Structural styles in the Perth Basin associated with the Mesozoic break-upof Greater India and Australia

The Perth Basin constitutes one of the principal tectonic features along th e western continental margin of Australia and formed through Permo-Cretaceo us rifting of Greater India and Australia. It is composed of northerly stri king sub-basins, troughs and ridges bounded by faults which display evidenc e for normal dip-slip, and possibly dextral strike-slip movement. Transfer faults divide the basin into compartmentalised regions of similar structura l style. Extension and transtension occurred during the Jurassic-Early Cret aceous associated with continental break-up. Stretching was accommodated ma inly by the reactivation of pre-existing northerly oriented faults which di splay both planar and listric geometries, The Darling Fault system along th e eastern margin of the basin has a planar profile. The hanging wall succes sion in the adjoining Perth Basin has undergone block rotation and tilting with syn-sedimentary depositional thickening of rock units towards the faul t. Listric normal faults occur in both the onshore and offshore portions of the basin and influence geometry of the sub-basins, Dip on these faults de creases through the basin sequence and probably soles out in the upper leve l of basement. Rollover anticlines develop within the hangingwall of these structures. Extension oblique to the main structural trends of the basin in the Late Jurassic-the earliest Cretaceous resulted in dextral strike-slip movement along major north-striking faults and the development of en-echelo n folds in the basin. Compressive deformation developed during this event a t constraining bends of the major fault systems. Two orientations of transf er zones are recognised and significantly influence basin structures. The f irst are east-west trending transfer faults which formed in the Permian and were reactivated during Jurassic extension but can only be recognised in t he northernmost Perth Basin. These transfer faults link basin segments of d ifferent characteristics and transfer dip displacement among the northerly striking faults. The transfer zones striking NW only influence Late Jurassi c-Early Cretaceous age deformation features. They are characterised by eith er a swing in a left-lateral sense in the orientation of northerly striking fractures as they cross the transfer zones or a termination of the fractur e at the transfer zone, The transfer zones are parallel to, and may be rela ted to, transform belts in the Indian oceanic crust, Basin-wide uplift occu rred during the break-up and resulted in basin inversion and erosion of up to thousands of metres of the sedimentary succession. Folding by dextral st rike-slip motion along the Darling-Urella fault system also inverted the pr e-break-up sequences in major onshore depocentres. (C) 2000 Elsevier Scienc e B.V. All rights reserved.