variations, we suggest that the Manning and Hastings oroclinal folds in forearc basin and subduction complex rocks developed as amplified buckle folds of large amplitude, the hinges of which can be tracked south-southwest along their axial traces into smaller amplitude folds along the old arc/forearc boundary. Rather than forming in response to either sinistral or dextral simple shear slip of hundred of kilometres on an inferred N-trending onshore or offshore master fault, these oroclines are reflections of changes in directions and amounts of shortening that occurred along the western margin of the New England Orogen during a lull in convergent margin tectonism.

N.B. May 2013. In response to feedback from readers, the authors have updated several image captions and improved the resolution of some of the figures to enable viewing at higher magnification. Earlier printed copies of the paper should be replaced by the current version.

Keywords: New England Orogen, orocline, megafold rotation, Permian